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So my name is 10 and I am ra radiology trainee here in the UK, Manchester and the lead of the radiology subgroup of C AC A being Surgery Group of Africa. It's a group of medical students and junior doctors from various countries that come together um to share um knowledge, research teachings and just to collaborate on furthering our um careers. So this is this teaching is being hosted by the radiology subgroup um of C A. Um Today we have um Doctor Mohammad Hamad um who is a radiology resident um from Islamic Hospital in Jordan. Um You'll be taking us on the basics of the CT abdomen. Now, I know it's, it's, it's a big topic. Um but we said basics because it would just be like an introduction. Um A lot of our members are like I said, just medical students and mostly junior doctors are not necessarily um radiologists. So it's more like a um an introduction and then we can do it from there. Um Subsequently, um Doctor Mohammad would just wait a few minutes and then we can start by six if that's ok by you. I yes. Ah I'm Doctor Mohamed Hamad. Yeah. As my colleague have introduced me, ah today we'll be talking about abdominal CD, which actually has books written about it. We will try to make it simple as possible. I think this was the most challenging part of the lecture that to make it simple as possible. Uh uh When we are ready, just tell me. OK. All right. That's fine. Yeah. All right. So most of the he was uh nonradiologic as I understand. Yeah. So most of them are looking to apply to radiology. Um and some, I also medical students that are yet to finish med school. So that's like the main um population. Really? OK. Yeah. Let me share my screen. Can you see my screen now? Yes, I can see your screen. Yeah. Is it changing or it's fixed? It's changing. OK. Good. It's changing the marker. Yes, good. Uh Throughout the lecture, any questions are welcome. Just type in, type them in the chart and Mister Tingle will collect them so I can answer them through the lecture or at the end. OK. Yeah. So it's um six o'clock now, six o'clock um UK time now. Um I think we just make a head start and I mean, others can join just because there have been some people that had like already joined quite early um when we had not started. So I think others would join as we go along. Ok. Ok. Um Doctor you ready to go? Yes. OK. Hello and welcome to my lecture about abdominal city basics for nonradiologic. I'm Doctor Mohamed Hamad Ar, a resident from the Islamic Hospital in Amman Jordan. Ah Let's start with the basics about city itself. The physics itself uh c utilize the same principles of X ray almost exclusively all about x-ray production detection. The main difference between X ray and CT is that in an X ray, it's a single projection and it's a single image. In CT, we take multiple projections 360 degrees around the patient. And we combine these projections ah to make the city cuts that we know. Now, ct as any other modality can have a can be used as a non enhanced or enhanced means enhanced that we will give contrast during the exam and not enhanced that it will be done without contrast. The value of non contrast C is limited uh in comparison to the MRI which gives higher value even without contrast, but it's the most used one and we will ah see why is that, why it is limited and why it's the most used one? OK. For the limitations. Uh First of all, uh it provides po soft tissue contrast leading to difficulties in reading the scan in thin patients with a grow with crowded structures. Ah CT is more suitable for patients who are, let's say overweight or obese because there is more space in the abdomen and we can see the structures uh separated that are for visualization of these structures. Second, uh the CT involves radiation and compared to other modalities like ultrasound and MRI ah these modalities do not involve any ah radiation exposure. And also when we compare it to the X rays, it's even higher radiation than X rays. But nowadays, we use what we call a low dose CT scans. So these uh radiation exposure rates are now much lower than we had previously in the uh last 12 or three decades. Uh In some cases, the CT itself will provide limited information about an abnormality. And the subsequent MRI or further evaluation may be required to confirm a specific diagnosis. For example, uh uh when we see a lesion in the thyroid or on the liver, we need to confirm that or maybe have further evaluation by an MRI or by having a biopsy to that lesion. So we can identify that lesion specifically. Of course, as we all know or all we might know that gallstones ah are not visible mostly on CT. So ultrasound is the investigation of choice for ah gallstones. Still CT can identify dense gallstones which will appear as hyperdense on CT S but these are only a fraction of the majority of gallstones. For the last limitation. A CT is obtained in axial axis. So we can't obtain the image itself. In other axis like coronal or sagittal, we can reconstruct that that is not obtained in coronal or sagittal sections or cuts. Uh It's only an axial and then it will be reconstructed to coronal or sagittal compared to MRI and ultrasound, which we can obtain the image in multiple planes. OK. Let's come to the advantages advantages of the city. It's high resolution. Ah it has higher resolution even than MRI. Uh physics wise, MRI has higher contrast. It means between different tissues. It has much uh much higher contrast, but for resolution itself, C has higher contrast. The second advantage is widely available in almost any center. Uh advantage is also it has a quick scan times compared to the MRI in which we sometimes in some uncompliant patients like maybe pediatrics units or elderly, ah we will use a general anesthesia. So, so we can obtain images for MRI and CT. It's mostly unneeded because the scan times can be in uh the whole scan can be in seconds, sometimes even one second or two seconds or half a second. Sometimes thin cuts are widely available and used for beta reconstructed images. Nowadays, uh thin cuts, uh up to half, half a milli cut, it can be obtained. And these will provide uh a high quality reconstructed images. Also, it's cheaper on the patient. And ah as we said, it's widely available and cheaper contrast itself is also widely available and cheaper in comparison to the contrast for MRI, the contrast material between MRI and CT will be different. Uh The MRI contrast is quite expensive, but for CT it's cheaper because it's the same contrast used even in x-ray and the fluoroscopy. OK. Let's start talking about CT density. Ah the density is the appearance of each pixel, the given number for appearance of each pixel on the CT scan itself. This is calculated using the attenuation coefficients of different materials. So the attenuation coefficient is how that tissue is attenuating the uh X ray beam or the CT beam. So for example, bone is highly attenuating. So x-ray will not pass that. So it's a high uh so bone has high attenuation coefficient. Uh CT density is an absolute number. It's not relative to anything else. So when we say that a lesion is dense on CT, that means it's absolutely dense. It's not being compared to something else. Now, for ultrasound and MRI uh in ultrasound, we call things echogenicity. It's hyperechogenic or hypoechogenic. And an MRI, if it's high signal intensity or low signal intensity, these terms should be used only in relative to something else. So when we say uh in an abdomen, ultrasound scan that a lesion in the liver is hyperechoic, that means it's has uh it's more white than the liver, parenchyma than the liver surrounding parenchyma. Uh Let's give an example quickly uh liver hemangioma and an abdomen ultrasound will appear as hyperechoic. Ok. Uh Let me see if I can show you something. Anyway, it will be a hyperechoic. But in a uh fatty liver, it will be hypoechoic, the hemangioma itself uh didn't change, but the part of the liver changed, that's why uh liver hemangioma can appear as hypoechoic because of the surrounding parenchyma, liver, liver parenchyma did change in echogenicity. On the other hand, ct uh appearance is absolute. So if hemangioma is hypo dense, it will be hypodense always uh for densities, fluid is assigned zero. And that will make the scale for us. And the next uh slide, it's called the house field scale at you in which the water is assigned zero. So it's in the middle, it's a gray and air will be minus 1000 and it will be pitch black. Now, other things will be across the scale in which metallic and bone is at the highest spectrum here, more than 1000 fat will be lower than water. So it will be darker than water and we will see across ah the lecture when we come to the examples. Uh Now water is zero only if it's pure water distilled, pure water, not as if the water content of the body in any compartment is pure. So for example, blood has water, but it will be higher than zero. A bile in the gallbladder has water, but it will be also more than zero, urine has water. So technically, we will not see a um and and as as straight zero, we will see something like from minus 10 to 20 across this field. Anything across this will be considered as fluid. Ok. For soft tissue, it's from 30 to 45 sometimes up to 50 or 60. And this uh will explain the limitation that we discussed earlier, which is poor contrast. As we know, most of the body is soft tissue also on the abdomen, most of the abdomen is soft tissue. So when we say that uh a soft tissue, for example, in the liver is 30 and we have uh HCC OK. Hepatocellular carcinoma. And this hepato carcinoma is like 35. Ok. So how much is the difference between 3035? It's only five. This will not make contrast when we visualize these two different structures. That's why it has a low contrast. Uh We try to uh we will try to make a better contrast using a contrast material and we will see how for acute blood it will be 60 to 90 this is clotted, fresh blood will usually be like uh fluid density here. It will not be so anything clotted blood will be 60 to 90. And after that, it will be, it will be resolved ah slowly toward ah going back to fluid density. Now, for iodinated contrast, the contrast that we use in CT it will be around 100 to 500 depending on the concentration itself. After that, we will have the trabecular bone, not the cortical, it will be less than the cortical bone. And uh the highest spectrum we have cortical bone and uh metallic, anything metallic will be very high. Also, this is the scale itself again, but this is for the brain as we can see that the white matter is lower than the gray matter a little bit, not too much. Uh This differentiation is higher on MRI. That's why it has higher uh contrast. OK. Next, let's talk about something called window and live. This is how we display the image itself, as we said that the AU unit is an absolute number. But how we display it on our monitors, we determine that for example, on this scale, uh the level is zero because zero is given the gray in the middle and the window will be 2000. That means we will have 2000 shades of gray from minus 1000 to uh positive 1000. We will see uh examples next have a different value set by the machine. So when we first open the images, there will be a different value for window and live and we can change that. And uh any P system have uh some presets that can be used in the abdomen or other modalities. OK? For example, one, this image for the abdomen which I made it look like this ugly. It has a level of 60 and a window of two uh window of two means that we only have two shades of gray. And when we talk about two shades of gray, what do you think that we have, we have only white or black. There are actually no shades, it's only white or black. And the level 60 means that um 60 here. So anything 60 uh more than 60 will be white and anything less than 60 will be itchy black. So we don't have this uh gray scale. So it will be here all white and here it will be all black. This is uh this is not practical. It's just for ah giving an example to make the point clear. OK? But in general anything with low window values is called narrow window and things will be ah elated like this, not like this maybe le less than this. But as we can see in this picture, we only have white or black, no, no shades of gray. OK. Uh Now you can be wondering why there are too much black or I think too much white in the liver. When we said that soft tissue is up to 50 or 60 in CT we calculate things in an area better than pixel to pixel. So for example, when we take this area, the mean density is 52 which is compatible with it being a soft tissue density. OK? But when we look at the minimum, uh the minimum pixel density in this area is only 19 which we can say that it's a fluid but it's not fluid. We take out, we talk about the area better than uh talk about each pixel by itself. And the max is 82 which can be said to be clot to the blood, but it's not the case. So it's always important c to uh to work with the area itself, the mean density of the area, not the individualized exons. And that's why here, in our example, we can see a lots of white dots and lots of black dots in, in our second example, we have a window of 1000 and a level of 50. That means we have 1000 shades of gray that is being displayed on this image. So it's a it's a fairly large window and it's a large window for the human eye to predict subtle differences at this window. So as we can see here, this is the liver and this is the kidney. The difference is not much between them. And also if we can talk about here, this is part of the of the duodenum wall. We can differentiate the liver from the duodenal wall because but if we make the window narrower, we can start to uh appreciate the differences the subtle differences between things on the city. OK. Now, because the window 1000, that means when the level is 50 we subtract 1000 from 50 we, and we get minus 90 150 anything below this uh value will be pitch black. So what do you think that we will have anything pitch black? In this image, nothing but air. So air will be the only thing that is pitch black on this image. And this can be used to determine if we have um to check the bowel or check if there is a ortoni, it will make it easier. But if we want to evaluate soft tissue, this one is doesn't have ah much use to evaluate the soft tissue itself. Ah Also on the other side of the spectrum, ah anything that is 1050 above will be bit white. Ah So metals will be appear pitch white on this. And the cortical bone of the spine here is pitch white. So this window will make it easier for us to determine if anything is contains air or if it contains metallic or bone. This is called a wide window and it's used as a bone window for bones, maybe stones. OK. For our th for our third example, we have a level of 50 window of 150. We can see here the difference between the liver and the kidney is much more. So we can differentiate them also from the duodenal wall. This is the duodenum and this is bowel content inside it. This is the duodenal wall. We can see there is difference between each one of these. Despite that the house and field unit, the actual unit is the same. It's the same in this one. It's the same in this one. It's just we play with the numbers, OK. The contrast types that we can give in a contrast study, we have the IV, the oral or rectal. Uh most widely used is only the IV. Now, for the type of the contrast itself, we have two types in general. Uh it's either positive or negative, positive. Anything that will appear white on the CT scan and negative is a contrast that will uh will appear as black. OK. For IV, we have only positive, we don't give negative contrast because negative, it can be only water or air because water and air will appear uh will not appear as white on CT scan. So we can use water and air only in um oral or rectal. So we can distend the bowel. So the bowel insides will be better displayed when it is ah distended. Yeah. OK. Let's come to the IV contrast phases. When we give IV contrast, uh we will there will be a timing that we will obtain the images. So, ah let's start with the classified depending on the timing, an early arterial phase in which it's the most. Uh it's the least timing after the post injection of the IV contrast. The contrast itself is mainly confined to arteries only and this phase is used to detect vascular pathologies and lead arterial uptake of contrast uh is uptake of the contrast is being taken by highly vascularized organs and lesions. For example, an HC will appear hyper on arterial phase. Also, for example, the kidneys are highly vascularized. They so they will enhance on the late arterial phase. Also if organs are more proximal to the heart. So anything is more proximal will enhance earlier. So for example, lungs and arterial phase for lungs is earlier earlier than arterial phase for abdomen. Ok. Then we have the portovenous phase in which the contrast is in the portal vein and start to be in the venous phase in the veno in veins. Also, this is called the hepatic phase. And this is the default phase for any abdomen. With contrast. After that, we have the venous phase in which the contrast is found mainly in the venous system. For example, the iliac veins. Uh also this phase is good for uh in general for organ enhancement. Also bowel wall enhancement because the the contrast by this phase uh will reach the capillaries and capillaries are responsible for any uh soft tissue enhancement. Ok. For delayed phase or may sometimes called excretory phase, we take this at a specific timing. So it's 7, 10 or 15 and this will show us mainly two things. The first is the contrast in the urinary collecting system or if there is any extravasated blood outside, outside the uh organs, if there is any bleed, ok. The other contrast phases can be classified depending on the structure organs, maximum enhancement. So, in a hepatic phase, as we talk about, it's in the porto venous phase. And in this phase, the liver will have the maximum enhancement. And by maximum enhancement, we mean maximum density in the pancreatic phase or corticomedullary phase. This is considered as left arterial and nephrogenic phase in which the nephrons and the collecting tubules are and the loop of Henle is enhanced. Ok. Now, for abdomen contrast, we have different protocols and protocols. It means the timing itself, we adjust the time to utilize the the phases that we talked about here. So for example, if we suspect that there is something wrong with the liver, we will do a liver protocol, which is the default abdomen protocol. Uh we will take in the porto venous phase. For example, we have something called adrenal protocol in which this protocol is a specified engineered to uh make any lesions in the adrenal that we can characterize any adrenal lesion pancreatic protocol also. And we have urinary protocol just to name few. For urinary protocol. For example, we have, we will take the patient in four phases, the nonenhanced corticomedullary nephrogenic phase and the secretory phase. Uh as we can see in this picture, this is the corticomedullary phase because the cortex and medulla is enhancing. OK. And this is, as we recall, it's lit arterial phase. Now, for nephrogenic phase, we can see that the contrast now is seen in the more in the medulla. So when the contrast reaches the loop of Henley and collecting ducts, it will appear like this. So this is the nephrogenic phase uh for excretory phase. As we can see, this is the ureter and the contrast is mainly found in the ureter. As we can see, the liver is very black and uh for the window and liver, this is a narrow window. As we may see, this is narrow window because there is not too much uh shades of gray. It's only uh black or near black or white or near white. So this is not a window. Ok. Now we will talk uh some of the radiological anatomy of the abdomen itself. This is a picture of the abdomen and this is the ah mostly uh portovenous phase. Um Excuse me, this is I think the arterial phase. So we can see that the kidneys are very enhancing and the aorta is enhancing. So it's the arterial phase. It's important to determine the phase that we are looking at. Uh when we view images and work, it will be given to you. So it's not hard to tell, but in exams and if you are questioned, sometimes you need to determine the phase that the image is obtained in without being told, what is the face? Um doctor, yes, there's um a question on the chat box. Um just when you were talking about the contrast, um someone is asking um a is asking what are the indications for oral contrast along with IV contrast? OK. For oral contrast as we talking about the oral contrast will be in the bowel. So it's good when we want to assess the, uh, intraluminal bowel content. If there is any lesion in the bowel itself, uh, if we want to see if there is any kind of obstruction, if there is any obstruction, that means the contrast that we gave oral, for example, will not pass that point of obstruction. Ah, we will have some common pathologies in in the emergency and think will be clearer by then. But when we talk about contrast itself as a concept, we can see that for example, here is fat. So it's black and we can see differentiate this from the wall of the stomach. So we have contrast, we say here we have contrast. If we can differentiate the fat from the wall of the stomach, we say that we don't have enough contrast to make that differentiation. Also, if you can see here, the kidneys are very bright. Um but we didn't see them bright like this in any of the phases. Why is it too much bright in this image? You can think for a moment we have we have it right here because the window itself is not helping the enhancement of the kidney. Here, the window itself, if we adjust the window and level, the kidneys will appear either like this or like this. But because we are not much concerned about the kidneys, the window and level is made for other structures. OK. On this cat, ah we have the pancreas here. This is the tail, the body, the head we have here, the splenic vein, splenic vein runs posterior to the pancreas. In comparison, the splenic artery will run superior to the pancreas. So it will be viewed viewed on upper cuts. We can see here that the liver enhances homogeneously. And we have these dots, these dots are the contrast in the vessel itself. So these are not lesions, these are only the blood vessels. And in this image, we can see that we have here oral contrast. So the content, the content of the stomach is enhancing because we gave a oral contrast. OK. This is a coronal cut and we can see that the liver is homogeneous enhancement. We can see the portal vein. The pancreas is here uh tip of the spleen here, the stomach, we can see the mesentery here, the vessels of the mesentery itself. We can see the ascending colon and the hepatic flexure. These are all small bowels, small bowels and this is the bladder. OK. Ah Just to give to give an example about the usage of the phases. We can see here the an image of the liver itself. We can see that there is some uh fuel enhancing uh lesions on the arterial face. That means that these lesions are highly vascularized. And when we see a look at the portal veins, um the the lesions disappear and on the delayed images, the some of the lesions reappear as hypodense because there is wash out. So there is early uptake and early wash out. This is suggestive of HCC. Also, we have uh free fluid, perihepatic, free fluid and also the edges of the liver itself is not smooth. This is suggestive of cirrhosis. So in in cirrhosis, the liver surface will be ah nodular. Ok. This is the same thing that we talked about hypervascular liver lesions early wash out. This is suggestive of HCC. OK. And now let's look for the spleen enhancement. We have something called the zebra spleen and it is the heterogeneous enhancement in the arterial phases. Uh by the way, this is normal. So when you see this, you don't think that it is abnormal. This is due to the anatomical uh the anatomy of the spleen itself and how the blood is being uptake by the spleen. Uh mainly it's due to the difference in uptake between the white bulb and the red bulb. So it's uh due to the anatomy of the spleen itself. But the catch is that this is in arterial phases and venous phases, the spleen will be homogeneous again. So there will be not this heterogenicity. OK. Let's talk about the anatomy cut by cut. So what do you think about this image? And what phase? What do you think? Which phase do we have here? Anyone can answer? I can look at the chart Yeah, I'm looking, I'm looking at the chart. Um No one has put an answer yet. Ok. Mainly this is the arterial phase. Why? Because the aorta is vividly enhancing. Uh this is the ortum, by the way, it's slightly to the left of the vertebra. So it's not directly in the middle uh to the left is always arterial face. Yeah, it's arterial face. Ah the aorta will be slightly to the left and the IVC will be slightly to the right. Ok. And in general and radiology, when we want to differentiate between an artery or a vein, we have some of these basic characteristics. Uh For example, this is the IVC arteries always will be more circular. The veins will be like s squished a little bit. It's not fully circular. So we can see that this is a vein, this is an artery. Uh OK. We have here, the azygous and hemizygous small veins here. Ok. Ah, we are do we are going down from top to bottom. Ok. So you can, ah understand the radiological anatomy. CT here we have the main hepatic veins of the liver, three hepatic veins mostly and they run into the IVC straight to the uh to the right atrium. Ok. When we go down more, the spleen starts to appear here. OK. To the left of the spleen to the left of the body. I mean, ok. As we can see here, the contrast itself can be seen in the vasculature of the liver and the liver itself has a homogeneous enhancement. This is the splenic uh the, excuse me, the portal vein branches and this is the stomach. And we can see this line. This is the diaphragm. This is the diaphragm. And what penetrates the diaphragm. Here, the esophagus, the lower esophageal sphincter or junction uh penetrates the diaphragm here to go into the stomach. When we go down more, the spleen now is in view fully and you, we go more, we start to see the porta hepatis, the base of the lung in which the portal triad enters the liver. What are uh what are the or what is the portal triad? The three structures are the portal vein, the hepatic bile duct and hepatic artery. Ok. We go down more. We can start to see the spleen spleen hilum in which the vessels will penetrate the spleen. So this is the splenic vein. Ok. And this is the splenic artery. Why this is the splenic artery? Because we are still high. And so the splenic artery is more superior than the splenic vein. And as we can see, this is the splenic artery and when we go down the splenic vein is here. So it's lower ah also in the superior cuts, we can see the adrenal glands, both adrenal glands, sometimes they are better visualized on coronal cuts. Uh adrenal anatomy can have lateral limb, medial limb and anterior limb. Ok. So this is the anterior limb, for example. And this is the medial limb of the right adrenal gland and this is the lateral limb. So when there is a lesion, we need to identify where that lesion is. If it's in the medial limb, lateral limb or anterior limb, sometimes the limbs are better visualized on coronal cuts. Ok. Also around the splenic vein, we start to see the pancreas, the tail of the pancreas. And when we go down, now it's the body of the pancreas and it's going around the splenic vein. And when we go down, this is the Picreus fully in view, we go down more, we go down more. What do you think this part of the pancreas is what's the most inferior part of the pancreas? It is the anchin process. So this is the inch process or slash the head itself because the pancreas is oriented uh oblique uh here, it will be more superior than here. OK. Now, we have the kidneys in view, start to be in view as we can see. This is the corticomedullary phase. OK. Or left arterial phase. Yeah. OK. Uh Where did we reach? Ok. This is the first uh uh what is it? One second. Yes, this is the first branch of the aorta or the first anterior branch of the abdominal aorta, which is the celiac trunk. Ok. That will give the splenic artery will give the uh common hepatic artery. Ok. And when we go down the second branch, which is the superior mesenteric artery will appear. This is the IVC and we can see there is a black dot inside the pancreas. Ah, do you think this is a lesion or what we can listen if there is any answers? What do you think that this black dot is represent? Let's look at the chart. Yeah, I can't see any answers here. Oh, someone's put pancreatic ducts, ah, quite close. This is quite close actually. So let's analyze things. We have the pancreas, it's enhancing and there is some kind of uh uh hypodense, let's say well defined. Uh it's almost fluid density. There are other answers to in the chat box. Now, um BUCA puts um vein is specify which though and Collins puts sa I mm OK. Veins could be but which vein is it? Is there a vein that penetrates the pancreas? And that it, it is that large? But it's a good answer because it's fluid density, blood will be fluid density. It's OK. Even this is contrast study and the veins will have some enhancement even if it's ah ah arterial phase. Uh OK. Let's go up with this thing. Anything that we see on CT we can go, just follow it and see the I will go up again and see as we can see. This is the dot Again, we will go up. It's here. It's here, it's here, it's here, it's here. It's here. It's here. So it went to the portal triad and what uh does go to the portal triad. It's the bile duct. But when it is this distally, it's the ampulla of water because this is after the uh after the uh after the pancreatic duct and the CBD combined. Uh So sometimes it's easier to follow the CBD distally to approximately because the uh it will be uh easier to detect the uh CBD distally because it's surrounded by the pancreas. Uh The answer of pancreatic duct uh is quite good actually. But this is not quite the pancreatic duct because if it was it will be dilated. So the answer is I'm full of arteries. OK. As we talked about the kidneys, we can see here the uh renal veins, the left and right. Also, we have the left renal artery, they are enhancing. OK. You can see them here. This is the renal artery renal arteries. Uh As we can see uh almost always the uh artery, the artery has less diameter than the vein. So the renal artery will be smaller than the vein itself. I think these advices are much appreciated more when we talk about non enhanced uh CT study because when we are talking about enhancement, it's easier to distinguish artery from vein. Ok. Now, the liver, ah the tip of the lever will disappear and we have the kidneys also the transverse colon. Now and the small bowel will start to appear all around we have here, the oral contrast is seen in the bowel. So we can know that these are the ge bowels. Ok. Now, for the inferior mesenteric artery, it's a small artery that will be distally in the abdominal aorta. And when we talk about uh inferior mesenteric artery and vein, the artery will be the opposite. Uh I mean, uh we talked about that the AORTA is to the left of the IVC. So this is vein artery for uh SMA and S uh and suber mesenteric vein, it's also the same order. So it's vein artery or are they let me get them? Ok. So this is the, ah, the S MA and this is the S MV. So it's also in the same order. But when we talk about the inferior is in, ah, it's the opposite order. So the artery will be to the left, ah, I mean to the right of the vein. Um OK. So where is it? I don't see the inferior mesenteric vein actually, maybe this is it. So this is the inferior mesenteric vein. This is the inferior mesenteric artery. So it's the opposite uh order. Ok. Anything we didn't talk about, maybe we'll talk about the duodenum for a little bit. The duodenum comes from the stomach, the stomach will arch. So this is the greater curvature of the stomach. This is the lesser curvature of the stomach. Ok. Then they will come here adjacent to the liver and adjacent to the gallbladder. Ok. So, it will come like this. This is the duodenum first part of the Duodenum, second part and you will go down and it will be, it will cross, it will cross behind the Asami. Ok. When it crosses behind the, this is the third part after it crosses, it will go up again. So I'm going up now, this is the fourth part of the duodenum. After that, it's the uh dun bowel loops. OK. Anything else we need to talk about? OK. Let's talk about the uh colon itself. This is the ah uh transverse colon. OK. It's the most anterior part. And we if we go up, this is the hepatic flexure in which uh proximally we have the ascending colon. This is the ascending colon. And at the end of the ascending colon, we have the cecum, the cecum will give us the ileocecal valve. You see this is the ileal valve and it has contrast within it. So the contrast actually in this image has reached the and the ileocecal valve and even further down when we go further down, what we will see at the end of the sea camp, we will see the appendix and here is the proximal part of the appendix and it will go down then up again. OK. So this is the retrocecal appendix. We know that the appendix has variations in a uh anatomical location. This is Retrocecal. OK. So this is a uh AUC valve and this is the appendix will be below it. This appendix has air in it, which is a uh which is a sign that it's normal. OK. What are we now any questions about the anatomy of the abdomen? If anyone has questions now, we can answer them because, because next we will be going into some pathologies. OK. Let's make a quick quiz. Uh Let me give question. And what is this? Anyone can answer this structure, right? You can think of no one else. OK. The left adrenal. Yeah, someone has a mhm Also a tip. If you are uh questioned about any anatomical structure, always, always you need to mention if it's right or left, if it is paired. OK. If you didn't say left Adrenal Gland, uh you will have minus one on your uh so you will take only one from two points and even sometimes zero. So this is the left adrenal gland. This is the splenic vein chile. OK. Another question, what is this here? This structure? I'm just looking on the chat box um Before I answer. Yeah. Um Correct, correct. This is the spleen. OK. OK. What do you think about this? Yeah. So just to be clear, the, the structure that has air in it, isn't it? Yes. OK. So it's black. So it's air in it. Yes. Just waiting to see if anyone has answer. Can I draw using the pointer? I don't think so. Yeah. Yeah, I can see it. I can see it. Yeah. This one. Mhm. Um, so someone put air, um, abu acid air accumulation in the spleen. Adnan said Colon Beverley said small bowel. Colin said left diaphragmatic recess. OK. We are talking first of all about normal anatomy. So it is not, uh, um, in this situation, it's not normal in the spleen. There are some situations that it can be there, but we're talking about normal anatomy. Ok. Small bowel or colon. Uh What do you think? Uh let's try to make some distinguish between small bowel and colon in general, other than the location itself, a small bowel will mostly be fluidfilled. So there will be mostly no large areas of air or feces and it's always in the mid uh it will not be on the lateral borders. A colon. On the other hand, will have feces in it. Uh So for example, feces, this is all feces and they are. And uh this is uh this also applied to this thing. So this is the descending colon to be precise. It's not the colon, it's the descending colon. It's collapsed here, it's collapsed. Uh It's a collapsed, uh descending colon. Ok. Let's go next. Ok. When we talk about general abdominal ct in an emergency sitting or any, any abdomen, actually, an abdominal, we will look for these two things. These are two very uh generalized things. They're not specific for something they will be present. In most uh of the pathologies that's present in the abdomen. So anything that has fat standing, when we talk about fat standing, we mean that the fat itself will be infiltrated by fluid. So it will be up here uh higher density. So we can see this is the the fat here, for example, it's homogeneous. OK. It's not white. And when we compare it to the other side, for example, here, it's the same. OK. Uh Now inside the mesentery itself, this is outside the mesentery. So this is the omentum most likely. OK. So this is omental fat. There is no vessels here. Not too much in the mesentery. We have a lot of vessels so we can see that the fat sometimes here is a bit higher in density than here. So we need to keep that in mind when we assist for fat stranding. So here we don't have fat stranding. We have only vessels that is branching. OK. And then we will see how fast stranding will appear. Also, we will look for any enlarged or prominent lymph nodes, either reactive or pathological. Whatever any lymph node will give us a clue about if there is any pathology or the location of that pathology in the abdomen. OK. Now, let's go for some specific entities concerning emergencies and abdominal ct detected on abdominal CT. Let's start with appendicitis, appendicitis. Uh The radiological features for appendicitis, it's enlarged diameter. So it's more than 0.6 centimeter outer to outer diameter. Uh And we measure that in the maximum thickness and where there is no air. So when there is intraluminal air in the appendix, we can't measure it there because the air will distend the appendix itself. For example, let's go back to our anatomy slides. We uh we said that this is the appendix, right? Um We can't measure it from here because there is air and air will distend the appendix. So this will be false positive. So for example, I will measure the appendix here, OK? Or here. OK. When there is no air, OK. Also one of the signs is thickened me wall. Now, we are not talking about the diameter itself. We are talking about the thickness of the wall of the appendix and how we will uh uh how we will say that this is the wall, as we say, the intraluminal content will be mostly fluid. Uh So when we talk about fluid and the wall, the wall is soft tissue, there should be contrast. OK? And we will see the wall if it's uh thickened or not. And when we talk about edematous, that means it has uh edema in it. And when there is edema in it, uh that means it has higher fluid content. And then, and when it has higher fluid content, it will be of less density. OK. So an edematous wall uh will have less density than a normal wall. When we compare it to, for example, uh, a wall of a normal small bowel, it will be fluid filled. So, absence of air in the appendix is a sign for appendicitis. Also, we can have an appendicolith if, uh, if it was the cause of the appendicitis. Yeah, actually, the presence of appendicolith, uh, is an indication that surgery should be done to remove, uh, appendectomy because in the presence of appendicolith, we call it obstructed, appendicitis. It's not reactive or just inflamed. Sometimes when the appendix is just inflamed, uh, we can give antibiotics, we can manage it conservatively. Many patients will, uh, improve on this. But in the uh, presence of appendicolith, uh, the cause of the appendicitis is that the appendicolith is closing, the, uh, is obstructing the tip of the appendix or the distal part of the appendix. So this should be, uh surgically removed also if perforated. If the appendicitis was complicated by a perforation, we will have surrounding free fluid and abscess formation and the pneumoperitoneum. And after perforation, the diameter of the appendix can, uh, back to normal because it was uh, appendicitis. It has enlarged diameter. It's fluid filled and with, and when it's perforated, it will pop out and the diameter will be back to normal but thickening of the wall will persist. Ok. Let's see examples. These are three different patients. The first one, as we can see, this is the appendix. Ok. It appears enlarged and uh, let's go back to the talk of the fat stranding. Let's compare this area of fat stranding in comparison to this area. What do you think it's a little bit higher? Don't you think so? So this is fat stranding. Also, this is fat stranding here. It's fat, this is all fat. There shouldn't be anything here other than fat. So in comparison to this area or this area, it has higher density. So it's fast stranding. We can also hear uh above my marker, not on it. We have oval shaped uh structure. Let me see if I can draw um got pen. OK. This thing is an oval shaped uh structure. This is a lymph node. So there is a reactive lymphadenopathy in this area. When we compare it here, we don't see any lymph nodes. OK. So it's uh right iliac fossa that's stranding with reactive lymph nodes and uh uh thickened uh also enlarged appendix. So this is typical appendicitis. This case was also the same as we can see here. Let's go back to the pointer. OK. Uh So this area here has fat stranding. The appendix itself is distended. In the last case, we have a coronal cut. OK. So we can see that the appendix has a dense appendicolith in which distally it's fluid filled. OK. And you see the thickened wall, let me draw the wall for you uh OK. Out to do this point that I draw here. This is intraluminal as we can see this is fluid filled, but here there is the wall, it's dense. So the wall is more dense than the lumen. Sometimes it's hard to appreciate. But this is the wall and it's thickened, considered like this. Um How do I remove the pointer there all in cocaine? Let's go back to the laser pointer. So the last case is a is an appendicitis caused by appendicolith. Sometimes appendicitis will be present with uh alongside an adjacent inflammatory process, for example, colitis. So it's considered only reactive appendicitis and this will resolve spontaneously. Uh most of the time. OK. Let's go next for api epiploic appendicitis. Sometimes it's considered a mimic of appendicitis, especially if it's on the right side of the abdomen because it will give uh almost the same physical examination of the appendicitis from tenderness to rebound tenderness. OK. The op placa bandage itself is a peritoneum line protrusion of the subserosal fat that arises on the surface of the large bowel as we can see in this image. So this is the like appendages. A this condition is mainly menaced conservatively and this is a huge difference from uh appendicitis which uh in some cases should be managed urgently by surgery. It's it's not an emergency but patients will usually present to the emergency room. OK? For the features. Uh Sorry doctor, just um questions from the chat box as you are going. So you showed the Coronal image for the appendis and Collins was asking that you had mentioned, we can't reconstruct images in the coronal plane for CT Yes. Uh II would say the second question after you, ah I said we can't obtain CT in a coronal view, but we can reconstruct it. So it's a reconstructed image but it's not obtained. So the image itself was not obtained in this view. Uh It was uh first of all, it was obtained axial. Then we made this by software. OK. But for MRI, no, we can obtain this directly without reconstruction by software. This is the main difference. So this is a reconstructed images. OK. Um And the second question was from who's saying that um can only is only IV contrast enough to diagnose acute is do you also need oral contrast? OK. And these images, what do you think? Do you think it's uh contrast or without? So, in these images you've shown there is it's just um I IV contrast, I can't see any oral contrast in it. Yes. So for acute appendicitis, it's either one of two. First of all, we will start with non enhanced uh contrast. In many cases, it's more than enough to diagnose acute appendicitis. Uh If it was inconclusive due to let's say crowded abdomen, we didn't see the appendix, then we can give IV contrast for better visualization of the ah appendix itself. Sometimes we can take the patient for ultrasound to help us diagnose if there is appendicitis. So IV contrast. Uh at least in our facility is uh not the first line for uh diagnosing uh acute appendicitis. We will start with non contrast first. If the scan itself, the non contrast was not uh diagnostic for acute amend and there is still a high suspicion for acute appendicitis, then we will go for IV contrast, oral contrast. On the other hand, is rarely used for uh uh diagnosing uh acute appendicitis because it doesn't add any value. Because first of all, the contrast, uh the oral contrast will take too much time to reach the appendix to reach the cecum because it needs to go all through the Jin jin and ilium. And we want to diagnose the patient as soon as possible. Also, uh oral contrast may complicate any surgeries. OK? Because uh this is uh this is an emergency and the patient can go to the theater room and they may resect um if it's complicated or something, they may resect something from the colon or so. So we need to keep the bowel without contrast uh clear. Does this answer the question? OK. Let's go back to the PLO meningitis. OK. It's not emergency, but uh you will get a look in the emergency room. The radiological features for appendagitis, we will see a fat density void structure adjacent to the colon, usually anterior and it will have a thin high density rim. So it's fat in the center and uh the rim will be high density. And when we say fat density, then it means it will be a little bit black. Uh central hyperdense dot Sometimes not all the time. Actually, it's rarely seen. Uh this central hyperdense dot represent the thrombosed vascular pedicle. So it's a clotted blood uh and it's the uh facility for a bit jets itself, but it's not seen most of the time it will be resolved by the time the patient will have uh his CT scan or sometimes this dot will be too small to be visualized on the CT scan itself. For the example, we can see this is the sing colon one second, excuse me. OK. This is the descending colon. And we see that the fat around the descending colon is not the same as here or even here. We can see that as we said, this is the mesentary, this is not fat stranding, these are vessels, but still when we compare it here, we can see that this is fat stranding. So we have something in here. And when we look further, what do you see? Ah we see that there is a void structure anterior to the descending colon and the rim is hypertense. OK. So this is a Pica bindis. OK. Let's go next, diverticulitis. This affect most commonly the sigmoid, but it can be present in any part of the colon. Why the sigmoid specifically? Because it has high intraluminal pressure and relatively normal caliber. And compared to the rest of the colon. OK. Complications of uh diverticulitis. It can perforate with subsequent peritonitis, abscess formation sepsis. And in chronic cases, it can lead to fistula formation and actually this complication and this perforation can be present also in appendicitis. So, perforated and Misys can lead to peritonitis, abscess formation sepsis. OK. For features, radiological features, of course, we are talking about uh we can see that there is outpouch from the colon. This will diagnose that uh the diverticula itself, not the itis of the of it. It may contain dense material or air, whatever the content of the diverticula itself. And we will see surrounding fat stranding which is required to distinguish diverticulosis from diverticulitis. In this example, we can see the uh uh descending column because it's on the left. Uh And we can see that there is fat stranding also fat stranding here. This is the same patient on Coronal section. And we can see the diverticula here out pouches from the colon itself and we can see some reactive lymph nodes. So this is diverticulitis but it's not perforated. OK. Yeah. So fat stranding, it's not perforation. We don't need to say that there is perforation. If it's fat stranding, fat stranding is a consequence of the inflammatory process surrounding the area. Only when this perforation. Mostly we will see air in the uh peritoneum or large amounts of localized fluid collections. OK. We see this also we are in the sigmoid. The last one, we were in the descending. This is the sigmoid and we can see these uh somehow large diverticula and they, there is air content, OK in it. And there is hyperdense uh wall. And we can see that there is here uh localized ascitis, localized free fluid. Uh This is most likely divertic colite. OK. Let's go to organ injuries or infarctions. This is a very large topic that we will talk to about it. Ah briefly. Mm This image you try to uh uh make an overview of any organ injury infarctions. So first of all, if there is, as we can see the liver, uh this is non enhancing area. So it's devascularized. This will appear as nonenhancing area on contrast CT scan. So when we suspect organ injury or infarctions, we can't ah make a diagnosis without a CT contrast uh laceration which is a direct uh cut through the organ tissue. This is most likely in a clinical setting of trauma patient for devascularization. It can be trauma or nontraumatic like uh thrombosis in the bal vein can lead to this entity. So the uh devascularization is not only by traumatic but laceration. Uh most likely there will be a history of a trauma, either blunt or penetrating. Also, we can have contusions in which there is patchy, patchy. Uh that means it's a scattered uh hyperdense areas, hemorrhage uh in which or or hemorrhage or hematoma in which there is a well defined not patchy, contusion is patchy. So it's scattered. Uh hematoma will be well defined hyperdense a content uh or a lesion that is nonenhancing hematoma uh is not enhancing. So that's how we differentiate hematoma from contusion. Also, uh we can have hemi peritoneum. It's similar to ascitis but it will be of higher uh density. Why it's higher density? Because blood is higher density relatively to uh ascitis which is clear fluid, let's say uh sometimes also we can have subcapsular hematoma. So, organs, most of the time has capsule uh surrounding uh the organs. This capsule is uh composed of uh heart uh tissue fibers. So it's uh not easy sometimes that this capsule will rupture. So when the, so when the uh hematoma uh accumulate in the capsular space, it will appear like a crescent like, OK, like crescent like and the organ itself will be pushed uh away from the capsule because the capsule is a connective tissue which is harder than the soft tissue of the organ. So it will be uh pushed. OK. Uh This is also an example, this is a laceration of the spleen. OK. This is subcapsular hematoma. This is intraparenchymal hematoma. This is uh laceration also, this is devascularization in which there is non enhancing areas. And this is called the shattered spleen in which all the spleen is non enhancing with multiple lacerations. OK. For the examples, splenic laceration. I think this is a simple one. First of all, we see that this is contrast because the aorta is enhancing. So the spleen is homogeneously enhancing, right? I think it's homogeneously enhancing. But we can see that this is a linear nonenhancing area. This is uh like uh presenting a splenic laceration likely due to trauma. Also, we need to talk about that uh in a case of non enhancing area, most likely it will be which shaped uh this is specific for infarctions. OK. Let's talk about renal infarct. As we can see, this is the kidneys. What is this phase of the CT image? We can take some answers if anyone know the answer we talked about this the arterial arterial phase. But ah in a case of the kidneys, anyone, what's the phase? Let's say the organ phase. Yeah, nephrogenic phase. Yeah. This is most likely the corticomedullary phase because it's still uh the medulla is not enhancing more than the cortex. Mm Corticomedullary, correct, correct for ECA uh This is the cortico medullary phase which is uh arterial phase. Yes, it's arterial phase, corticomedullary. It's the same whatever you say uh is correct. But you need to say it whenever you question about this. Uh for example, about this image, uh what we see, what we see is a nonenhancing which shaped area in the kidneys. OK. So this is ah in a case of ah the clinical scenario, uh this is an emboli of the renal infarct caused by atrial fibrillation. OK. So it's a vascular compromise of the left kidney, of the right kidney uh leading to non enhancing area. So, so this is renal infarct. So this is not an injury, this is not an a set of a trauma. Ok. What else do we see as a renal segmental infarction? Ah This case, we have something called the cortical rim sign. We see that this area is non enhancing but a small area small, let's say subcapsular cortex or the edge of the cortex is enhancing. Can you see it if anyone don't see it? They can tell me. But it's this line, this line is enhancing in comparison to the other one which we see there is no enhancing here at all. This is called the cortical rim sign. When cortical rin sign is present, this exclude lobar nephronia or acute pyelonephritis because acute pyelonephritis will also uh have a nonenhancing area. But uh pyelonephritis is a local inflammatory process. So it will involve all the tissue in a sitting of uh renal infarctions. It's most likely due to vascular compromise. And in vascular compromise, the cortex, the blood supply of the cortex is supplied by the uh what we call as the capsular uh renal capsular artery, which is a branch of the renal artery, but it's an early branch. So it's not, it's proximal. Uh So this artery, if the vascular compromise is not involving the proximal part of the renal artery, this will be preserved. Ok. So in this case, it's not preserved. It's still an impact. This is not a pyelonephritis. OK. And in this case, it's preserved. So we can know that the ah vascular compromise is distal to the branch. Ah There is a question, please. Can you compare uh contrast renal infarct with renal segmental infarction? Uh It's the same actually, this is the same uh renal infarct or segmental infarction the same but segmental it involves a segment only. Uh this one is also segmental. When we say renal infarct, sometimes it's the whole kidney. So this is actually a a renal segmental infarction. But what we, what we must know the differentiate is the lobar nephronia or the acute pyelonephritis. And as we said, as uh we have the cortical lymph sign, we can differentiate. So in lobar nephronia, there is absence also to make a diagnosis of lobar nephronia or pyelonephritis. Uh that's why in radiology also the uh clinical scenario and the clinical information is very important to us to be provided to us because sometimes we can't make a diagnosis without some clinical information. For example, in this patient, uh how am I supposed to know that this is adrenal infarct or acute pyelonephritis? We can't make that differentiation. The only thing that will make this differentiation for me to know that this patient has fever. Uh for example, fever has a positive urinalysis for uh for infection, whether it is a culture or high whites or whatever So these things will uh if, if given to us, we will make a diagnosis of uh lobar nephronia or acute Byars. Otherwise, we might try that as an infarct. Uh So a lumbar nephronia also, it's a reduced or non enhancing which shaped area. And it is uh it has an absence of cortical re sign all the time. But for renal segmental infarctions, the cortical sign may be present may be absent depending on the location of the vascular compromise, absence of cortico sign does not exclude infarction. The presence of corticaine exclude uh e exclude lobar nephronia. Ok. Let's go for obstructive uropathy. This is the most case that I faced in emergency in the er uh too many people has obstructive uropathy. Nowadays, no one is drinking water, uh obstructive uropathy caused by any urine collecting system, obstructing pathology. Most commonly unobstructed stone, three common locations for ureteric obstruction, uh not exclusive. So you can see the obstruction at any site. But these sites, these three sites are the most common. Why? Because uh it has a a narrowing of the urethra. So the ureter at these locations will somehow be ah uh like less, be narrowed, more than the other parts cause it will be squished by uh uh adjacent structures. For example, the iliac arteries here or it's normally a junction. So it's narrower than the other locations. So we have three locations, Vasa ric junction. This is the most common pelvi junction in the top. This is in the down crossing the iliac arteries by furcation. This is almost at the 2nd 3rd of the ureter. For the radiological features, we can see that uh there will be a proximal proximal to what proximal to the obstructing pathology. For example, if it's a stone, there is a proximal hydroureter hydronephrosis, there will be periureteric or uh slash perinephric stranding. There might be kidney swelling. Uh the obstructing cause may not be visualized sometimes. Why would the obstructing cause may not be visualized. Sometimes not because it's not present. It's sometimes not visualized because the CT didn't visualize it. For example, if we have uh a mass, uh sometimes uh urothelial masses uh may not be picked up by CT. Ah So we need MRI for that. Sometimes the stone itself will be passed because the passing of the stone sometimes is the most uh painful uh for the patient. So sometimes the patient will present to the er room uh when he passed, when he already or they already passed the stone. So when we do a CT scan for them, we can see these signs but there will be no stone but we know that sometimes it's a passed stone. OK. This case actually uh uh came to me in the hospital. It's a quite interesting case of obstructive uropathy but not for uh not for a stone. Uh Let's analyze the first picture. OK. Let's see. This is an a Coronal image of the abdomen. This is most likely the arterial phase. We can see the arteries are white. OK? And this is the or but it's not not very white. Why it's not very white? Anyone can answer why the whole image is a bit darker. Come on, we're almost finished. We need people to wake up. OK. I'm just looking at your chart but there's nothing there, right? No someone has said um late arterial late phase. OK. It's it's actually arterial phase. Yeah. But uh why the image itself contrast is not too much white abu acid presence of blood. Yeah. OK. It's blood and it's contrast. But why the contrast is uh not very bright on this image? Um I mean for example, let's say another example OK. You see here the or it's very bright. Um why the art here is not very bright. Exactly colon is it's a narrow window. Yes, it's a narrow window. So we can visualize the contrast uh much better when we suppress it's a narrow window. So soft tissue all will be black. So we can focus on the contrast within the artery itself. OK. What do we see in this image? This is the orta we can see uh this is uh I think uh he was an elderly patient actually, it's not too much. He he he was middle aged, he was 57 almost, but he was a heavy smoker. We can see too much calcifications within the arterial wall as he changes, you can see these white dots. This is not contrast, these white dots are a plas OK. Uh Also this patient went uh uh went into uh Ortho feral bypass surgery. Uh a graft Orem oral by, by surgery. So and present after I think, I don't know but present somewhile after the surgery with abdominal pain, especially uh right sided abdominal pain. As we can see, this is the graft. This is the graft. OK. This is the a and as we can see, the graft has a black area. Here is a black area. Let me grab the uh highlighter. OK. This is a black. Yeah. Also the contrast is not visualized distally. OK. So the bypass surgery itself, uh the graft itself is not patent but the patient has uh has some collaterals. So we saw the contrast uh distally in the iliac vessels. Uh I mean in the femoral vessels, the femoral vessels were opacified. Ah So we know now that the patient uh yeah, has uh you mean the graft failed? But there is no vascular compromise because vessels can see opacified distally in the in both femoral arteries. OK. Let me raise this. OK. Let's go to the next image of the same patient. What do you think we see now? And what phase is this? So I can't see any chat box, but you can see some contrast in the collecting dots of the left kidney and in the bladder. So it might be like the delayed phase. Yes, this is the delayed phase. Exactly. And we can see the contrast in the bladder. Uh let me grab the pointer. Yes, this is uh contrast in the bladder. So it's in the extra phase, the late phase. We can see that there is severe hydronephrosis in here compared to the other side, it's normal and this is less enhancement of the cortex of the kidney. And there is no uh excretion of urine in this kidney. Ah ok. But why this patient has no other medical history other than the or femoral bypass. So when we look further into it, I have captured these two images, ah we can see again that this is the excretory phase we can see here. This shiny is the ureter itself on the other side, it's this one, it's dilated, right. So the ureter is dilated here in comparison to the normal side, the normal left side distally uh in the pelvis. This is the unit. This is the ureter. Let me grab it. This is the ureter and this is the other ureter. There is no excretion, but we can see that the other ureter is not much dilated distally. So actually, when we try to see the point of obstruction, we can see that it is close to the auto femoral graft. So in this case was an uh was an obstructive uropathy due to tethering to the auto femoral graft, the graft itself is foreign to the body. So, fibers and connective tissue can form around the graft itself. Uh So the ureter is close to the iliac arteries or it crosses the bifurcation of the iliac arteries. So, the the fibrosis and uh the fibrotic process involving the aortic uh orf graft affected the ureter and it tethered to it. So it caused the proximal uh obstructive uropathy and obstruction of the ear at that point. And it caused all this hydronephrosis and pain to the patient. Ok. Let's talk quickly about intestinal obstruction. It can be either functional or mechanical functional is always simple obstruction in which we don't find any uh any transition point, transition point. Uh It's the point where the bowels is dilated proximally but collapsed distally. So, unfunctional, there is no transitional point and we can see that there is diffuse bowel dilatation. So it's not just focal to one area or one bowel loop. If it's diffused, this uh goes with functional uh intestinal obstruction. And this dilatation is usually milder than that of mechanical obstruction. Most common cause is a dynamic areas. Post surgery. As we all know the other type, we have mechanical obstruction in which there is something mechanically obstructing the intestines. Uh And this type, we should have transition or what we call as lead points. And sometimes we can have either one or two and this make a huge difference, one point, mechanical obstruction or what we call a simple or nonclosed lobe obstruction can be managed nonsurgically. Why is that? First of all, because bowel blood supply will be preserved in most cases. Uh, most of the time the bowel can't go into strangulation if it's a one point obstruction. The other cause is the, the proximal dilatation. The proximal dilatation to the obstruction can be decompressed by the stomach and G tube. Ok. The third cause is that, ah, the cause may resolve spontaneously. Uh For example, uh examples, for one point, mechanical obstruction is a gallstone ileus. Ok. So, a gallstone, sometimes after ERC B or something can go into the intestines, uh, sometimes even through a fistulated, uh a fistula, uh ga a fistula between the gallbladder and the intestines. For whatever reason, the gallstone will go down into the abdomen into the bowels and it will make an obstruction. This obstruction will have, uh, one lead point but it will not compromise the vasculature of the bowel. The bowel can be decompressed and it may resolve spontaneously. The gallstone may pass at the end of the day. Uh OK. The other type two point mechanical obstruction, also known as a closed globe obstruction. Some of the causes are adhesions, hernias or volvulus. And we can have dilated B ah, ok. Uh In two points, mechanical obstruction, there can be strangulation and, uh, ischemia of the bowel in general, uh, in mechanical obstruction, we will have dilated bowels, proximally collapsed, bowels distally and we will have something called small bowel feces, as we explained in the normal anatomy, small bowel, uh, don't usually have feces in it. It will be fluid filled, uh, or collapsed in most times. But if there is feces sign, then it's a sign that there is an obstruction, uh, near the fe sign close to the FES sign location. Ok. Let's talk about close globe obstruction. This is what we call as a closed group. You can see here is a lead point. This is a transition point. This is two transition point or two lead points. Let's say this is proximal and this is distal proximally. The bowel can be dilated, distally, it will be collapsed and the closed lobe itself uh can go into strangulation. So this is an emergency. Uh The patient needs to go to the theater room immediately. In comparison, let's imagine that it's only one point, one point. It's impossible for the proximal part to uh uh or not impossible. It's hard uh for the proximal part to go into a strangulation. Why does it go into strangulation in closed loop? Because this area is it closed. Now, this wall will be thickening, thickening and will be edim until the or the vessels are uh pressured and closed. And this will lead to bowel ischemia. And because this area will be severely dilated also because it's closed, nothing goes proximal, nothing goes distal in this closed loop. It's a closed system So, uh, it will keep, ah, dilating until it goes into ischemia. Ok. Most common causes are adhesions. Then hernia adhesions can cause a closed loop or simple. It's not necessarily uh to a closed loop obstruction, but hernias are always closed loop. Hernia obstruction is always closed loop. Ah, ok. We make a diagnosis, we make a, we made a diagnosis of closed loop obstruction, but that doesn't mean that the bowel itself is, uh is ischemic. So we need to assess the viability of the affected closed loop, which we will discuss ah later on. This is an example, we can see this patient has oral contrast. OK. We can see here is dilated, right? And here it's narrowed. Now this is a transition point and this is the proximal one. OK. Now the bowel goes into here, you see here it's dilated, then it goes into here. This is another transition point. Sometimes it's easier to see when you can scroll through the images because we don't see the continuous, the direct continuation of the image. But we can see that this is transition point. This is a dilated bowel. The oral contrast is not passing through the proximal lead point and we can see the distal lead point here, the other one. So this is a closed globe obstruction. And now we'll go for bowel me ischemia. Uh the mesenteric ischemia or bowel ischemia is decreased, uh decreased or absence of bowel perfusion trilogies include arterial occlusive, veno occlusive, mixed or non occlusive and arterial occlusive and mean it's straightforward uh artery is closed. Why is it closed? It's either thrombotic or emboli. Mostly it's an, it's an emboli. Ok. And venoocclusive the vein is closed. Uh Mostly the uh serum is in vein. It's a thrombosis of the serum is in vein is the most common cause mixed when it is a closed, low obstruction. The etiology can be related to partial arterial, partial venous occlusive. It's a combination in closed global obstruction and we have other non occlusive uh ts, for example, if there is a systematic cause for hypoperfusion, for example, am I uh in patients with uh a huge ah myocardial infarctions, they can go into bowel ischemia. Ok. For radiographic signs to diagnose ischemia, we have edematous bowel wall or what we call as a water hall sign. It's the most sensitive sign, but it's not uh specific for uh that condition, uh non enhancing bowel wall. This is the most specific sign and that's why IV contrast is very important in uh diagnosing bowel ischemia because it will give us the most specific sign, the enhancing of the bowel wall, dense bowel wall. Uh Of course, when you say dense bowel wall, it's on uh nonenhanced act scan or non contrast, not on enhancement. And this represent intramural hematoma because hematoma is dense as we talked about. And why we see this on non contrast because if we see this on uh contrast CT, we can differentiate if it's dense from enhancing or from the hematoma itself. So how we differentiate hematoma from a normal enhancing bowel wall? We look at the non contrast uh study if the non contrast study is dense, also the density didn't change between the uh non contrast and the contrast phase. Uh Then we say it's an intramural hematoma. OK. Also, we have what we call as misti entry uh in which the fluid there is fluid infiltration around the mesentery. This is caused by congestion, a proximal congestion to the vessels. And also we have a pneumatosis intestinalis. And this is a, a very concerning uh sign and it is a gas within the wall of the bowel itself. And this is due to the increased mucosal permeability in gas for uh which result in gas forming bacterial translocation into the wall and subsequent gas formation within the b. Uh That means it's an infection within the uh wall of the intestine. Why is it important because the wall will become fragile when it is infected? This will lead to higher incidence of perforation. This is considered a late event in the course of bowel ischemia. And it's concerning, concerning for impending rupture, signs of bowel perforation, neili or portal venous gas also also normally present postoperatively. So, distinguishing the causing is important as not to over call it as perforated viscous, a postoperative. Uh we can have some physiological or uh postoperative changes. We can find the pneumoperitoneum within the abdomen, within the peritoneum. So this is for uh normal after uh operations. So we need to distinguish this from a perforated ah owl or viscous, especially that also post operative is a risk factor for adhesions and other causes to cause uh intestinal obstruction. So it's a complicated uh topic to over call it as a perforated viscous. Sometimes we need to identify the point of perforation itself to call it as a perforated viscous. So not any pneumo Brioni is a, is always called as a perforated bowel. OK. Let's look at some of the signs start with the normal B wall enhancement. This is the normal, it's dilated a little bit, but this is normal enhancement. OK. These predictions are called valvula contis. These are, ah, these will make differentiation between small bowel and large bowels, OK, target or double hall or water hollow sign appearance. This is the schematic for it. We can see that the mucosa is enhancing and the cirrhosa is enhancing. And in between, we have the submucosal edema which is nonenhancing. So we can see here it's uh water Haine, OK. This is enhancing and this is enhancing bowel wall thickening and target sign also. OK. Also, as you can see, this is fluid density. If we measure this, we will see that it is fluid density. That's why it's called uh water hall sign. There's another sign similar sign, it's called fat. Hello sign in which this layer will be a fat density. When we measure it, it will be uh less than zero, it will be minus 40 or something. A fat Haine is a specific for uh uh Crohn's disease. But also obese patients can present with fat Haine, lack of contrast enhancement in the small bowel loops. This is very concerning for ischemia. As we can see this bowel is enhancing normally, this bowel on the other hand is non enhancing. OK. Uh This cut is a venous face. The bowels are best CT and venous face. OK. Not in arterial face. If this was arterial phase, then uh sometimes this appearance is normal because uh the still the blood or the contrast didn't reach all the bowel. So we need to assist the bowels in the venous face which is here is the venous face because both the AORTA and the IVC uh are bright, OK. This patient and these are the subsequent CT scans for the same patient. This patient presented with uh SMV. As we can see, this is the, this is the IVC. Remember this is circular slightly to the left and this is a little bit squished. And what do you think this vessel anterior to the aorta? This is the SMA which is, which looks good on this image. OK. So the SMA is patent but what is uh to the right of the SMA, to the right of the S MA is the MV. And where is the contrast in the SMV? There is no contrast in the SMV. This is a filling defect in the SMV. So this is a uh asem thrombosis. So this patient presented with SMV, thrombosis uh and thickening in the bowel wall. OK. After a few days, still, there is thickening. And after nine days or on subsequent images, the patient developed a pneumatosis intestinalis. And as we can see here, we used a wide window. Why did you, we use a wide window in this image because we need to see the wall within uh the the gas or the air within the wall. OK. OK. Any questions? So this uh talk more than I have anticipated? Yeah. Um I'm just checking the chat box. Um No questions for now but yeah, I think it was, it's a very um as you said, broad topic that would still need like for the um not even but actually it's very uh very hard topic for uh medical students. And I think if it was brain, I think it would be much easier for uh medical students especially to understand. Mm mm especially for CT brain doesn't have much uh yeah, much value. So it's limited value, very limited value for in in the brain CT scans. I think you really gave like a good um foundation in terms of the explanation of the um science behind the CT and then um going to the anatomy and, and all of that. I think that was, that was a very good um background honestly. Um the chart book just um everyone um saying thank you for the great session. You're all welcome. Anyone can message me later on even on my email if they have any question, um would appreciate um you guys fill in um a feedback. I've put it on the chat box, but you'd also get an email, everyone that attended. We get an email to fill in the feedback and that's how we can give certificates and we can also provide feedback to our speaker. Um So please, please, please, um, let's try and fill the feedback form. Um Is there any video to watch? So if, if we feel the feedback, um the platform will send you an email when I'll just uh when the recording is available. Um, you get an access to the recording so you can watch it later. Well, you need to feel um the feedback and get the certificate and that's how you get access to the video. Thank you so much. Um, Doctor Mohamed. Thank you for listening. Yeah. Ah I appreciate you having me. Thank you for your efforts. Thank you. All right. Um Thank you everyone and um we'll see you for um our next um session. Ok. Mhm.