This on-demand teaching session is relevant to medical professionals and explores abdominal CT scans and how to interpret the images. We will discuss the three planes of imaging, density and contrast, as well as what abdominal pathologies to look for and the importance of the timing for contrast agents. We will also cover kidney problems such as renal pain and hydronephrosis caused by stones, and suggestions on how to improve interpretation by experienced radiologists. Don't miss out on this informative session highlighting the fundamentals of abdominal CT scans to enhance your medical knowledge.
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This is the 2023 Radiology Teaching series hosted and organised by Anna. This series will include some high yield exam contents with helpful SBAs and interactive segments to keep everyone engaged. Please find the recordings and slides of these sessions here and we hope you will find them useful.

Please note that these slides and recordings are properties and should be credited to their respective authors. There are no affiliations between these speakers and the St George's University of London teaching curriculum.

Please find the session titles here:

  • Interpretation of Abdominal X-Ray - Dr Mohamed Adam Ali
  • Interpretation of Chest X-Ray - Dr Manjiri Joshi
  • Important signs in surgical radiology - Dr Naren Govindarajah
  • Interpretation of MSK X-Ray - Dr Gabie Reiff
  • Important signs in abdominal CT - Dr Pardis Zalmay
  • Important signs in CT head - Dr Olutobi Meadows

Learning objectives

Learning Objectives: 1. Identify key elements of abdominal CT, including the apical and coronal planes, anatomy and types of contrast. 2. Demonstrate an understanding of terminology used to describe the density of tissue on an abdominal CT. 3. Recognize important signs and structures on abdominal CT, including the aorta, vertebral bodies, liver, spleen and renal medulla. 4. Explain common sources of abdominal pain and relevant pathology that can be seen on CT. 5. Describe etiology and diagnosis of pathologies including aortic aneurysms and kidney stones, as seen via CT.
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Computer generated transcript

The following transcript was generated automatically from the content and has not been checked or corrected manually.

Screen ana just to double check before I go into it. Yes, I can see you. Sweet. Perfect, great. So, um I'm going to talk about a few important signs, an abdominal ct, just looking at which years of medical school you're in. Um uh this, this presentation won't last an hour long. It'll be probably half that time just or just a little bit more. Um I don't think that you should worry too much about abdominal CT. It's quite a complex and challenging part of the body to CT and even amongst radiologists. Um, a lot of on court radiologists struggle when it comes to interpreting an abdominal CT. So I'm just gonna touch on a few important findings, um Just what they look like, but don't, don't worry too much if you have no idea what I'm talking about. It's, it's nothing that you really need to know at this stage in medical school. Um If you do have any questions, obviously just put it in the chat and I'll periodically check or uh yeah, and I just um if I forget to check, just flag to me. So just to start with a quick background on CT. So the world's first CT scan was in a roundabout way done at Saint George's Hospital. It was actually done at the Atkinson Morley Hospital, which in 1971 was actually in Wimbledon Central. Um, but since has been relocated to ST George's and is considered a part of uh Saint George's. So people like to brag the first CT scan was at Saint George's Hospital, but there's a little bit more to it than that. Um And that was done by Sir Godfrey Hounsfield and doctor Jamie Ambrose. Now, um depending on how much radiology you've done so far, Hounsfield might be a familiar name. Um Hounsfield essentially is a, is a word or a term that we use daily in our practice to describe the density of a particular tissue on CT. So we, we say, uh you know, it's 100 Hounsfield units or 1000 house hands field units and I'll get onto that a bit more a bit later. So uh just a general idea of how the technology works you have on one side. So it is X ray technology exactly the same as a chest, X ray or abdominal X ray. And in that, I mean that on the one side of the patient, you've got an X ray tube that shoots out X rays. And on the other side of the patient, you have a detector that essentially records how much of that X ray gets through the patient. Uh the only difference is in a CT scan. Er, well, uh simplifying it, the only difference isn't that in a CT scan, er, you have that X ray tube and detector sort of unit spinning very high speeds around the patient. So we're getting a three D reconstruction of what's inside them. Um And obviously, X rays, depending on the density of the patient travel and the density of the tissues, um different amounts of X ray, X rays are absorbed and blocked from reaching the detector. And that gives us information that we can then feed into mathematical formula. And they give us uh an idea of uh you know what's going on. So a radiologist toolbox consists of three planes, we have the axial plane, uh the corona plane and the sagittal. So um I'm not, I hope hopefully you can see my mouse here, but we have the actual plane on the left side of the screen here. Now, the top of the screen is uh anterior. So it's the front of the patient and the bottom of the screen is the back of the patient. Essentially. Um Now, in every actual blue view of three D cross sectional imaging, we were looking at the patient as if their head is on the other side of the image and their feet are towards us. So this side were motioning with my mouse cursor is the left side and this side is the right side of the patient Um Now, the other one of the view we have is the corona, which you will find more familiar and recognizable because it's more oftenly used than anatomy textbooks. Um This is essentially just cutting a slice through the patient from head to toe. So on a corona, all slice we have where I have my mouse cursor here is the left of the patient. So we're, we're facing the patient essentially as if they're looking at us. And on this side is the right side of the patient. So we've got liver here, spleen here and two kidneys here. Now, the sagittal is the final dimension in our three D planes. And that is essentially once again, it's a slice from head to toe of the patient. But um we're looking at the patient side on. So on the right side here, we have the patient's back and this is their spine. And on the left side here, we have their front. So we've got their abdomen and their sternum here. So just to point out a few different things while we've got these images here, generally in ct imaging black is the least dense uh thing that the X ray is traveling through. So black means that um most of the X ray has reached the detector and it's not being absorbed by this tissue. So what we're seeing on this actual image here is the left lung and then the right lung here, this little island of gray is the top of the liver because you, you have to imagine that we're, we're looking at very thin slices. And if we look at the anatomy of the liver, we catch just the tip of it. And on either side, we get lung. Um, in the middle here, we've got the heart and this large round structure just to the left of the midline is the thoracic aorta. So that's the major vessel in your body. Um So we've already mentioned on the Corona. Well, it's, it's, I generally find it much easier to interpret. So you've got your liver on the right, just tucked under the right hemidiaphragm on the left here, you've got your spleen, which tends to look quite similar to the liver. Um, depending on the phase of contrast, which again, I'll come onto in a second just here. You've got a cross section of the stomach with its squiggly stomach rug. I um you've got kidney, kidney, you've got spine coming through in the middle. You've got ribs on either side and we've got bony pelvis here which would just about catching. Um And then you can't really make it out here, but coming I/O of view, we've got probably bits of sigmoid colon here. Uh And then looking at the sagittal, sagittal is a very good view for interpreting for looking at and interpreting things that are going on in the spine. So I've said that white black is the least dense. So that tends to be aired or aerated lung. Um On the opposite hand side of that white tends to be very dense. So here we've got bone and the bones here are the vertebral bodies in the spine. We've got the spinous processes here. Um And everything else tends to be on a spectrum in terms of density between the black which is a rare and the white, which is uh either bone or something hard like a metallic prosthesis. Uh So everything else tends to be a gray scale sort of image. Um just to point out important structures on the sagittal. We've got the abdominal aorta here which is just coming down nicely uh anterior to the spinal cord. Um So I mentioned contrast. So just before I move on, on um contrast is something else that we use to help us interpret what's going on inside a patient. Uh I'm sure my colleague probably talked about it in his talk involving uh CT scans. But contrast is essentially a, usually it's a liquid agent and it's a liquid agent that shows up is very bright on CT scan. So um it helps us to target different types of tissue. So we inject contrast into someone's veins and then depending on how much after we've injected the contrast, we imaged them, we'll get the contrast in different parts of the body. So let's say we were looking for a abdominal aortic aneurysm or an aortic dissection, we could um essentially weight, uh you know, a very short amount of time. Um So that the contrast goes through the vein we've injected into the patient's right atrium, right ventricle out into the lungs and then back into the left side of your heart and then pumped out into your aorta. And then at that point, we would image the patient and then we'd see this aorta look nice and bright white, uh same color as these vertebral bodies, if not brighter. So that's something else to take into account. Now, um I was going to make this a bit more interactive. It's a bit easier to do in person, but virtually, um I just wanted you all to take a moment to think about what abdominal pathologies we might want to look for on a CT scan. So let's say a patient has come into A and E and they've got abdominal pain. Can you all just start typing into the chat? Any ideas that you have as to uh what we might want to look for on a CT scan? So, any differential diagnosis uh for abdominal pain or abdominal pathology, I'll just give you a minute or two to do that. So just think about the directions. So it's all right. We have obstructions. Yeah, exactly. So, obstruction. So we've got a small or large bowel obstruction. So definitely that's, that's something that we like to uh image anything else uh bleed. Yeah, bleed is another thing. Uh so a bleed can be um into the gastrointestinal tract or it can be outside of the gastrointestinal tract. So, yeah, that's another thing. Keep going. And same said kidney problems, kidney problems. Yeah, exactly. Can you narrow that down at all into any more specific kidney problems? Things that might cause pain or things that might cause raised inflammatory markers as well as pain. I think she mentioned hydro phoresis yet. So, hydronephrosis iss is essentially what that means is. Um So if I show you so if you guys can hopefully see my mouse pointer here, I'm pointing at the left kidney. Now, the left kidney has an outline and it has a cortex which is this brighter stuff on the outside. And then here it has what we call renal pyramids um or the renal medulla, which is where essentially you're collecting, tubules start um draining your blood and producing urine. Now, eventually these get drained into this central area in the hilum of the kidney, this slightly darker area here that I'm outlining. Now, this is called the renal pelvis and you can't see it on this slice. But if I were to go a few slices back, you would start to see a tube coming down all the way into the pelvis and plugging into the back of the bladder. Now, hydronephrosis means dilation of this renal pelvis. And can anyone think of anything that might cause dilation of the renal pelvis that we might want to look for in a CT scan. And he says stones. Yeah, exactly. So the gold standard scan for looking for a renal or you're a Terek stone or calculus is something called a noncontrast c uh C T K U B. Uh And that essentially just stands for ct kidneys, ureters and bladder. Now, can anyone think why we might do, why it might be more useful to do a non contrast scan than a contrast scan? And don't worry too much if you don't get, it's quite a hard question. Would you expect a stone to be bright or dark on CT scan? Uh Right. Yeah, exactly. So you expect a stone to be bright. Um If we give contrast, we are injecting something bright into the patient. So if we're looking for something bright, when the background tissues are all very bright, it can be quite difficult. Whereas if you've got a noncontrast CT scan, then you expect the background tissues to be darker. And so in that case, a bright little stone will stand out more. So that's, that's generally why a noncontrast CT KUV can be uh slightly more, it can be slightly easier to find a stone on a non con. So yeah, we've discussed bleed um kidney problems. So kidney stones, can anyone think of anything else? So, think of the organs we've got in the um in the abdomen and just go through them and think of any pathologies in those organs that, that we might want to know about. So you can't see on this slice of picture here, but just underneath the liver, you have a gall bladder tucked in. So it'll be just anterior to the, to this kidney. Uh Is there anything that can go wrong with the gallbladder that can cause pain, um, stones, but Tommy mentioned and max as well. Oh, sorry, I didn't catch that. Did you say to me mentioned? Mass mentioned? Yes. Yeah. Yeah, great. So, yeah, so two things there. So gallstones. Yeah. So, um, actually a lot of gallstones are not radiopaque. So they're difficult to see on a CT scan and often we don't see them unless they're very chronic and they've calcified, but there are securely of gallstones that we can see on a CT scan. So if someone's come in acutely with pain and fever, uh, and they're tender in the right upper quadrant, that can be a, that can be a presentation of colecystitis. And there are findings that we can see on colecystitis that will come on to in a second. Um So yeah, that's something and then, uh, masses. Yep. So traditionally, um, uh, the two week wait rules for unexplained weight loss, uh, would be something like a, uh, like a colonoscopy to look for a gi malignancy. Um And for unexplained anemia would be an O G D and a colonoscopy. What we're finding more and more is that people are relying more on CT to investigate for malignancy. So we're finding a lot of the more frail patient's who clinicians don't think would be able to tolerate an O G D or a colonoscopy. Uh They'll just have CT scans of their chest abdomen, pelvis. And yeah, so that would give us a better look at their organs and the lymph nodes in their body. Um just to see if there are any masses or any, any malignant looking masses. So yeah, that's a good thought. So, moving on to the next slide there, there are loads of things that we can look for in a CT scan. So you mentioned small and large bowel obstruction, perforation is another very important thing. Um So, you know, it doesn't, doesn't, you don't exactly need a CT scan to look for perforation. You can find signs of perforation on a, for example, in a wreck chest X ray. Um I'm sure one of my colleagues might have discussed in a previous talk, but once you've seen the signs of a perforation, it's important to get a CT scan to figure out what else is going on, what, what the cause of the perforation might be and where the perforation exactly might be. Um So we discussed hemorrhage that was a good thought. Other things to consider a bowel ischemia. Um sort of on the commoner side of the spectrum, appendicitis colitis diverticulitis. These are things that often get scanned in E D. These are patients that come in with acute onset abdominal pain, uh and raised inflammatory markers. Uh you mentioned a mass which is a really good thought. Um And then we said kidneys, so stones. So pylon arthritis really is a clinical diagnosis. We shouldn't really be scanning people who we suspect have pylon arthritis unless we're suspecting that they have an abscess as a result of it. Um But yeah, you can see a good going pylon arthritis. You can see abscess is um what else? So, yeah, so pancreatitis, that's an important one. Um problems in the liver such as, you know, a mass. We discussed uh an abscess in the liver can be spotted. Um But we, we, we've mentioned the main ones. So just going on to some of the important signs to look out for now. So one of the first things we look for when we open up a CT scan is free air. Um So on the Corona scan, on the right, we've got the chest and the abdomen included, but on the actual, on the left, we've got the upper abdomen included. And all of this black here is essentially air that is contained within the peritoneal cavity, but it's not within bow. You can tell it's not within bow just because as in, at your, at your stage, I don't expect you to be able to tell this, but there's just no bowel ward around it. It's, it's very separate from bowel wall. It's very irregular. There aren't any house Traore. Um, you know, valvular con Aventis, uh, that, that might suggest that this is all contained within bow, this is an area of bow here and you can see a thin wall around it. You can see some folds. Um, and the other thing with it is that it tends to float to the top. So if the patient's lying on their back for long enough, then the air generally will go upwards um to wherever it's contained. So free air is probably the most important thing we look for. First, free fluid is something we look for as well. So often on abdominal CT stands, you might find the first line that says something like no free air or fluid in the uh in the abdomen. And those are generally bad signs. Free air is a really bad one. Free fluid can be physiological as well. So I think the normal person can have something like 20 or 30 mils of free fluid uh in their abdomen and generally, you know, opposite to air. It sits gravity dependent. So if the person is lying on their back, it just pulls lower down. So this all of this here are bowel loops and this is probably large bowel here at the top of this patient's abdomen. The reason it's so bright is because this patient has ingested oral contrast. And this is something that we see quite often uh when I was searching a lot of these images on Radio Pedia and Google, most of the images contained oral contrast. And I wonder if it is just something used much more often across the pond in America because we don't use it as often at ST George's. Um So just try, try not, try not to let it distract you because it can take your eye away. But all of this stuff here, this sort of middle gray color, this is all free fluid. So just it's sort, it's about just getting an eye and for what free fluid looks like, it sort of pulls around here. You've got peritoneal lining here that's uh not letting it sink any lower down. All of this. This is the color of fat. So it's a nice dark, it's not black, but it's a dark gray and this is all what we call clean fat. So it's quite homogenous and homogeneous means it looks the same. So it's not bright here, it's not patchy bright and then patchy dark, then patchy bright, it's all roughly the same shade of gray. And that's an important word we use quite often homogeneous. That's important because the next important finding is something called fat stranding. So essentially, uh so attenuation is something that, you know, it is a word that's thrown around a lot in CT scanning and don't worry too much about what it means. Increased, attenuation just means brighter, decrease the attenuation means darker. So you get this like hazy stranding pattern of the fat. Um So just for comparison, you've got the abdominal fat here, which is all nice and homogeneous, nice and same shade dark. And then here around this section of bowel, you've got this same, you've got fat here, but then as you come closer to the section of bow, it just becomes hazier and actually you've got little tiny bits of free fluid here. So where it's all the same kind of color of lighter gray, it's just a tiny bit of free fluid there and a little pocket there. And this is all called fat stranding. Now, this is important because it often suggests that there's inflammation happening at the, you know, around the area where you're looking. Um and it, it, it essentially is local adama often but not always as a result of information. Um So moving on using these signs that we've discussed, we can have a look at diagnosing some important conditions. So, um just looking at time, it looks like we probably will use the whole hour. Does anyone have any questions up until now? Any slides you want me to look at again before you move on? Uh We have one question from James. Um He said for gallbladder, how, how often do you use CT versus M R C P? An ultrasound? Yeah. So we M R C P is difficult to get an, an acute setting. So, when a patient presents the hospital with pain, the M R C P if they end up having one tends to happen days later. Um The two options that we have. Well, three options that we have imaging wise when a patient presents our X ray CT scan and depending on availability, ultrasound scan. Now, colecystitis can be diagnosed on an ultrasound scan quite uh reliably. So, a lot of the time if the surgeons are happy that a patient probably has bond or colecystitis, they won't ct scan the patient and they will just request an ultrasound scan. Now, if the patient's inflammatory markers are really high and they're really unwell, then so and or they're really unwell, then they might opt for a CT scan because whilst they might still think that colecystitis is the most likely thing because they're so unwell, they might not be able to rule out a perforation or, you know, a local abscess or um uh necrosis of the gallbladder. These things are easier to see on a CT scan. Um So in those cases where someone's really unwell surgeons might opt for a CT scan. But if the patient's relatively well, all of the pain is localized to the right upper quadrant, um they might just, you know, often we just start with an ultrasound scan and just see if we can diagnose it based on that. Okay. Uh Any other questions before I move them looks like the job good. Okay. So moving on. Um So on the left, I've got a Corona all slice here and on the right. I've got an actual slice here and this is an abdomen with a pathology. Now, would anyone like to have a stab, what might be going on here? Okay. So I'm just gonna start outlining a few things for you guys. So we've got the liver here at the top of the image. Um This is a relatively normal liver. It might be a little bit nodular around the edges, but I can't really comment on one slice. Um What we're looking at in the middle of the abdomen here are these, these are loops of small bowel, okay. All of these and on the actual slices, it's these structures here, there's a little bit of fief free fluid there, a little bit there. Um The bladder's squished down. So this is the, this is what small bowel obstruction looks like essentially. So we've got, if you measured these, they would be more than three centimeters. So three centimeters is our cut off for dilated loops of small bowel. Six centimeters is our cut off for dilated loops of large bowel. And then the cecum essentially is just a very flabby sort of structure that, that has a upper limit of nine centimeters. But these all look like they would be sort of around 4 to 5 centimeters. These are all quite dilated. Um And in a scan like this, we'd look for a cause of the small bowel obstruction. Um, so we look for things like hernias or, uh, what we call a transition point, which is where suddenly the dilation stops and it, you can't see it on these scans but abruptly tapers off and that can be a sign of additional small bowel obstruction. So, adhesions from previous surgery. Um, what else? Uh, those two are generally the most important causes of small bowel obstruction. So just essentially imprint that in your mind. That's what it looks like. This is, uh, we're just catching a bit of an N G tube in the stomach here. So when we see this kind of scan, this is when we call the surgical t you would say this patient a small bowel obstruction if you haven't already put in an N G tube and yeah, use an N G tube, keep them near by mouth, um, give them IV fluids and then it's up to them to decide whether to manage conservatively or, uh, surgically depending on the cause. Okay. So next important diagnosis to make on a CT scan, can anyone venture a guess as to what's going on here? So just there's a clue. We said that the black would be air. Um, can anyone think what important ct finding we've got here? Okay. All right. So this is, we have, yeah. Uh, we have perforation in the chance. Yeah, exactly. Perfect. Well done. Um, so this is a large volume of free air in the abdomen. So, uh we can see on this actual slice that there is a big layer of free air up here. Um The stuff here, the black here is contained within bowel wall. So this is all probably uh normal air inside the bow. But then all of this stuff isn't contained by any bowel wall. So this is free air and uh on the corona leaves, you can see it all up here. So this is probably a very enlarged stomach here. That's possibly the pylorus first part of duodenum. Um But yeah, these little islands are the air that's escaped bow. So this, this patient is perforated from somewhere good. So that's important to notice. All right. Now, we're getting into the territories of some of the more difficult diagnoses. Uh So don't worry if you have no idea what's going on. But so we're looking at the abdomen here, we've got to corona slices and again, it's very difficult to judge a CT scan based on still images. When we're actually interpreting, these were scrolling through them. So we can kind of in our heads map out what the patient's anatomy looks like. But so we've got, if I tell you this is the cecum, and if I just tell you this is a structure coming off of the cecum and the fat here next to the structure is a little bit more hazy than the normal subcutaneous fat that they've got, can anyone venture what this diagnosis might be? Could it be appendicitis? Yeah, exactly. Well done. So, um, this is a subsequent appendix. So, you've got the cecum here and then you've got the appendix coming down. Um, and what we can see is that there's stranding. So there's local little bits of a Dema around the appendix. There's a little pocket of free fluid here, which is probably from all of this inflammation that's just pulled in the gravity dependent area. Um This structure here is the appendix. This is me outlining it. Uh This is the wall which normally shouldn't be so thick looking. It's a, it's thick looking and be, it's edematous. Don't worry too much about what edematous means in terms of CT findings. It's, it's, it's no point confusing ourselves. But what we've got here is a brighter area, a brighter sort of circular area inside the appendix and this is probably an appendicolith. So, uh so it's sort of a calcified substance. I think it's calcified feces that gets into the appendix blocks it off and then often is the cause of appendicitis in a subset of people. So, if this was left untreated, this appendix would eventually necroes, it would perforate and there'd be just one big inflammatory mass here. But yeah, so this is what appendicitis looks like well done, right? This one is very tricky. Um ignore all of this bright white, it takes your eye, but this is just again, someone's given this person oral contrast for some reason. Um And it's, yeah, it's just, it's just the distractor, there's some of it in the stomach. Um Can anyone sort of tell me what region of the abdomen, the abnormality might be? So, we've got, let's say right, upper quadrant, left, upper quadrant, right, lower quadrant left, lower quadrant or central bearing in mind, ignore the bright, ignore the really bright stuff cause that's just contrast. Can anyone think where the abnormality might be? Uh we have right, lower close. So, um so I think a lot of this is just your i possibly being taken by the oral contrast. Um There's some feces in the cecum mixed in with the oral contrast uh and then going up into the ascending colon, but this is generally not too abnormal looking. Um Especially on this scan here. It looks here. You might argue that some of the walls look a bit thickened, but when you look at the next slice, um it's probably just, it's probably just the slice we were looking at, it looks, it looks quite normal. Um Where else? So we've got liver here, spleen. You can't see on this slice. We've got some mush here. Uh Look at, so look at the fats, the fats here look quite normal compared to the subcutaneous fat. Is there anywhere where the gray becomes weirdly bright or you know, like a light of fuzzy gray? Um That isn't an organ that you can see. Um James says has the liver got deposits in it and fasteners uh right. Upper quadrant, yeah, close. So it's, it's very difficult to say because these are still images, but these are just the, these are just the vessels in the liver. So this will be different parts of the various sort of branches of the portal vein. And just because we've sliced through this image where you know, catching different parts of it that look like deposits. But you're right, it is the the abnormality is close to the liver. Um So that that might be what's um taking your eye, but it's this whole central area here. There's nothing really that should look like this. Um So I wonder so, yeah. So if we look at the center of this abdomen, you can make our crisp lines of bow here. You can see a blood vessel coming here. Everything looks quite crisp and sharp. Um bit of probably pancreas here and you've got like bowel walls, you can't quite make out which part is stomach, which part is what about? But you can make out walls. Whereas on here, everything is very fuzzy, the gray is lighter, you can't make out the walls of anything. Um And it's a bit clearer on here. So this structure that is quite difficult to catch on one slice of a CT scan because it, it spans across the abdomen. It sort of goes from here to here. Uh and it's sort of dips anterior and then posterior. This is the pancreas and all of this is inflammatory fat stranding surrounding the pancreas. So, what diagnosis is this? So, we've got inflammatory changes around the pancreas. What, what is that if you change pancreas and inflammation to Latin, what do you get uh pancreatitis? Yeah, great. So this is what pancreatitis um in it's severe form looks like uh CT scan isn't the uh imaging modality of choice to diagnose pancreatitis. You should be able to diagnose it based on clinical presentation and um biochemical markers. So, an amylase or lipase blood test, but often if you can't get both of those. So say you've got a raised amylase or alli pays and, but the clinical presentation doesn't quite match or you've got a, you know, fit and clinical presentation but not a matching raised amylase or lie pays. Then sometimes surgeons can ask for a CT scan to take that second box. Um And if it is a rip roaring pancreatitis, this is what that would look like. Um What did I want to say? I can't remember. But yeah, this, this is again, we're using the finding of fat stranding too fat stranding in an area. Generally not always whips refers to inflammation of one of the structures in that area. So here we've got some fat stranding around an appendix and that's appendicitis. Here, we've got some fat stranding around. Uh again, it's very hard to tell on a CT, on a single ct slice that this is a pancreas. But if you see fat stranding centrally here, usually you should look at the pancreas because it, it probably is coming from that good. So, next, uh, diagnosis, uh, just remind myself what this is. This is very difficult. So I will just tell you. Um, so again, we've got Corona Seiss, we've got liver here, we've got stomach here and here and we've got the gallbladder here and this is uh or bile within the gallbladder. Um Just looking at the bowel. Now, we've got some large bowel coming up, probably going along there somewhere transverse colon coming down and then just as the descending colon becomes sigmoid colon here, you've got these little outpouchings and some of these are filled with air. So this one's got Aaron it, this one's got something bright and white in it. And if we look at the axial slice, this is the same section. So you've got the sigmoid colon coming across here. You've got outpouchings. Can anyone think what these outpouchings are called? Where of the diverticulum? Yeah, perfect. So, these are diverticular, these are relatively common finding in older patient's especially ones that have struggled with constipation for several years. Um These bright bits inside the pouches are called fecalith. So when, when feces get stuck somewhere and it just impact and impacts and impacts, it becomes quite hard and dense and So that's why it looks quite bright on CT and if it blocks off the diverticular, so the little out pouching then it can become inflamed, infected and eventually perforate. I found it very hard to find a good picture for you guys of a diverticulitis, but that you'll have to take my word for it. The fat around here is the slightly hazier and brighter than the fat here or the fat here. Um and this patient did have raised inflammatory markers. Um Yes, it's slightly brighter but sometimes it, it's a bit more obvious, but I, I just couldn't find a very obvious picture on radio pedia. Okay. I'm just gonna move. So I couldn't fit all of the pictures on to one slide. So I'm just going to move on to the next one. Um, just bear with me. Uh What is this? Okay? Fine. So corona slice, actual slice. Um, again, someone's given this person or, or contrast. So please ignore the bright inside the gut. Uh If I tell you that the abnormality is over the patient's right. Upper quadrant. Can anyone think what might be going on? So, we've got the liver here. Yeah, we have, um, cleanse your carcinoma and, um, maybe a stone. Yeah. Yeah. Yeah. So, um, yeah, very good. So you both, whoever don't know, sent those, both those answers managed to get the area of interest. So there's an abnormality in the gallbladder. Um So this is it on the corona slice. This is it on the actual slice on the corona slice we can see within the gallbladder, there's this brighter area and another one here and possibly another one behind. Um And these are stones that have been there for a while and developed layers and layers and become hardened. Um I can see why you think where you might have thought Cholangio carcinoma because on this actual slice, you can see that the wall of the gallbladder is really thickened. Um It's thickened, there's some stranding around it, there's some stranding there, possibly some free fluid building up their same on here, you can see a thickened wall of, of the gallbladder. Um But these findings off are more in keeping with acute colecystitis. Um Cholangio carcinoma, I wouldn't worry about too much is, uh, you would see some, you would expect to see some bile duct dilatation in uh, potentially, if it was causing a blockage, it just wouldn't look as, uh as angry. And, uh, you know, this stranding pattern is more in keeping with a colecystitis. So, essentially inflammation of the gallbladder. And in this case, we can see, we can say that it's probably to do with um, gallstones causing a blockage in the duct somewhere good. So well done on identifying the region of interest. Next case. So in this case, what's happened is the patient has been given contrast and then instead of waiting 30 seconds and taking the picture where we might have contrast in uh say the portal vein. Uh we've waited maybe, I don't know, maybe like 15 minutes here. And all the contrast is being excreted in the renal system. So this is the left renal pelvis and the right renal pelvis. So, corona slice, actual slice, um Can anyone see what might be abnormal? Can anyone see any asymmetry on this scan? Uh We have the kidneys. Yeah, perfect. And do we think the abnormality is in the left or the right kidney? Uh right close. So the abnormality is actually in the left kidney but it's very difficult to tell. Essentially, I think it's a bit easier to see on this actual slice but on the right side of the kidney. So on the right kidney, the contrast is in the renal medulla. So um it's being excreted properly and it's making its way. Now, the left side just looks a bit boggy. Er the renal medulla aren't as contrast contrast pacified. Um and something a word we often, well a phrase we often use when describing the kidneys on ct and ultrasound is cortic oh medullary differentiation. And what that means is can we is there like a crisp boundary between the cortex which is all of this outer stuff of the kidney and the medulla and we can see a nice, well, a crisper line on the left kidney. So it's nice and crisp here. Whereas on the right side it's fuzzy they're just two shades of gray and, you know, sometimes it's forward, sometimes it's back. You can't really tell which part is cortex in which part is medulla on this anterior aspect of the left kidney. And these findings are all in keeping with pylon arthritis. Now, if this person had more fat inside their abdomen, you would probably be able to see a lot of inflammatory fat stranding around this kidney. But this person is quite slim. And so it's hard to make that out. And that's something that inherently makes interpretation of CT scans very difficult is people that have a lack of fat inside their abdomen because fat gives us a nice separation of bowels. Um And it gives us something that uh it helps us identify stranding. If there's no fat, then we can't see fat stranding and just makes things a bit more difficult. So this is what pylon arthritis looks like. Um What do we think is going on here? Now, the abnormality on these pictures is a structure that I talked about very briefly when I was first going through the different planes. Does anyone want to hazard a guess? So this is a sagittal slice of the patient. So this is their back, this is their front, this is their spine. Uh So on the actual back, front spine, what what is this tubular structure here in the middle and on this side, just in front of the spinal cord, uh we have triple A's. Yeah, exactly. So this is the aorta and the aorta is really large and aneurysmal and invariably what we see. So here you can see it bulges all the way out. What tends to happen is that a large section of the aneurysmal part of the triple A becomes filled with from bus. And that's because if you imagine your heart is pumping blood and the blood has one direction to go down and into your legs as it reaches somewhere. Like here, it bounces and it all becomes very turbulent and bounces off here, bounces off here, bounces off here. The flow up here becomes quite turbulent and sometimes can become a bit static and eventually thrombose. So just thinking of work auvs triad uh for clotting, uh I can't, not sure I can remember them, but uh stasis was one of them. I think hypercoagulable state is another. Uh And I can't remember the third, but essentially you get some, you get some stasis of blood here and you get clotting and that's what's happened here. And then in the context of a person in their later years coming in with severe abdominal pain and massive hypertension always be worried about a ruptured triple A. But yeah, this is what an abdominal aortic aneurysm looks like. Yeah, okay to see how many more we've got. Cool. So onto our last two and then we've got a few questions. So uh so far we've only talked about um, a traumatic causes of abdominal pain. But trauma is another reason why we ct scan people. Um So in particular, in an abdomen, if someone's had something like a handlebar injury or they've fallen into a fence and it's, uh, you know, dug into their abdomen, then there are certain things that we look for. We look for solid organ injury. Um, on this uh corona slice of this person's body, we can see a normal sized liver and gallbladder here and we can see these little dark areas and then we can see these little wispy streaky areas. So this up here is probably an area of lacerations to the liver and these darker, more globular areas are probably a mixture of lacerations and bleeding into the liver. Um And this person might have cracked if we, you know, went a few slices forward, we might see cracks in the ribs of this person and the ribs, uh might have injured their liver. Um, on this slice. Can anyone tell me what organ might be damaged? So, I'll tell you it's not the liver. What's everyone think, uh, got spleen's? Yeah, spleen. Exactly. So the spleen healthy spleen is here and then all of this here is blood essentially, um replacing the spleen. If we went a few slices back, would probably see a little bit more healthy spleen behind it. But yeah, this spleen has had a really severe injury to it. Um And there's one other organ that's really damaged. Look for asymmetry. Uh kidney, yeah, perfect. So the left kidney is essentially just this shriveled up thing here. So the left kidney has been lacerated and there's been massive bleeding that's essentially essentially squished the kidney into this little structure here. Um The right kidney looks okay. There's all this free fluid in the abdomen, which is essentially blood in the person's abdomen. So this person, you'd expect to have a massive drop in their BP from all this bleeding. Um What is this? Uh this is quite a difficult one again, just to end the examples. Um I will tell you the finding and if you guys can think what the diagnosis might be. So on this slice of the actual abdomen, there is some free fluid here sitting in the right paracolic gutter. Um And this section of bow is darker. So the wall is what we call hypo enhancing. It's not enhancing as we would normally expect it to where as this is all small bowel that's enhancing nice and brightly. And then looking at this slice that's a bit lower down in the patient's body, but more free fluid, we've got loads of segment loads of sort of sections of bowel here that are just really dark and then not enhancing and the wall is thickened. So this is the wall here, it's thickened. This is a bit of healthy bowel up here. Can anyone think what would do that. Well, we have a scheme. Yeah. Yeah, perfect. So this is, this is essentially bowel ischemia. Um, the reason the bowel wall is darker is because the bow, the wall of the bowel has lost its blood supply. So the contrast that we've given the patient that's making all of this bowel nice and bright, it can't reach this, this section of bowel. So it just looks a lot darker. Um, the free fluid is probably a combination of inflammation and they're probably has been some perforation of one of the or like a defect of one of the elements of the bowel wall here. In which case, some of the small bowel content which we know is tends to be liquid, uh might have leaked out. Um This bow will go on to continue to Niekro's, uh, it will die off. Uh It will become very friable. It will, you know, different sections of it will perforate and you'll have leakage of small bowel contents. You'll have intraabdominal collections from the small bowel context and uh severe septicemia eventually untreated. So, this patient needs to have their bowel opened up and the section of dead bowel removed essentially good. So that is, those are all the sort of important diagnoses I wanted to cover. Um, I've got three little multiple choice questions, but before I get onto them, does anyone have any questions? No good. All right. So, uh yes, the finding here. So, uh is just gonna put out a poll for you guys to answer and then we'll have a look at what you guys answer and take a look at the correct answers. So, uh multiple choice. So option one is Hepatitis. Option two is pancreatitis and option three is pneumoperitoneum. Yeah, so I'll just give you guys a moment to have a think. Okay. I think that's everyone. Um Yeah, well done. So that's normal personae. Um So when it's this obvious, it's very easy to uh well, it's very hard to miss. Um there's free air, essentially, we've seen this picture already. Um One thing that's important to know is that free air in the abdomen isn't always a bad thing. So when someone has the has a laparotomy, uh sorry, a laparoscopy. Um and surgeons are sticking their port holes inside the abdomen, they inflate the abdomen with air or with gas so that they can see what's going on. Um So if someone's immediately POSTOP a couple of days and you see a little bit of free air and the abdomen, that's probably just from the operation. Okay, next question. Um So I guess the finding here we've got option eight or option one is free fluid. Option two is appendicitis and option three is pylon arthritis. Okay. I'll just give you guys a few more moments. Yeah, perfect. So that is a whole load of free fluid in the abdomen. Um And when it's this much free fluid, we we tend to call it ascites. Um This is probably large volume societies and there's an abnormality here in the liver, um which uh is probably some kind of malignant process in the liver, uh that's causing all of the societies. So we've got a nice and healthy liver tissue enhances nice and brightly. Um We've got these little dark spots, but here you've got loads of little dark spots that coalesce to form larger sort of mass like structures. Um um That the differentials for this might be something like an abscess, but more commonly would probably be uh malignancy, uh could also be injury to the liver. So, lacerations as well. Good, well done. Last question. So it's been a bit more difficult than the other two. Um So I guess the finding option, a colecystitis, option one, option one, coach cystitis to pile on arthritis or three appendicitis. I'll just give you guys a moment to that and just remember when we're looking at CT scans symmetry is the thing that we tend to rely on the most to help us get the answer. Um It's why as radiologists, we can often fall into traps because there are certain structures that might be singular in the body, uh like pituitary ground, pituitary gland, for example, or you might have symmetrical abnormalities. In which case, symmetry can trick us into thinking that something is normal when it's not. But generally as a rule of thumb, it's, it's what we rely on to help us get to our answer. So question three, everyone said option too, which was yeah, pyelonephritis. Perfect. Um Can anyone go the next step and tell me which side is the abnormal side? So remember the thing we said about cortical medullary differentiation. So making out the bright outer part of the kidney from the darker renal medulla sort of the renal pyramids which side looks abnormal. Who can, who is brave enough to have a guess? Yeah. Perfect. Right kidney is the abnormal one. So left kidney, we've got a nice and bright outer cortex and we've got these little renal medullary pyramids that are making RP for us. Um And we can make the distinction between cortex and pyramid quite well. Uh The contour is quite crisp here. The outer uh bright part of the cortex is not as bright as on the left and essentially, it's just all fuzzy. It's all quite boggy and edematous. Um So this is a right sided pylon arthritis. So, yeah, well done. That's really good. Um Any questions? You're welcome, James. Um anyone else? Great.