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Hello, everyone. Thank you to the faculty for the invitation to speak. I am Doctor Alyson Court. I'm a consultant radiologist who was previously working in ST Mark's Hospital in the UK, but I've recently relocated to a hospital in Dublin called Saint James's Hospital. And I have to apologize for having to pre record this talk. Unfortunately, I am, it's actually a bank holiday weekend over here in Ireland and I'm down in the Wilds of West Cork. So the wifi has become a bit of an issue. So I'm now pre recording, but I'll be logging back in for any questions at the end. So I'm going to talk about the fundamentals of Luminal ct interpretation. It's going to be a bit of a whistle stop tour because of the time limitation, 20 minutes to get to grips with interpretation of CT of Luminal imaging. So we'll try to do our best. Um I suppose where I thought was a good point was talking about the CT protocols that are most commonly used for Luminal imaging um and their benefits uh in the various disease pathologies. So the standard CT abdomen pelvis with portal venous contrast, we'll talk about that. We'll talk about the use of positive oral contrast in various CT protocols and its benefits. I'll talk about the use of CT enterography uh and specific pathologies that are more appropriately imaged with CT angiogram imaging. Um I'll touch on CT mesenteric angiography and of course CT colonography at the end. So the standard CT abdomen and pelvis um in port a venous phase of intravenous contrast imaging. What does that mean? That basically means that we give an iodine based intravenous contrast agent to the patient. And we trigger scanning at 75 seconds after the administration of the intravenous contrast that optimally enhances the Puerto venous system and gives us really good imaging of all the visceral structures within the abdomen and pelvis. So we use this for staging most cancers. Um some cancers that are arterial e enhancing such as some renal cell carcinomas, hypervascular lesion's thyroid cancers are better imaged and net tumor's are better imaged in the arterial phase. But for the vast majority of cases, Puerto venous phase staging is what we utilize. Um we use Puerto venous phase ct abdomen and pelvis for any patient coming through the department with non specific abdominal symptoms that is going to go forward for cross sectional imaging in the first instance and the bread and butter of the emergency department when it comes to abdominal imaging, any acute abdomen that comes into the department in general will go for a CT abdomen and pelvis with the portal venous phase of contrast administration. So for example, this is case number one, this is a 71 year old male patient. A PFA was performed in the emergency department as he had abdominal distension, altered bowel habit in the in the form of um not passing any bowel motions at all for three days. And on the PFA, you can see there very dilated loops of large bowel, you can see the house drill folds here. Um And this patient went on to have a CT. So PFA really very limited in its use in acute abdominal imaging, but generally ends up being a starting point for a lot of acute abdomens that come through the emergency department still. So he went on to have a CT. This is a CT portal venous phase study. You can see that this contrast within the vascular structures here with appropriate enhancement of the soft tissues. And what we're seeing in the actual phase here are markedly distended loops of colon. And what we start to see is that there's a transition point within the left lower abdomen or upper pelvis just here. So I've tried to demonstrate that on the still views where there's a bird, speaking of the sigmoid colon at this point here and then when we come down further, were scrolling through the CT. In this case, the mesenteric um structures are distorted or contorted and that happens just at the bird, be king of the colon here with no gas within the rectum. And this is what a sigmoid volvulus looks like on CT imaging. So when you see distended loops of small bowel on CT imaging for any exam, um, purposes or within the emergency department, when you're working up your own patient's, it's really beneficial to try to decipher whether it's smaller large bell that you're looking at that's distended, um, small bell, as you know, the valve Elocon event is our uh concentric lines of uh folds across the full diameter of the small bell. Whereas the large bell, we'll have houseful folds that do not extend from one side to the other of the bowel wall. And therefore, we know that it's large fell in this case. And as we know, there are multiple causes of large bowel obstruction. But certainly in this case, with the Peking, the sharp transition point of the sigmoid colon with markedly decompressed colon downstream of that and rectum with the twisting of the mesentery at that site is very typical of a sigmoid volvulus case number two. Again, this is a case who came in with an acute abdomen um and ended up being filtered into radiology with a portal venous phase study performed. Um This was a 49 year old female patient and we can see that there is an abnormality of the small bowel in this case. Um I don't know if you can appreciate these slightly unusual appearing loops of small bell throughout this patient's abdomen. And what were appreciating here is an interception. So you can see the inter cicippio Inns here on the inside of the small bell and the intercept, um, around it. Um, that is very typical of an interception. Um, in many cases of interception, you can see a lead point or a cause of the interception. Often. Um, in younger patient's, it could be a mucus ball such as uh cystic fibrosis patient's where they get high density mucus within the small bowel and are more prone to interception for that reason. But in adult cohorts, it's often a polyp or a tumor that's causing the small bowel intussusception. And in this case, um Andy latch furred in ST Mark's hospital did a colonoscopy on the patient because there was an abnormality in the terminal ileum as well. And that turned out to be a brown, dark brown lesion at colonoscopy within the terminal. I'll um over here, um lower down and when it was biopsied, it turned out to be metastatic melanoma tous deposits throughout the small bowel that were causing intussusception. So this is what intussusception looks like on a CT portal venous phase study just honing in on the intussusception here. So you can see the tumor deposit in the wall of the small bell causing in folding of the small bell at that point. And you can see the fat of the peri enteric fat being pulled in. Um into the inside or the lumen of the small bowel around that. This is another case of a an 83 year old female patient who came in with a acute abdominal pain, um significantly elevated lactate and was filtered into the emergency department to the surgical um, surgeons on call. They asked for a ct abdomen um to exclude any acute pathology. She was very unwell at the time and what we start to see here when you really hone in on the liver. So this is the liver in the right upper quadrant, we can see these lines of gas throughout the parenchyma of the liver. And really at that point, what we need to decipher is is this very standard new mobili A which is not going to be particularly concerning in any patient coming through the department probably indicates a previous sphincterotomy at ERCP and is very commonly seen within the department. Or is this something catastrophic where we see pneumatosis throughout the liver, parenchyma? You can see there's another serpiginous structure within the liver here, that's gas filled. Um This turned out to be gas throughout the portal venous system within the liver. So we'll scroll down to some more imaging in that patient, but just to differentiate what we see when we see new mobile eah. So the biliary system does not extend to the periphery of the liver. So bile ducts terminate approximately one centimeter from the paddock capsule versus the venous structures which extend um Two sorry, trying to go back on myself here to go back. I can't go back, apologies. So the the venous structures do not extend to the do extend to the periphery of the paddock capsule, unlike the biliary system. So that's one way of differentiating portal venous gas from new mobile eah on CT imaging. So look for the gas serpiginous structures extending to the paddock capsule. And then when you scroll down in this patient's imaging, you can appreciate that there is nondependent gas throughout the wall of the small bowel here. Um This is what pneumatosis looks like. This is pneumatosis throughout the intestine. So pneumatosis, intestinal issue can see it um circumnavigating the entire wall of the small bell. So we'll often see dependent or sorry, nondependent gas in patients who are lying down where the gas is raised to the anterior or superior surface of the lumen of the bell. That's normal, that's we're seeing in this case. But what's not normal is when there's bowel gas around the posterior or dependent aspect of the bell. And that's very convincing for pneumatosis. Intestinal is this beading of gas throughout the poorly enhancing loops of small bell. In addition, in this case, what's very convincing is you can see that there's serpiginous gas extending up through the mesenteric vessels themselves. So you should never see fat in this kind of or sorry gas in this configuration within the medicine tree. And that indicates gas within the mesenteric vessels. It's a very ominous sign and often leads to pneumatosis throughout the portal venous system. Just honing in on that, you can see the pneumatosis intestinal is throughout the posterior wall of the bowel. In this case, a pencil thin bowel wall and very poorly enhancing. So all very signs. So when do we use positive oral contrast in CT? So we've talked about IV contrast in the context of Puerto venous face scan, but positive oral contrast can be very beneficial. In certain cases, we don't give it in all cases that come through the emergency department orange in post operative cases. But there are certainly very, um, standout uses of positive oral contrast in CT imaging of the abdomen and pelvis. So when do we use it? We use, we administer positive oral contrast in the form of ingested gastrograph in dilute Gastrografin when we're trying to decipher complex enteric anatomy. That's very true. In the case of ST Mark's imaging, where we have very difficult about failure, intestinal failure, patient's coming through who've had innumerable previous surgeries and receptions. And it isn't always clear what the anatomy is. Um, so we can really just end up the small bowel loops, the residual small bowel loops up in that case, uh in those cases with positive oral contrast. And that gives us a really good roadmap of bowel throughout the abdomen. We can give pretty accurate measurements of residual small bowel and we can decipher how much small bowel lies upstream of a fistula. So very good. In addition, for mapping out enteric fistula, a, um it's also very useful for assessing enteric anastomosis. So particularly those within the upper gi tract, the lower gi tract is often more appropriately assessed with the administration of positive contrast through a fully catheter in the form of an enema. But certainly for upper gi anastomosis, it's very beneficial. It can be useful in gastric cancer staging in order to just end up the stomach. And can also be a very good adjunctive uh agent in the PCI assessment of patient's with personal carcinomatosis or suspected personal Carson carcinomatosis. So it really just takes the una pacified bowel loop out of the equation when you're trying to decipher whether something is a soft tissue deposit or is indeed just a decompressed bowel loop. So you can see here, this is a patient who is having imaging of their upper abdomen at the level of the liver here and the spleen in the left upper quadrant. And this patient has been given positive oral contrast. This is the decompressed stomach here, they've had a gastric anastomosis and and you can probably appreciate that there's a leak of contrast post yearly here at the level of the gastric pull up and this confirms the presence of an anastomotic leak in this case. So positive oral contrast has real uses in many cases. Okay. So we'll move on to another positive oral contrast study. So this is what the small bowel loops look like when we've given positive oral contrast versus those that are nano pacified. So, this is a loop of colon. This is the descending colon with no contrast within it. Just because of the timing of the study will often give patient's a liter of positive oral contrast and wait for an hour for the oral contrast to transit, at least the level of the IOC kal valve to distend up the small bowel loops. And this really nicely delineates an abdominal wall hernia. You can see there's a midline abdominal wall hernia with transgression of Eylea loops into the hernial sac. It's relatively tight necked and you probably expect some upstream debilitation if you scroll through this CT scan. So, moving on to CT enterography, when do we use CT enterography? And what is it? So CT enterography focuses on the administration of intravenous contrast in the entire a graphic phase. So, we've already touched on the fact that the 75 2nd trigger is the port of Venus phase optimization of intravenous contrast CT angiographic uh studies really triggered the scan after 55 seconds, post administration of intravenous contrast. So it's an herb early phase study. Um An arterial phase study generally triggers that about 25 seconds and then an entire entire a graphic phase study triggers at about 55 seconds. So sort of between an arterial and a portal venous phase study. And that really highlights the mesenteric vessels. Um If you think about the pumping of blood from the left ventricle through the systemic system, and then coming back into the portal venous system from the gut, the enteric system will be oh pacified prior to the portal venous phase. So we ask the patient's to drink neutral oral contrast. That basically means that akin into water, um the got will be distended but it won't be bright as it is with the ingestion of positive oral contrast such as gastrograph in. And that is so that we don't mask any underlying mural pathology. So the bowel wall and the stomach, the gastric wall is nicely visualized and that is triggered so that the mesenteric vessels are optimized in terms of contrast enhancement. So when do we use this? We use it for um investigation or imaging of inflammatory bell disease. We'll talk about the benefit of em are enterography um as an alternative, which is used much more frequently now, but certainly in patient's who can't tolerate an MRI or in patient's where there is um difficult anatomy to be delineated. Ct enterography is still a really good study. We also use it to stage net tumor's or neuro endocrine tumor's um of the small Bell and can be very beneficial for assessment of burden of small bowel polyp osis. So, for example, in these cases, were going back to very old school imaging here that we still utilized very frequently in ST Mark's actually um this is a barium contrast study, double barium contrast study. So this is really looking at the fold anatomy of bell. Um And what we're seeing in this case is the terminal ileum coming here in here at the level of the ileocecal valve in the right lower quadrant. And we're seeing spacing or very uneven distribution of the loops of small bells. You can see they're nicely closely opposed here, which is what you would normally see within the abdomen. And what we're seeing here is marked spacing between the bowel loops and that is secondary to fat wrapping that we see on both MRI and CT. So this patient went on to have a CT intra gram and I don't know if you can appreciate the degree of inflammation of the terminal ileum here. So when we zoom in on that, you can see that there's transmural inflammation. So there's thickening of the wall of the terminal ileum. There's marked hyper enhancement versus the other loops of small bowel, which are unaffected. And there's a lot of graying of the or haziness of the peri terminal ideal fat and then hypertrophy or fat wrapping around the affected segment of small bell. So that's a really nice um demonstration of the entire a graphic phase where you can see the mesenteric vessels are really nicely enhanced versus a portal venous phase study where we're really not honing in on the mesenteric vessels to such a degree. So this is what an MRE looks like. And really, this is the bread and butter of small bowel inflammatory disease like Crohn's. Uh in terms of staging of disease and assessment of response to treatment, it's far superior to CT enterography because we get multiple sequences demonstrating various different aspects of the inflammatory process. We can better differentiate whether the thickening of the small bell is due to fibrosis or edema or active inflammation. So a much better test in most patient's with mobile inflammatory disease. But there's still a very significant role for CT angiography. So this is another case of a to patient's with abdominal symptoms, sort of non specific, a little bit of weight loss and they went on to have a CT intra graham. And what we're seeing here is a Mesenteric mass. So there's a 2 to 3 centimeters spiculated soft tissue deposit within the ileocolonic mess entry here within the right lower abdomen. And what I always look for when I see these speculated types of masses is any abnormality within the terminal ileum. So to me, this looks like something beyond a standard mesenteric lymph node. It's speculated it's cicatrizant, it's pulling in the mesenteric fat. And that is quite pathognomic, particularly if you see partial calcification within that mesenteric mass of carcinoid tumor. And what you often see and this usually represents a nodal deposit relating to a primary small bowel lesion. So if you skip down to the second case, you can see that there's an these enteric deposit here again. And what we've done is really honed in on the terminal ileum relating to that medicine tree. So you can track the blood vessels down into the relating segment of small bell. And here we see an enhancing soft tissue mass within the small bowel, very compatible with Illumina lll um carcinoid or net tumor with a nodal deposit within the knees entry. These patient's will often go on to be disgusted mg tea and have a gallium dotatate scan to fully stage the degree of. So. So mesenteric angiography is pure angiography which looks at the arterial vascular anatomy of the gut. Um It's very useful for delineation of the arterial anatomy and complex preoperative cases or in cases of an acute gi bleed. It can be very useful in determining if there's an active arterial bleeding. So this is what a CT arterial angiography angiogram looks like mesenteric angiogram. You can see there's dense contrast within the aorta and in this case, the superior mesenteric arterial branch in the midline. What's very um on vogue at the moment is the fusion of a CT Colonna graphic studies or a CT colon study with an arterial phase study. In order to delineate measure the vascular anatomy and supply of a colonic tumor. So, there's a clinic tumor in the left upper quadrant or in this region of the splenic flexure, there's an Endoclip here that's showing up on a CT colon at the level of the tumor. And they've really nicely mapped out the arterial blood supply of this colonic tumor, which can be very beneficial for surgical planning given the variation and variability of the blood supply in that region. So, speaking of uh ct colonography, when do we use CT colons? And is it a good test? So, really good test for patient's who are not fit or decline, formal colonoscopic evaluation. There are other uses as well and it's becoming um much more commonly used who are fit and well, but may benefit from visceral assessment as well. So, patient's with more nonspecific symptoms, patient's who are considered a lower risk for colonic tumor. So maybe a lower fit level when they're first triaged into clonic assessment. Um CT colonography can be a really good test, excellent test for patient's with failed colonoscopy of course. Um And for those with previous incomplete colonoscopic evaluations for various reasons. So how do we prep these patient's? We start these patient's on a low residue diet two days before they have their study performed. They're given gastrograph and prep, which is a small bottle of gastrograph and they drink half of that the night before the test and half of that the morning of the test. And what does that do? The gastrograph in basically tags any residual feces. So it makes any residual fluid or feces within the bell very bright in color. And that's very useful when we go to look at the CT Coghlan's in terms of three D assessment on the software that we use for Luminal assessment. So we insufflate the bowel, the patient comes and they lie on their left side. Initially, we put a fully catheter or equivalent into the anal canal into the rectum and we use um an automated pump device to insufflate the colon with carbon dioxide. So CO2 until we reach a set pressure level. So it's a very safe test. We used to hand pump gas into the colon, which was less safe, safe and that we didn't have any feedback in terms of the pressures within the colon at the time. But now the machine will cut out or feedback to us when the pressure has got to a certain point, we then turn the patient on to their back and scan them in both the supine and prone position usually. So two views um to try to move the tagged fecal agent onto the other side of the clonic wall. Um So that we make sure there aren't any polyps or lesions lying within the tagged residue on the three D view. Um Okay. So is it a good test? We've basically got a good body of evidence. Now showing that the adenoma detection rate within well performed CT colonography is equivalent to colonoscopy that's for polyps over the size of 6 to 7 millimeters. The interval cancer rate is equivalent to colonoscopic assessment. This is all within high volume centers. So what we need to do next and what has been worked on really thoroughly and in a very thoughtful way by um some by both Doctor Annual Bahru who is a or was a phd Registrar in Radiology in ST Mark's Hospital. She's now a consultant at ST Mark's along with a cohort of radiologists and radiographers have put together what is called the effects program, which is a UK wide NHS England funded training initiative for CT colonography. So that's to try to optimize um and standardize the performance of CTC and interpretation. So that's akin to the standards within mammography and endoscopy to date. So the problem up to recently is that there hasn't been a any performance measure for those either performing or interpreting C T C. And it is great that we now have an N H S um funded program for assessment and audit for quality in CTC. So watch that space. I think everyone who's performing this in a high volume will be very much embracing of the new program um to try to maintain our standards within CT colonography. Um and that is it, I think we're actually out of time. I'm going to just very quickly touch on the contraindications or dangers, I suppose in a way of CT imaging in abdomen, abdominal and pelvic imaging, really for Luminal assessment, really, what we just need to touch on very briefly is that the newer non ionic or low as motor I automated contrast agents that we use currently versus in the past 20 years ago, are extremely safe. So 5 to 10 times safer than the older agents, there's a very, very low rate of adverse events when we administer intravenous contrast, about 0.4 to 0.15% undergo an adverse event with IV contrast agents. Most are extremely mild, a bit of your you shake area. Um and very, very rare to result in any significant renal impairment. So really the the boundaries on the use of IV contrast in patient's with compromised renal function are loosening and rightly. So, and I think some, some departments will still maintain some boundaries in terms of administering intravenous contrast to patient's with low renal function. Um just I suppose bear in mind your local um protocol for that. But certainly, I think over the next 5 to 10 years, we'll see, you know, us turning away from even having to monitor very stringently patient's renal function coming down for CT scans. So, in pregnancy, um if we're giving IV contrast, obviously, we try to use um ultrasound and MRI where appropriate in patient's who are pregnant sometimes that it's unavoidable where there's a very acute abdomen in a trauma patient or a very significantly unwell patient. And we do need to scan patient with intravenous contrast. I automated contrast. There's no real evidence um for altered thyroid function in the newborn um in these contexts, but we do still monitor or advised monitoring of patient's who've been administered intravenous contrast, either gadolinium or iodinated contrast when pregnant for the first week or so of the newborn's life. In terms of lactation, really, negligent negligible concentration enters breast milk. Um So no real concerns gadolinium more so than I ordinated CT contrast. So with MRI contrast agents, which is gadolinium based, the patient's are asked to um to throw away their breast milk for the 1st 24 hours after gadolinium administration. But there's no need with coordinated contrast agents. So that is all we're going to squeeze in in this very short 20 minute time. I hope it was helpful in terms of preparation for assessment of abdominal imaging. I'll be around for any questions at the end of the session.