Hi, I'm Dr. Robin Levenson, Director of Emergency Radiology at Beth Israel Deaconess Medical Center in Boston, and I'm going to talk about GI causes and CT imaging findings in patients presenting with acute lower abdominal pain. Again, I'm going to review GI causes of acute lower abdominal pain and discuss pertinent CT imaging findings using case review. Abdominal pain is a common symptom in patients presenting to the emergency department, representing approximately 10% of ED patient visits. Patients presenting with abdominal pain can represent a diagnostic challenge, since the differential diagnosis can be broad and include numerous entities with clinical signs and symptoms that may overlap, and the symptoms may be nonspecific. This includes both gastrointestinal and non-gastrointestinal etiologies. CT plays an important role in assessing GI causes of lower abdominal pain. Surveys have looked at CT utilization in ED visits for acute abdominal pain, and not surprisingly, over the last 20 to 25 years, there has been drastic increase in the use of CT for the assessment of abdominal pain in the ED. In 1997, only approximately 4% of ED visits for acute abdominal pain had an associated CT, and with the increase in availability of CT in the ED and increase in quality of CT and speed of CT, in 2016, almost 40% of ED visits for acute abdominal pain had CT to help in diagnosis. Also, a prospective multicenter study showed that CT changed the leading diagnosis in approximately 50% of patients presenting to the ED with abdominal pain. So this underscores the importance of CT in the assessment of abdominal pain in ED patients. Appendicitis is the most common surgical cause of right lower quadrant pain, and so we are often, in patients with right lower quadrant pain, we're often asked to rule out or rule in appendicitis, and in patients with left lower quadrant pain, we're asked to rule out diverticulitis. Diverticulitis, particularly of the sigmoid colon, is the most common cause of acute left lower quadrant pain in the United States. We as radiologists, however, may encounter a number of different etiologies of right and left lower quadrant pain, so I'm going to show cases of other less common entities you may encounter on your journey of reading CT of acute lower abdominal pain. Here we have a patient, 40-year-old, with right lower quadrant pain. We can see that there is an oblong fat-containing structure along the anti-mesenteric side of the ascending colon. There was some haziness and inflammation of the adjacent fat, and as we look in the right lower quadrant, we also see that the appendix is normal. And this patient with epiploic appendicitis. In epiploic appendicitis, there's inflammation of an epiploic appendage, epiploic appendage being a fat-containing structure along the anti-mesenteric side of the colon. Torsion of an epiploic appendage causes venous or vascular occlusion in the majority of cases, which may result in ischemia, thrombosis, or infarction. Epiploic appendicitis can also be caused by hernia incarceration or bowel obstruction. The most common location of epiploic appendicitis is the sigmoid colon, with the right colon and descending colon being less common. It is seen most commonly in the fourth to fifth decades of life. When epiploic appendicitis involves a sigmoid colon in the left lower quadrant, it may clinically mimic diverticulitis. When it involves the cecum or ascending colon, it may mimic appendicitis. And again, these are seen along the anti-mesenteric side of the colon. Epiploic appendicitis is predominantly an imaging diagnosis. It is difficult to make based on symptoms and physical exam alone. Before the widespread use of CT, the correct diagnosis was made in only approximately 2% of cases, and most were diagnosed at surgery. And as I mentioned before, on CT, you see an ovoid fat-containing structure, potentially measuring up to 5 or so centimeters, but most commonly 1 and 1 half to 3 and 1 half centimeters in size. One may see associated information of the adjacent fat or fat stranding. One may see what's called a central dot sign, which is either a punctate-dense focus within the inflamed epiploic appendage, or sometimes it looks like a linear internal density, which is thought to represent a thrombosed vessel or venous thrombosis within the inflamed epiploic appendage. However, at least one study has shown that this is seen in approximately 50% of cases, so its absence does not exclude diagnosis. The colonic wall may be thickened, but more commonly, it is not, and treatment is conservative. This is non-surgical condition. Here we see a patient with left lower quadrant pain, and we can see that, as we scroll through, there is this ovoid fat-containing structure that's extending into the spaghelion hernia. And this patient, and there's some adjacent inflammation in this patient that had epiploic appendagitis herniated through a spaghelion hernia in the left lower quadrant. Next we have another patient with lower abdominal pain. We can see that there is some haziness in the right lower abdomen. There is some thickening of small bowel here, and there is this circular ovoid structure containing fluid with adjacent inflammation. And in this case, we don't see fat in the structure. It's low density, and it is associated with the small bowel as opposed to the large bowel. And we can see some still images here. Again, we see this fluid-containing structure arising from the ileum in this patient that had Meckel's diverticulitis. Meckel's diverticulum is the most common congenital structural anomaly of the GI tract. It is a true diverticulum. From medical school, many of you may remember the rule of twos, or at least that there is a rule of twos. And this applies to Meckel's diverticulum. It is present in approximately 2% to 3% of the population. It tends to be around 2 inches long, or 5 centimeters for those using the metric system. It tends to be approximately 2 feet, or 60 centimeters, from the ileocecal valve. Meckel's diverticulum may invert, resulting in an intraluminal polypoid appearance on CT. And complications include diverticulitis, obstruction, hemorrhage, and endosysteption. And on CT in Meckel's diverticulitis, we see a blind-ending tubular structure arising from the ileum. These are cases from four different patients that had Meckel's diverticulitis here. One may see wall thickening of the diverticulum, wall thickening and enhancement, which may involve not only the diverticulum, but also the adjacent small bowel. The diverticulum also demonstrates, you'll see adjacent inflammation of the fat. The diverticulum may contain fluid, air, or fecal-like debris. And the treatment of Meckel's diverticulitis is surgical. Here we have a patient that presented with left lower quadrant pain, rule-out diverticulitis. And we can see that there is this round, fluid-containing structure in the left lower quadrant with adjacent inflammation. However, it seemed to be separate from the sigmoid colon. And as we look further, we notice that the cecum actually was coursed, this patient had a mobile cecum. It was coursed beyond the midline into the left abdomen. We also saw the calcification in this associated tubular structure in the left lower quadrant. And here we can see that again as we scroll through, there's this dilated tubular structure which arises from the cecum here. It has a calcification or appendiculitis in this patient that had appendicitis in the left lower quadrant. So patients presenting with left lower quadrant pain when looking for diverticulitis, you want to keep in mind other entities that may cause this pain, including conditions that typically reside in the right lower quadrant. And the same is the case for things that typically arise in the left, involve the left lower quadrant. Here we had a 45-year-old with right abdominal pain. You see that there is an inflamed diverticulum arising from the ascending colon. There's adjacent inflammation in this patient with the right-sided diverticulitis or diverticulitis of the ascending colon. Right-sided diverticulitis is more common in Asian and black African populations. It represents approximately 50% of diverticulitis, colonic diverticulitis cases. And you want to look for inflammation that is centered at the diverticulum along the colon and not at the appendix. And patients that have diverticulitis involving the ascending colon or cecum, this may cause right lower quadrant pain, clinically mimicking appendicitis. Here we have a patient that presented with right lower quadrant pain and rebound tenderness. What is the best diagnosis? Do people think, could this be small bowel obstruction, colitis, mucosal diverticulitis? Is this a hot dog for people awake out there? It looks sort of like a hot dog, but we're here in radiology. And this was a mucosal of the appendix. Mucosal of the appendix, in mucosal of the appendix, obstruction of the appendiceal lumen leads to accumulation of mucus and dilation of the appendix. It can be due to benign or malignant causes. And it is rare, but it's important to be aware of the possibility of the diagnosis. On CT, we see a blind-ending tubular structure arising from the base of the cecum. Typically, it is greater than 1 and 1⁄2 centimeters in diameter, but can be several many centimeters in diameter. Wall calcification suggests the diagnosis, but is seen in less than 50% of cases. Intraluminal bubbles of gas with adjacent inflammation suggest superinfection. The main concern with appendiceal mucosals, not only is that they're a concern for appendiceal neoplasm, but if there is rupture, it can lead to mucin deposits throughout the abdomen. And if the cause of the rupture is malignant, then there's a risk of this concern for pseudomyxoma peritonei. The mucosal of the appendix is surgical. Again, there's concern for benign or malignant neoplasm-causing mucosal. This is a patient that had an inflamed mucosal. You can see that there is air in this dilated tubular structure that arose from the cecum, and there's adjacent inflammation. At surgery pathology, this patient had mucinous cyst adenoma of the appendix. Here we have a patient with abdominal pain status post-colonoscopy. And some thoughts about what this diagnosis could be. There's some thickening along the descending colon here. Is this transmural burn syndrome, bowel perforation, diverticulitis, or osteocoraclitis? This patient had transmural burn syndrome, or also called post-polypectomy syndrome, after removal of a polyp of that patient along the descending colon. Here we have a patient that had a polyp removed from the cecum one day prior to the CT, and we can see there's extensive wall thickening. Post-polypectomy syndrome is rare. It's only seen in up to 2% of patients that have post-colon polypectomy. These are post-polypectomy with a hot snare as opposed to a cold snare technique. Patients tend to present within 12 hours, but can present up to five days post-procedure. And symptoms may mimic bowel perforation, so imaging plays an important role in differentiating the presence of perforation versus not. And in this case, in post-polypectomy syndrome, electrocoagulation injury to the bowel from electrical current applied during hot snare polypectomy induces a transmural burn and potentially localized peritonitis leading to the bowel wall thickening. On CT and post-polypectomy syndrome, we'll see focal bowel wall thickening near or at the site of polypectomy. Lack of extraluminal air differentiates it from perforation, and the treatment is conservative. Here we have another patient around the theme of post-colonoscopy abdominal pain. This patient presented with a lower abdominal pain after colonoscopy. And on these scout images of an abdominal pelvic CT, we see that there was linear lucency along the left abdomen along the course of the left psoas muscle, raising concern for pneumoretroperitoneum. As we look more closely, we see that there was also air in the retroperitoneum adjacent to the right kidney in the perinephric region. As we learned about this patient's history further, it was discovered that the patient presented with lower abdominal pain and neck popping, which is an interesting combination of symptoms. The patient also had a rectal polypectomy during their colonoscopy. Here we can see on the CT images, there is rectal wall thickening with a decent amount of adjacent extraluminal gas and some free fluid in the pelvis. As we look further up in the abdomen, we can see that there was extensive pneumoretroperitoneum extending from the rectum to purely through the abdomen, throughout the abdomen to this appear aspect at least. And here we see that air adjacent to the kidney. Since the patient presented with neck popping, the ED also obtained a neck CT, which demonstrated extensive subcutaneous emphysema along the neck. And the upper images of the chest also demonstrated pneumomediastinum here. So this patient had rectal polypectomy with bowel perforation, which led to pneumoretroperitoneum, which extended into pneumomediastinum, since the retroperitoneum and mediastinum are in continuity. And from the pneumomediastinum led to subcutaneous emphysema, and the patient presented with neck popping or was likely crepitus. Here we have another patient with lower abdominal pain. You can see there's some thickening of the cecum and ascending colon. It's the best diagnosis here. I'll give you a hint. This patient recently did some long distance running, and the patient had no recent history of colonoscopy. So would this be transmural burn syndrome, bowel perforation, ulcerative colitis, or reversible ischemic colitis? This is a case of reversible ischemic colitis, or what has also been termed runner's colitis. Patients may present with acute abdominal pain after exercise, particularly seen in long distance running or in marathon runners. Patients may also present with abdominal pain and diarrhea. The abdominal pain may start during exercise or up to 48 hours later. It is a reversible ischemic colitis. It is thought to be due to dehydration, volume depletion, leading to basal constriction in a low flow state. On imaging, we see circumferential bowel wall thickening and edema, predominantly involving the cecum and, to a variable degree, the ascending colon. The transverse colon may be involved to a variable extent, and the descending and sigmoid colon are less likely to be involved. We also notice that the vessels are patent. There's no evidence of vascular thrombosis. And the treatment for this condition is conservative. It is non-surgical. Here we have a patient with three days of lower quadrant pain. And we can see that there is this thin, linear, radiopaque or dense structure coursing through the walls of the sigmoid colon. And there's adjacent inflammation. And this patient that had a foreign body lodged in the sigmoid colon. This was a toothpick. This patient underwent segmental sigmoid resection, since the toothpick was unable to be retrieved endoscopically. Here's another patient. Again, we see this best on SIN-A images. You can see that there is a subtle, linear, dense structure in the sigmoid. This is another patient, a different patient with left lower quadrant pain, best seen on SIN-A images. Patient underwent colonoscopy with a toothpick seen in the sigmoid colon. However, the toothpick was embedded through both walls of the colon, and it could not be removed on colonoscopy. And this patient also underwent surgery for removal of this foreign body. So in summary, CT plays an important role in the differential diagnosis of GI causes of acute lower abdominal pain. Be familiar with potential CT findings. In causes of lower abdominal pain beyond, you know, you want to think about appendicitis and diverticulitis, since those are most common, but you also want to be aware of the variety of potential other conditions that you may see that are causing acute lower abdominal pain. You want to think outside the box. And history can play an important role in the differential diagnosis. Thank you. Thanks so much for the opportunity to be here, and thanks to our in-person and virtual audience for joining us first thing Monday morning. I just wanted to acknowledge some of my partners, colleagues, mentors, and friends for contributing content and expertise for this case. So for the next 20 minutes or so, I want to talk about selected cases of patients presenting to the emergency room with abdominal pain arising from a hepatic, pancreatic, or biliary source. So these are three different patients presenting with pancreatitis of varying severity, which we see commonly in the emergency department. But in addition to helping establish the diagnosis and discussing the severity, we also want to think about unexpected causes and potential complications in pancreatitis. And one paper we discussed recently at our journal club in the abdomen section was this paper looking at unsuspected pancreatic cancer as the cause of pancreatitis. And according to the literature, somewhere between 7% and 14% of patients may have an underlying pancreas cancer. And in this paper, they suggest patients who have distal pancreatitis or to the left of the SMV may be higher risk to have an unsuspected pancreatic cancer. So this is a patient who had a known history of pancreas cancer and had undergone a Whipple procedure but was thought to be disease-free and presented to our emergency department with pain. And you can see that she does look like she has a distal pancreatitis with some pancreatic ductal dilation. And you can see she's got a recurrent mass at her surgical anastomosis, a new pancreas cancer. This is a 66-year-old male who presented to our emergency department with pain. And you can see already that something not good is happening here. And he looks like he's got some pancreatic ductal dilation, some inflammatory stranding, so kind of a distal pancreatitis with this infiltrative mass here and multiple lesions in the liver and peritoneal metastatic disease. So this was a pancreas cancer with pancreatitis, but not really a mystery, unfortunately, already fairly extensive. But this case was maybe a little bit more subtle. This was a 45-year-old woman who presented with pancreatitis. And in this case, it's not distal. It's in the head. So you can see the head looks kind of expanded. And there's some edema here. But she also has a fair amount of biliary and pancreatic ductal dilation. So even though it was hard to tell if there was a mass or not, we recommended follow-up. And here one month later, you can see that she has a locally advanced pancreas cancer that was unfortunately metastatic to the lung. Here's another case. This was a 72-year-old male with a history of pancreas cancer. You can see this infiltrative lesion with some surrounding inflammatory stranding, metastatic disease to the liver. So he had a metallic biliary stent placed and was sent home and returned to the ER with abdominal pain. And now you can see he's got multiple fluid collections in the liver containing gas. And it looks like his stent has eroded into and perforated his gallbladder. So presented with pancreatitis and then a follow-up complication of stent placement. This is another patient, 33-year-old male, history of recurrent pancreatitis. Gallstones were the cause. So he had been in the ER multiple times. And you can see already, he has multiple fluid collections in his pancreas. This time he presented with new pain and a decreasing hemoglobin. And as we scroll through that pancreas, you start to see these areas of serpiginous high attenuation. Some of the fluid collections look like maybe they have blood in them. As we get down lower into the expected location of the gastroduodenal artery, you can see a couple other areas here. So this is a known complication of pancreatitis, arterial pseudoaneurysm formation. It tends to occur in about 10% of patients. And usually it's subacute, because those vessels are being bathed by pancreatic juices and it weakens the wall, and you get this pseudoaneurysm formation. But when you see it, it's an emergency, because these can rupture and bleed with very high mortality rates. So we usually send these patients to our interventional radiologist for embolization. And here's another case, 73-year-old male with pancreatitis. You can see kind of that same look along the course of the gastroduodenal artery and the inferior pancreaticoduodenals. And this is a common location for pseudoaneurysm. You can see these had bled. He had large hemorrhage and was subsequently embolized. We can also see these on ultrasound and MR. So on ultrasound, they look like pseudoaneurysms elsewhere. So you see that sort of classic to and fro flow, both on color doppler and pulse waveform. And on MRA, you can see this structure that's following blood pool. Sometimes you can identify the vessel that it's arising from. And again, here it's a communication between the pancreaticoduodenals and the gastroduodenal artery. Another time we might suspect a bleeding pseudoaneurysm is when a patient has fluid collections that have gotten bigger or have blood products in them. So this was a 52-year-old woman who presented with right upper quadrant pain. Her collections had gotten bigger, and you see those blood products in the collection. This was a pseudoaneurysm that had ruptured into her collection. This is another patient. This is a 49-year-old woman with a history of recurrent pancreatitis, and she presented with GI bleeding. And you can see that she also has pseudoaneurysm formation, but there's gas surrounding the pseudoaneurysm, and it's fistulized to the adjacent colon. So it's bleeding into the colon, which was the source of her GI bleeding. Incidentally, she also had some portal vein thrombus and some developing hepatic abscess. Another patient with GI bleeding. This was a 47-year-old male with recurrent pancreatitis. And you can see on his non-contrast CT, he's got that tubular high attenuation along the expected course of the pancreas duct at the blue arrowhead. And in the tail, you see that rounded structure at the yellow arrow that looks like a pseudoaneurysm on an MR. So he went to get embolization of his pseudoaneurysm, but you can see that when they injected it, there's filling of the pancreatic duct. So this pseudoaneurysm has fistulized the pancreatic duct and is bleeding into the GI tract. So this is so-called hemosuchus pancreaticus, and this was the source of his GI bleeding. So this was another woman, 56-year-old woman, who presented with coffee ground emesis. So concern for GI bleeding, but here you see she's got this really dilated gallbladder. And definitely, she has some high attenuation stones, but there's a lot of other high attenuation material in there that looks like blood products. And you can see the blood in her stomach when they went to do EGD. She had a known history of factor V Leiden, so she was anticoagulated chronically. And this was a case of hemorrhagic cholecystitis. And this is a rare, potentially fatal complication of acute cholecystitis that we tend to see in patients who have some sort of bleeding diathesis. So either chronically anticoagulated, or their platelets don't work for some reason, renal failure, cirrhosis, et cetera. And they often present with hemobilia and subsequent hematemesis, as our patient did. This is another case, and here you can see it almost looks like there's some active extravasation into this gallbladder. And you can see blood and stones outside the gallbladder this one had perforated. On ultrasound, you can see these non-mobile, non-shadowing internal echoes. And you can see on this Cine, if it'll play here, this gallbladder is filled with blood. And on CT, this is a different patient. You, again, see that high attenuation blood in the gallbladder. Sometimes you see fluid-fluid levels, as with our prior case. Sometimes you see active extravasation. And you can see this patient had hemorrhagic cholecystitis and pancreatitis. Here's another patient. This is a 54-year-old male with diabetes who presented with right upper quadrant pain. And in this case, you can see gas in that gallbladder wall. So here we would worry about a gas-forming infection, like emphysematous cholecystitis. This tends to occur a little bit more commonly in male patients, usually in their sixth to seventh decade. Usually, this is considered a surgical emergency. But sometimes, we'll place a percutaneous cholecystosomy tube just as a temporizing measure. And his biocultures grew a clostridial species, so a gas-forming bacteria. Here's another case. This is an 89-year-old male. And you can see the gas is kind of subtle in the wall there. And we always want to differentiate that gas from pneumobilia, so gas in the gallbladder lumen, or nitrogen-containing gallstones. But when you see it like this, tracking along the wall, especially when you've got a thickened, inflamed gallbladder, we worry about emphysematous cholecystitis, which is what this was. Sometimes, this can be hard to see on ultrasound. This case, you can see that sort of dirty shadowing of the gas in the wall. Sometimes, when it's more subtle, we may go on to CT for confirmation. So another case, a 75-year-old male, also with an abnormal gallbladder. Here, you can see it looks inflamed, but the wall is really thickened with these cystic spaces in the wall. And it seems to be really locally aggressive. So extending into the adjacent liver, you can see the gallstones on MR. So we weren't sure if this was some sort of aggressive cholecystitis, or if this was a gallbladder cancer. So we set him up to come in for a biopsy, but in the meantime, he was treated with antibiotics and steroids. And you can see, by the time he came for a biopsy, this had almost resolved. And so this was a case of xanthogranulomatous cholecystitis, which can look very locally aggressive like this. This is another case, 30-year-old woman. And you can see kind of the same look, that gallbladder wall thickening with those small cystic spaces in the wall. Lots of stones, and this was radiotracer avid on PET. She went to cholecystectomy, and you can see that exuberant gallbladder wall thickening with those yellow fatty deposits in the wall, this classic granuloma formation, and these foamy lipid-laden cells in the background that we see with xanthogranulomatous inflammation. Regular acute cholecystitis, as well as these more complicated forms of cholecystitis, can go on to gallbladder perforation. Usually this happens subacutely, not in the acute phase, and it can rupture directly into the peritoneum and give you hemoperitoneum and drop gallstones like we see here, or it can rupture other places. So this was a patient with a new pancreatic cancer, had had a biliary stent placed, and you can see all this fluid along the falciform ligament. So this is just a local gallbladder perforation with a small adjacent fluid collection. And you can kind of see it here, tracking in the falciform ligament and around the liver. This was another person who came in recently, 72-year-old male with right upper quadrant pain. And you can see he's got a complex collection in his liver along the gallbladder fossa. So this was a perforated cholecystitis that perforated into the adjacent liver. These can also perforate into the adjacent duodenum. Here's another patient, 69-year-old woman with right upper quadrant pain. You can see she's got this really big gallstone sitting in the gallbladder neck, some surrounding inflammatory changes. But in addition, on her MRCP, you can see as we scroll down, there's dilation of the central intrahepatic bile ducts, dilation of the common hepatic duct there, that transitions at the level of this stone. So the stone's not actually in the duct, just pushing on the duct, causing the obstruction. And this is Maritzi syndrome, where you get stones impacted in the gallbladder neck or the cystic duct that can cause mechanical obstruction as well as recurrent inflammation in the common duct. And although this is relatively uncommon, if you see this configuration and you're thinking about it, it's worth mentioning because it will change the surgical approach because of the risk of associated fistula. This is a 32-year-old male, kind of same story, right upper quadrant pain. You can see that stone in the gallbladder neck on ultrasound with that intrahepatic biliary ductal dilation right adjacent to the stone. You can see the same findings on MR, another case of Maritzi syndrome. Here's a case that came in recently. This was a 36-year-old woman, also right upper quadrant pain. And in this case, you can see there's inflammation in the fat adjacent to the gallbladder, but the gallbladder wall is really not that thick. And you can maybe see this better on the image stack. There's all this inflammatory change, kind of along the falciform ligament, right next to the gallbladder, but not necessarily in the gallbladder. And this is fatty falciform ligament appendage torsion, or F-flat, and this is on the spectrum of what Dr. Levinson just showed, epiploic appendicitis, appendagitis, or a mental infarct. But in this case, you have torsion of the extraperitoneal fat within the falciform ligament. And so you see the same sort of findings, except they're sitting right next to the gallbladder. And like those other entities, this is managed conservatively. Here's another case. This is a 61-year-old male with known hepatocellular carcinoma being treated with an anti-angiogenic agent, who presented with right upper quadrant pain. And you can see that as we scroll through his images, he's got multiple lesions in his liver. They're very heterogeneous, and there are these serpigenous areas of high attenuation within the tumors. All of the tumors looked bigger than the prior exam. And this is a different patient, but kind of the same story. So you can see, these are the pre-images. Multiple lesions in the pancreas was also being treated with an anti-angiogenic agent, and presented to the emergency department with the lesions looking much bigger and much more heterogeneous. And both of these patients have not worsening tumor or tumor progression, but intratumoral hemorrhage, which can be related to the neoplasm itself if it's hypervascular, classically described with HCC or adenoma, but also can be treatment-related. And we see it with some of our targeted chemotherapeutic agents, especially those that have vascular effects. We can also see it with things that we do, so local regional therapy or biopsy, and then finally, sometimes trauma is superimposed. So this was an 82-year-old male who presented after a fall. He had AFib, was on Coumadin, also had a history of liver disease. You can see that he's got a lot of hemoperitoneum here with a probable tumor that's actively bleeding, and this turned out to be an actively bleeding HCC. The bleeding was probably from the anticoagulation and the trauma. Here's another case. This was a 41-year-old woman who came in with pain, and you can see that she also has this bleeding, hepatic lesion with some active extravasation. And you can see some of her prior imaging. She had multiple enhancing lesions that we thought were adenomas that had been slowly growing over time. And we know that adenomas can bleed. It's hard to know exactly what the risk is, but when they get bigger, so in the four to five centimeter range, and when they're subcapsular like this, they tend to be higher risk. Here's another patient. This was a young woman who presented with pain. You can see she's got a big lesion in that blood. In this case, she has gas in it, even though it wasn't instrumented. So this one had blood and was super infected. And here's one more case. This is an 85-year-old woman, metastatic gallbladder cancer, who presented with sepsis. And here you can see she's got gas in a non-instrumented tumor. So these gas-forming infections can happen in the gallbladder, but they can also happen in the liver, and they can happen in tumors as well. And this was a super infected gallbladder met with a Clusterdale species. Here's another case that presented recently. This is a 37-year-old male. He was having more abdominal distension and leg swelling. And you can see as we scroll through his images, clearly he has new ascites. It kind of looks like he has some sort of hepatic venous outflow obstruction. It sort of looks like there's something here near his cabal atrial junction. And so he went on to get multiple images. You can see ultrasound, MR, PET. He got the full works here. And you can see that there is a mass in the suprahepatic IVC there that's causing a new onset blood Chiari syndrome. And he went on to get resection. You can see his growth specimen here. And this was a sarcoma of the IVC that was causing an acute blood Chiari, which is what brought him to the ED. And we can see a spectrum of causes for outflow obstruction in the liver. It can be a patient who has bland thrombus related to hypercoagulability. It can be tumor invasion, as we saw in our last case and the case I have here. Or it can be obstruction at the level of the sinusoids, which we see with some of our chemotherapeutic agents or our patients who have had stem cell transplant. And this can present acutely or go on to be a more chronic form. So here's another patient who presented with blood Chiari-like symptoms, 64-year-old male. You can see he's got a big renal cell carcinoma invading the renal vein, extending all the way up to the right atrium and causing a new blood Chiari. Another patient, this was a patient with liver disease. You can see that infiltrative HCC that's invading the hepatic veins in the IVC, another tumor-related blood Chiari. This patient was a 36-year-old woman on oral contraceptive. So this is your kind of more typical hypercoagulable history. You can see that she has this diffusely enlarged liver, which is what we typically see with blood Chiari. Often there's maintained or increased apparent central enhancement around the caudate because it often has its own venous drainage that's not occluded. And then you can see the liver that has outflow obstruction gets enlarged and low attenuation. And so you get sort of this differential enhancement. Often patients also present with new ascites. When it goes on to be chronic, we start to see these spiderweb collaterals as the liver tries to move around the thrombus. And patients can go on to develop fibrosis and portal hypertension with associated complications. So here's a patient she presented with an acute blood Chiari, but you can see that three years later, even with tips, she developed clear hepatic fibrosis, portosystemic collaterals, and spondyomegaly. So it had portal hypertension as a result of her blood Chiari. So in summary, there are a spectrum of causes of hepato, pancreatic, or obiliary pain. And we want to be aware of both the regular versions, but also the more complicated versions that can bring these patients to the emergency department. Thanks very much for your attention. Internal hernias are probably not a topic that most of you are excited about though. So we'll hopefully we'll help demystify them, explain them a little, and talk about how they really are challenging. And there's a wide variety of findings and imaging features. This picture is actually a picture of Cincinnati. It's not AI generated. This is during our every two year blink festival. Internal hernias, they're actually not that common. We all hear about them and we're all a little worried about finding one. I know that I didn't learn them well in residency. And I guess we're going to try and do that today. 6% of our small bowel obstructions are a result of internal hernias. However, what's important about them and why they're concerning or scary is because they have a much higher morbidity and mortality. Anatomic versus surgical. So the congenital fossa exist and historically were the most common reason for internal hernias and complications from internal hernias. However, now with the increase in Roux-en-Y, particularly gastric bypass surgeries, we're seeing a lot more post-surgical internal hernias. How do they present? Well, very often they are asymptomatic and we may find an internal hernia in a patient who came in for trauma or diverticulitis. And you'll see the internal hernia and it may behave just like a non-obstructed ventral hernia. Frustratingly for the patients, however, very often they're having symptoms. Those symptoms are vague. Those symptoms are colicky pain. Those symptoms can even resolve, come and go, because these hernias can reduce even though the patient is obviously unaware of it at the time they may reduce and have symptoms resolve. On CT, what we'll see is a loop or mass-like cluster of small bowel. Very often the small bowel is described surgically as being encapsulated. It's not necessarily something we can see on CT, but you get the idea that this is a well-organized cluster of particularly small bowel loops in a location where it's not normally seen. The most telling finding on CT, in my opinion, is the architectural distortion of the small bowel. The architectural distortion of the mesenteric fat and mesenteric vessels that we can see. If, however, there is an acute complication secondary to this internal hernia, we'll see our typical findings of small bowel obstruction or bowel ischemia where you'll have dilated bowel loops. You may have edema within the mesentery, engorgement of the mesentery. You may have decreased enhancement of bowel loops or if there is perforation, sequela of perforation, including free air or abscess. There are numerous types of internal hernias. We're gonna talk about these four. Certainly don't limit yourself to these. And even when I was reading the literature, you'll find an article where it'll say there are four different types of periodontal hernias, for example, but nobody talks about those four different types. What people really focus on is the internal hernias that are most likely to result in clinical complications. Historically, and this is what's quoted in most of the literature, is the historical prevalence of these different types of internal hernias. Periodontal hernias are by far the most common. Pericical, foramen of Winslow, and transmesenteric. Transmesenteric are the type of hernias that you get from a Roux-en-Y gastric bypass. So while those did exist before surgical intervention, they're now significantly more frequent. So periodontal hernias, historically, 53% of hernias. Interestingly, and unlike all other types of internal hernias, there is a sex predilection. It's three to one, male's more common. The left-sided hernias are also much more common than right-sided hernias. So we'll start off with those left-sided hernias. In this case, bowel prolapses through the foramen, or sorry, Lanzert's fossa, which is the left side Lanzert's fossa, which is present in about 2% of people. Patients typically, when they're not presenting acutely, patients will have a chronic postprandial pain that they experience. The fossa is located behind the fourth portion of the duodenum and extends towards the left, as the name would imply. It is posterior, and this is probably the most important thing to note when you're trying to identify it accurately on CT. It's posterior to the inferior mesenteric vein and the left colic artery. So you'll see, even if you don't see displacement of that vein, significant displacement, you will see bowel posterior to it, which is not normal. Illustration from the literature, and you have bowel here, you have our last portion of the duodenum, ligament of trites, and now you have these jejunal loops that extend to the left. They are posterior to the vessels here, the IMV, which is most reliably identified on CT. You can see displacement of other structures, such as the stomach or duodenal flexure, but typically I would say the most important thing to look for is the position of the IMV in relation to those bowel loops. This is a case of a left periduodenal hernia. As we start scrolling, you can see, see if we can move back just a smidge, you start seeing these bowel loops in an area where we're not typically used to seeing them, and what we see here that's important is that you have pancreas here, and bowel loops posterior to the pancreas. That's one of the key findings in these cases, and as we scroll down, the other thing we're seeing is that you have the IMV anterior, this is the inferior mesenteric vein, this is anterior to these bowel loops where the inferior mesenteric vein is actually normally right about here. So it's very posterior in the normal patient, and there typically isn't any bowel behind it. So this is really the giveaway, but one of those other features that I didn't mention on those didactic slides earlier was bowel posterior to the pancreatic tail. You can also see bowel between the stomach and pancreas, but this case is really a classic appearance of that type of hernia. Just took some still shots in case I wasn't able to freeze the video. This is that IMV in this case where it's displaced anteriorly. You can see the mesenteric, the architectural distortion of the mesenteric vessels. This is the IMV down in the pelvis. This is a more normal location for the IMV, and typically it just runs cranial-caudally along this plane. So clearly having it displaced here is abnormal. I grabbed a few of what I'm calling mimics, and these are cases that I found in our system where somebody described a finding as the type of hernia. However, it isn't actually the case. So in this particular patient, we have some bowel loops in the left abdomen where they, oops, excuse me, where they shouldn't necessarily be. However, if you're looking at this, you say, well, there is some bowel right there between the stomach and the pancreas, but as we scroll down, we can see that the inferior mesenteric vein is actually in the correct location where it should be here. And so we can tell that this is not actually a typical left periduodenal hernia. While there are a few other duodenal hernias and certainly transmesenteric hernias that can appear similar, this is not a left periduodenal hernia. So moving on to the right periduodenal hernias, these project through the Waldeyer's fossa, which is just to the right of midline. And again, we will have vessels that are going to be the most helpful feature for us when we're trying to identify this on CT. Waldeyer's fossa is present in about 1% or less than 1% of the population. And these patients will present clinically similar with chronic postprandial pain. Here's our image from the literature. We have bowel prolapsing through Waldeyer's fossa. It's just inferior to this third portion of the duodenum. So in these cases, these periduodenal hernias will be more caudal than our left periduodenal hernias. These are our vessels that we're keeping an eye out for. So you're looking out for some displacement of the superior mesenteric vessels. So this is a case where the patient did have surgery. However, they also have some abnormal proximal duodenum, but they also have herniation of the right periduodenal hernia. And you can see displacement of the mesenteric vessels as they're getting pushed anteriorly. And this is the mesentery that's heading into that defect right here. I don't think we're gonna be able to scroll that that easily. But you've got this. This is our mesenteric architectural distortion in this particular case. Another case where we're seeing, whoops. This patient doesn't have any acute abnormality associated with their internal hernia. However, well, I'm sorry, they actually do. But there's a very large cluster of small bowel loops. This is also distorting the superior mesenteric vasculature. And so here is an end lying in close approximation to that third portion of the duodenum. So this is another right periduodenal hernia. Now we have a few mimics where this was called on report a right periduodenal hernia. However, what we can see most clearly is that the location of our superior mesenteric vessels remains essentially normal. Now you're seeing some swirling of the mesentery and you will see that they're abnormally located small bowel loops. However, this is not a case of a right periduodenal hernia. Another one of those mimics. Clearly, there are abnormal small bowel loops in this particular case. I think that it's likely adhesions. But was initially thought to reflect a right periduodenal hernia. You can see here that the mesenteric vessels, the SMV, is normally positioned. So if you're a resident and studying for boards, how do you keep this straight? Left periduodenal hernia, Lanzer's fossa, right periduodenal hernia, Waldeyer's fossa. We'll just spell right a little bit differently. Moving on to paracecal hernias, these are really much, much simpler. We're not dealing with quite as much of the complexity of the anatomy of the upper abdomen. These, you're looking at predominantly ilial bowel loops that herniate posterior to the cecum. They'll displace the cecum anteriorly or medially. And it's generally fairly apparent when you're seeing one of these hernias. Our first patient. This is the ascending colon here. It's being displaced medially. These are all the bowel loops that are being positioned laterally. I'll scroll through that. Very atypical to see all those small bowel loops lateral to the colon. Again, this is our ascending colon. These are our bowel loops. The colon, basically at the hepatic flexor, takes a hard detour and heads medially to make room for that herniated small bowel. Here's another patient. This was an interesting case because we had a couple things going on at the same time. This is a patient who had a herniated small bowel. This is a patient who had a herniated small bowel and a herniated small bowel. This is what's going on at the same time. This patient had a paracecal hernia, but they also had appendicitis. So this is the appendix. This is the cecum that's been displaced. And these are our laterally positioned bowel loops. Even more interesting is that, if you remember these images, just see if we can move forward here. We have our laterally positioned small bowel loops, our appendix, and our cecum. This is one day later, and the patient's paracecal hernia has resolved. Their appendicitis has not. But you can see how different a position— sorry about that— how different a position the appendix and cecum are compared to the initial study. Now our colon is lateral and our small bowel is medial. And you can see the appendix right here. So these do resolve. These do reduce spontaneously in many instances. These are just some still shots that I took in case I couldn't freeze the videos like I just couldn't. Our colon is here. Our appendix now here. Appendix here. So this demonstrates nicely how quickly these hernias can reduce. Foramen of Winslow hernia, if there's one foramen that's the most famous, this is it. Congenital communication between the greater and lesser sac account for 8% of all internal hernias. So the foramen of Winslow is inferior to the caudate lobe, anterior to the inferior vena cava, superior to the second portion of the duodenum, and posterior to the hepatic artery and portal vein. It's still not necessarily that easy to identify on imaging, and we'll look at a few cases where we can see hernia kind of from different directions. Here's a diagram. This is our foramen of Winslow, small bowel, transverse colon, and this is our lesser sac. So the lesser sac can actually, you know, it can expand a fair amount, especially when you jam it full of small bowel. So we'll see some, we'll see a case like that. This is a patient with a foramen of Winslow hernia. And what we have essentially is the mesentery is heading cranially, basically, as you can see the open, you can see the distortion of the mesenteric vessels in the midline, and those bowel loops are heading cranially into that left upper quadrant. And this is one of the challenges is that the foramen of Winslow hernias can mimic a left periduodenal hernia, even though that doesn't logically make sense, because you think of the foramen of Winslow as being a slightly right-sided structure, but those bowel loops can end up left of midline and look like a left periduodenal hernia. This is another case, a similar case, though the neck of the hernia appears a bit tighter. We can get to right here, you can see that this is where the vessels and bowel loops are entering the hernia. You also have pneumatosis in this case. So this patient is fairly critical because of this hernia. It's another case where we're seeing large bowel. Now, typically, these hernias contain small bowel. However, in this case, you're seeing a small amount of large bowel being pulled medially here into that hernia sac in this patient, who does not have an obstruction, or actually it may. But it's certainly a very different appearance, and that's one of the challenges with internal hernias, is that even the formative Winslow hernias, for example, are going to look a lot different. The past two patients had large amounts of small bowel within that left upper quadrant region, and this patient has a small amount of small bowel and a portion of their large bowel, which is more midline. Our final type of hernia is the transmesenteric hernia. This is now the most common. These are essentially post-surgical hernias in adults. In children, they've always been the most common type. But I don't see children, so I don't have much experience with that. Typically, these complications result fairly distant from surgery. So the more Roux-en-Y procedures we do, the greater in frequency, the more we'll see of these. Part of the issue is that the mesocolic defect created in surgery is maybe incompletely closed. The suture material may break down, and when the patients lose a lot of weight, it's noted that that defect can enlarge. Additional cause for an increase in this, and a reason for seeing this 10 to 14 months down the road, is that it's hypothesized that this hernia is sort of dilated by bowel loops that kind of enter it and reduce, and enter it and reduce, so kind of repeated dilation of that fossa. Three different types. The most common type is the transmesocolic. You're typically going to find bowel loops in the left upper quadrant, causing mass effect on the gastric remnant, and the small aperture of this defect is hypothesized to be a reason that these patients have quite a few complications. The Peterson type, I think, is fairly rare now, because I think that this surgical approach is not as popular. So we'll look at a couple of these. This particular patient, clearly there's an abnormality here. Their remnant and their pancreatic ovary limb are dilated, with dilated bowel loops extending all the way down into the pelvis. Unfortunately, on surgery, this patient was found to have ischemic pancreatic ovary limb. This is another patient who had a gastric bypass, a very different appearance. Clearly there's abnormal bowel, but it's more midline and lower, and we can better appreciate it on our sagittal, where you can see these abnormal bowel loops, and our mesentery herniating through the defect right here. It's a bit wider mouth defect, but there's obviously mesenteric engorgement and abnormality within these bowel loops that extend anteriorly and inferiorly. Postoperative changes of RU and Y are not the only cause of small bowel internal hernias. This is a patient that had a C-section and now has significant small bowel. They have clearly abnormal small bowel here, anterior to the uterus, with the mesentery. You can see the mesenteric architectural distortion extending anterior to that uterus. This patient had a cesarean section, as we said, so there's certainly a lot more going on in their abdomen, and unfortunately for this patient, those bowel loops were dead when they went to the OR. So we're seeing a lot of misplaced bowel loops here, anterior to the uterus. It's clearly abnormal on CT. Another interesting case, as we talk about trauma being a potential cause for internal hernias, this patient actually had herniation of small bowel into their retroperitoneum, essentially into their renal fossa, which is certainly an unusual finding. They also had a complicated congenital abnormality of their kidney that made this diagnosis more challenging, but trauma is certainly a potential. This is another interesting case that I saw very recently, where a patient had an internal hernia. As you can see, there's small bowel lateral to the colon. This was their presentation, and one day late, 16 hours later even, those bowel loops were abnormal looking. I read this study, suggested that there was ischemia or a vascular issue. The patient went to the OR, and it turned out that all of this was the result of a CT occult gallbladder injury and the reactive changes from the bile bath the bowel was receiving. Hopefully that helps demystify internal hernias, and I thank you for your attention.

acute lower abdominal pain

CT imaging

gastrointestinal causes

appendicitis

diverticulitis

epiploic appendicitis

Meckel's diverticulitis

diagnostic challenge

Beth Israel Deaconess Medical Center