Imaging Pearls ❯ Colon ❯ Inflammatory Bowel Disease
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- Severe inflammation may result in mural ulcers, and penetrating complications such as inflammatory mesenteric mass, sinus tract, abscess, and fistula. The hallmark of Crohn’s disease is multifocal segmental involvement of the bowel with intervening areas of normal appearing bowel, also called ‘skip lesions’. The terminal ileum is the most commonly involved part of the bowel followed by distal and mid ileum and ascending colon; however, any part of the small or large bowel can be affected. Long-standing Crohn’s disease can develop bowel strictures characterized by luminal narrowing of the involved segment and upstream bowel dilatation, sacculation, and intramural fat deposition. Mildly enlarged reactive mesenteric lymph nodes are commonly seen in Crohn’s; however, bulky lymphadenopathy is uncommon
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Ulcerative colitis is characterized by diffuse contiguous mucosal inflammation of the colon, predominantly affecting the rectum. The cross-sectional imaging feature seen in acute ulcerative colitis is symmetric oedematous mural thickening of the colon referred to as ‘target or double halo sign’ due to its stratified appearance. The target sign describes stratified mural thickening with alternating hyperattenuating mucosa and serosa and hypoattenuating submucosal edema. This appearance is nonspecific and may be encountered in a variety of infectious, inflammatory, ischemic, and immune-mediated enterocolitides.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Long-standing ulcerative colitis can lead to luminal narrowing with loss of haustrations making the colon appear featureless called as ‘lead pipe colon’. Inflammation of the terminal ileum is seen in severe ulcerative colitis and causes patulous inflamed ileo-cecal junction called as backwash ileitis. Skip areas of inflammation which is a characteristic of Crohn’s disease is not typical for ulcerative colitis. Similarly, the presence of fistulizing disease favours’ Crohn’s disease over ulcerative colitis. The most dreaded complication of ulcerative colitis are toxic megacolon and perforation. There is a significant risk correlation between long-term ulcerative colitis and colonic cancer.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Toxic megacolon may affect a focal colonic segment or involve the entire colon. Toxic megacolon is diagnosed as total or segmental non-obstructive colonic dilation (dilation of the colon more than 6 cm) with systemic toxic features. The systemic features required include at least 3 of the following: fever (> 38 degrees Celsius), pulse rate over 120beats/min, neutrophilic leucocytosis exceeding 10500/micro/l, or anemia. Furthermore, at least one of the following: dehydration, altered sensorium, electrolyte disturbances, and hypotension.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Viral gastroenteritis is usually a self-limiting illness; however, it can be debilitating and life-threatening in immunocompromised patients. Norovirus is the most common causative pathogen responsible for acute gastroenteritis in the United States, both in immunocompetent and immunocompromised hosts. It clinically presents as copious watery diarrhoea, vomiting, stomach pain, and fever. Imaging features seen on cross-sectional imaging are nonspecific including distended fluid-filled stomach and small bowel mimicking paralytic ileus or low-grade obstruction. However, the presence of small bowel edema, mural hyperenhancement and mesenteric lymphadenopathy supports the diagnosis . Laboratory confirmation is achieved through the detection of virus-specific antigens or RNA in stool samples.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - The classic finding of vasculitis includes abnormal wall thickening, fat stranding of the mesenteric arteries with or without vascular wall irregularity, luminal narrowing, and microaneurysms. On CT, the bowel findings of mesenteric vasculitis include circumferential thickening of the intestinal wall and mucosal folds resembling a ‘stack of coins’, luminal dilation, submucosal edema, abnormal bowel enhancement, intramural hemorrhage, mesenteric edema, and signs of bowel ischemia in acute presentation. Vasculitis can result in lupus enteritis, which typically manifests as diffuse stratified thickening and mural enhancement of the small bowel due to submucosal edema, often accompanied by mesenteric edema and ascites.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Vascular ischemia, whether arterial or venous in origin, typically presents with acute abdomen or subacute- chronic abdominal pain, often in the setting of cardiovascular risk factors or prothrombotic states. While not a primary cause of enterocolitis, its imaging manifestations may overlap with those seen in ischemic enterocolitis, making recognition essential in the emergency setting. Similarly, hypoperfusion complex does not represent a true enterocolitis but may radiologically mimic it due to bowel wall thickening and mucosal enhancement abnormalities in the context of systemic hypoperfusion. For the radiologist, distinguishing these mimickers is crucial, as they often necessitate different clinical management pathways
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Arterial ischemia accounts for 40–50% cases of acute mesenteric ischemia and can occur due to arterial thrombosis or embolism. The most common underlying risk factors for emboli formation are cardiovascular conditions such as heart failure, myocardial infarction, cardiomyopathies, and atrial fibrillation . Superior mesenteric artery is the most susceptible artery for emboli, typically, distal to its first jejunal branch, due to acute angle origin from the aorta and high-velocity flow giving rise to a classic ischemic pattern that spares the proximal small intestine . Risk factors for mesenteric ischemia due to arterial thrombosis include atherosclerosis, dyslipidemias, hypertension, diabetes and an estrogen-based oral contraceptive.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - On routine portal-venous phase CT, signs of hypoperfusion complex include decreased enhancement of the solid organs such as spleen and liver with increased enhancement of the bowel mucosa (Fig. 16a, b) due to splanchnic autoregulation, and hyperenhancement of the adrenal glands due to sympathetic response. In addition, there is reduction in the caliber of the aorta (less than 1.3 cm in diameter when measured approximately 1 cm below the origin of superior mesenteric artery), flattening of IVC (less than 9 mm AP diameter of the intrahepatic and infra-renal IVC) with circumferential zone of low attenuation fluid around the IVC and pancreas due to a hyper-permeable state secondary to a systemic inflammatory response syndrome, referred to as the “Halo sign”. Small bowel loops may be fluid-filled, occasionally dilated and thickened . The colon is typically normal appearing. At least 2 or more vascular, visceral, or parenchymal signs are necessary to establish the presence of a CT hypo perfusion complex .
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Neutropenic colitis, formerly referred to as typhlitis, occurs in patients with neutropenia, most commonly those undergoing chemotherapy for malignancy, following hematopoietic stem cell transplantation, or receiving other forms of immunosuppressive therapy. In its early stages, the inflammatory process is typically confined to the mucosa, manifesting as diffuse hyperemia, ulceration, and edema, most prominently involving the right colon, particularly the cecum and ascending colon. However, any segment of the colon may be affected [61]. As the disease progresses, it may evolve into transmural inflammation, resulting in bowel wall necrosis and eventual perforation, a complication associated with high mortality. Given this potentially fulminant course, prompt radiologic evaluation is essential for early diagnosis and appropriate management.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Since the small bowel is very sensitive to radiation therapy, high dosage abdominal-pelvic radiation therapy causes bowel wall injury and dysfunction, which can lead to long-term chronic complications. On CT, acute radiation enteritis resembles both inflammatory bowel disease and ischemic enteritis. Cross-sectional imaging aids in determining the segmental extent of the afflicted bowel lumen and any consequences such as stricture or fistula formation, localized abscess, or ureteral dilatation.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - Acute enterocolitis presents a diagnostic challenge due to its wide range of etiologies and overlapping clinical features. In this landscape of uncertainty, CT emerges as a powerful tool, providing critical clues that not only help differentiate causes but also guide clinical management. For the emergency radiologist, particular attention should be directed to time-sensitive entities such as mesenteric ischemia, which may not always demonstrate an intraluminal filling defect, and C. difficile colitis, which is critical to recognize due to its association with toxic megacolon. Awareness of pitfalls is essential, as nonspecific findings such as bowel wall thickening and the target sign can occur across infectious, inflammatory, and ischemic processes.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988
- It is important to note that most cases of enterocolitis are self-limiting and do not routinely require cross-sectional imaging. Indications for CT arise in patients with severe abdominal pain, peritoneal signs, systemic toxicity, or sepsis, as well as in those with underlying comorbidities or immunosuppression. Imaging is also justified in cases of diagnostic uncertainty, atypical presentations, failure to improve with conservative management, or when complications such as perforation, ischemia, or toxic megacolon are suspected.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Inflammatory bowel disease (IBD) is a non-infectious cause of chronic relapsing–remitting gastrointestinal inflammation that occurs due to the combination of genetic, host, and environmental factors. IBD has a rising worldwide prevalence affecting 2.4–3.1 million people in the United States [6]. Crohn’s disease and ulcerative colitis constitute the two principal subtypes of inflammatory bowel disease (IBD), both commonly presenting with abdominal pain, diarrhea, and weight loss, with or without gastrointestinal bleeding in the form of melena or hematochezia. Acute gastroenteritis may serve as the initial clinical manifestation in patients with previously undiagnosed IBD, or may represent an acute exacerbation in those with established disease.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Severe inflammation may result in mural ulcers, and penetrating complications such as inflammatory mesenteric mass, sinus tract, abscess, and fistula. The hallmark of Crohn’s disease is multifocal segmental involvement of the bowel with intervening areas of normal appearing bowel, also called ‘skip lesions’[9]. The terminal ileum is the most commonly involved part of the bowel followed by distal and mid ileum and ascending colon; however, any part of the small or large bowel can be affected. Long-standing Crohn’s disease can develop bowel strictures characterized by luminal narrowing of the involved segment and upstream bowel dilatation, sacculation, and intramural fat deposition. Mildly enlarged reactive mesenteric lymph nodes are commonly seen in Crohn’s; however, bulky lymphadenopathy is uncommon.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Toxic megacolon may affect a focal colonic segment or involve the entire colon. Toxic megacolon is diagnosed as total or segmental non-obstructive colonic dilation (dilation of the colon more than 6 cm) with systemic toxic features. The systemic features required include at least 3 of the following: fever (> 38 degrees Celsius), pulse rate over 120beats/min, neutrophilic leucocytosis exceeding 10500/micro/l, or anemia. Furthermore, at least one of the following: dehydration, altered sensorium, electrolyte disturbances, and hypotension. Abdominal radiographs and computed tomography (CT) typically demonstrate marked colonic dilatation-defined as a transverse diameter exceeding 6 cm-often accompanied by air-fluid levels .
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - A plain abdominal radiograph may reveal a dilated colon with the classic thumbprinting sign, indicative of submucosal edema and inflammation . Once pseudomembranous colitis is clinically suspected, radiographs serve a valuable role in serial monitoring to assess for progressive colonic dilatation and to identify complications such as perforation or toxic megacolon. CT provides a more detailed assessment, typically demonstrating diffuse or segmental colonic dilatation with edematous mural thickening. Pan colitis, is usual with this particular bacterial infection. Thickened haustral folds may be visualized, producing the characteristic thumbprinting sign, and in some cases, the accordion sign, reflecting trapped oral contrast between thickened haustral folds. These features are characteristic of pseudomembranous colitis but not pathognomonic. Peri-colonic fat stranding and ascites are commonly present in ancillary features.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Whipple disease is a multisystemic infection caused by the Tropheryma whipplei bacteria resulting in a constellation of insidious clinical features including abdominal pain, diarrhoea, weight loss, arthralgia, anemia, and lymphadenopathy. The classic imaging findings seen with Whipple disease are edematous wall thickening of the proximal small bowel, with or without nodular appearance; fluid distended bowel loops, characteristic low attenuation mesenteric lymphadenopathy and ascites. On ultrasound, the mesenteric lymphadenopathy appears typically hyperechoic, and the involved small bowel demonstrates loss of normal mural stratification. The gold standard test for diagnosis is histopathologic examination with periodic acid-Schiff (PAS) staining.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - GI tuberculosis accounts for 1 to 3% of all tuberculosis cases worldwide and is frequently caused by the dissemination of primary pulmonary infection; however, infrequently it can present as an isolated gastrointestinal infection.The ileocecal region is involved in 90% of the cases, however, any part of the gastrointestinal tract can be involved, including the colon and rectum. The classic CT features are circumferential asymmetric thickening of the ileocecal junction, terminal ileum and cecum that can lead to luminal narrowing and multifocal skip involvement of the small bowel similar to Crohn's disease. The presence of necrotic mesenteric necrotic lymphadenopathy, peritoneal thickening, peritoneal nodules, and ascites favour tuberculosis over Crohn’s disease. Peritoneal involvement can result in thickening of the peritoneum encasing the bowel loops, central clustering or matting of the bowel loops and obstruction
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - CT findings of parasite-infested intestine are non-specific with thickened, edematous bowel wall and effacement of mucosal folds. Worms such as Ascaris can be seen as elongated luminal filling defect in a contrast filled bowel on CT studies or as mobile echogenic linear intraluminal strips with acoustic shadowing on ultrasound. The worms typically demonstrate a "triple line" sign on ultrasound with a central anechoic tube (gut of the worm) between parallel echogenic lines. Parasitic infection of the GI tract can result in bowel obstruction, mesenteric inflammation and lymphadenopathy, and extra-intestinal complications like recurrent cholangitis, liver abscess, and pancreatitis due to the migration of worms into the biliary tract. Massive worm accumulation can result in occlusion of mesenteric vasculature, leading to intestinal infarction and gangrene.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - The classic finding of vasculitis includes abnormal wall thickening, fat stranding of the mesenteric arteries with or without vascular wall irregularity, luminal narrowing, and microaneurysms. On CT, the bowel findings of mesenteric vasculitis include circumferential thickening of the intestinal wall and mucosal folds resembling a ‘stack of coins’ , luminal dilation, submucosal edema, abnormal bowel enhancement, intramural hemorrhage, mesenteric edema, and signs of bowel ischemia in acute presentation . Vasculitis can result in lupus enteritis, which typically manifests as diffuse stratified thickening and mural enhancement of the small bowel due to submucosal edema, often accompanied by mesenteric edema and ascites.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - The incidence of immunotherapy-related enterocolitis is increasing, paralleling the growing use of immune checkpoint inhibitors in the treatment of various malignancies. Commonly implicated agents include Ipilimumab, Pembrolizumab, Nivolumab, Atezolizumab, Durvalumab, Avelumab, and Tremelimumab. Among these, colitis is more frequently observed than isolated small bowel enteritis, with diarrhea being the predominant clinical manifestation. On cross-sectional imaging, the most frequently encountered findings include segmental or diffuse colonic wall edema, luminal distension, mural hyperenhancement, and pericolic fat stranding—features reflective of active inflammation. Small bowel inflammation can present with diffuse inflammation or multifocal segmental inflammation mimicking Crohn’s disease. Optimal management of immune-mediated enterocolitis requires early recognition, and timely use of immunosuppressive agents, often requiring cessation of the immunotherapy in symptomatic patient.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Arterial ischemia accounts for 40–50% cases of acute mesenteric ischemia and can occur due to arterial thrombosis or embolism. The most common underlying risk factors for emboli formation are cardiovascular conditions such as heart failure, myocardial infarction, cardiomyopathies, and atrial fibrillation [54, 55]. Superior mesenteric artery is the most susceptible artery for emboli, typically, distal to its first jejunal branch, due to acute angle origin from the aorta and high-velocity flow giving rise to a classic ischemic pattern that spares the proximal small intestine [56]. Risk factors for mesenteric ischemia due to arterial thrombosis include atherosclerosis, dyslipidemias, hypertension, diabetes and an estrogen-based oral contraceptive [55]
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - These account for nearly 10% of cases of intestinal ischemia. They can present up to 1–4 weeks after onset with non-specific symptoms such as abdominal pain and diarrhea. Nearly 60% of patients have a prior diagnosis of peripheral venous thrombosis or pulmonary embolism. Contrast-enhanced CT scan typically demonstrates a filling defect in the mesenteric vein with rim enhancement of the venous wall, often with prominent collateral veins in the mesentery. The bowel wall is significantly thickened in cases of venous ischemia, unlike the thinned-out wall seen in arterial-associated ischemia. The continuous inflow of arterial flow with an impeded venous outflow results in an increased intramural hydrostatic pressure and hypoattenuating edema with the submucosa layers presenting as the “target sign”. Due to the prolonged nature of the condition, there is usually prominent peri-enteric fat stranding and oedema.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - On routine portal-venous phase CT, signs of hypoperfusion complex include decreased enhancement of the solid organs such as spleen and liver with increased enhancement of the bowel mucosa due to splanchnic autoregulation, and hyperenhancement of the adrenal glands due to sympathetic response. In addition, there is reduction in the caliber of the aorta (less than 1.3 cm in diameter when measured approximately 1 cm below the origin of superior mesenteric artery), flattening of IVC (less than 9 mm AP diameter of the intrahepatic and infra-renal IVC) with circumferential zone of low attenuation fluid around the IVC and pancreas due to a hyper-permeable state secondary to a systemic inflammatory response syndrome, referred to as the “Halo sign”. Small bowel loops may be fluid-filled, occasionally dilated and thickened. The colon is typically normal appearing. At least 2 or more vascular, visceral, or parenchymal signs are necessary to establish the presence of a CT hypo perfusion complex.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press) - Features of neutropenic colitis seen on CT are circumferential wall thickening, peri-colonic fat stranding, and free-fluid predominantly in acute cases. Severe cases can show cecal pneumatosis, necrosis, mesenteric abscess formation, and perforation. Although it is difficult to differentiate it from other causes of enterocolitis, predominant inflammation of the right colon in a patient with neutropenia should raise concern for neutropenic colitis.
CT patterns of acute enterocolitis - a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra · Pranav Ajmera · Ashish Khandelwal
Emergency Radiology 2025 (in press)
- “Mycophenolate mofetil (MMF), an immunosuppressive, is a pharmacologically inactive compound of mycophenolic acid, which has been widely used in solid organ transplant and autoimmune conditions. It mostly exerts gastrointestinal (GI) adverse effects, which include diarrhea, abdominal pain, nausea, and vomiting. It can lead to MMF-colitis, a challenging condition to diagnose due to its similarity with other GI-related conditions and infections. This case report discusses a heart transplant recipient who developed severe MMF-induced colitis. It adds significantly to the limited literature available for this difficult-to-diagnose condition. It also highlights the severity of the condition and underscores the importance of vigilant monitoring and the need for future cohort studies to set guidelines for diagnosing and treating MMF-associated colitis due to its widespread use.”
Mycophenolate-associated colitis in an orthotopic heart transplant patient- an unusual case presentation
Hajra Arshad, Mohammad Yasrab, Alejandra Blanco, Jacqueline E Birkness-Gartman, Elliot K. Fishman
R a d i o l o g y Cas e R e p o r t s 2 0 ( 2 0 2 5 ) 1 8 2 2 – 1 8 2 6 - “Mycophenolate Mofetil (MMF), a prodrug of the immunosup- pressant mycophenolic acid, is used in various solid organ and bone marrow transplants and for treating autoimmune con- ditions such as lupus nephritis, autoimmune hepatitis, myas- thenia gravis, and autoimmune cytopenia. Lymphocytes are dependent mostly on de novo purine synthesis and thus are affected by mycophenolate the most, as it inhibits IMPDH, the rate limiting enzyme in purine synthesis. However, enterocytes rely around 50% on de novo purine synthesis and the dependency increases in conditions of anorexia, thus they are affected by MMF’s inhibition of this pathway. As seen in our patient, she had decreased oral intake, which could have contributed to the disease process.”
Mycophenolate-associated colitis in an orthotopic heart transplant patient- an unusual case presentation
Hajra Arshad, Mohammad Yasrab, Alejandra Blanco, Jacqueline E Birkness-Gartman, Elliot K. Fishman
R a d i o l o g y Cas e R e p o r t s 2 0 ( 2 0 2 5 ) 1 8 2 2 – 1 8 2 6 - “With advances in medicines and an increase in organ transplants, Mycophenolate mofetil is widely being used in post- transplant immunosuppression. Despite the pros, the gastrointestinal (GI) side effects are a major con to its use. As radiologists become more cognizant of the GI complications associated with MMF, they are increasingly identifying cases of MMF-related colitis—an infrequent but complex condition that is often difficult to diagnose. The limited existing literature on MMF colitis underscores the importance of reporting these cases. By documenting and studying such instances, we can enhance our understanding of this condition, improving our ability to diagnose and manage affected patients effectively in the future.”
Mycophenolate-associated colitis in an orthotopic heart transplant patient- an unusual case presentation
Hajra Arshad, Mohammad Yasrab, Alejandra Blanco, Jacqueline E Birkness-Gartman, Elliot K. Fishman
R a d i o l o g y Cas e R e p o r t s 2 0 ( 2 0 2 5 ) 1 8 2 2 – 1 8 2 6
- “The use of diverse types of drugs can result in a variety of acute and chronic complications that affect almost any organ. The bowel is one of the organs impacted by the side effects of medications. Imaging frequently plays a crucial role in the detection and characterization of complications occurring in the bowel. They include pseudomembranous colitis or antibiotic-associated colitis; angioedema induced by angiotensin-converting enzyme inhibitors; nonsteroidal anti-inflammatory drug-induced enteropathy; cocaine toxicity; clozapine-induced hypomobility; and bowel toxicity induced by chemotherapeutic agents. It is imperative that radiologists are fully aware of these complications and toxicities as well as the relevant findings.”
Drug‐induced bowel complications and toxicities: imaging findings and pearls
Sitthipong Srisajjakul et al.
Abdominal Radiology (2022) https://doi.org/10.1007/s00261-022-03452-1 - ”Pseudomembranous colitis (PMC) is a form of acute colitis. It usually presents as a complication of antibiotic treatment, especially clindamycin and second- and third-generation cephalosporins and fluoroquinolones. Other possible but less common causes of PMC are abdominal surgery, uremia, colonic obstruction, and prolonged hypotension. A clostridium difficile (C. difficile) infection with toxin production (toxins A [enterotoxin] and B [cytotoxin]) is the culprit in most cases of PMC. Pathologically, the toxins stimulate the immune system by recruiting neutrophils to invade the colonic mucosa.”
Drug‐induced bowel complications and toxicities: imaging findings and pearls
Sitthipong Srisajjakul et al.
Abdominal Radiology (2022) https://doi.org/10.1007/s00261-022-03452-1 - ”CT is immensely helpful in diagnosing PMC, particularly when the disease is not clinically suspected. The most common CT finding is wall thickening, which usually ranges from 3 to 32 mm in diameter (mean 14.7 mm). The degree of wall thickening is generally greater than other inflammatory or infectious forms of colitis, and is typically diffuse in distribution. The accordion sign, when detected, is highly suggestive of PMC, but it can only be detected in advanced cases.”
Drug‐induced bowel complications and toxicities: imaging findings and pearls
Sitthipong Srisajjakul et al.
Abdominal Radiology (2022) https://doi.org/10.1007/s00261-022-03452-1 - ”Imaging findings include diffuse thickening of the small bowel wall, hyperenhancement of the mucosal layer, and submucosal edema (target sign). Long segments of the small bowel tend to be involved, with a jejunal predilection. Other associated findings are fluid accumulation that results in dilatation of the small bowel lumen, preservation of luminal transit, mesenteric vascular engorgement, and ascites. Scheirey et al. described a straightened small bowel wall, which was believed to be related to a primary increase in tissue turgor (i.e., stiffening) of the small bowel wall.”
Drug‐induced bowel complications and toxicities: imaging findings and pearls
Sitthipong Srisajjakul et al.
Abdominal Radiology (2022) https://doi.org/10.1007/s00261-022-03452-1
- Infectious Colitis: Location
- Pseudomembranous Colitis
• Clostridium difficile overgrowth
• Often due to antibiotic use
• Most commonly involves entire colon (pancolitis)
• may be limited to right colon in up to 40%
• CT signs:
• Significant wall thickening (can be > 3cm)
• Irregular or eccentric wall thickening
- Mural hypoattenuation (edema) or hyperattenuation (acute inflammation)
- Thumbprinting- thickened haustra
- “Accordion sign”- oral contrast between thickened haustra 
- CT of IBD: Crohn’s vs UC
- “ Inflammatory bowel disease (IBD) is a fairly common enteropathy that occurs in one per 1000 people in developed countries. The etiology of IBD is still unknown. The peak incidence of IBD is between the ages of 15 and 40 years, with a possible second peak between 50 and 80 years. Although controversial, several studies have reported a slight female predominance in Crohn disease and a male predominance in ulcerative colitis.”
Inflammatory Bowel Disease: Current Role of Imaging in Diagnosis and Detection of Complications Pedro Sergio Brito Panizza et al. RadioGraphics 2017; 37:701–702 - “The inflammatory mesentery group corresponds to three main findings: lymphadenopathy, fat changes, and engorged vasa recta. Reactive mesenteric lymphadenopathy can be characterized by nu- merous hyperenhancing small mesenteric lymph nodes. Fat changes represent fat stranding, which is a marker of active disease, and fibrofatty proliferation that is usually seen in patients with long-standing disease. Engorged vasa recta, also known as the “comb” sign, can be found surrounding the involved intestinal loop.”
Inflammatory Bowel Disease: Current Role of Imaging in Diagnosis and Detection of Complications Pedro Sergio Brito Panizza et al. RadioGraphics 2017; 37:701–702 - “The bowel wall disorders group represents three findings: wall thickening, strati cation, and permanent structural changes. Wall thickening is present in almost all patients with IBD, and evaluation of the thickening pattern and mural stratification provides important data to differentiate active from inactive disease. The “lead pipe” sign is the most important permanent structural change, represented by loss of haustrations in the colon, which is frequently related to ulcerative colitis.”
Inflammatory Bowel Disease: Current Role of Imaging in Diagnosis and Detection of Complications Pedro Sergio Brito Panizza et al. RadioGraphics 2017; 37:701–702 - “The disease complications group is striated into two subgroups: luminal complications (strictures, dilatations, and cancer) and extraluminal complications ( fistula, abscess, and perforation or toxic megacolon). Half of the patients with Crohn disease have intestinal complications within 20 years of disease onset. Strictures occur because of long-standing inflammation, may vary in length, and
are commonly associated with proximal bowel dilatation.”
Inflammatory Bowel Disease: Current Role of Imaging in Diagnosis and Detection of Complications Pedro Sergio Brito Panizza et al. RadioGraphics 2017; 37:701–702 - “Colorectal cancer has a much higher inci- dence in patients with IBD, and it occurs most often in the rectosigmoid, being that lymphoma
is more prevalent when there is involvement of the small bowel. Other important related cancers are cholangiocarcinoma and melanoma. Perforation and toxic megacolon represent the two main conditions that require emergency surgery.”
Inflammatory Bowel Disease: Current Role of Imaging in Diagnosis and Detection of Complications Pedro Sergio Brito Panizza et al. RadioGraphics 2017; 37:701–702
- “Acute colitis with megacolon occurs in approximately 10% of patients with ulcerative colitis and 2.3% with Crohn colitis. The definition of a megacolon varies between 5.5 and 8 cm depending on the author and the location of segment along the course of the colon. Most clinicians consider a colonic lumen greater than 6 cm to be a megacolon when colitis is present.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271 - “The findings of a severe colitis on plain films and cross-sectional imaging (usually CT) include nodular or asymmetric fold thickening, submucosal edema, effacement of the fold pattern with thinning of the colonic wall, pericolonic soft tissue changes and/or edema, and uncommonly free intraperitoneal gas.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271 - “When there has been thrombosis of a major vein, such as the superior mesenteric vein, cross- sectional imaging generally shows a long segment of symmetric small bowel wall thickening with mucosal hyperenhancement and submucosal low attenuation caused by edema. There is often adjacent mesenteric fat edema as well as ascites. If intravenous contrast has been injected, thrombus in the vein will be identified. Depending on the de- gree of ischemia and infarction, there may be pneumatosis and/or portal venous gas.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271 - “In general, infections can affect both the small and large bowel. In the colon, most infections can cause a pancolitis. Right-sided disease tends to occur in Campylobacter, Salmonella, Yersinia, tuberculosis, and amebiasis. Left-sided disease tends to occur in schistosomiasis, shigellosis, herpes, gonorrhea, syphilis, and lymphogranuloma venereum. Cytomegalovirus (CMV) and Escherichia coli tend to be diffuse.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271 - “Neutropenic colitis is an inflammatory process affecting the right colon, especially the cecum and terminal ileum in neutropenic patients. The neutropenia in most cases results from chemotherapy, commonly high-dose chemo- therapy used for patients after bone marrow transplant. When acutely ill with a fever and abdominal tenderness, these patients are commonly evaluated with CT.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271 - “On CT, the cecum and/or right colon is thick walled and may have pneumatosis. There is pericolonic soft tissue stranding and often pericolic gutter fluid. It is often impos- sible to determine whether these findings are caused by neutropenic colitis or pseudomembranous colitis because these patients are both neutropenic and C difficile positive. Even so, patients are managed conservatively unless they show signs of toxicity.”
Acute Infectious and Inflammatory Enterocolitides Baker ME Radiol Clin N Am 53 (2015) 1255–1271
- “Clinical guidelines often recommend imaging of the abdomen with CT for the acute presentation of LUQ pain, given the relatively broad differential diagnosis for left upper quadrant abdominal pain, some of which are potentially life- threatening. While renal and adrenal causes of abdominal pain more classically localize to the flanks, acute disease in these organs results in referred pain to the upper quadrants often enough to merit inclusion in the differential diagnosis.”
Computerized tomography of the acute left upper quadrant pain Tirkes T et al. Emerg Radiol DOI 10.1007/s10140-016-1410-5 - “The results of this investigation revealed sensitivity for the CT abdomen and pelvis to be 69 %, which is moderately good in the setting of acute left upper quadrant pain. However, specificity was 100 %, indicating that if a specific diagnosis is made on CT examination, it is highly likely to represent the underlying pathology of the left upper quadrant pain.”
Computerized tomography of the acute left upper quadrant pain Tirkes T et al. Emerg Radiol DOI 10.1007/s10140-016-1410-5 - “Abdominal CT had 100 % specificity and 69 % sensitivity for finding the etiology of acute left upper quadrant pain. The underlying etiologies of left upper quadrant pain are quite variable. The most common etiologies that were correctly diagnosed with CT included renal stones, pancreatitis, diverticulitis, hernia, pneumonia, and rib fractures. The most common etiologies that were not detected on CT were gastritis, pancreatitis, urinary tract infection, and esophagitis.”
Computerized tomography of the acute left upper quadrant pain Tirkes T et al. Emerg Radiol DOI 10.1007/s10140-016-1410-5
- Toxic Megacolon: Facts
- Acute transmural fulminant colitis with neuromuscular degeneration and colonic dilatation
- Dilated ahaustral colon with pseudopolyps and air-fluid levels
- No specific diameter although often markedly dilated
- Patients are sick - Ulcerative Colitis: Federle Facts
- Chronic, idiopathic diffuse inflammatory disease
- Primarily involves colorectal mucosa and submucosa
- Diagnostic clue: pancolitis with decreased haustration and multiple ulcerations
- Location:
- Rectum (30%)
- Rectum + colon (40%)
- Pancolitis (30%) - Large Bowel Infections: Facts
- Number of different possible etiologies including pseudomembranous colitis, bacterial organisms (campylobacter, shigella, salmonella, E. coli, etc.) and parasites (E. histolytica)
- Clostridium difficile is by far the most common in daily practice
- Often arises in the setting of prior antibiotic therapy or chemotherapy
- Can be a fulminant colitis with high morbidity and mortality, and not uncommonly presents with GI bleeding
- Pancolitis with extensive pericolonic fat stranding, free fluid, and inflammatory change.
- Isolated involvement of right or transverse in up to 5% of cases - Aorto-Enteric Fistulae: Facts
- Life-threatening disorder with mortality of virtually 100%
- Primary or secondary forms
- Secondary most common – prior aortic surgery or raft placement
- Classic triad: Abdominal pain, massive GI hemorrhage, and pulsatile abdominal mass
- CT is the best initial modality:
- Ectopic gas within aortic lumen or adjacent to aorta
- Direct contrast extravasation from aorta to bowel or vice-versa is rare
- Effacement of fat plane between the aorta and adjacent bowel
- Focal bowel wall thickening adjacent to the aorta
- Periaortic soft tissue thickening and fluid, - Stercoral Colitis: Facts
- Primarily seen in elderly patients
- Overdistension of rectal lumen from impacted stool
- Increased luminal pressure results in rectal wall ischemia (disrupts blood supply)
- Ulcers of rectal wall result in bleeding and perforation
- Affects up to 6% of elderly patients in long-term care
- Active extravasation almost never visualized
- Slow, intermittent bleeding
- MDCT shows distended rectum with wall thickening and perirectal stranding
- Small and Large Bowel Infections
- Common cause of diarrheal illness in the US
- Vast majority are not imaged with CT
- Can be viral (norovirus, rotavirus), bacterial (Salmonella, E. coli, Clostridium perfringens, C. Dificile), or protozoal (cryptosporidum, microsporidum, etc.)
- Probably most common cause of bowel wall thickening in day-to-day practice
- Severe infections with any organism can cause lower GI bleeding; certain organisms more likely - Large Bowel Infections
- Number of different possible etiologies including pseudomembranous colitis, bacterial organisms (campylobacter, shigella, salmonella, E. coli, etc.) and parasites (E. histolytica)
- Clostridium difficile is by far the most common in daily practice
- Often arises in the setting of prior antibiotic therapy or chemotherapy
- Can be a fulminant colitis with high morbidity and mortality, and not uncommonly presents with GI bleeding
- Pancolitis with extensive pericolonic fat stranding, free fluid, and inflammatory change.
- Isolated involvement of right or transverse in up to 5% of cases - Aortoenteric Fistula
- Life-threatening disorder with mortality of virtually 100%
- Primary or secondary forms
- Secondary most common – prior aortic surgery or graft placement
- Classic triad: Abdominal pain, massive GI hemorrhage, and pulsatile abdominal mass
- CT is the best initial modality:
- Ectopic gas within aortic lumen or adjacent to aorta
- Direct contrast extravasation from aorta to bowel or vice-versa is rare
- Effacement of fat plane between the aorta and adjacent bowel
- Focal bowel wall thickening adjacent to the aorta
- Periaortic soft tissue thickening and fluid
- GI Tract Complications: Chemotherapy
- Stomach- ulcers and gastritis
- Small bowel-enteritis with changes including ulceration, target sign, strictures
- Large bowel-pneumatosis (benign or malignant), necrosis, ischemia, neutropenic colitis, pseudomembranous colitis, perforation, typhlitis
- Complications of oncologic therapy in the abdomen and pelvis: a review
Ganeshan DM et al.
Abdom Imaging (2013) 36:1-21 - Typhlitis: Facts
- Triad includes fever, abdominal pain, and neutropenia
- Distension and diffuse circumferential thickening of the cecal wall
- Stranding in pericolonic fat around cecum
- Pneumatosis, perforation or pneumoperitoneum may also occur - GI Tract Complications: Radiation Therapy
- Stomach- ulcers and gastritis
- Small bowel- radiation enteritis which usually resolves 2-6 weeks post therapy
- Large bowel- radiation colitis
- Liver- fatty infiltration in geographic pattern
- Complications of oncologic therapy in the abdomen and pelvis: a review
Ganeshan DM et al.
Abdom Imaging (2013) 36:1-21
- Infectious Enterocolitis : Key Facts
- May be caused by agents including Yersinia, Campylobacter or Salmonella
- CT shows terminal ileum thickening without inflammatory mass but often with nodes - Crohns Disease : Key Facts
- Patients with crohns may initial present as suspected appendicitis
- Key is symmetric wall thickening and fibrofatty proliferation - "Our results suggest that CT findings of colonic wall thickening in end stage liver disease should be considered benign, and colonoscopy is unnecessary for the evaluation of malignancy or colitis unless it is clinically indicated."
Colonoscopy Findings in End Stage Liver Disease Patients with Incidental CT Colonic Wall Thickening
Ormsby EL et al.
AJR 2007; 189:1112-1117 - "The colonoscopy changes primarily ranged from mild mucosal edema to increased vascularity and telangiectasia, probably from hypoproteinemia or portal hypertension."
Colonoscopy Findings in End Stage Liver Disease Patients with Incidental CT Colonic Wall Thickening
Ormsby EL et al.
AJR 2007; 189:1112-1117