GI – Bowel

“‘Mucosal hyperenhancement’ is erroneous descriptor as mucosa is often absent at endoscopy in inflamed loops with stratified segmental hyperenhancement.”

“Intramural fat indicates chronicity and is unrelated to whether inflammation is present or not.”

“Intramural edema indicates active inflammation if due to Crohn’s disease.”

“In comparison to normal small bowel, increased hyperintensity on T2-weighted images is associated with more severe inflammation.”

“In regions of Crohn’s disease-related inflammation on gadolinium-enhanced images, increased diffusion-weighted signal abnormality is associated with more severe inflammation.”

“Segmental mural hyperenhancement and wall thickening have a moderately high sensitivity and specificity for small bowel Crohn’s disease at CTE or MRE.”

“Mural hyperenhancement without wall thickening is a nonspecific imaging sign and may reflect inflammation or other processes.”

“CTE and MRE may detect small bowel inflammation not seen at ileocolonoscopy.”

“CTE and MRE with only oral contrast will not detect or stage colonic inflammation as well as ileocolonoscopy.”

“Unenhanced MR enterography with diffusion weighted imaging has a moderate sensitivity and specificity for detection of ileal Crohn’s disease.”

“Most Crohn’s disease strictures have both inflammation and fibrosis. “

“A stricture is present when the lumen is narrowed, and there is proximal small bowel dilation.”

“Visualization of ulcers at cross-sectional enterography is a marker of severe inflammation.”

“Reactive lymphadenopathy 1−1.5 cm in short axis diameter is considered normal in Crohn’s disease.”

“CTE and MRE have similar and moderately high accuracy for penetrating Crohn’s disease (fistulas, inflammatory mass, abscess).”

“Penetrating complications detected at CTE and MRE may occur in unsuspected patients.”

“Pelvic MRI is the most accurate test for the detection and characterization of perianal Crohn’s disease, but every CTE and MRE should image the anal sphincter complex and perineum.”

“Acute mesenteric vein thromboses and chronic mesenteric vein occlusions can be detected at CT and MR in Crohn’s disease patients, and may be central or peripheral.”

“Extra-intestinal findings: sacroiliitis, primary sclerosing cholangitis, avascular necrosis, pancreatitis, nephrolithiasis and cholelithiasis, and cutaneous findings.”

“Radiologists should indicate that inflammatory small bowel Crohn’s disease is likely when either (i) in known Crohn’s patients when mural hyperenhancement and wall thickening are present, or (ii) when enteric inflammation is asymmetric or co-exists with the typical penetrating complications of Crohn’s disease. “

“Radiologists should report the number of involved bowel segments, approximate location (proximity to ileocecal valve or ligament of Treitz), length and degree of upstream dilation of Crohn’s strictures so that gastroenterologists and surgeons can decide on the best therapeutic option and approach.”

“Because intramural T2 hyperintensity, restricted diffusion, peri-enteric stranding, wall thickness and mural ulcerations seen at cross-sectional enterography generally correlate with severity of endoscopic and histologic inflammation, radiologists should comment on these findings and describe them when present.”

“The water halo sign indicates stratification within a thickened bowel wall that consists of either two or three continuous, symmetrically thickened layers. Common diagnoses with this sign include idiopathic inflammatory bowel diseases, vascular disorders, infectious diseases, and radiation damage.”

“The water halo sign is used as a generic term to indicate stratification within a thickened bowel wall that consists of either two or three continuous, symmetrically thickened layers. A halo sign with two layers (double halo) is composed of either a higher-attenuation outer annular ring (muscularis propria) surrounding a second, luminally oriented annular ring of gray attenuation or a higher-attenuation inner layer and an outer ring of gray attenuation. A third variant, the target sign, is composed of three rings: outer high-attenuation muscularis propria, a middle ring of gray attenuation, and a luminally oriented ring of high attenuation. The lower-attenuation (gray) layer of the water halo sign is believed to represent edema (thought to be its dominant component) and can be assumed to be located in the submucosa.”

“The water halo sign is most valuable as an unequivocal observation of bowel wall injury, often of an acute nature. Furthermore, although a myriad of small or large bowel pathologic conditions can produce these signs, malignancy rarely manifests with the classic water halo sign.”

“The fat halo sign refers to a three-layered target sign of thickened bowel in which the middle or “submucosal” layer has a fatty attenuation. Common diagnoses with this sign include Crohn disease in the small intestine and idiopathic inflammatory bowel diseases in the colon.”

“Pitfalls: Intramural fat may exist in both the distal ileum and colon as a “normal” variant in patients without gastrointestinal symptoms or a history of gastrointestinal disease. In the small intestine, normal intramural fat is seen most commonly in the terminal ileum. In the colon, it is found most often in the descending colon.”

“The normal intramural fat layer is generally very thin, usually thinner than the fat stratum. The observation of the normal fat halo sign is most frequently made in undistended or poorly distended bowel loops.”

“Mesenteric adenitis was considered present if a cluster of three or more lymph nodes measuring 5 mm or greater each was present in the right lower quadrant mesentery. If no other abnormality was detected on CT, then mesenteric adenitis was considered primary. If a specific inflammatory process was detected in addition to the lymphadenopathy, then mesenteric adenitis was considered secondary.”

“Mesenteric adenitis can be divided into two broad categories, primary and secondary. Primary mesenteric adenitis has been defined as right-sided mesenteric lymphadenopathy without an identifiable acute inflammatory process or with mild wall thickening of the terminal ileum.”

“In most cases of primary mesenteric adenitis, an underlying infectious terminal ileitis is thought to be the cause.”

“First, right lower quadrant mesenteric nodes do not occur in the general, asymptomatic, immunocompetent adult population. Second, an isolated cluster of right lower quadrant mesenteric lymph nodes is an uncommon finding in patients with acute abdominal symptoms, and this finding is often associated with a focal inflammatory process. Third, CT detection of right lower quadrant mesenteric nodes in patients with acute abdominal pain is usually associated with a detectable intraperitoneal inflammatory process in the majority of patients. Failure to identify a concurrent pathologic process leads to a presumptive diagnosis of primary mesenteric adenitis and explains the patient’s symptoms.”