Category: GI

“‘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.”

“The proximal rectum is covered by peritoneum anteriorly and laterally, and the mid rectum is only partially covered anteriorly. The distal rectum is entirely extraperitoneal and is surrounded by perirectal fat, mesorectal lymph nodes, and vessels, all of which are encased by the mesorectal fascia. The mesorectal fascia tapers inferiorly and fuses with the anal sphincter.”

“The anatomic rectosigmoid junction is often defined at the sacral promontory or S3 to aid in treatment planning.”

“High-resolution T2-weighted imaging is the key sequence in the magnetic resonance (MR) imaging evaluation of primary rectal cancer. This sequence generally consists of thin-section (3-mm) axial images obtained orthogonal to the tumor plane, with an in-plane resolution of 0.5–0.8 mm.”

“This technique allows differentiation between rectal tumors confined within the rectal wall (stage T2 tumors) and those that extend beyond the muscularis propria (stage T3 tumors). Most important, the depth of invasion outside the muscularis propria can be assessed with a high degree of accuracy. In addition, high-resolution T2-weighted images allow the morphologic assessment of pelvic nodes, thereby improving accuracy in the characterization of nodes as benign or malignant, since size criteria have proved to be of limited value.”

“Even with TME (total mesorectal excision), however, the presence of a tumor or malignant node within 1 mm of the CRM (circumferential reference margin) remains an important predisposing factor for local recurrence.”

“These studies also revealed that radiation therapy yields little survival benefit and results in significant morbidity when used to treat stage T1–T2 or favorable-risk early stage T3 tumors (<5 mm invasion outside the muscularis propria) in contrast to more advanced stage T3 tumors (>5 mm invasion outside the muscularis propria)”

“Recent studies have shown that high-resolution MR imaging is a reliable and reproducible technique with high specificity (92%) for predicting a negative CRM, the relationship of the tumor to the CRM, and the depth of tumor invasion outside the muscularis propria.”

“On T2-weighted images, stage T1 tumors are confined to the submucosa, which manifests as a hyperintense layer; stage T2 tumors extend into, but not beyond, the muscularis propria, which manifests as a hypointense layer; and stage T3 tumors extend beyond the muscularis propria into the mesorectal fat.”

“A distance greater than 1 mm between the tumor and the CRM at histopathologic examination has been shown to correlate with a decrease in local recurrence. At our institution, we consider a measured distance of 1 mm or less on high-resolution T2-weighted images to be indicative of CRM involvement. It is critical to remember that this measured distance is the distance to the mesorectal fascia from either (a) the tumor margin, (b) a tumor deposit in the mesorectum, (c) tumor thrombus within a vessel, or (d) a malignant node.”

“If a malignant node or tumor deposit abuts (ie, is less than 1 mm from) the mesorectal fascia, this information is important to the surgeon, who must stay well clear of the tumor at that margin. In the United States, nodes outside the mesorectal fascia along the pelvic sidewall are not routinely resected. However, if involvement of these nodes can be established preoperatively, it is important to modify the treatment approach to avoid recurrence in untreated nodes. Involved extramesorectal lymph nodes can be targeted with a widened field for preoperative radiation therapy and extended surgical resection.”

“It is well established that nodal size is of limited value in assessing for the presence of metastasis. The most frequently used size criterion for distinguishing malignant from nonmalignant nodes (ie, 5 mm) has a sensitivity of 68% and a specificity of about 78%. The limited accuracy of nodal size is likely related to the fact that 30%–50% of metastases in rectal cancer occur in nodes that are less than 5 mm. Recently, it was reported that nodal margins and internal nodal characteristics are the most reliable indicators of malignancy. Features that are suggestive of malignancy include irregular or spiculated nodal margins and heterogeneous signal intensity.”

“The most significant landmark of the anal canal is the dentate line, which lies 2.5–3 cm proximal to the anal verge and is visible macroscopically but not on MRI. Its position can be estimated either by measuring 2.5 cm above the anal verge or by dividing the anal canal into thirds so that the dentate line lies at the junction of the middle and upper thirds.”

“At initial staging, most tumors are T1 or T2, lie within 1.5 cm of the anal verge, have a circumferential extent of less than 50%, and are located predominantly along the anterior aspect of the anal canal.”

“The sphincter complex is the most commonly infiltrated structure, followed by the rectum. It should be emphasized that direct invasion of the rectal wall, perianal skin, subcutaneous tissues, or sphincter muscles does not signify a T4 tumor. Invasion of organs such as the vagina, urethra, prostate, or bladder is required to diagnose T4 disease.”

“MRI is especially useful in staging large tumors, particularly when the craniocaudal dimension is the largest dimension or when tumors protrude beyond the anal verge, because endoscopy is inadequate in these cases.”

“Nodal drainage depends on which side of the dentate line the anal cancer has its epicenter. Anal margin and anal canal tumors inferior to the dentate line spread to the inguinal and femoral lymph nodes, whereas anal canal tumors superior to the dentate line drain into the perirectal, internal iliac, and retroperitoneal nodes.

“Nodal staging evaluation relies on the distance from the primary tumour rather than on the number of involved nodes. MRI is highly helpful to assess lymph node metastatic involvement, although the mere size criterion is far from accurate and associated with both false-positive and false-negative results. Short-axis threshold values of 8 mm, 5 mm and 10 mm have been suggested for pelvic, perirectal and inguinal lymph nodes, respectively. Additional helpful features to increase specificity include loss of the normal bean-shaped morphology and fatty hilum, internal T1 and T2 signal heterogeneity with central necrosis, and inhomogeneous enhancement.”

“Intravenous gadoxetate disodium [Eovist] can result in acute self-limiting dyspnea that can have a deleterious effect on arterial phase MR image quality and occurs significantly more often than with intravenous gadobenate dimeglumine.”

“For the purposes of this study, a typical hepatic hemangioma was considered to be present when the lesion was (a) well defined, homogeneously hyperechoic with or without central hypoechoic areas, and without posterior shadowing, or (b) hypoechoic or isoechoic with a hyperechoic rim. The presence of posterior acoustic enhancement was not considered in this analysis.”

“We considered patients to be at high risk for hepatic malignancy if they had a prior history or current evidence of malignant neoplasm, primary hepatic malignancy, or chronic hepatic disease at the time of the initial US examination.”

“Hepatic hemangioma is the most common benign hepatic tumor, with an approximate prevalence of 4% of the population and a frequency at autopsy of up to 7.3%.”

“Lesions known to simulate hemangiomas include metastases from a variety of primary tumors and hepatocellular carcinomas. Benign lesions such as focal fat, liver adenoma, and focal nodular hyperplasia can also occasionally mimic hemangioma.”

“Patients with a known extrahepatic malignancy capable of metastasizing to the liver and patients at risk for hepatocellular carcinoma should undergo additional imaging to confirm the diagnosis of hemangioma or to prove the presence of a hepatic malignancy.”

“It is controversial whether additional imaging is necessary when a suspected hemangioma is identified in a patient without any of the previously mentioned risk factors for malignancy.”

“In applying the results of our study to one’s own clinical practice, one can choose to exclude patients with abnormal liver function test results or other potential risk factors (such as multiple lesions or large lesions) from one’s low-risk group.”

“In conclusion, results of this study show that a hepatic lesion with a US appearance typical of hemangioma is extremely unlikely to be a malignancy, provided that the patient has no prior or current evidence of an extrahepatic malignancy or chronic hepatic disease. On the basis of these results, we no longer recommend follow-up examinations of any type on our patients who fit into this group.”

“In the presence of superior vena cava obstruction, the left hepatic lobe may occasionally demonstrate areas of focally increased blood flow in the collateral veins that can be seen on images. Typically, the collateral venous pathway comprises the internal mammary vein that connects to the left portal vein via the paraumbilical vein.”

“The flow of blood through the collateral veins may result in areas of focally increased blood flow to the liver. Specifically, an area of increased activity in segment IV of liver (ie, within the medial segment of the left hepatic lobe in what was formerly known as the quadrate lobe) has been well documented in patients with superior vena cava obstruction; this area of increased activity can be seen on ^99mTc–sulfur colloid scans of the liver and spleen and is referred to as the focal hepatic hot spot sign. The equivalent of this sign may also be seen on contrast material–enhanced computed tomographic (CT) scans.”

“Some other causes of hepatic hot spots include Budd-Chiari syndrome, liver abscess, hemangioma, focal nodular hyperplasia, and hepatocellular carcinoma. With the exception of Budd-Chiari syndrome, which causes the hot spot sign to occur in the caudate lobe, all other entities can cause the hot spot sign to occur anywhere in the liver, including segment IV.”

“Also known as oriental cholangiohepatitis, recurrent pyogenic cholangitis is a complex disease that is characterized by intrahepatic pigmented stones and recurrent attacks of cholangitis.”

“Although its exact cause is not known, there are strong associations between recurrent pyogenic cholangitis and parasites such as Ascaris lumbricoides and Clonorchis sinensis. It has been postulated that chronic infestation of the biliary tree by parasitic organisms induces inflammatory and fibrotic changes in the bile duct walls, leading to stricture formation, bile stasis, and intrahepatic stones. Men and women are affected with equal incidence, most frequently in the third and fourth decades of life.”

“The intrahepatic calculi lead to progressive biliary obstruction and recurrent infection, which in turn can result in multiple cholangitic hepatic abscesses; further biliary strictures; and, in severe cases, progressive hepatic parenchymal destruction, cirrhosis, and portal hypertension.” Complications: Hepatic abscess, biloma, PV thrombosis, malignancy (chlangiocarcinoma, HCC secondary to cirrhosis).

“Characteristically, there is disproportionate dilatation of the extrahepatic and central intrahepatic ducts, with little if any dilatation of the more peripheral biliary ducts. Pneumobilia…is also a common finding in recurrent pyogenic cholangitis. Hepatolithiasis is easier to detect on unenhanced CT because 90% of the stones are hyperdense to normal unenhanced liver parenchyma.”

“Hepatic parenchymal atrophy is a common feature of recurrent pyogenic cholangitis. It occurs most frequently in the left lateral segments, with the right posterior segments next most commonly involved.”

Although diffusion-weighted MRI has been shown to improve the detection of liver lesions and may have some role in the imaging of recurrent pyogenic cholangitis patients, it does not appear to confer any advantage in the differentiation of benign from malignant pathologic processes.”

“Therapeutic options for patients with recurrent pyogenic cholangitis include antibiotic therapy for acute attacks, stricture dilatation, biliary drainage, stone removal, biliary bypass, liver resection, and trans plantation. The goal of therapy is to completely clear the biliary tree of calculi and to eliminate bile stasis to prevent acute attacks of cholangitis and further stone formation. Where possible, patients are treated relatively conservatively using ERCP or PTC to achieve these goals, with surgical management reserved for those patients in whom endoscopic and percutaneous techniques have been unsuccessful.”

“Worrisome features on imaging include cyst of 3 cm, thickened enhanced cyst walls, MPD size of 5-9 mm, non-enhanced mural nodules, abrupt change in the MPD caliber with distal pancreatic atrophy, and lymphadenopathy. Cysts with obvious high-risk stigmata on CT or MRI (i.e., obstructive jaundice in a patient with a cystic lesion of the pancreatic head, enhanced solid component, MPD size of 10 mm) should undergo resection without further testing. All smaller cysts with worrisome features should be evaluated by EUS to further risk-stratify the lesion. Patients with cysts of >3 cm and no worrisome features can also be considered for EUS to verify the absence of thickened walls or mural nodules, particularly if the patient is elderly. All patients with cysts of 3 cm in size without worrisome features should undergo surveillance according the size stratification.”