Imaging in Crohn Disease: Overview, Radiography, Computed Tomography. Traditionally, MRI has had a well- defined role in evaluation of anorectal complications of Crohn disease. With a regular fast spin- echo technique, the pathologic entities of a fistula, a sinus tract, and an abscess can be detected in the static anorectal region by using MRI. With fat suppression, the fluid signal is further intensified and easily seen as being hyperintense on T2- weighted images. An abscess often appears as an isolated collection of high- signal- intensity areas on the T2- weighted image, especially in ischioanal fossa. Defining whether an abscess, fistula, or sinus tract is above or below the levator ani muscle is important for drainage, because any part of the abscess above the levator ani muscle will not drain adequately in the inferior direction, and vice versa. MRI sequences. The development of faster pulse sequences (eg, single- shot fast spin- echo, steady- state free precession, and gradient- echo sequences) and higher- gradient systems has made T1- and T2- weighted breath- hold imaging possible. This breath- hold imaging has been a major breakthrough in overcoming physiologic motion artifacts in abdominal imaging. GI bleeding occurs when an abnormality on the inner lining begins to bleed. Approximately 5% of all GI bleeding comes from the small bowel. Abnormal blood vessels. Original Article. Infliximab, Azathioprine, or Combination Therapy for Crohn's Disease. Jean Frédéric Colombel, M.D., William J. Sandborn, M.D., Walter Reinisch, M. Crohn’s disease is a digestive disorder that can cause a variety of symptoms. There’s no single diagnostic test for Crohn’s disease. Most patients with abdominal pain can be diagnosed and treated successfully. See your physician and appropriate specialists if you have persistent or severe abdominal. C Papi, M Bianchi, A Ciaco, F Del Sette, M Koch, L Capurso. Diet and inflammatory bowel disease: a computer aided method of assessing individual dietary habits. Learn about Gastrointestinal Disorders symptoms, diagnosis and treatment in the Merck Manual. HCP and Vet versions too! It has made routine abdominal MRI feasible. The single- shot fast spin- echo sequence, in which T2- weighted images are acquired by using half- Fourier transformation and a long echo train. Diagnosing Crohn's disease. A number of different tests may be needed to diagnose Crohn's disease, as it has similar symptoms to several other conditions. The diagnosis of Crohn's disease is suspected in patients with fever, abdominal pain and tenderness, diarrhea with or without bleeding, and anal diseases, such as. What is a small bowel obstruction? A small bowel obstruction is a blockage anywhere inside your small intestine. The small intestine starts at the end of the stomach. Clinical Guidelines. Authored by a talented group of GI experts, the College is devoted to the development of new ACG guidelines on gastrointestinal and liver diseases. Each image section is acquired independently in less than 1 second, and the method eliminates physiologic motion from the bowel and the need for breath holds. Fat suppression can be added to increase specificity for bowel and mesenteric edema. The steady- state free precession imaging is based on a low flip angle gradient echo series with short repetition time. It is another series of sequences that is insensitive to motion artifacts and can provide T2- type imaging. It can have black boundary artifacts along the bowel wall that mask small lesions, but fat suppression can reduce the artifact. The major feature of the sequence is the ability to acquire an entire series within a single breath hold. In fact, MR fluoroscopy is performed with cine of steady- state free precession imaging and a frame rate of 0. Contrast evaluation is often imaged with 3- dimensional spoiled gradient echo T1 fat- suppressed sequences. Images are acquired with breath hold. For bowel imaging, series are taken after intravenous glucagon at 3. Because of a decrease in cumulative radiation exposure and because of the capability of attaining high- quality coronal images correlating with barium studies, MRI is currently an alternative for monitoring disease activity in Crohn disease. MRI enterography and enteroclysis. With the development of faster imaging sequence and with the use of intravenous 0. MRI enterography or enteroclysis, often with 1. L of solution containing biphasic intraluminal contrast agents (low T1 and high T2). Some of these agents are Volumen (EZ- E- M; Westbury, NY), mannitol (2. Image is performed for 4. MRI enterography and enteroclysis. Oral ingestion of the intraluminal contrast is performed in enterography, while nasojejunal intubation and infusion of intraluminal contrast is performed in enteroclysis. Nasojejunal intubation under fluoroscopy is required for MRI enteroclysis; it provides excellent bowel distention and provides detailed luminal information. Nevertheless, several studies have shown better patient tolerance of enterography over enteroclysis, and some studies have shown similar sensitivity for both techniques. After adequate luminal distention, intravenous 0. T2- weighted single- shot fast spin- echo series. The coronal and axial T2- weighted single- shot fast spin- echo images can show edema in the small bowel mesentery and small bowel wall deep ulcers, while fat- saturated images can determine chronic mural fat changes. Lastly, after administration of a gadolinium- based intravenous contrast agent, coronal volume gradient- echo sequences are acquired to assess vascular engorgement, mucosal hyperemia, mural enhancement, inflammatory hyper- enhancing lymph nodes, abscess, and fistula. There are currently ongoing investigations into the use of MRI enterography and assessment of active disease in the colon. Active Crohn disease. Assessment of inflammatory activity is fundamental to the managing Crohn disease. There is no single reference standard for defining active disease. Clinical scores such as the Crohn disease activity index and biochemical markers such as C- reactive protein are widely used, but they lack utility for assessment of the entire bowel. It has the key advantages of direct visualization and sampling of disease, but it is limited in its assessment of the entire small bowel. MRI currently serves as a viable method for global assessment. Many of MRI criteria of disease activity are based on luminal and extraluminal disease. In terms of luminal disease, active disease includes ulcer, wall thickening, mural and perimural T2 intensity, and bowel wall enhancement with gadolinium- based contrast agents. There are 3 main patterns of enhancement in determining the level of disease. The layered or stratified enhancement is seen with enhancement of the mucosa, and relatively poor submucosal enhancement and submucosal edema are seen in active disease. The general consensus is that concentric bowel wall thickening greater than 4 mm is suggestive of active disease. In study by Maccioni et al, active disease is characterized by a thickened bowel wall with gadolinium enhancement, but inactive disease is not. Mural T2 increased signal intensity is a well- validated marker of disease activity. Deep ulcers appear as thin lines of high signal within a thickened bowel wall on single- shot fast spin- echo series and can be seen more readily on MRI enterography, whereas aphthous ulcer, with a nidus of high signal with surrounding intermediate signal, can be seen on high- resolution MRI enteroclysis. See the image below. Fibrofatty proliferation is hyperintense on T2- weighted images and is related to regional mesenteritis or edema and dilatation of local vessels. The dilatation of the local vessels is seen supplying a local inflamed bowel segment, akin to the “comb sign” seen on CT examination; this finding is well depicted in postcontrast gradient- echo images and steady- state free- procession images. Inclusive in the term fibrofatty proliferation is “fat wrapping,” whereby there is chronic enlarged mesenteric fat leading to increased separation of the mesenteric bowel loops. Fat proliferation is a distinguishing feature of Crohn disease and is indicative of the diagnosis. See the image below. Mesenteric edema in active disease is seen accompanying bowel wall edema and hyperenhancement and is seen often with the comb sign of the mesentery. Active lymph nodes are enlarged, hyperenhancing, and edematous, typically along the vascular supply of affected bowel segment. The nodal enhancement is usually homogenous and is greater than or equal to one of the adjacent lymph node for active disease. Fistulae are sequelae of deep transmural ulcers that extend through the musculature, leading to the formation of small abscesses and sinus tracts. The sinus tract can involve and communicate with adjacent hollow organ and form fistulae. MRI depiction of fistulae is often seen as fibrotic star- shaped reactions of the mesentery, with tethering of the adjacent communicating structures. It has avid enhancement post contrast and, on occasion, shows a linear T2- hyperintense tract. The chronic mesenteric inflammation can eventually form fibrous bands with enhancement similar to sinuses and fistulas. However, they often lead to tenting and segmental obstruction with MR fluoroscopy, showing kinking and stretching of the adjacent bowel loops. Fibrostenotic disease is often depicted as bowel obstruction without bowel wall thickening. The bowel stricture has low T1 and T2 mural signal and has mild nonhomogenous enhancement. With asymmetric bowel wall involvement, pseudosacculation can occur. Regenerative disease is depicted on MRI as luminal narrowing without inflammation or obstruction. On steady- state free- procession imaging, filiform polyposis may be suggested without enhancement or obstruction. Neoplasia is also a concern in chronic disease, since Crohn disease patients are at increased risk of developing adenocarcinoma of the affected bowel segment. The disease has occurred in patients with moderate to end- stage renal disease after being given a gadolinium- based contrast agent to enhance MRI or MR angiography scans. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. Degree of confidence and impact of MRIGadolinium- enhanced spoiled gradient- echo MRI has a reported sensitivity of 8. MRI, which has a sensitivity of 5. In a retrospective study of 1. MRI enterography patients, 5.
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August 2017
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