CASE DISCUSSIONTang Chun Xiang 2016/5/25Axial arterial phaseAxial arterial phaseAxial venous phaseCoronal arterial phaseSagittal venous phaseCrohn disease An inflammatory disease of the gastrointestinal tract that typically has an indolent course Characterized by intestinal ulceration, strictures, and fistula formation Commonly affects young adults, small bowel, particularly the terminal ileum Small bowel involvement in Crohn disease is typically transmural, with skip lesions CT and MRI Introduction-Crohn disease CT and MRIu Useful for differentiating between active and fibrotic bowel stricturesu Allowing visualization of the entire thickness of the bowel wallu Depicting extraenteric involvementu Providing more detailed and comprehensive information about the extent and severityIntroduction-Crohn disease Comb sign Fat halo sign Bowel wall enhancement Bowel wall thickness Stricture and fistula Mesenteric/intra-abdominal abscess (15%-20%) or phlegmon formation Ulcerations and loss of haustration Creeping fatImaging findings on CT and MRI Comb signu Prominence of the vasa recta adjacent to the inflamed loop of bowelu Transmural extension of inflammation across the serosa and to engorgement of the hyperemic vasa recta surrounding the inflamed bowel segmentu Not pathognomic of Crohn diseaseImaging findings on CT and MRI Fat halo signu Infiltration of the submucosa with fat, between the muscularis and the mucosau Confused with the fat ring sign of mesenteric panniculitisu Nearly pathognomonic of inflammatory bowel disease (Crohn disease and ulcerative colitis)Imaging findings on CT and MRI Bowel wall enhancementu The result of increased vascular permeability and angiogenesisu The most sensitive indicator of active Crohn diseaseu Enhancement can be graded by comparing to the precontrast imagesu Minor increased enhancementu Moderate enhancementu Marked enhancementu No abnormal enhancement: equivalent to normal bowel wallImaging findings on CT and MRIHomogeneousMucosalLayeredPattern of enhancement Bowel wall thicknessu Normal bowel wall thickness： lumen distended， 1-2 mm； lumen collapsed, 3-4 mmu Mild: 3-5 mmu Moderate: 5-7 mmu Marked: 7mmu One of the most common signs, but not specificu Correlates well with the severity of the disease activityuMeasure when lumen distended welluBlack border artifacts can distort thickness measurementsImaging findings on CT and MRI Strictureu A complication of Crohn diseaseu Reversible strictures produced by active diseaseu A lack of enhancement and loss of stratification might be seen in the presence of transmural fibrosisImaging findings on CT and MRI Fistulau The detection of penetrating disease is important and may redirect or alter managementu Enteroenteric fistula, enterovesical fistula, and interloop abscessu CT enterography resulted in accurate detection of fistulas in 94% of casesImaging findings on CT and MRI Abscessu Often seen in patients with severe active Crohn diseaseu Extraluminal fluid collections without communication with the bowel lumenu Fluid collections with an enhancing wall with or without associated airImaging findings on CT and MRI Ulcerationu Moderate to deep ulceration can be seen, small ulcerations can be difficult to distinguishu Active spots of inflammationu Increased enhancementImaging findings on CT and MRI Loss of haustrationu Both the colon and the small bowel are involved in 30%60%u Involvement of the colon alone in 20%35%u A decrease of haustral foldsu A common finding in ulcerative colitisImaging findings on CT and MRI Creeping fatu Fibrofatty proliferation of fat wrapping, different name for hypertrophy of the subserosal fatu Common finding in longstanding Crohn diseaseu The image shows creeping fat surrounding bowel loopsImaging findings on CT and MRI CT and MRIu Useful for differentiating between active and fibrotic bowel stricturesSummary CT features of active Crohn diseaseu Mucosal hyperenhancementu Wall thickening (thickness 3 mm)u Mural stratification with a prominent vasa recta (comb sign) CT features of inactive longstanding Crohn diseaseu Submucosal fat deposition (fat halo sign)u Surrounding fibrofatty proliferation (creeping fat), and fibrotic strictures u Pseudosacculation CT and MRIu Allowing visualization of the entire thickness of the bowel wallSummary Normal bowel wall thickness： lumen distended， 1-2 mm； lumen collapsed, 3-4 mmu Mild: 3-5 mmu Moderate: 5-7 mmu Marked: 7mm CT and MRIu Depicting extraenteric involvementSummary Fistula and abscessu Enteroenteric fistulau Enterovesical fistulau Interloop abscessu Etc. CT and MRIu Providing more detailed and comprehensive information about the extent and severitySummary The extent and severity correlates with the diseaseu The degree of thickeningu The intensity of enhancementu Fistulas and abscessu The presence of ulcerations and loss of haustrationTHANK YOU!