64 Attenuation Patterns in the Abnormal Bowel Wall

CLINICAL IMAGAGINGAN ATLAS OF DIFFERENTIAL DAIGNOSIS

EISENBERG

DR. Muhammad Bin Zulfiqar PGR-FCPS III SIMS/SHL

• Fig GI 64-1 White attenuation in shock bowel. Increased enhancement in the jejunum (black arrows). Note that the attenuation is greater than that of the inferior vena cava (curved arrow). The enhancement qualities could be mistaken for oral contrast material in the lumen, but none was given. (Straight white arrow = fluid in stomach.)81

• Fig GI 64-2 White attenuation in acute ulcerative colitis. Uniform increased enhancement (straight black arrow) in the thickened wall of the rectosigmoid. The attenuation of this segment of the colon is similar to that of the external iliac vein (curved arrow). The pericolonic vessels are dilated (white arrow).81

• Fig GI 64-3 Gray attenuation in ischemic colitis. The attenuation of the enhancing walls of the colon (solid straight arrows) falls short of that of the superior mesenteric venous branch (curved arrow) and inferior vena cava (open arrow). Therefore, interpretation in this case should be assigned to the gray attenuation pattern.81

• Fig GI 64-4 Gray attenuation in colon carcinoma. The thickened wall of the mid-descending colon (straight arrow) has an attenuation similar to that of the adjacent muscle (curved arrow).81

• Fig GI 64-5 Water halo sign in bowel obstruction. Inner layer of a strangulated, ischemic segment of small bowel (small straight solid arrows) is surrounded by a lower attenuation layer (curved arrows). Note the brightness of the dilated, obstructed proximal small bowel wall (open arrow), which approximates the attenuation of the external iliac vein (arrowhead). However, since the wall of the dilated bowel is not thickened, it would not be considered abnormal (large straight arrow indicates ascites).81

• Fig GI 64-6 Target sign in angioedema. Several segments of small bowel demonstrate three uniformly thick layers. The layers grossly correspond to the muscularis propria (straight solid arrows), submucosa (curved arrow), and mucosa (open arrow). Arrowhead indicates ascites.81

• Fig GI 64-7 Fat halo sign in ulcerative colitis. An outer enhanced layer (straight solid arrows) surrounds a fat-attenuation layer (curved arrows). Contrast material is seen within the colonic lumen (open arrow).81

• Fig GI 64-8 Fat halo sign in chronic radiation enteritis. Several segments of small bowel have walls thickened by a central band of lower attenuation consistent with fat (arrowheads). The target configuration is evident in one segment that lacks luminal oral contrast material (solid arrow). Other segments with a fatty layer have luminal contrast enhancement, which conceivably could be obscuring a higher attenuation “mucosal” layer (open arrows).81

• Fig GI 64-9 Black attenuation in cecal pneumatosis. There are rounded collections of mural gas attenuation (straight solid arrows) in this patient with ischemic colitis. Mural gas attenuation is also seen at the outer margin of the colonic wall (curved arrows) and lumen (open arrow).81