Sigmoid volvulus has a spectrum of imaging findings. A classic appearance is absent on approximately one half of scanograms and one fourth of CT scans. Use of new signs that model the pathophysiologic characteristics of volvulus (X-marks-the-spot sign for more complete twisting and split-wall sign for less severe twisting) may improve diagnostic confidence.

When cecal volvulus is suspected, the absence of distal colonic decompression on CT topograms makes the diagnosis very unlikely. Whirl, ileocecal twist, transition points, X-marks-the-spot, and split wall have high specificity for cecal volvulus.

Six patients in whom errors of diagnosis and therapy occurred because of reliance on colonoscopic tumor localization are presented. Three of the patients required a second laparotomy for surgical resection of a tumor that was missed at the first exploration. While endoscopy is regarded as the diagnostic gold standard, there are problems in its use for colonoscopic localization. Reliance on distance measurements may be misleading. Anatomical variants can be confusing. For this reason, a preoperative barium enema for precise delineation and localization of tumors is recommended. When a barium enema is not feasible, such as when a malignant polyp has been removed endoscopically, preoperative endoscopic localization with injection of India ink or intraoperative colonoscopy must be performed.

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