Diagnostic accuracy of sigmoidoscopy compared with histology for ischemic colitis after aortic aneurysm repair

Clinically relevant rates of ischemic colitis (IC) causing diarrhea, systemic involvement, colon necrosis, and, ultimately, death by multiple organ failure affect only a small proportion of patients after aortic reconstructions, with reported incidences of 2.7 to 3.3%. The key to treating and saving patients with this complication remains early detection and consequent treatment. The aim of this retrospective analysis of prospectively collected data was to compare the diagnostic accuracy of colonoscopy for detecting postoperative IC compared with histology and to evaluate the interobserver difference of two experienced surgeons. One hundred patients with infrarenal aortic aneurysms, operated on electively from March 2001 to December 2003, who had on postoperative days 3 to 6 a sigmoidoscopy by two independent surgeons and a histologic sample of the sigmoid mucosa, were included in the study. Patients with previous colon resection or inflammatory bowel disease were excluded from the study. All patients gave written informed consent. The study was approved by the Institutional Review Board. Histologic examination of the sigmoid mucosa revealed IC in 13 patients. The combined sensitivity of both investigators for detecting IC by sigmoidoscopy compared with histology was 84%, the specificity was 92.0%, the positive predictive value was 61.1%, the negative predictive value was 97.6%, and the diagnostic accuracy was 91.0%. There was no statistically significant difference between investigator 1 and investigator 2 (p=1.0) and between both investigators and histology (p=.380). Histology remains the gold standard for detecting IC after aortic surgery. Sigmoidoscopy, however, is a valid diagnostic tool allowing immediate clinical decision making with a negative predictive value of more than 94% and a diagnostic accuracy of 92%.