Diagnostic Yield of the Colonic Biopsy in the Investigation of Diarrhea

Abstract

Purpose: Colonoscopy with mucosal biopsies is an integral part of the clinical investigation of patients with diarrhea. While the diagnostic yield of the duodenal and ileal biopsy have been investigated, the percentage of colonic biopsies in which a likely cause for the patient's diarrhea is identified remains unknown. This study was designed to analyze the histopathologic diagnoses in a national database of patients who underwent colonoscopy. Methods: We analyzed electronic records from the Caris database, which includes data from patients whose gastrointestinal biopsies are diagnosed at Caris Life Sciences, a gastrointestinal pathology laboratory receiving specimens from private outpatient endoscopy centers across the U.S. Records include demographic, clinical, and endoscopic information, biopsy location, and histopathologic report. Pertinent clinical and pathologic data were extracted from adults who had colonic biopsies between 1/2008 and 12/2010. Results: A total of 718,951 unique adults (49.5% male) were analyzed; 89,861 (12.5%) had diarrhea; 399,313 (55.5%) had screening colonoscopy; 25,364 (3.5%) had a history of inflammatory bowel disease (IBD); the remaining 204,413 had other indications (bleeding, anemia, abdominal pain), but no diarrhea. Patients with diarrhea did not differ significantly from those with other indications (except IBD) with regards to biopsy sampling strategies: the right colon was sampled in 30% of all patients, the transverse colon in 15%; the left colon and the rectum in 27% each. Histologic findings likely to be etiologically related to diarrhea were detected in 10.2% of biopsies from patients with diarrhea, but only in 1.6% of patients without diarrhea (p<.0001). A history of IBD was associated with significant pathology (mostly chronic and chronic active colitis) in 46.7% of the patients. Table 1 depicts the yields of colonic biopsies in the different groups.Table: Percentage of patients with each type of colitis stratified by indication for colonoscopyConclusion: The most common findings associated with diarrhea were lymphocytic and collagenous colitis; amalgamated into a single entity (microscopic colitis), these two conditions accounted for 7% of all diagnoses in diarrhea patients. Unsuspected IBD was diagnosed in <3% of patients, while all other conditions, including infections, were exceedingly rare. While this study confirms the usefulness of colonic biopsies for the investigation and follow up of IBD, one might be tempted to regard the 10% diagnostic yield in diarrhea patients as unsatisfactory. However, we conjecture that a negative biopsy result is as useful as a positive one. The absence of organic disease provides support for functional entities (e.g., irritable bowel syndrome) and offers emotional and psychological solace to patients who may otherwise fear more serious conditions.