Development of a Score to Predict Positive Colonic Histology in Chronic Diarrhea Assessed in Open-access Colonoscopy

To evaluate the diagnostic yield of colonoscopy and esophagogastroduodenoscopy with biopsies and to identify predictors of positive colonic histology in patients with chronic diarrhea.

Colonoscopy with biopsies is performed in chronic diarrhea with negative initial work-up.

We reviewed electronic medical records of 1022 consecutive patients with chronic diarrhea referred for a first colonoscopy (including 25% open-access referrals). Predictors of positive colonic histology were investigated using logistic regression.

Four hundred thirteen patients with macroscopically normal colon were divided into derivation (n=275) and validation (n=138) cohorts. All patients underwent colonoscopy; 369 had ileoscopy (biopsies in 43%), and 289 underwent esophagogastroduodenoscopy (duodenal biopsies in 93%). In patients with endoscopically normal colon, histology was positive in 13.3%: 10.6% microscopic colitis; 1.5% other colitides. Among 358 patients with negative histology, the recorded diagnoses were: 48% unexplained, 25% irritable bowel syndrome, 5.6% small intestinal bacterial overgrowth, and 4.7% bile acid diarrhea. The rates of diagnoses based on positive histologies were 4% for ileal and 5% for duodenal biopsies. Older age [odds ratio (OR)=1.05] was a positive predictor, whereas body mass index (OR=0.93) and duration of diarrhea (OR=0.98) were negative predictors of positive histology. A clinical diagnostic scoring system could correctly predict 41% to 54% of patients with normal colonic histology, with a false-negative rate of 0.8% to 2.6% and a negative predictive value of 95% to 98%.

Positive colonic biopsies were detected in <15% of patients with chronic diarrhea with normal colonoscopy; a clinical score correctly predicts likelihood of normal histology in about half the patients.