4479 Is routine mucosal biopsy of value in patients with diarrhoea and normal colonoscopy in an open access setting

BACKGROUND: Routine mucosal biopsy in patients undergoing colonoscopy for diarrhoea, in whom macroscopic examination is normal, remains controversial and practice varies widely without clear guidelines. Reported rates of clinically significant microscopic abnormalities vary from 2-27%.It is unclear if ileal biopsy adds anything to colonic biopsy alone. OBJECTIVES: We sought to evaluate the diagnostic yield of colonic and ileal mucosal biopsy in patients undergoing colonoscopy for diarrhoea in whom the macroscopic examination was normal. METHODS: We retrospectively reviewed all colonoscopies performed over a nine year period in a tertiary referral centre with an open access endoscopy service. Cases were selected where the sole indication for colonoscopy was diarrhoea, the musosa was macroscopically normal (other than diverticulosis) and biopsies were performed. Cases were excluded if the examination was inadequate. The histopathology reports of the selected cases were then reviewed. RESULTS: 362 cases were identified. Colonoscopy and biopsy was normal in 260 patients.Ileal biopsies were performed (in addition to colonic biopsies) in 158 cases, none of which revealed clinically significant abnormalities. Clinically significant histological findings were present in 18 cases (5%). Findings included collagenous colitis (5 cases), lymphocytic colitis (1 case), possible lymphocytic colitis (1 case), possible collagenous colitis (1 case), inflammatory bowel disease (2 cases), melanosis coli (2 cases) and significant eosinophil mucosal infiltration (6 cases). 28 patients (8%) had minor histological abnormalities with no specific diagnostic features. The diagnostic yield was highest in patients above 60 years old, where 10% had clinically significant histological abnormalities. All patients with collagenous colitis were female and only 1 was less than 60 years old. CONCLUSIONS: When colonoscopy is normal in patients with diarrhoea, routine colonic biopsy identifies significant pathology in 5% of cases. The diagnostic yield is highest in patients over 60 years old. Routine ileal biopsy is unhelpful.