Diagnostic yield and economic implications of endoscopic colonic biopsies in patients with chronic diarrhoea

Random colonic biopsies are recommended to exclude microscopic colitis in patients with chronic diarrhoea especially when mucosa is macroscopically normal at endoscopy. This study aimed to assess the clinical outcome and economic impact of such a policy in an unselected group of patients with macroscopically normal mucosa.

All new patients undergoing colonoscopy for investigation of chronic diarrhoea between April and December 2009 were included. Patients were divided into two groups: macroscopically normal mucosa and macroscopically inflamed mucosa. Endoscopic findings were correlated with histology of random biopsies and haematological parameters. Symptom status and any treatment were established from follow-up. The breakdown and overall cost of random biopsies for each patient with a macroscopically normal mucosa were determined, and cost incurred per diagnosis of microscopic colitis was established.

Altogether 137 (90.1%) of 152 patients with chronic diarrhoea had macroscopically normal mucosa at colonoscopy. Overall incidence of microscopic colitis in the study was 1.3% (2/152); both patients belonged to the macroscopically normal mucosa group. At follow-up, both these patients had spontaneous symptom resolution without any specific treatment. The policy of undertaking random biopsies in patients with macroscopically normal mucosa incurred an extra cost of £22,057 to diagnose two cases of microscopic colitis but did not alter medical treatment.

In unselected patients with chronic diarrhoea and macroscopically normal mucosa, random colonic biopsies have a low diagnostic yield and incur a high cost. Continued research for predictive markers to improve patient selection for targeted biopsies is needed to develop a cost-effective investigative algorithm in chronic diarrhoea.