SIMPLE OBJECTIVE CRITERIA FOR DIAGNOSIS OF CAUSES OF ACUTE DIARRHEA ON RECTAL BIOPSY

Aim-To identify simple, objective, accurate histological criteria for distinguishing acute infective-type colitis, chronic idiopathic inflam matory bowel disease, and irritable bowel syndrome on rectal biopsy in patients with acute onset diarrhoea at first presentation, one to 10 weeks after onset. Methods-Cell counts and measurements of mucosal arc hitecture were made on initial rectal biopsies from 18 patients with a cute infective-type colitis, 17 patients with first acute presentation of chronic idiopathic inflammatory bowel disease, and 23 patients wit h irritable bowel syndrome. The data were analysed by ANOVA and discri minant analysis. Results-Lamina propria cells were mainly in the upper third in irritable bowel syndrome patients. Increased lamina propria cellularity, mainly in the middle third, and numbers of crypt intraepi thelial neutrophils distinguished acute infective-type colitis from ir ritable bowel syndrome in 93% of cases. Chronic idiopathic inflammator y bowel disease differed from irritable bowel syndrome and acute infec tive-type colitis in a decreased number of crypts and altered crypt ar chitecture. Chronic idiopathic inflammatory bowel disease showed highe r lamina propria cellularity, especially in the basal third, with an i ncreased number of lamina propria neutrophils. On discriminant analysi s, crypt numbers distinguished 86% of the cases of chronic idiopathic inflammatory bowel disease from the other groups. Conclusion-At one we ek or more from onset, acute infective-type colitis is characterised b y a superficial increase in lamina propria cellularity, with only a sl ight increase in the number of polymorphs. At this stage, chronic idio pathic inflammatory bowel disease is characterised by a transmucosal i ncrease in cellularity together with crypt loss and architectural abno rmality. Thus, measurement of mucosal architecture establishes simple, accurate, objective criteria for routine biopsy diagnosis of chronic idiopathic inflammatory bowel disease from acute infective-type coliti s and irritable bowel syndrome at initial presentation, one to 10 week s after onset.