Morphological consequences of bisacodyl on normal human rectal mucosa: effect of a prostaglandin E1 analog on mucosal injury.

Bisacodyl causes acute injury to the human rectal mucosa. Our objectives were to test whether pretreating the human rectum with an enema of 400 micrograms of a prostaglandin E1 analog (misoprostol) would ameliorate the mucosal injury provoked by an enema of 10 mg of bisacodyl, and to follow the evolution of the bisacodyl-induced injury in normal volunteers. Mucosal biopsies were taken 10 cm from the anus with an endoscopic forceps through a straight sigmoidoscope. Histological sections were interpreted blindly. In a preliminary experiment without bisacodyl, biopsies obtained from six subjects after misoprostol administration were indistinguishable from those taken from another six subjects after enemas of saline. In a parallel treatment experiment involving 30 subjects, all subjects sustained injury to the superficial epithelium and upper third of the crypt within 30 min after bisacodyl. Pretreatment with misoprostol also failed to prevent deeper injury to the lower third of colonic crypts. In a cross-over trial, a subset of four volunteers had biopsies at five different intervals after an enema of bisacodyl or saline. For up to 30 hours after bisacodyl, there was histological evidence of mild inflammation. Bisacodyl-induced colitis might confound the assessment of patients with suspected inflammatory bowel disease.