Evaluation of techniques for chemical debridement of colonic mucosa.

Rectal mucosectomy may be technically difficult to perform on certain patients with severe ulcerative colitis involving the rectum, in whom a colectomy and endorectal ileal pull-through operation is planned. The present study evaluates the effectiveness of the following caustic agents in causing severe injury to the colonic mucosa of dogs after ten minutes of exposure, as determined by light and scanning electron microscopy: 1.0 normal sodium hydroxide; 0.5 normal sodium hydroxide; 1.25 per cent formalin solution, and silver nitrate sticks. The 1.0 normal sodium hydroxide solution caused injury to both mucosa and muscularis. The 0.5 normal sodium hydroxide produced mucosal injury without damage to the muscularis; the mucosa could be rubbed off with minimal bleeding. Although the mucosa exposed to 1.25 per cent formalin solution or to silver nitrate sticks showed varying degrees of injury, the remaining mucosa was not readily removed by rubbing. Repeat exposure of the mucosa to 0.5 normal sodium hydroxide three days after the first exposure made it easy to remove the mucosa by gentle rubbing but did not cause gross or microscopic injury to the muscularis. Chemical debridement of colonic or rectal mucosa may be a helpful adjunct when the mucosa cannot be removed readily by standard surgical dissection during endorectal pull-through operations.