The Colon

Abstract

The large bowel contains up to 400 different bacterial species with concentrations of 10^12–13/ml of feces. All require an intact intracolonic environment to prosper and stay in balance for the benefit of the host [1, 2]. The colon wall has a mature host defense system to keep bacteria in check and prevent their transmural migration into the peritoneal cavity. Structural bowel wall changes such as diverticula, inflammatory bowel disease, and cancer interfere with the colonic wall's ability to contain bacteria and a perforation may result. Similarly, impaired blood supply may diminish oxygen and nutrient supply to cellular structures of the colonic wall, impair colon function in general and cellular defense in particular. Perfusion deficits may progress to frank ischemia when several factors add up. Such a scenario may be seen when edema increases intra-abdominal pressure and reduces venous and arterial blood flow, and when surgical sutures strangulate perianastomotic arterioles [3]. Rather than a barrier and defense against bacterial invasion, the ischemic colon wall now serves as nutrient for bacterial growth, fostering their access to the peritoneal cavity.