Surgical pathology of the infected gut.

In the normal digestive tract, interaction of the mucosa with a large and varied microbial flora is inevitable. In fact, the "normal" state of the digestive tract reflects the impact of the resident flora to a significant degree. The pathogenesis of various infectious conditions encountered by the surgical pathologist in the gut is understood more readily when the gastrointestinal tract is viewed as a complex ecosystem. Significant disease may result from perturbation of the normal flora, as well as from exogenous infection, and susceptibility of the host may vary with disturbances of the digestive ecosystem. An ecologic perspective is essential in the consideration not only of the "infected" gut, but of conditions as diverse as ischemia or even carcinogenesis in the gastrointestinal mucosa.