1. Introduction

This chapter presents an overview of colonic physiology and diseases affecting the colon. It discusses lower gastrointestinal bleeding, infectious diseases affecting the colon and diseases specifically involving the anus. The main inflammatory bowel diseases have been discussed in Chapter 10. Diarrhea and its causes are examined in Chapter 7, "The Small Intestine." Other infections are presented in Chapter 7 and in Chapter 9, "Gastrointestinal Manifestations of Human Immunodeficiency Virus Infection."