What is a fistula in ano?

A fistula in ano refers specifically to an abnormal connection or passage that forms between the anal canal and the skin near the anus. This tubular tract is often the result of an abscess that has formed in the anal area, leading to drainage and ultimately creating a channel that opens externally beside the anus.

The presence of a skin opening near the anus is characteristic of a fistula in ano, typically accompanied by discharge, discomfort, and sometimes infection. In understanding this condition, it is important to recognize that it entails both the internal aspect (the connection to the anal canal) and the external aspect (the skin opening).

The other options describe different conditions or anatomical structures. A cyst near the tailbone pertains more to conditions like pilonidal cysts, while severe protrusion of rectal tissue pertains to rectal prolapse. A type of colitis refers to inflammation of the colon and does not have a direct relationship with the concept of a fistula. Thus, the choice that accurately defines a fistula in ano is the one that highlights its tubular nature and the resultant opening beside the anus.