Sacral flexure of rectum

The sacral flexure of rectum is the anteroposterior curvature of the rectum that follows the concavity of the sacrum and coccyx. It is a permanent curve with its concavity directed anteriorly and its convexity directed posteriorly. This flexure results from the rectum conforming to the curvature of the posterior pelvic wall as it descends from the sigmoid colon to the anal canal. The sacral flexure is present in the median plane and is distinct from the three lateral flexures of the rectum, which are produced by the transverse rectal folds (valves of Houston).

Functional correlate

The sacral flexure contributes to the maintenance of faecal continence by creating an angulated pathway that helps prevent the involuntary passage of faeces.