Lateral flexures of rectum

The three lateral flexures of rectum are permanent lateral curvatures or bends of the rectal lumen that correspond internally to the transverse rectal folds (valves of Houston). Unlike the sacral flexure, which lies in the median plane, these flexures (or bends) occur in the coronal plane and impart an alternating side-to-side course to the rectum.

Typically, there are three lateral flexures:

• Superior lateral flexure it located in the upper third of the rectum, just below the rectosigmoid junction (near S3 vertebral level). The convexity of this bend projects to the right side and is associated with the superior transverse rectal fold which projects internally into the flexure from the left rectal wall).

• Middle lateral flexure (Kohlrausch's fold) is the most prominent bend of the rectum with its convexity facing leftwards. It lies approximately 6-8 cm above the anal verge (opposite the middle of S3 vertebrae). It corresponds with the middle transverse rectal fold which projects internally into the flexure from the right rectal wall.

• Inferior lateral flexure projects to the right side and is associated with the inferior transverse rectal fold. It lies opposite the S4 vertebral level.

Alongside the transverse rectal folds (valves of Houston), these lateral flexures help support the weight of accumulated faecal matter, thereby contributing to continence by preventing the premature descent of faeces into the anal canal.