Hemorrhoid.net - Anatomy - Anus and Rectum

Hemorrhoid.net - Anatomy - Anus and Rectum

The Rectal Valves
The rectal valves are crescentic plications, which have a definite structure, including the circular muscle coat of the bowel wall. In the strict sense they are not valves, and the degree to which they are able to function as such, is still debatable. Occasionally, the valves are absent.

The valves are quite variable in number, location and degree of development. Usually there are three: an inferior, middle and superior but occasionally there are five. The inferior valve is usually located in the left posterior quadrant from 2.5 to 3.5 cm above the anal margin. The middle valve, usually more prominent and more constant in location, is situated over the base of the bladder or a little to the right, about 5-9 cm from the anal margin. It is referred to as the plica transversalis of Kohlrousch. The superior valve lies 3-4 cm above the middle valve.


Figure 7: Houston’s valves

According to Stanton, Houston described the rectal valves which bear his name. These valves are reflections of the rectal mucosa, which contain some fibers of the circular muscle coat of the rectal wall. They lie obliquely and transverse to the length of the rectum and project into the length of the rectal lumen (Fig. 7). Their purpose seems to be, to serve as steps or spiral supports to modify the flow of the feces as they descend into the lower rectum.

There are usually three, sometimes four, Houston’s valves. The lowest valve is located to the left of the midline and extends somewhat anteriorly. It is a convenient landmark in that it marks the usual limit of the downward reflection of the peritoneum anteriorly. The next valve is on the right side. This valve is said by some authorities to be on the level of the pouch of Douglas in the female, and the rectovesical pouch in the male.