Friday, 21 February 2014

Pelvic floor imaging part 4: what is a rectal prolapse?

So far in this series, I have covered what is involved in having a proctogram (variously known as defaecating, defecating, voiding or evacuating proctogram), and what a rectocoele looks like.

This post focusses on another important finding: a rectal prolapse.

A rectal prolapse is suspected when people complain of a feeling of a lump coming out of the back passage. The problem starts with the lining of the bowel becoming thicker and looser (rectal mucosal thickening) and starting to droop down. This is known as mucosal thickening and intussusception. This by itself will not cause a feeling of a lump coming out but commonly makes people feel a fullness in their back passage even when they don't need to go to the toilet. 
The intussusception - prolapse spectrum


Eventually, the whole thickness of the wall of the bowel droops down into the anal canal (recto-anal intussusception) and may end up drooping down all the way to the anal verge (the outside of the back passage, known as a full thickness external prolapse). Usually the prolapse will go back in by itself or with some gentle pressure but sometimes it can stay outside permanently. This movie clip shows the development of a rectal prolapse:


When someone describes symptoms of a prolapse, a proctogram test is done because sometimes it is difficult to see a prolapse in clinic. Not only can the proctogram test reveal the prolapse but it can also show how small or big it is, and show other problems such as an enterocoele or a rectocoele.

The final image of the proctogram shows some of the rectum lying outside of the back passage:



There is some confusion on the internet about the terminology. Many people refer to a weakening and bulging of the front wall of the rectum as a rectal prolapse but this is incorrect. Weakening and bulging of the front wall of the rectum into the back of the vagina is a rectocoele, which I described in the previous post in this series. In my experience, the two different problems aren't commonly seen together. When someone has a rectocoele and a rectal prolapse, it is usually the back wall of the rectum that prolapses out and the front wall bulges forward into the back of the vagina.

In the next post, I will describe another type of prolapse: an enterocoele, which is prolapse of the small bowel.


Dr Vikas Shah
Consultant Radiologist
Leicester

(If you think you need this test, it is advisable to see your doctor first and then I am happy to be involved in any consultations. Please see the Contact Me page for more details).