Friday, 4 April 2014

Pelvic floor imaging part 6: what is anismus?

This is the latest post in my series about pelvic floor imaging, you can catch up with all the previous articles here. This post focusses on what is arguably the most difficult (and controversial) diagnosis to make: anismus or anorectal dyssynergy

The video above is of a defaecating proctogram showing the features of anismus. This disorder is defined by abnormal relaxation or failure of relaxation of one of the core pelvic floor muscles: puborectalis. This muscle forms a sling around the back of the lower part of the rectum, and is normally contracted (tense). When someone attempts to open their bowels, it should relax, and allow the angle between the rectum and anal canal to straighten. In anismus, there is either a failure of relaxation, or what is known as paradoxic contraction, i.e. the muscle tenses even more.

Graphical representation of pelvis, with puborectalis labelled "A", forming a sling behind the lower rectum ("C"). (image from Wikipedia)

This means that the angle between the rectum and anal canal doesn't straighten properly, and usually very little or none of the barium paste is expelled. In the video, you can see that the patient is attempting to open their bowels but none of the paste is expelled.

It is important to try to distinguish anismus from the effects of anxiety caused by the test. If someone feels anxious and tense, they may not be able to fully relax the muscle and the appearances then (wrongly) suggest anismus. The ways that this can be avoided include a full explanation of the test, time taken to go through any queries or concerns, a cohesive team of radiographers and radiologists, and most of all, showing empathy for the patient. This is not a pleasant test to undergo, and it takes place in a cold sterile hospital room. The conditions are not the best to be able to do something that people have great difficulty doing at home. It is an important part of the radiologist and radiographer's jobs to put the patient at ease to ensure that a false diagnosis of anismus is not reached.

The next post in this series will look at how proctograms are done using MRI instead of xrays.

Dr Vikas Shah
Consultant Radiologist