Imaging fistula-in-ano

This review has detailed the pathoanatomy of fistula-in ano, and attempted to explain why pre-operative classification is so important to both patient and surgeon. This is one area in which recent radiological developments, most notably MRI, have made real and tangible differences to patients. MRI is now generally available and high quality examination does not require special equipment. It suffers from none of the drawbacks associated with other imaging modalities and for these reasons it could be argued there is little reason to request anything else when assessment of a complex fistula is required. Although usually more expensive than other investigations, it should displace EUA just as MR imaging of the knee has displaced arthroscopy. The added advantage of multiplanar imaging enables fistula anatomy to be imaged in a way that is directly related to surgical planes and exploration. MR imaging is so pre-eminent for fistula classification, that at our institution it is believed to be correct where there is discrepancy between it and other investigations, including EUA. As with any imaging technique, the final arbiter will be the radiologist's familiarity with the condition being investigated, so that he or she can provide relevant clinical information of the highest quality.