Assessment and classification of fistula-in-ano in patients with Crohn's disease by hydrogen peroxide enhanced transanal ultrasound

Crohn's disease is well known for its perianal complications, among which f istulas-in-ano are the most common abnormalities. Fistulas-in-ano in Crohn' s disease tend to be complex and have a high recurrence rate. Therefore the role of surgery is generally more conservative. Hydrogen peroxide enhanced transanal ultrasound has proven superior to physical examination, fistulog raphy, computed tomography, and conventional ultrasound in demonstrating th e fistula tract. This study examined the fistula tracks in patients with Cr ohn's disease. Forty-one patients with Crohn's disease and fistula-in-ano w ere investigated using physical examination, sondage of the fistula, procto scopy and transanal ultrasound. Hydrogen peroxide was infused via a small c atheter into the fistula. The main track and the ramification of the fistul a were classified according to the anatomical Parks' classification. Only 9 (22%) patients had a single inter- or transsphincteric fistula. In 5 (12%) patients a single supra- or extrasphincteric fistula (high fistula) was fo und, in 14 (34%) more than one fistula track (ramified), and in 13 (32%) an anovaginal fistula. Thus 78% of patients had a surgically difficult to tre at fistula. In the ramified fistula the main track follows the Parks' class ification, but ramifications can have a bizarre pattern which is not in agr eement with this classification. Optimal documentation by means of hydrogen peroxide enhanced transanal ultrasound is therefore mandatory before surge ry or before other therapies such as anti-tumor necrosis factor treatment.