Contrast studies are commonly performed to identify the presence of a fistulous connection between urinary tract and rectum in children with ano-rectal malformation (ARM) before definitive repair. It is usually carried out by a micturating-cystourethrogram (MCUG) and/or by distal loopogram (DL) via a mucous fistula if a colostomy was performed. We wanted to evaluate the efficacy of these contrast studies in predicting the presence of fistula.
Records of all patients who underwent surgical repair for ARM at a single centre over 20yrs period were reviewed. Boys who had no fistula, or presence of fistulous connections between the rectum and urinary tract at operation were identified. Male patients with perineal fistula and all females were excluded. We compared the results of pre-operative contrast studies with operative findings to evaluate the accuracy in predicting the presence and level of fistulous connection.
Total 42 boys with intermediate or high ARM were identified. Fistulous connection at operation were noted in 26; 6 vesical, 9 prostatic and 11 bulbar-urethra. 25/26 had contrast studies prior to definitive surgery. 12/25 (48%) failed to demonstrate any fistula; 2 vesical, 8 prostatic and 2 bulbar. Only 13/25 (52%) identified a fistula; MCUG and DL alone identified the fistula in 6 and 5 cases respectively whereas both studies revealed fistula in further 2 cases.
Pre-operative contrast studies identify fistulas only slightly more than half the time. However, MCUGs have the added benefit of identifying other urological abnormalities such as reflux. MCUG or DL by themselves are far less sensitive than combined studies.