Internal sphincter-saving in imperforate anus with or without fistula. A manometric study.

Manometric assessment was performed in 54 infants with congenital ano-rectal anomalies including those with a blindly ending rectum (6 cases) or with an ectopic bowel outlet either in the perineum (25 cases), vulva (8 cases), vagina (8 cases), urethra (5 cases) or bladder (2 cases). Infants with an externally accessible orifice were investigated preoperatively whereas those with an internal orifice or no orifice could only be evaluated after surgical correction. In all operated cases presented, the ectopic rectal opening was preserved together with its surrounding smooth musculature. It was transplanted ventral to the puborectalis sling into the anal dimple if present. A normal functioning internal sphincter was observed in all infants even after transplantation. Anal resting tone was normal in all cases with mean values in the various subgroups ranging from 32 +/- 10 mmHg to 51 +/- 6 mm Hg. Frequency of anal slow pressure wave activity ranged from 11.6 +/- 1.5/min to 15.7 +/- 1.3/min. The recto-anal inhibitory reflex was present in all cases. The term fistula should be reserved for morphologically and physiologically abnormal microscopic communications. Failure to appreciate the presence of a normal internal sphincter may account for poor functional results after surgery. The results demonstrate the importance of preserving the internal sphincter in surgical correction of anorectal anomalies.