[Anteposition of the anus. A cause of constipation in children].

Certain forms of severe constipation, unresponsive to medical treatment and classified as "idiopathic", have been thought to be anatomical anomalies due to anterior-displacement of the anus. The difficulty in defecation varies with the anal anomaly: this may range from passing of feces every 3-4 days to sub-occlusion episodes due to obstruction of the rectum from phecaloma and with sign of malnutrition, anemia and hypotrophy. Anatomically the anomaly is characterized by an anterior positioning of the anus which deviates the terminal part of the rectum in a horizontal plane creating a "cul-de-sac" which arrests normal fecal advancement. Fecal stasis in the rectal ampulla leads to an increase in the distensibility of the rectum with loss of the normal stimulus to defecate and contractile activity. Diagnosis is made by physical examination, barium enema (which reveals the rectal "cul-de-sac" and the distension of the colon) and ano-rectal manometry to rule out Hirschsprung diseases. The authors report their experience with 11 cases of anterior displacement of the anus, presenting a simple surgical treatment and the favorable results.