The prenatal diagnosis of imperforate anus with rectourinary fistula: dilated fetal colon with enterolithiasis.

The finding of extraluminal calcifications is commonly reported and usually indicates intrauterine intestinal perforation with intraperitoneal extravasation of meconium, most often associated with intestinal obstruction and/or atresias. Intraluminal calcification of meconium is more rare and appears to result from the mixing of stagnant urine and meconium in utero. The presence of the intraluminal calcifications in a dilated loop of intestine, particularly with an associated urinary tract abnormality, should suggest a rectourinary fistula. Two cases of prenatally diagnosed imperforate anus with rectourinary fistulae are reported.