Complicated meconium ileus

Meconium Ileus can be complicated even prenatally:

Dilated loops can twist resulting in atresia of the small intestine or the dilated loops can perforate with the meconium being extruded into the peritoneal cavity.  In patients with perforation, a large cyst can form which attracts fluid into the cyst and this cyst can reach  a significant diameter.  Perforation can also leave calcification of the meconium in the peritoneal cavity.  This can be seen by prenatal ultrasounds or by a post natal flat plate XR of the abdomen.