A sterile chemical peritonitis that occurs in utero from fetal bowel perforation and spillage of meconium into the peritoneal cavity. The bowel perforates as a result of bowel obstruction, such as atresias or meconium ileus. Usually the perforation seals off and the bowel is intact at birth. Intraperitoneal meconium usually calcifies, sometimes within 24 hours. If the processus vaginalis is patent at the time of perforation, calcification may also be seen in the scrotum. Complications are ascites, bowel obstruction from the formation of fibroadhesive bands, and meconium pseudocyst (a walled-off mass of meconium surrounded by a calcific rim).

References:
1. Blickman H. Paediatric Radiology The Requisites, 2nd edition. Mosby 1998
2. Dahnert W. Radiology Review Manual, 5th edition. Lippincott, Williams and Wilkins 2003

Credit: Dr Donna D’Souza
http://www.radpod.org