Fetus-in-fetu presenting as cystic meconium peritonitis: Diagnosis, pathology, and surgical management

Fetus-in-fetu (FIF), a rare congenital anomaly, is a fetus incorporating th e well-differentiated tissue of its twin. The authors describe a newborn wh o presented with massive abdominal distension and severe respiratory distre ss. Abdominal x-rays showed multiple calcifications. The diagnosis of mecon ium pseudocyst was made. At emergency laparotomy an irregular fetiform mass was found in the retroperitoneum lying within a fluid-filled amniotic sec. It contained a vertebral column, 10 limblike structures, and cranial and c audal ends, supporting the diagnosis of fetus-in-fetu. This case highlights several important points. FIF often is overlooked in the differential diag nosis of a newborn abdominal mass and, as in this case, may be confused wit h meconuim pseudocyst. FIF should be differentiated from a teratoma because of the latter's malignant potential. Because this diagnosis is not made un til pathological analysis, all parts of the mass should be removed to preve nt malignant recurrence. Copyright (C) 2000 by W.B. Saunders Company.