Sirenomelia with associated systemic anomalies: an autopsy pathologic illustration of a series of four cases.

Sirenomelia, a developmental defect involving the caudal region of the body, is associated with several internal visceral anomalies. We report a detailed spectrum of anomalies in an autopsy study of four fetuses with sirenomelia (gestational ages - 20, 21, 22.4, and 22.5 weeks). Three of the fetuses had single umbilical artery, with genitourinary and gastrointestinal anomalies. Central nervous system anomalies were evident in two of the fetuses, with alobar holoprosencephaly in one and lumbar meningomyelocele in another. The most common gastrointestinal anomaly was blind ended gut (imperforate anus), while esophageal atresia and omphalocele were noted in one case each. Renal hypoplasia was seen in two fetuses, renal agenesis in one and cystic renal dysplasia was noted in one case. Literature regarding pathogenesis of this condition is briefly discussed.