Six-month survival of a monochorionic monoamniotic twin with sirenomelia

Sirenomelia is a congenital malformation of the lower body characterized by a single midline lower limb and severe urogenital and gastrointestinal malformations. Sirenomelia is rare (estimated incidence of approximately 1/100,000) and usually lethal in the perinatal period.

A 2,042 g Japanese male infant, one of monochorionic monoamniotic twins, was born at 34 weeks of gestation by elective caesarean section. Sirenomelia was prenatally diagnosed. Single midline lower limb, bilateral dysplastic kidneys, an omphalomesenteric fistula, colon atresia, imperforate anus, indiscernible genital structures, and myelomeningocele were detected at birth. The amniotic fluid volume was normal throughout the pregnancy course, which led to appropriate lung maturation of the twin with sirenomelia. Although renal replacement therapy was initiated soon after birth, stable peritoneal dialysis was difficult because of the limited intraperitoneal space, and the infant frequently developed peritonitis. He died of sudden cardiorespiratory arrest at 6 months of age. Postmortem examination showed bilateral dysplastic kidneys, agenesis of the ureters and urinary bladder, abnormal branching and agenesis of the distal colon, bilateral inguinal hernias, and small testes.

Infants with sirenomelia, even those with end-stage kidney disease at birth, may survive if they have a stable cardiorespiratory status at birth and renal replacement therapy is appropriately initiated.