Case 246: MR Imaging of a Complex Cystic Mass in a Newborn Girl.

History A 6-day-old female neonate presented to the outpatient pediatric surgery clinic for evaluation of a possible prenatal abdominal mass. The neonate was delivered at term via cesarean section due to macrosomia, with a reported birth weight of 11 lb 8.7 oz (5.23 kg). The patient's postnatal course was remarkable for resolving neonatal hyperbilirubinemia. A physical examination was remarkable for a palpable mass in the abdomen. Maternal risk factors included class II obesity, type 2 diabetes, and metabolic syndrome. Prenatal images obtained at an outside institution were not available at this time. Ultrasonography (US) of the abdomen and pelvis was performed 6 days after birth. Follow-up US at 29 days of life revealed no substantial change in the appearance of the findings. This patient remained asymptomatic, and gadolinium-enhanced (Magnevist; Bayer Pharma, Berlin, Germany) magnetic resonance (MR) imaging of the abdomen and pelvis was performed at 84 days of life. The mass was excised surgically at 89 days of life, and the patient had an uncomplicated postoperative course.