Embryology USMLE Step 1 Practice Question
A 2-month-old girl is brought to the emergency department by her parents who noticed a pulsatile abdominal mass during diaper changes. The infant has been feeding poorly over the past week and had one episode of dark, tarry stools yesterday. Vital signs show: HR 145/min, BP 82/50 mmHg, RR 36/min, temperature 37.0°C. Physical examination reveals a tender, pulsatile mass in the periumbilical region. Laboratory studies show hemoglobin 9.8 g/dL (previously 11.5 g/dL 2 weeks ago) and normal prothrombin time. Abdominal ultrasound demonstrates a dilated vascular structure originating from the umbilicus with heterogeneous echogenicity and no active arterial flow. Bilirubin and liver function tests are normal. Which embryologic remnant is most likely responsible for this presentation?
Answer choices
- AIncomplete obliteration of the ductus venosus
- BPersistent vitelline (omphalomesenteric) arteryCorrect answer
- CMeckel diverticulum with heterotopic gastric mucosa
- DPatent urachus with focal inflammation
- ERemnant of the mesonephric (Wolffian) duct
- FPersistent truncus arteriosus with umbilical origin
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