A term newborn boy is evaluated in the neonatal intensive care unit for respiratory distress. Apgar scores are 2 and 5 at 1 and 5 minutes, respectively. Respirations are 84/min. On examination, the patient has a barrel chest with a scaphoid abdomen and mild cyanosis of his extremities. Auscultation shows absent breath sounds on the left; right lung aeration is normal. Chest x-ray reveals multiple fluid-containing cystic areas on the left and a mediastinal shift to the right. Which of the following embryologic events most likely failed to occur in this patient?
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This newborn with respiratory distress and unilateral decreased breath sounds has a scaphoid abdomen and chest x-ray revealing cystic structures. These findings are consistent with a congenital diaphragmatic hernia (CDH), a congenital malformation caused by failure of the pleuroperitoneal folds to close.
In general, the diaphragm forms from 4 distinct tissues: the septum transversum, esophageal mesentery, musculature from the body wall, and pleuroperitoneal folds. Extension of the pleuroperitoneal folds to these other structures ultimately leads to division of the pericardioperitoneal canal into the peritoneal cavity and thoracic cavity. Failure of closure results in an abnormal communication between the thorax and abdomen. This defect is usually located on the left posterolateral side, allowing bowel, stomach, spleen, and/or liver to herniate into the thorax. Because this malformation occurs during organogenesis in the first trimester, compression of the developing lung leads to pulmonary hypoplasia.
Affected newborns have respiratory distress at birth. Displacement of abdominal organs into the thorax causes the abdomen to appear scaphoid and the chest barrel shaped. Ipsilateral breath sounds are decreased or absent. Chest x-ray findings supportive of CDH include mediastinal shift and thoracic bowel loops, which may appear as cystic, fluid-filled structures.
(Choice B) Failure of ventral body wall closure results in gastroschisis, which is characterized by bowel evisceration without a protective membrane. A full-thickness abdominal wall defect is apparent on examination.
(Choice C) The pleuropericardial membranes, which become the fibrous pericardium, fuse to separate the pericardial and pleural cavities. Fusion defects are rare, often asymptomatic, and result in communication between these two thoracic cavities, not between the thorax and abdomen.
(Choice D) Malrotation, characterized by incomplete physiologic rotation of the bowel in utero, usually presents with bilious emesis in infancy due to duodenal obstruction from abnormally positioned peritoneal bands. Respiratory distress and thoracic bowel loops would not be seen.
(Choice E) Abnormal separation of the dorsal (gastrointestinal tract) and ventral (respiratory tract) foregut results in esophageal atresia with or without a tracheoesophageal fistula. Symptoms include respiratory distress and choking with feeds; chest x-ray would not show cystic thoracic structures.
Educational objective:
Congenital diaphragmatic hernia is caused by failure of the pleuroperitoneal folds to close. Immediately after birth, newborns have respiratory distress, unilateral decreased breath sounds, and a scaphoid abdomen, with imaging revealing thoracic bowel loops and mediastinal shift.