A newborn boy is examined in the nursery shortly after birth. He was born at term by vaginal delivery to a 40-year-old woman who did not receive prenatal care. Temperature is 36.7 C (98 F), pulse is 132/min, and respirations are 38/min. Examination shows slanted palpebral fissures, epicanthal folds, thick nuchal folds, and a single palmar crease. The patient has a large, reducible midline abdominal protrusion covered by skin that is more pronounced when he cries. The umbilical stump is at the center of the protrusion. Which of the following is the most likely cause of this patient's abdominal finding?
Pediatric abdominal wall defects | ||
Diagnosis | Pathophysiology | Clinical features |
Congenital umbilical hernia |
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Omphalocele |
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Gastroschisis |
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This patient's abdominal examination is consistent with a congenital umbilical hernia. Normally, the umbilical ring (ie, the congenital fascial opening for the umbilical cord) closes and forms the linea alba, a midline band of fibrous tissue. Umbilical hernias are caused by an incomplete closure of the umbilical ring, thereby allowing protrusion of bowel through the abdominal musculature. This generally benign condition is often an isolated defect, but patients with certain genetic conditions are more likely to develop an umbilical hernia, as in this newborn with features consistent with Down syndrome (eg, palpebral fissures, epicanthal folds, single palmar crease).
Almost all congenital umbilical hernias are reducible and asymptomatic. They often appear larger and more prominent with increased abdominal pressure (eg, crying). Incarceration and strangulation are very rare.
Most umbilical hernias resolve spontaneously in the first few years of life as the fascial layers fuse.
(Choice A) During midgut development in the first trimester, the abdominal contents undergo physiologic herniation, followed by a rotation of the midgut and physiologic reduction. Failure of this reduction may contribute to omphalocele, which presents as a midline herniation of abdominal contents contained within a thin, membranous sac. It is not covered by skin, in contrast to this patient.
(Choice C) Midgut development in the first trimester involves a physiologic occlusion of the intestinal lumen followed by recanalization. Failure of recanalization results in duodenal atresia, which is associated with Down syndrome. However, symptoms include vomiting, often bilious, in the first 24 hours of life.
(Choice D) Malrotation results from an incomplete rotation of the midgut prior to physiologic reduction into the abdominal cavity; malrotation alone is asymptomatic. Its main complication is volvulus (intestinal torsion), which results in bowel ischemia and necrosis from constriction of the blood supply. In contrast to this patient, volvulus typically presents with bilious emesis in the first month of life.
(Choice E) Congenital inguinal hernias develop when the processus vaginalis, an outpouching of the peritoneum, fails to obliterate, allowing bowel contents into the inguinal canal. Inguinal hernias are more prominent with increased abdominal pressure, but they present as a mass in the groin, not the umbilicus.
Educational objective:
Umbilical hernias are caused by a defect in the linea alba and present as protrusions at the umbilicus that are soft, reducible, and benign. They can occur in isolation or in association with other conditions (eg, Down syndrome).