A 2-week-old boy is brought to the clinic by his parents for evaluation of his umbilicus. The parents report that since the umbilical cord stump separated 2 days ago, there has been drainage from the umbilicus that increases when the patient cries. He is exclusively breastfed and continues to have normal wet diapers and stool output. The patient was born at term, and the pregnancy and delivery were uncomplicated. Vital signs are normal. Physical examination of the abdomen shows clear to pale yellow fluid leaking from the umbilical stump site with mucosal tissue at the base of the umbilicus. Samples are obtained for complete blood count. Laboratory results are as follows:
| Hemoglobin | 14 g/dL |
| Platelets | 240,000/mm3 |
| Leukocytes | 11,000/mm3 |
| Neutrophils | 60% |
| Lymphocytes | 32% |
Which of the following is the most likely cause of this patient's umbilical findings?
Neonatal umbilical drainage | ||
Diagnosis | Anatomy | Clinical findings |
Umbilical granuloma |
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Patent urachus |
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Patent omphalomesenteric duct |
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Omphalitis |
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Umbilical drainage in a neonate may be due to granulation tissue, infection, or congenital anomaly. In this case, the patient's persistent pale-yellow drainage (consistent with urine) is suggestive of a congenital urachal abnormality.
In utero, the caudal yolk sac normally forms a tubular outpouching called the allantois, which extends from the embryologic bladder to the umbilicus. As the bladder descends into the fetal pelvis, it stretches the allantois, which becomes thin and narrow. Epithelial proliferation obliterates the allantois lumen by 12 weeks gestation, forming a fibrous cord known as the urachus.
Failed obliteration of the allantois can lead to a patent urachus. This connection between the bladder and the umbilicus results in urinary umbilical drainage that increases with intraabdominal pressure (eg, crying, straining, prone positioning). Partially failed obliteration can result in a range of defects, including a urachus that is open to the umbilicus (urachal sinus), open to the bladder (urachal diverticulum), or open only centrally (urachal cyst).
(Choice A) Leukocyte adhesion deficiency is characterized by impaired leukocyte migration due to defective adhesive molecules. Patients typically have leukocytosis and delayed (>1 month) umbilical cord stump separation, findings not present in this case.
(Choice B) A duplication of the renal collecting system (eg, 2 ureters originating from a single kidney) can result in aberrant insertion of a ureter into structures such as the urethra or epididymis. The umbilicus is not involved, so umbilical drainage does not occur.
(Choice C) Incomplete closure of the anterior abdominal wall describes gastroschisis, in which viscera protrude through an abdominal wall defect adjacent to the umbilicus. Isolated umbilical drainage is not consistent with this diagnosis.
(Choice D) The omphalomesenteric (or vitelline) duct is a diverticulum of the yolk sac that extends from the embryologic midgut to the umbilicus; it normally involutes in early gestation. Persistent patency connects the bowel to the umbilicus, and patients may exhibit fecal (not urinary) umbilical discharge.
Educational objective:
The urachus is a remnant of the allantois that extends from the bladder to the umbilicus. Failed obliteration of the allantois lumen can result in a patent urachus, which presents with urinary drainage from the umbilicus in the neonate.