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Physical examination of a young boy reveals discharge of urine from the umbilicus. The physician concludes that the urachus has failed to fuse. Which of the following structures is the normal adult remnant of the fused urachus?
A. Lateral umbilical fold
B. Medial umbilical fold
C. Medial umbilical ligament
D. Median umbilical fold
E. Median umbilical ligament
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E is correct
The correct answer is E. The urachus is the derivative of the allantoic duct, which passes from the urogenital sinus to the umbilical cord. Normally, this duct fuses and is no longer patent. The adult derivative is the median umbilical ligament, which lies in the midline along the interior surface of the anterior abdominal wall. It passes from the upper end of the bladder to the umbilicus.
The lateral umbilical fold (choice A) is the fold of parietal peritoneum that covers the inferior
epigastric artery and vein on the interior surface of the anterior abdominal wall.
The medial umbilical fold (choice B) is the fold of parietal peritoneum that covers the medial umbilical ligament, the adult derivative of the umbilical artery (see below).
The medial umbilical ligament (choice C) is the adult derivative of the distal portion of the umbilical artery. The umbilical artery arises from the internal iliac artery. It passes along the bladder and then the anterior abdominal wall to reach the umbilicus. Prenatally, this artery carries fetal blood to the placenta, where it gains oxygen and nutrients. Postnatally, the proximal part of the umbilical artery remains patent and supplies blood to the superior surface of the bladder. Distal to the bladder, the artery becomes fibrotic and is known as the medial umbilical ligament.
The median umbilical fold (choice D) is the fold of parietal peritoneum that covers the median umbilical ligament, the adult derivative of the urachus.
