Urachus: A canal connecting the bladder of the fetus with the allantois, a structure that contributes to the formation of the umbilical cord. The lumen (inside) of the urachus is normally obliterated during embryonic development, transforming the urachus into a solid cord, a functionless remnant.
Failure for the lumen of the urachus to be filled in leaves a patent (open) urachus. The telltale sign is leakage of urine through the umbilicus. A patent urachus needs to be surgically removed. (from MedineNet)
Images and case from NEJM N Engl J Med 2011; 365:1328 October 6, 2011
A 1-day-old male neonate was transferred to our hospital for evaluation of a 2.5-cm mass arising from the umbilicus. The mass was covered in granulation tissue. When the patient cried, straw-colored fluid leaked intermittently from an orifice in the lesion (Panel A). There were no urinary symptoms, and the remainder of the physical examination was remarkable only for bilateral undescended testicles. Infusion of water-soluble radiopaque contrast material into the orifice under lateral fluoroscopic imaging showed a fistula tract (Panel B, white arrow) leading from the urinary bladder (arrowhead) to the umbilical lesion (black arrow). Surgical exploration confirmed that the tract was a developmental abnormality known as a patent urachus. When the urachal tract is not completely obliterated during embryonic development, a bladder diverticulum, urachal cyst, umbilical polyp, or patent urachus may result. This infant’s urachal tract was surgically excised, and his bladder was repaired. After an uneventful postoperative course, he was discharged home to the care of his parents. He continues to be screened for the development of vesicoureteral reflux. Ming-Shian Tsai, M.D., Ph.D. Ming-Lun Yeh, M.D. E-Da Hospital, Kaohsiung, Taiwan
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