Final answer:
A patent urachus is a condition where the urachus, an embryonic duct, fails to close and instead remains as an open channel from the umbilicus to the bladder.
Step-by-step explanation:
A patent urachus is a condition resulting from the incomplete closure of the embryonic duct that connects the fetal bladder to the umbilicus. Normally, the urachus becomes a fibrous cord that obliterates and becomes a part of the umbilical ligament after birth. If it fails to close, a patent urachus forms, maintaining a physical connection between the umbilicus and the bladder. The process of clamping and cutting the umbilical cord includes the obliteration of the umbilical blood vessels which should, in time, become fibrotic remnants as part of the mature circulatory system. In a patient with a patent urachus, this does not happen properly, and instead of fibrotic remnants, there remains an open channel from the umbilicus to the bladder.