- 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.
* * *That portion of the reduced allantoic stalk between the apex of the bladder and the umbilicus; postnatally, the u. is normally merely a fibrous cord, the median umbilical ligament, but occasionally the old allantoic lumen may persist as a vesicoumbilical fistula. [G. ourachos, the urinary canal of a fetus]
* * *ura·chus -kəs n a cord of fibrous tissue extending from the bladder to the navel and constituting the functionless remnant of a part of the duct of the allantois of the embryo
* * *n.the remains of the cavity of the allantois, which usually disappears during embryonic development. In the adult it normally exists in the form of a solid fibrous cord connecting the bladder with the umbilicus, but it may persist abnormally as a patent duct.• urachal adj.
* * *ura·chus (uґrə-kəs) [Gr. ourachos] the derivative of the allantoic stalk in the fetus that connects the urinary bladder with the umbilicus; it persists throughout life as a fibrous cord, the median umbilical ligament, into which a patent canal may extend for part of the distance to the umbilicus. urachal adj
Medical dictionary. 2011.