The urinary duct (urachus, lne; synonym: urinary tract, urachus) is a thin duct that in the prenatal period connects the bladder to the amniotic cavity. It is formed from the vitelline duct and is a remnant of the allantois. After birth, the urinary duct becomes obliterated and becomes the median umbilical vesical ligament. Sometimes the urinary duct can be partially preserved and give rise to various cystic formations.