Urachus

The urachus is a fibrous remnant of the allantois, a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord. The fibrous remnant lies in the space of Retzius, between the transverse fascia anteriorly and the peritoneum posteriorly.Inguinal fossaeCT scan (sagittal reconstruction) showing an urachus rest as an incidental finding in a 44-year-old man, the trajectory moves forward and upward from the bladder to the umbilicus in the midline.Ultrasound of fetus showing urachus duct from bladder to the umbilicus.Ultrasound of fetus showing urachus duct from bladder to the umbilicus.Ultrasound of fetus showing urachus duct from bladder to the umbilicus.Ultrasound of fetus showing urachus duct from bladder to the umbilicus.Ultrasound of fetus showing urachus duct from bladder to the umbilicus. The urachus is a fibrous remnant of the allantois, a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord. The fibrous remnant lies in the space of Retzius, between the transverse fascia anteriorly and the peritoneum posteriorly. The part of the urogenital sinus related to the bladder and urethra absorbs the ends of the Wolffian ducts and the associated ends of the renal diverticula. This gives rise to the trigone of the bladder and part of the prostatic urethra. The remainder of this part of the urogenital sinus forms the body of the bladder and part of the prostatic urethra. The apex of the bladder stretches and is connected to the umbilicus as a narrow canal. This canal is initially open, but later closes as the urachus goes on to definitively form the median umbilical ligament.