apex of urinary bladder

The apex of the urinary bladder is the anterior angle of the superior surface of the bladder. It is the pointed anterior tip where the median umbilical ligament attaches, connecting the bladder to the umbilicus.

The urachus is an embryonic tube that connects the developing bladder to the allantois and eventually to the umbilicus. In embryos, the apex of the bladder is connected to the umbilicus through the urachus. After birth, the urachus normally closes and becomes the median umbilical ligament, a fibrous cord attached to the bladder apex.

The median umbilical ligament is the fibrous remnant of the urachus in adults. It runs from the apex of the urinary bladder to the umbilicus along the midline of the anterior abdominal wall, lying beneath the peritoneum in the space of Retzius. It is distinct from the medial umbilical ligaments, which are remnants of the umbilical arteries.

If the urachus fails to fully obliterate after birth, various urachal remnants can persist: a patent urachus (open tube from bladder to umbilicus), urachal cyst (fluid-filled cavity along the tract), urachal sinus (opening at the umbilicus), or urachal diverticulum (outpouching at the bladder apex). These can become infected or, rarely, undergo malignant transformation into urachal carcinoma.

In newborns, the bladder is predominantly an abdominal organ and the apex lies at or above the pubic symphysis. As children grow, the bladder descends into the pelvis and the apex moves to a more pelvic position. In adults, the apex is located at the level of the superior pubic ramus when the bladder is empty, but rises as the bladder fills.