Expansion
Patent urachus, urachal sinus, urachal cyst and bladder diverticulum
Expansion
The urachus is the obliterated remnant of the allantois, running from the apex of the bladder to the umbilicus in the median umbilical ligament. Failure to obliterate gives:
- Patent urachus - the whole tract persists; urine leaks from the umbilicus
- Urachal sinus - the umbilical end persists; discharging umbilicus
- Urachal cyst - the middle persists; presents later with infection and a suprapubic mass
- Vesicourachal diverticulum - the bladder end persists; usually asymptomatic
Patent urachus is associated with posterior urethral valves or other bladder outflow obstruction, since the raised pressure keeps the tract open, so the whole urinary tract must be assessed.
In adults, a persistent urachal remnant is a rare site of adenocarcinoma, which typically presents with haematuria and a midline suprapubic mass.