Urachal

Urachal refers to the urachus, a tubular structure in fetal development that connects the bladder to the umbilicus. In the adult, the urachus normally obliterates and becomes the median umbilical ligament, a fibrous cord extending from the bladder dome to the umbilicus. This remnant lies in the space between the bladder and the anterior abdominal wall and is usually clinically insignificant unless pathological changes occur.

Embryology and anatomy: The urachus arises from the allantois, an extension of the primitive urogenital sinus during fetal growth. After birth, the tract typically involutes completely, leaving behind a fibrous ligament. Abnormal persistence of any portion of the urachus can create congenital urachal anomalies that may present in infancy or adulthood.

Urachal anomalies include patent urachus (vesicourachal fistula), urachal sinus, urachal cyst, and vesicourachal diverticulum. A patent urachus allows urine to discharge from the umbilicus; a urachal sinus opens at the umbilicus but not the bladder; a urachal cyst represents a closed central segment with both ends obliterated; a vesicourachal diverticulum is an outpouching at the bladder end. Infections or inflammation of these remnants can occur and lead to tenderness, discharge, or abdominal symptoms.

Carcinoma arising from urachal remnants is rare but recognized, most commonly presenting as an adenocarcinoma at the bladder dome with mucin production and possible pelvic symptoms. Diagnosis typically involves imaging with ultrasound, computed tomography, or magnetic resonance imaging, sometimes followed by cystoscopy. Management commonly requires surgical excision of the urachal remnant, often including partial cystectomy, with additional therapy as indicated by pathology.