During a radical hysterectomy (Wertheim's operation), the ureter is at risk of injury at several points. The most common site of inadvertent ureteral ligation is at which location?

• A At the pelvic brim, where the ureter crosses the bifurcation of the common iliac artery
• B Where the ureter crosses under the uterine artery ('water under the bridge') at the base of the broad ligament ✓
• C At the ureterovesical junction, as the ureter enters the trigone of the bladder
• D In the pararectal fossa, where the ureter lies medial to the internal iliac artery

Explanation

The classic mnemonic 'water under the bridge' refers to the uterine artery crossing superior to the ureter approximately 1.5–2 cm lateral to the cervix at the base of the broad ligament. This is the most dangerous point in hysterectomy, as the ureter lies just beneath the uterine artery when it is clamped and ligated. Failure to identify the ureter at this point leads to inadvertent ureteral ligation or transection, causing postoperative hydronephrosis or urinary fistula. The ureter also crosses the pelvic brim but injury there is less common in routine hysterectomy.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.