A woman undergoes uterine artery ligation for postpartum haemorrhage. At what anatomical relationship must the surgeon be careful to avoid the ureter?

• A The ureter passes 1–2 cm lateral to the cervix, under the uterine artery ('water under the bridge') ✓
• B The ureter passes superior to the uterine artery at the pelvic brim
• C The ureter runs in the broad ligament superior to the uterine artery at the level of the internal os
• D The ureter is medial to the uterine artery throughout its pelvic course

Explanation

The mnemonic 'water under the bridge' summarises the critical relationship: the uterine artery crosses OVER (superior to) the ureter at a point approximately 1–2 cm lateral to the cervix at the base of the broad ligament. The ureter (water) passes UNDER (inferior to) the uterine artery (bridge). This relationship is the most common cause of iatrogenic ureteric injury in gynaecological surgery — if the artery is clamped or ligated without identifying the ureter below it, ureteric injury (ligation, kinking, or transection) results in postoperative hydronephrosis and urinary fistula.

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

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Written and medically reviewed by the StethoPrep medical team.