A 45-year-old woman undergoing radical hysterectomy develops urinary retention postoperatively. This most likely results from inadvertent injury to which structure?

• A Hypogastric nerve (sympathetic) within the parametrium
• B Pudendal nerve supplying the external urethral sphincter
• C Obturator nerve in the obturator canal
• D Pelvic splanchnic nerves (S2-S4) carrying parasympathetic fibers to the bladder detrusor ✓

Explanation

Pelvic splanchnic nerves (nervi erigentes, S2-S4) carry preganglionic parasympathetic fibers that provide the main motor supply to the detrusor muscle of the bladder (causing bladder contraction and voiding). These nerves run lateral to the rectum in the rectal pillars and are vulnerable during posterior dissection in radical hysterectomy (Wertheim's hysterectomy). Their injury causes acontractile detrusor and urinary retention. The inferior hypogastric plexus (sympathetic) injury causes the reverse — inability to maintain continence. Pudendal nerve injury impairs the external sphincter only.

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

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Written and medically reviewed by the StethoPrep medical team.