Describe the mechanism and candidacy criteria for sacral neuromodulation in urinary incontinence.

• A. It uses pelvic floor exercises; candidate with early-stage incontinence
• B. It electrically stimulates sacral nerves to regulate bladder function; candidates with refractory urge or stress urinary incontinence who failed conservative therapy and have intact sensory signaling
• C. It surgically removes the bladder; candidates with mild symptoms
• D. It uses chemotherapy to reduce bladder sensitivity; candidates with cancer

Answer: (B)

Sacral neuromodulation works by delivering electrical stimulation to the sacral nerves, typically the S3 nerve root, through a implanted lead and pulse generator. This stimulation modulates the neural reflexes that control bladder storage and voiding, altering afferent signaling and efferent reflexes to reduce involuntary bladder contractions and improve continence. In practice, this can increase bladder capacity and stabilize the storage phase, helping both urge and some forms of stress incontinence.

Candidacy focuses on patients who have not responded to conservative measures (such as pelvic floor exercises, bladder training, and medications) and who have intact neural signaling and bladder function. Ideal candidates generally have refractory urge incontinence or stress incontinence with no evidence of detrusor underactivity or bladder outlet obstruction. They must be able to undergo surgical implantation and tolerate the device, have no active infection, and typically undergo a trial period of temporary stimulation to assess response before permanent implantation.