A 48-year-old woman comes to the office due to a 6-month history of involuntary passage of urine when sneezing or coughing. Recently, she has experienced urine leakage even with normal daily activity, which has been embarrassing and has caused her to limit social activities and quit playing tennis. The patient has no weakness, numbness, or fecal incontinence. She has hypertension and type 2 diabetes mellitus. The patient has had 4 uncomplicated vaginal deliveries. Supine blood pressure is 126/82 mm Hg and upright blood pressure is 120/80 mm Hg. Pelvic examination shows normal vaginal rugae and physiologic discharge. A small amount of urine leaks from the urethra when the patient is asked to cough. Neurologic examination is normal. Which of the following is the most likely cause of this patient's condition?
Differential diagnosis of urinary incontinence | ||
Etiology | Symptoms | |
Stress |
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Urge |
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Overflow |
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This patient has urinary incontinence. Continence is maintained by the bladder (detrusor muscle) and external and internal urinary sphincters. The external urinary sphincter (EUS) is a skeletal muscle that receives somatic motor innervation (voluntary control) from the perineal branches of the pudendal nerve (S2-S4). In contrast, the bladder and internal urethral sphincter (IUS) receive autonomic innervation: Sympathetic stimulation promotes urine storage and continence by increasing IUS tone and inhibiting detrusor contractions, and parasympathetic activity relaxes IUS tone and stimulates detrusor contractions, thereby promoting micturition.
Stress incontinence is the leakage of urine with increased intraabdominal pressure (eg, coughing). A common cause is urethral sphincter dysfunction, which usually occurs in women with multiple prior vaginal deliveries. Vaginal delivery is associated with obstetric trauma, which can cause urethral sphincter injury or pudendal nerve injury that contributes to decreased EUS tone. Because of low urethral sphincter tone and increasing pelvic floor laxity with age, sudden increases in intraabdominal pressure (eg, coughing, sneezing) can cause the pressure within the bladder to exceed the urethral closing pressure. This leads to intermittent leakage of urine.
(Choices A, B, and D) Bladder outlet obstruction (eg, tumor obstructing the urethra) and detrusor muscle inactivity (often secondary to diabetic autonomic neuropathy) both lead to urinary retention. In patients with urinary retention, urine slowly accumulates in the bladder until the intravesical pressure exceeds the urethral closing pressure, causing leakage. Because urine is constantly accumulating in the bladder, patients have persistent involuntary dribbling of urine (overflow incontinence) rather than urine leakage with cough. In addition, this patient's normal neurologic examination with no associated numbness or orthostatic hypotension makes diabetic autonomic neuropathy unlikely.
(Choice C) Detrusor overactivity is the underlying mechanism of urge incontinence, which typically presents with a sudden urge to urinate followed by the immediate, involuntary loss of urine. This patient's incontinence episodes typically follow an abrupt increase in intraabdominal pressure (eg, coughing, sneezing), making urge incontinence less likely.
Educational objective:
Stress incontinence, involuntary leakage of urine with increased intraabdominal pressure, can occur due to urethral sphincter dysfunction (eg, decreased sphincter tone). Risk factors include multiple prior vaginal deliveries, which can injure the external urethral sphincter or pudendal nerve.