Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 50-year-old man is evaluated for a 1-year history of increasing urinary frequency and urgency and occasional urge incontinence. He has no symptoms of urinary hesitancy or incomplete emptying. The patient has primary progressive multiple sclerosis. Medications are dalfampridine and vitamin D.

On physical evaluation, temperature is 36.8 °C (98.2 °F), blood pressure is 120/55 mm Hg, and pulse rate is 68/min. Findings of abdominal and digital rectal examinations are normal. Finger-to-nose testing reveals dysmetria bilaterally. Leg tone is increased bilaterally. Muscle strength is 4/5 in both legs. Gait testing reveals spasticity and ataxia.

A urinalysis is negative for infection.

Which of the following is the most appropriate treatment?

A: Finasteride
B: Intermittent urinary catheterization
C: Oxybutynin
D: Prophylactic antibiotics

MKSAP Answer and Critique

The correct answer is C: Oxybutynin.

This patient should be treated with an anticholinergic medication, such as oxybutynin, for bladder spasticity due to myelopathy from multiple sclerosis (MS). Several different patterns of bladder dysfunction are associated with MS, with urge incontinence due to uninhibited detrusor function caused by denervation at the level of the spinal cord being the most common. This form of bladder dysfunction responds well to anticholinergic medications, which reduce the intensity and frequency of bladder spasms and reduce urgency, frequency, and incontinence. Other forms of dysfunction include bladder inactivity (leading to overflow incontinence), the loss of the sensation of bladder fullness, and other sensory deficits that also may impair bladder emptying. These conditions are more difficult to treat because anticholinergic agents can worsen urinary retention and lead to predisposition to urinary tract infection. Patients with mixed bladder symptoms may require further diagnostic testing to better delineate the cause of incontinence.

Finasteride is a 5α-reductase inhibitor used to treat benign prostatic hyperplasia (BPH) and would have no effect on bladder spasticity. This patient is unlikely to have BPH given the normal findings on digital rectal examination and the absence of urinary hesitancy.

Intermittent urinary catheterization also has no role in isolated bladder spasticity. This patient had no symptoms or signs of urinary retention, which would be relieved by catheterization. It may, however, have a role in selected patients with complex bladder dysfunction due to MS who are not appropriate candidates for or do not respond to medical therapy.

Although patients with bladder dysfunction are at increased risk for urinary tract infection, assessing the type of bladder dysfunction present and providing appropriate treatment are indicated. Prophylactic antibiotics would not be indicated as management of this patient’s urinary incontinence in the absence of evidence of infection or recurrent infections due to bladder dysfunction refractory to therapy.

Key Point

• In patients with multiple sclerosis, anticholinergic agents reduce the intensity and frequency of bladder spasms and thus may reduce symptoms of urgency, frequency, and incontinence.

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