A 36-year-old woman comes to the office due to frequent urination since an exacerbation of multiple sclerosis 2 months ago. Most of her symptoms, including dizziness, leg weakness, and numbness, have improved with corticosteroid treatment. However, she has continued difficulty holding urine, and on several occasions has passed a small amount of urine while trying to reach the bathroom. She has no urine leakage during coughing or sneezing. The patient has no other medical problems. Her abdomen is soft and nontender. Neurological examination shows hyperreflexia and increased tone in the lower extremities. Her postvoid residual volume is low.
Glucose, serum 160 mg/dL Urinalysis Blood negative Leukocyte esterase negative Bacteria none White blood cells 3-4/HPF
Which of the following is the most likely explanation for her urinary symptoms?
Differential diagnosis of urinary incontinence | ||
Etiology | Symptoms | |
Stress |
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Urge |
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Overflow |
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This patient's presentation is consistent with urge incontinence, which is due to detrusor overactivity causing a sudden and/or frequent urge to urinate and empty the bladder. The micturition reflex is an autonomic spinal reflex mediated by both sensory and motor fibers from nerve centers at the S2-S4 levels. Parasympathetic stimulation causes detrusor muscle contraction and internal urethral sphincter relaxation. Sympathetic fibers cause internal sphincter contraction and also help with sensing a full bladder.
Multiple sclerosis (MS) is likely an autoimmune disease that causes varying degrees of demyelination, inflammation, and gliosis in the central nervous system (eg, optic nerves, spinal cord, brainstem, periventricular white matter, and cerebellum). Regions in the pons and cerebral cortex partially inhibit the micturition reflex and also regulate contraction/relaxation of the external urethral sphincter. Spinal cord lesions above the sacral region cause a loss of higher center control of micturition and lead to detrusor hyperreflexia and urge incontinence. Patients typically develop a frequent urge to urinate and pass a small amount of urine. As the disease progresses, the bladder can become atonic and dilated leading to overflow incontinence.
(Choice A) Overflow incontinence can be due to impaired detrusor contractility or bladder outlet obstruction (eg, tumor obstructing urethra). Patients usually develop involuntary and continuous urinary leakage when the bladder is full and often have incomplete emptying. Post-void residual urine volume is usually high.
(Choice B) Osmotic diuresis due to hyperglycemia can occur in uncontrolled diabetes mellitus and causes polyuria. However, it more commonly occurs with blood sugar >250 mg/dL. This patient's blood sugar of 160 mg/dL and absence of glycosuria make this less likely.
(Choice C) Bladder infection (cystitis) can cause irritation of the bladder wall and findings similar to urge incontinence with urinary urgency, frequency, and incontinence. However, this patient's relatively normal urinalysis (no leukocyte esterase, hematuria, or bacteria seen) makes this less likely. Up to 5 wbc/hpf is normal.
(Choice D) Stress incontinence occurs in patients with sphincter dysfunction or weakness when intraabdominal pressure exceeds the urethral sphincter pressure (eg, sneezing, coughing), causing involuntary urine leakage. This patient's absence of urinary leakage with coughing or sneezing makes this less likely.
Educational objective:
Patients with multiple sclerosis most commonly develop urge incontinence due to loss of central nervous system inhibition of detrusor contraction in the bladder. As the disease progresses, the bladder can become atonic and dilated, leading to overflow incontinence.