Urinary Incontinence for USMLE Step 3
Urinary Incontinence for the USMLE Step 3 Exam
- Definition:
- Urinary incontinence is the involuntary leakage of urine. It can be classified into stress, urge, overflow, and functional incontinence. Mixed incontinence occurs when more than one type is present.
- Types of Urinary Incontinence:
- Stress Incontinence:
- Occurs when intra-abdominal pressure (e.g., from coughing, sneezing, or physical activity) exceeds urethral sphincter resistance.
- Pathophysiology:
- Commonly caused by pelvic floor muscle weakness, seen in women after childbirth or menopause. In men, it can occur after prostate surgery.
- Risk Factors:
- Vaginal delivery, obesity, pelvic surgery, and aging.
- Urge Incontinence:
- Characterized by a sudden, strong urge to void, followed by involuntary urine leakage.
- Pathophysiology:
- Caused by detrusor overactivity, which may be due to neurological disorders (e.g., Parkinson’s disease, multiple sclerosis) or idiopathic overactivity.
- Symptoms:
- Urgency, frequency, and nocturia.
- Overflow Incontinence:
- Results from incomplete bladder emptying, leading to continuous dribbling of urine.
- Pathophysiology:
- Caused by bladder outlet obstruction (e.g., benign prostatic hyperplasia [BPH]) or impaired detrusor muscle contraction (e.g., diabetic neuropathy).
- Risk Factors:
- BPH, neurogenic bladder, and spinal cord injury.
- Functional Incontinence:
- Occurs when physical or cognitive impairments prevent timely access to a toilet, despite normal bladder function.
- Risk Factors:
- Dementia, severe arthritis, postoperative immobility.
- Evaluation:
- History and Physical Examination:
- Obtain a detailed history of incontinence episodes, including the frequency, triggers, and associated symptoms (e.g., urgency, nocturia). Perform a pelvic exam in women to assess for pelvic organ prolapse and a digital rectal exam in men to evaluate for prostate enlargement.
- Postvoid Residual Volume (PVR):
- Measured by ultrasound or catheterization to assess for incomplete bladder emptying. High PVR suggests overflow incontinence.
- Urinalysis:
- Helps exclude urinary tract infections (UTIs) or hematuria.
- Bladder Diary:
- A diary documenting voiding patterns, fluid intake, and leakage episodes helps identify the type of incontinence.
- Management:
- Lifestyle Modifications and Behavioral Therapy:
- Pelvic Floor Exercises (Kegel Exercises):
- First-line treatment for stress incontinence, aimed at strengthening the pelvic muscles.
- Bladder Training:
- Recommended for urge incontinence, it involves scheduled voiding and progressively increasing the time between voids.
- Weight Loss:
- For patients with obesity, weight loss decreases intra-abdominal pressure and improves symptoms of stress incontinence.
- Fluid Management:
- Reducing caffeine, alcohol, and fluid intake can help control urge and stress incontinence.
- Pharmacologic Therapy:
- Anticholinergics (e.g., oxybutynin, tolterodine):
- First-line drugs for urge incontinence, which inhibit detrusor overactivity.
- Beta-3 Agonists (mirabegron):
- An alternative to anticholinergics for urge incontinence, mirabegron relaxes the bladder and increases capacity.
- Alpha-Blockers (tamsulosin):
- Used in men with overflow incontinence due to BPH, alpha-blockers relax the prostate and bladder neck.
- 5-Alpha Reductase Inhibitors (finasteride):
- Also used for BPH to shrink the prostate and relieve obstruction.
- Surgical Treatment:
- Midurethral Sling:
- The most common surgery for stress incontinence in women, which provides support to the urethra and prevents leakage.
- Prostate Surgery (TURP):
- For men with overflow incontinence due to BPH, transurethral resection of the prostate (TURP) relieves bladder outlet obstruction.
- Artificial Urinary Sphincter:
- Implanted in men with post-prostatectomy stress incontinence, providing urethral compression to prevent leakage.
- Prognosis:
- Many patients experience significant symptom improvement with lifestyle modifications, pelvic floor exercises, and pharmacologic therapy. Surgical treatments are highly effective for stress and overflow incontinence.
Key Points
- Urinary incontinence is classified into stress, urge, overflow, and functional types, with mixed incontinence involving more than one type.
- Evaluation includes a thorough history, physical exam, postvoid residual volume measurement, and urinalysis to guide diagnosis.
- First-line treatments include pelvic floor exercises for stress incontinence and bladder training for urge incontinence.
- Pharmacologic options include anticholinergics and beta-3 agonists for urge incontinence, and alpha-blockers for overflow incontinence.
- Surgical treatments, such as midurethral slings and TURP, are effective for stress and overflow incontinence in selected patients.