Urinary Incontinence for USMLE Step 2
Urinary Incontinence for the USMLE Step 2 Exam
- Definition:
- Urinary incontinence is the involuntary leakage of urine and can be classified into several types: stress, urge, overflow, and functional incontinence. Mixed incontinence refers to the coexistence of more than one type.
- Types of Urinary Incontinence:
- Stress Incontinence:
- Occurs when increased intra-abdominal pressure (e.g., from coughing, sneezing, or laughing) overwhelms the urethral sphincter, causing leakage.
- Pathophysiology:
- Common in women due to pelvic floor muscle weakening from pregnancy, childbirth, and menopause. In men, it can occur after prostate surgery.
- Risk Factors:
- Vaginal delivery, obesity, aging, and pelvic surgery.
- Urge Incontinence (Overactive Bladder):
- Characterized by a sudden, strong urge to urinate followed by involuntary leakage.
- Pathophysiology:
- Caused by detrusor overactivity, which may be idiopathic or related to neurological conditions (e.g., multiple sclerosis, Parkinson’s disease, stroke).
- Symptoms:
- Urgency, frequency, nocturia, and involuntary leakage.
- Overflow Incontinence:
- Results from chronic bladder overdistention due to incomplete bladder emptying, leading to dribbling and leakage.
- Pathophysiology:
- Typically caused by bladder outlet obstruction (e.g., benign prostatic hyperplasia [BPH] in men) or impaired detrusor muscle function (e.g., diabetic neuropathy).
- Risk Factors:
- BPH, neurogenic bladder, or spinal cord injury.
- Functional Incontinence:
- Occurs when patients cannot reach the toilet due to physical or cognitive impairments, despite normal bladder function.
- Risk Factors:
- Dementia, severe arthritis, mobility issues, or postoperative immobility.
- Evaluation:
- History and Physical Examination:
- A comprehensive history includes the onset, frequency, and circumstances of incontinence. A pelvic exam in women evaluates for prolapse, while a digital rectal exam in men assesses prostate size.
- Postvoid Residual Volume (PVR):
- Measured via ultrasound or catheterization to assess for incomplete bladder emptying. High PVR suggests overflow incontinence.
- Urinalysis:
- Screens for infections, hematuria, or other pathology (e.g., bladder cancer).
- Bladder Diary:
- A patient-kept diary that records voiding times, fluid intake, and leakage episodes to help differentiate between types of incontinence.
- Management:
- Lifestyle Modifications and Behavioral Therapy:
- Pelvic Floor Exercises (Kegel Exercises):
- First-line treatment for stress incontinence, aimed at strengthening pelvic muscles.
- Bladder Training:
- Effective for urge incontinence, involving scheduled voiding to train the bladder to resist urgency.
- Weight Loss:
- Reduces intra-abdominal pressure and improves symptoms of stress incontinence.
- Fluid Management:
- Avoid caffeine, alcohol, and excessive fluid intake to reduce incontinence episodes.
- Pharmacologic Therapy:
- Anticholinergics (e.g., oxybutynin, tolterodine):
- First-line drugs for urge incontinence, reducing detrusor overactivity.
- Beta-3 Agonists (mirabegron):
- An alternative for urge incontinence, relaxing the detrusor muscle and increasing bladder capacity.
- Alpha-Blockers (tamsulosin):
- Used for overflow incontinence due to BPH, relaxing the prostate and bladder neck to improve urine flow.
- 5-Alpha Reductase Inhibitors (finasteride):
- Used for BPH to reduce prostate size and alleviate overflow incontinence.
- Surgical Treatment:
- Midurethral Sling:
- A common surgical intervention for stress incontinence in women, providing support to the urethra.
- Transurethral Resection of the Prostate (TURP):
- Used in men with BPH and overflow incontinence to relieve bladder outlet obstruction.
- Artificial Urinary Sphincter:
- Implanted to provide urethral compression in men with post-prostatectomy stress incontinence.
- Prognosis:
- Most patients experience symptom improvement with lifestyle modifications and pharmacotherapy. Surgical interventions are highly effective for stress and overflow incontinence in selected patients.
Key Points
- Urinary incontinence is classified into stress, urge, overflow, and functional types, with mixed incontinence involving more than one mechanism.
- Evaluation includes a thorough history, physical examination, postvoid residual volume assessment, and urinalysis.
- First-line treatments include pelvic floor exercises for stress incontinence and bladder training for urge incontinence.
- Pharmacologic therapies include anticholinergics and beta-3 agonists for urge incontinence, and alpha-blockers for overflow incontinence.
- Surgical interventions, such as midurethral slings and TURP, are effective for stress and overflow incontinence.