Distinguishing Urinary Incontinence Subtypes
Stress, urge (urgency), overflow, and mixed incontinence are fundamentally different conditions based on their underlying mechanisms: stress incontinence occurs from urethral closure failure during increased abdominal pressure, urge incontinence results from involuntary bladder contractions with urgency, overflow incontinence stems from either bladder outlet obstruction or detrusor underactivity, and mixed incontinence combines both stress and urge components. 1, 2, 3
Stress Urinary Incontinence
Mechanism and Presentation:
- Involuntary urine leakage occurs specifically during physical activities that increase intra-abdominal pressure—laughing, coughing, lifting, bending over, or exercise 1
- The underlying pathophysiology involves a poorly functioning urethral closure mechanism and loss of anatomical urethral support 1
- Leakage happens when intra-abdominal pressure exceeds urethral closure pressure 1
Diagnostic Features:
- History reveals leakage during specific physical activities without urgency 1
- Positive cough stress test demonstrates visible leakage with coughing 1, 4
- Assessment should identify pelvic organ prolapse and urethral hypermobility 1
Urge Urinary Incontinence (Urgency Incontinence)
Mechanism and Presentation:
- Involuntary leakage accompanied by or immediately preceded by urgency—a sudden, compelling desire to void that cannot be deferred 1, 2
- Results from bladder overactivity causing involuntary detrusor contractions 3
- Often associated with frequency (>8 voids/day) and nocturia 2
Diagnostic Features:
- Urgency episodes documented in voiding diaries are the hallmark 1, 2
- Frequency and nocturia patterns support the diagnosis 1
- Leakage occurs with urgency sensation, not with physical stress 2
Overflow Incontinence
Mechanism and Presentation:
- Results from either bladder outlet obstruction OR detrusor underactivity (bladder muscle weakness) 5, 3
- Presents as continuous dribbling or frequent small-volume leakage 3
- Bladder cannot empty adequately, leading to chronic overdistension 3
Diagnostic Features:
- Elevated post-void residual urine volume is the defining characteristic 4, 6
- Post-void residual measurement is mandatory before treating any incontinence to rule out overflow 4
- In men, consider benign prostatic hyperplasia as the obstructive cause 7
Mixed Urinary Incontinence
Mechanism and Presentation:
- Simultaneous presence of both stress AND urge incontinence symptoms 2, 4
- Patients experience leakage both with physical activities and with urgency 2
- Represents a combination of urethral underactivity and bladder overactivity 3
Diagnostic Features:
- History reveals both stress-related leakage (with coughing, laughing) and urgency-related leakage 2
- Voiding diaries document both types of incontinence episodes 4
Treatment Approach:
- Target the most bothersome component first 1, 2, 4
- Combine pelvic floor muscle training (for stress component) with bladder training (for urge component) as initial therapy 4
- If behavioral interventions are insufficient, add antimuscarinic agents or β3-agonists for the urge component 4
Critical Diagnostic Pitfall
Always measure post-void residual volume before initiating treatment for stress or urge incontinence to exclude overflow incontinence, as treatment approaches are fundamentally different and treating stress/urge incontinence when overflow is present can worsen the condition. 4, 6