What are the causes of urinary incontinence?

Causes of Urinary Incontinence in Women

Urinary incontinence results from distinct pathophysiologic mechanisms that determine its classification into stress, urgency, mixed, and overflow subtypes, each with specific underlying etiologies that must be identified to guide appropriate treatment. 1

Primary Mechanisms and Types

Stress Urinary Incontinence

• Urethral sphincter failure and loss of anatomical urethral support are the primary mechanisms, causing leakage during activities that increase intra-abdominal pressure such as coughing, sneezing, lifting, or exercise 1
• Pelvic floor trauma from vaginal delivery directly damages supporting structures 1, 2
• Urethral hypermobility or bladder-neck descent allows urine to escape during physical stress 1
• Weakened pelvic floor muscles fail to maintain adequate urethral closure pressure 1

Urgency Urinary Incontinence

• Detrusor muscle instability and overactivity cause involuntary bladder contractions, producing sudden compelling urge to void with leakage 1
• Urothelial dysfunction with altered prostaglandin release and impaired bladder sensation contributes to urgency symptoms 3
• Neurogenic causes from diabetes mellitus produce detrusor muscle paralysis and impaired bladder sensation through chronic hyperglycemia 3

Overflow Incontinence

• Detrusor underactivity prevents complete bladder emptying, leading to chronic retention and overflow 4, 5
• Bladder outlet obstruction from urethral masses, severe cystocele with urethral kinking, or complications from prior urethral sling procedures blocks urine flow 1, 5

Mixed Incontinence

• Combination of stress and urgency mechanisms occurring simultaneously, affecting 30-50% of incontinent women 6, 4

Major Risk Factors and Contributing Causes

Age-Related Factors

• Advancing age is the strongest independent risk factor, with prevalence increasing from 20-30% in young women to 75% in elderly women aged 75+ years 1, 3
• Menopause and estrogen deficiency cause atrophic vaginitis and urethral changes 1, 7

Obstetric and Gynecologic Factors

• Pregnancy and vaginal delivery cause pelvic floor trauma and nerve damage 1, 2
• Increasing parity progressively weakens pelvic support structures 2
• Hysterectomy disrupts pelvic floor integrity 1
• Pelvic organ prolapse (cystocele, rectocele) alters anatomic relationships and causes urethral obstruction 7, 2

Metabolic and Systemic Factors

• Diabetes mellitus increases risk by 30-100% through neurogenic bladder, polyuria, and altered urothelial signaling 3
• Insulin-treated diabetics have considerably higher risk than those on oral medications 3
• Obesity mechanically increases intra-abdominal pressure on pelvic floor 1, 3

Reversible Causes (Critical in Elderly Women)

• Urinary tract infection causes transient urgency and frequency 7, 6
• Fecal impaction mechanically obstructs bladder outlet 7, 2
• Medications including diuretics, anticholinergics, sedatives, and alpha-blockers alter bladder function 7, 6
• Restricted mobility and cognitive impairment prevent timely toileting 7, 3
• Chronic constipation increases pelvic floor strain 7, 2

Lifestyle and Behavioral Factors

• Chronic cough from smoking damages pelvic floor through repeated strain 1, 3
• Excessive caffeine consumption stimulates detrusor overactivity 3, 6

Anatomic Abnormalities

• Urethral diverticula or masses obstruct normal voiding 1
• Bladder masses or significant bladder wall thickening from chronic obstruction 1
• Anal sphincter tears associated with pelvic floor weakness 1

Clinical Pitfalls to Avoid

• Do not assume single etiology: Mixed incontinence affects 30-50% of women and requires addressing both stress and urgency components 6, 4
• Always identify reversible causes first in elderly women—UTI, fecal impaction, medications, and restricted mobility account for the majority of cases and must be treated before complex evaluation 7
• Distinguish stress-induced detrusor overactivity from true stress incontinence, as the former involves involuntary detrusor contractions triggered by increased abdominal pressure rather than sphincter failure 1
• Functional and cognitive impairment fundamentally alter treatment approach and must be assessed 3, 6