Urinary incontinence is an involuntary leakage of fluid. Urinary continence is typically maintained by a balance of anatomic support, detrusor muscle contractions / relaxation, and abdominal versus intra-urethral pressure.

Urinary incontinence affects about 25% of young women, 50% of women aged 30-50 years, and 75% of older women. Urinary incontinence is typically divided into 3-5 categories. For this review, we will divide urinary incontinence into 5 categories: stress, urge, overflow, neurogenic bladder, and mixed. Stress incontinence and neurogenic bladder are discussed separately. Urge and overflow are discussed in this topic. Mixed incontinence is a combination of multiple categories of urinary incontinence typically requiring referral to a specialist for further management.

Urge incontinence (overactive bladder)
Urge incontinence is often referred to as overactive bladder (OAB). This condition stems from the detrusor muscle (the working smooth muscle) in the bladder. Patients typically report a sudden urge to void followed by involuntary leakage of urine. The detrusor muscle can either be overactive, have poor compliance, or be overstimulated. Unlike stress incontinence, which typically peaks in women aged 30-50 years and then declines in prevalence, urge incontinence continues to increase in prevalence as age increases. While urinary incontinence itself has a high prevalence in the female population (50%-75%) and low prevalence in the male population (3%-11%), approximately 40%-80% of males with urinary incontinence experience urge incontinence. Risk factors include obesity, urogynecologic cancer, cardiorespiratory disease, chronic cough, dementia, urinary tract infection (UTI), and sleep apnea, among others.

Overflow incontinence
Overflow incontinence involves overdistension of the bladder leading to involuntary leakage of urine due to an overly full bladder. When the patient feels the urge to urinate, they typically only experience dribbling. This can either stem from a decrease in detrusor contractility or a bladder outlet obstruction. Risk factors include, but are not limited to, diabetes (type 1, type 2), nerve damage, spinal cord injuries, and, in men, prostate problems.