Merck Manual

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Some Mechanisms of Incontinence

Some Mechanisms of Incontinence



Weakness of the urinary sphincter or pelvic muscles (bladder outlet incompetence)

Atrophic urethritis, vaginitis, or both


Pelvic muscle weakness (for example, caused by having had several vaginal deliveries or pelvic surgery)

Prostate surgery

Blockage (bladder outlet obstruction)

Prostate enlargement (benign prostatic hyperplasia) or cancer


Overactivity of bladder wall muscles (overactive bladder)

Bladder irritation (for example, caused by infection, stones, or rarely cancer)

Disorders that can affect brain centers that control urination (such as stroke, dementia, or multiple sclerosis)

Cervical spondylosis or spinal cord dysfunction (which can put pressure on the spinal cord and thus impair bladder function)

Bladder outlet obstruction

Underactivity of bladder wall muscles

Nerve damage (for example, by herniated disks, other spinal cord disorders, surgery, tumors, injury, diabetes, or alcohol use disorder)


Longstanding bladder outlet obstruction

In women, often no identifiable cause

Poor coordination of the bladder wall with the sphincter muscles

Damage to spinal cord or brain nerve pathways to the bladder

Functional problems



Psychoactive drugs that can decrease awareness of the need to urinate (for example, antipsychotic drugs, benzodiazepines, drugs that cause drowsiness such as sedatives and sleep aids, or tricyclic antidepressants)

Restricted mobility (for example, caused by injury, weakness, restraints, stroke, other neurologic disorders, or musculoskeletal disorders)

Situational limitations (such as not having a toilet nearby or traveling)

Increase in the volume of urine

Disorders such as diabetes mellitus or diabetes insipidus

Use of diuretics (usually furosemide, bumetanide, or theophylline, but not thiazide diuretics)

Excessive intake of caffeinated beverages (such as coffee, tea, cola, or some other soft drinks) or alcohol