What is the pathophysiology of urinary incontinence?

Updated: Jan 22, 2021
  • Author: Sandip P Vasavada, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Micturition requires coordination of several physiological processes. Somatic and autonomic nerves carry bladder volume input to the spinal cord, and motor output innervating the detrusor, sphincter, and bladder musculature is adjusted accordingly. The cerebral cortex exerts a predominantly inhibitory influence, whereas the brainstem facilitates urination by coordinating urethral sphincter relaxation and detrusor muscle contraction.

As the bladder fills, sympathetic tone contributes to closure of the bladder neck and relaxation of the dome of the bladder and inhibits parasympathetic tone. At the same time, somatic innervation maintains tone in the pelvic floor musculature as well as the striated periurethral muscles.

When urination occurs, sympathetic and somatic tones in the bladder and periurethral muscles diminish, resulting in decreased urethral resistance. Cholinergic parasympathetic tone increases, resulting in bladder contraction. Urine flow results when bladder pressure exceeds urethral resistance. Normal bladder capacity is 300-500 mL, and the first urge to void generally occurs between bladder volumes of 150 and 300 mL.

Incontinence occurs when micturition physiology, functional toileting ability, or both have been disrupted. [10] The underlying pathology varies among the different types of incontinence (ie, stress, urge, mixed, reflex, overflow, and functional incontinence).

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