Article Sections

Introduction

Urinary incontinence (UI), the involuntary loss of urine, is often divided into three subtypes: stress, urgency, and overflow.  The treatment and management are dependent on the predominant subtype.

Physiology

Continence ( Figure 1) is normally maintained through a combination of voluntary and involuntary control.

  • The cerebral cortex (upper motor neurons) maintains continence by inhibiting micturition through the pontine micturition center within the brainstem.
  • The external urinary sphincter is a skeletal muscle with nicotinic receptors that receives somatic motor innervation (voluntary control) from the perineal branches of the pudendal nerve (S2-S4).
  • The detrusor muscle and the internal urethral sphincter (IUS) receive autonomic innervation (involuntary control).  Sympathetic stimulation (from the inferior hypogastric plexus [T11-L2] traveling through the hypogastric nerve) promotes urine storage and continence by increasing IUS tone through alpha-1 receptors and by inhibiting detrusor contractions through beta-3 agonist receptors.

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