Section 5: Urogynecology

NORMAL URINARY FUNCTION

Anatomy

• Detrusor: “Bladder muscle”—smooth muscle; innervation is parasympathetic (muscarinic acetylcholine—M2, M3; contraction) and sympathetic (β3-adrenergic receptors; detrusor inhibition or relaxation) (Figure 5-1)

• Urethral sphincter

  • Internal urethral sphincter (IUS): Smooth muscle; sympathetic (α1) innervation; muscarinic acetylcholine, α- and β-adrenergic receptors

  • External urethral sphincter (EUS): Striated muscle; somatic motor innervation via pudendal nerve (S2–S4); nicotinic acetylcholine receptors

  • Submucosal endovascular cushions

  • Surrounding tissue support—hammock hypothesis—the anterior vaginal wall with its attachment to the arcus tendineus of the pelvic fascia forms a hammock of tissue under the urethra and bladder neck that prevents urethral and bladder neck descent, such that the urethra compresses shut with increased intra-abdominal pressure

Physiology

• Bladder filling = SYMPATHETIC = “STORAGE”

  • L1–L3 → lumbar sympathetic ganglia → forms hypogastric nerve to pelvis

  • Norepinephrine released → decreases smooth muscle tone in bladder

    • Relaxation of detrusor muscle: β3-adrenergic receptors in bladder stimulated (bladder fills)

    • Contraction of IUS: α-Adrenergic receptors in IUS stimulated (sphincter tightens)

    • Contraction of EUS by trained voluntary action (pudendal nerve originates from S2 to S4 to innervate EUS and perineal muscles—acetylcholine)

• Micturition (emptying of bladder) = PARASYMPATHETIC = “PEEING”

  • Full bladder sensed by mechano-receptors in bladder

  • S2–S4 → sacral spinal cord → forms pelvic nerve

  • Stimulates bladder using acetylcholine and relaxes the urethra employing nitric oxide

    • Contraction of detrusor muscle: Muscarinic cholinergic (M3) receptors stimulated (bladder contracts)

    • Relaxation of IUS: M3 receptors stimulated (sphincter relaxes)

    • Relaxation of EUS by trained voluntary action (pudendal nerve originates from S2–S4—acetylcholine)

URINARY INCONTINENCE (UI)

Definition

Involuntary loss of urine. Prevalence in the United States is about 50% of adult women.

Types

• Stress urinary incontinence (SUI): Most common type (50–70% of UI)

  • Involuntary leakage during effort, exertion, sneezing, or coughing

  • Risk factors include age, parity, vaginal delivery

  • Leakage with stress test. Bladder capacity and post-void residual (PVR) normal (PVR generally considered normal if <150 cc or <1/3 void volume)

  • Urethral hypermobility (straining angle ≥30 degrees on Q-tip test) present in many women with SUI

  • Urodynamic SUI: During filling cystometry, involuntary urine leakage with increased intra-abdominal pressure and without detrusor contraction

• Urge incontinence

  • Leakage accompanied by or immediately preceded by urge to void

  • Typically results from sudden, involuntary detrusor contractions

  • Usually idiopathic; but can be from inflammation/irritation, calculi, neurologic disorders, outlet obstruction, increased urine output

  • Urodynamics: If detrusor contractions are seen on ...