Incontinence Flashcards
Describe detrusor muscle (structure, function)
3 layers of smooth muscle which gives strength irrespective of direction of stretch
It has stretch receptors in its wall which give rise to afferent pelvic nerves
Describe the internal urethral sphincter (structure, function)
Continuation of detrusor muscle acting as a physiological sphincter at the bladder neck
Prevents retrograde transport of ejaculate in males
Describe the external urethral sphincter (structure)
Anatomical sphincter derived from pelvic floor muscles under somatic control (skeletal muscle)
Nerve supply of detrusor muscle
Parasympathtic - pelvic nerve (S2-4) releases ACh which acts via M3 receptors causing contraction
Sympathetic - hypogastric nerve (T10-L2) releases NA which acts via B3 receptors causing relaxation
Nerve supply of IUS
Sympathetic - Hypogastric nerve (T10-L2) releases NA which acts via A1 receptors causing contraction
Nerve supply of EUS
Somatic - pudendal nerve (S2-4) from Onof’s nucleus of the ventral horn releases ACh which acts via nicotinic receptors causing contraction
Describe the storage phase of micturation
As the bladder receives urine from the ureters it distends to keep intravesical pressure constant until ~400ml
At low activity of the afferent pelvic nerve (low detrusor stretch) there is increased sympathetic stimulation so the hypogastric nerve causes detrusor relaxation and IUS contraction
The L centre of PONS stimulates the pudendal nerve to cause EUS contraction
Describe the voiding phase of micturation
At high activity of the afferent pelvic nerve (high detrusor stretch) there is increased parasympathetic and M centre stimulation.
The pelvic nerve causes detrusor contraction.
The M centre (when stimulated by cerebral cortex) stimulates parasympathetic neurones and inhibits sympathetic neurones and the L centre, leading to rhythmic detrusor contraction and relaxation of both urethral sphincters.
Describe the volume pressure graph of micturation
Pressure on y axis, Volume on X axis
Pressure is constant for first ~300ml because of detrusor relaxation and then pressure increases rapidly
As volume decreases during voiding the pressure rapidly increases and decreases with progressive decreasing peaks (rhythmic contraction)
Effects of spinal cord transection below T12
Damage to parasympathetic outflow to bladder so there is a low detrusor pressure
Bladder becomes abnormally distended with no action and overflow incontinence will occur
Effects of spinal cord transection above T12
Damage to sympathetic outflow to bladder so there is high detrusor pressure
Bladder empties frequently with little volume
Detrusor sphincter dyssynergia occurs where the detrusor muscle and EUS contract together (dramatic increase in pressure) which may result in diverticulae or urine reflux into the kidneys
Symptoms of storage problems
Frequency
Urgency
Nocturia
Symptoms of voiding problems
Slow urine stream Intermittency Hesitancy (delay before stream) Straining Terminal dribble
Symptoms of post micturation problems
Incomplete emptying
Post micturation dribble
What is urinary incontinence and what are the types
UI - any involuntary urine leakage 4 types: Stress Urge Mixed Overflow
