S8: micturition & incontinence Flashcards
What are the two phases of micturition?
Micturition – process of eliminating water and electrolytes from the urinary system
Storage/continence phase: urine is stored in the bladder
Voiding phase: urine is released through the urethra
Describe the sympathetic innervation in the storage phase
Signals are sent from the L centre (pontine continence centre) to sympathetic nuclei -> detrusor muscle and internal urethral sphincter
At the bladder this stimulates:
-relaxation of the detrusor in the bladder wall – via stimulation of B3-adrenoreceptors
-contraction of the IUS – via stimulation of A1-adrenoreceptors at neck of bladder
Describe the sensory innervation in the storage phase
Senses the bladder stretch
Stimulates the sympathetic action
Communicates with cerebral cortex – conscious appreciation for how full our bladder is
Describe the somatic innervation in the storage phase
EUS is under voluntary somatic control
Impulses travel to the EUS via the pudendal nerve to nicotinic receptors on the striated muscle -> contraction of the EUS, which prevents any urine from leaking out
Describe the parasympathetic innervation in the voiding phase
Upon voluntary decision to urinate, neurones of the M centre fire to excite the sacral preganglionic neurones
Subsequent parasympathetic stimulation causes a release of acetylcholine -> works on M3 receptors on the detrusor muscle -> contract & increases intra-vesicular pressure
Describe the sensory innervation in the voiding phase
Senses the bladder stretch
Stimulates the parasympathetic action (positive feedback loop)
If stretch is high enough, directly communicates with M centre which causes activation of parasympathetics
Explain why we do not micturate even when bladder is full
M centre is not autonomous – conscious control of it Paracentral lobules (medial side of cerebral cortex) send both excitatory and inhibitory influences onto the M centre = voluntary decision is made here M centre sends inhibitory connections to the L centre – when you decide to void, inhibits the L centre -> relaxation of the external urethral sphincter due to pudendal nerve being turned off
What is stress urinary incontinence?
Complaint of involuntary leakage on effort or exertion, or on sneezing or coughing
What is urgency urinary incontinence?
Complaint of involuntary leakage accompanied by or immediately proceeded by urgency
What is mixed urinary incontinence?
Complaint of involuntary leakage associated with urgency and also with exertion, effort, sneezing or coughing
What is overflow incontinence?
Involuntary release of urine when the bladder becomes overly full – due to weak bladder muscle or blockage
What is an overactive bladder?
Frequent or sudden urge to urinate that may be difficult to control
List the risk factors for urinary incontinence
Pregnancy and childbirth Obesity Pelvic prolapse Race Pelvic surgery/DXT
Describe the initial investigation of patients with urinary incontinence
Urine dipstick – rule out other differentials
Basic non-invasive urodynamics – frequency-volume chart, bladder diary, post-micturition residual volume
Optional – invasive urodynamics, pad tests & cystoscopy
Describe the initial management of patients with urinary incontinence
Conservative management – modify fluid intake, weight loss, stop smoking, decrease caffeine intake, avoid constipation, timed voiding
Contained incontinence – patients who are unsuitable for surgery who have failed conservative management: indwelling catheter, sheath & incontinence pads
Describe specific management for stress urinary incontinence
Pelvic floor muscle training
Duloxetine – combined noradrenaline & serotonin uptake inhibitor (increased activity in the EUS during filled phase)
Surgery:
-females: permanent intention – open retropubic suspension procedures/classical autologous sling procedures; temporary intention – intramural bulking agents
-males: artificial urinary sphincter & male sling procedure
Describe the male artificial urinary sphincter
Gold standard
Urethral sphincter deficiency
Cuff stimulates action of normal sphincter to circumferentially close the urethra
Describe the initial management for urge urinary incontinence
Bladder training – at least 6 weeks duration
Schedule of voiding: void every hour during the day, must not void in between, intervals increased by 15-30 mins until interval of 2-3 hours is reached
Describe pharmacological management of urge urinary incontinence
Anticholinergics – act on muscarinic receptors (M2,M3)
Side effects due to effects on M receptors at other sites
B3-adrenoreceptor agonist – mirabegron
Describe botulism toxin
Potent biological neurotoxin
Inhibits release of ACh at pre-synaptic neuromuscular junction causing targeted flaccid paralysis
Duration of action 3-6 months
List surgical intervention of urge incontinence
Sacral nerve neuromodulation
Autoaugmentation
Augmentation cystoplasty
Urinary diversion
What is enuresis?
Bedwetting = involuntary wetting during sleep at least 2x/week in children > 5 years with no CNS defects
Primary – never achieved sustained continence at night
Secondary – restarted having been dry at night for 6+ months
How do you manage enuresis in children?
Primary without daytime symptoms – usually managed in primary care -> reassurance & positive reward system
Primary with daytime symptoms – caused by disorders of the lower urinary tract
Secondary – treat underlying cause if it has been identified eg. UTIs, constipation, diabetes, psychological problems etc
