JC71 (Surgery) - BPH, Bladder outlet obstruction, Urinary retention Flashcards
Physiology of bladder storage
- How does the bladder accommodate urine at low pressure and retain it?
Storage: efficient and low-pressure filling, lower pressure storage and perfect continence
→ Bladder outlet remain closed at rest or despite ↑intra-abd pressure
→ No involuntary bladder contraction (detrusor overactivity)
Receptive relaxation of bladder: ↓tension in response to ↑volume → maintain low intravesical pressure
□ Pathological: bladder pathologies may lead to hypocompliant bladder → ↑↑pressure during filling
Physiology of bladder emptying
How does the bladder expel urine and control emptying rate?
Emptying: periodic voluntary urine expulsion at low pressure
→ Coordinated contraction of bladder smooth muscles at adequate magnitude and duration
→ ↓resistance at bladder outlet
- Proximal sphincter mechanism (PSM) at bladder neck by autonomic control
- Distal sphincter mechanism (DSM) by somatic control
→ No anatomical obstruction
Afferent sensory pathway from bladder to brain?
Afferent:
→ Stretch receptors detects bladder distension
→ Pathway:
- Aδ for signals for distension
- C-fibres for signals for irritation/pain
- Along hypogastric, pelvic (majority), pudendal nerves
→ Target: higher centres
Brain centers for micturition?
- Pontine micturition centre (PMC, Barrington’s nucleus) → coordinates between filling/voiding
- Suprapontine control by cerebral cortex → conscious inhibition of involuntary voiding
(not inborn, developed from toilet training)
Efferent pathways from brain to control micturition?
- Parasympathetic, sympathetic, somatic
SN: from T10-L2
- Pathway: lumbar splanchnic → hypogastric plexus
- Action: maintain continence by ↓detrusor contraction (β3-adren) + ↑bladder outlet contraction (α1-adren)
PN: from S2-4
- Pathway: pelvic splanchnic
- Action: initiate voiding by ↑detrusor contraction (M3-musc)
Somatic: from Onuf’s nucleus
- Pathway: pudendal n.
- Action: maintain continence by ↑external sphincter contraction (nAChR)
Neural control of bladder storage phase
- Afferent
- Reflex
- Efferent
- Effector organs
□ Initiation: bladder empty → afferent Aδ sensory fibres send low-level firing signals to higher centres
□ Vesicosympathetic (storage) reflex initiated
□ Effects:
→ +ve SN pathway
→ -ve PN pathway
→ +ve somatic pathway
□ Actions:
→ Detrusor relaxation (β3-adren)
→ Internal urethral sphincter contraction (α1-adren)
→ External urethral sphincter contraction (nAChR)
Neural control of bladder storage phase/ Guarding reflex
- Afferent
- Relay pathways
- Efferent
- Effector organs
□ Initiation: bladder empty → afferent Aδ sensory fibres send low-level firing signals to higher centres
□ Vesicosympathetic (storage) reflex initiated
□ Effects:
→ +ve SN pathway
→ -ve PN pathway
→ +ve somatic pathway
□ Actions:
→ Detrusor relaxation (β3-adren)
→ Internal urethral sphincter contraction (α1-adren)
→ External urethral sphincter contraction (nAChR)
Neural control of bladder emptying/ Voiding reflex
- Afferent
- Relay pathways
- Efferent
- Effective organ actions
□ Initiation: bladder distension → afferent fibres to cortex → Higher center/ Cortical signals to PMC + removal of inhibition from cerebral cortex → PMC initiates voiding reflex
□ Effects:
→ -ve SN pathway
→ +ve PN pathway
→ -ve somatic pathway
□ Actions:
→ Detrusor contraction (M3-musc)
→ Internal urethral sphincter relaxation
→ External urethral sphincter relaxation
List the efferent receptors in Detrusor muscle, Bladder neck/ prostate, and external/ Rhabdosphincter
Detrusor:
B3 adrenergic receptor - relaxation
M3 muscarinic receptor - contraction
Bladder neck/ prostate:
a1 adrenergic - contraction
External/ Rhabdosphincter:
- Nicotinic - contraction
Effect of spinal cord injury to micturition control?
Detrusor sphincter dyssynergia (DSD):
□ Cause: spinal cord injury, pontine stroke
□ Mechanism: interruption of descending control by pontine micturition centre → i.e. failure of detrusor-sphincter coordination → synchronous contraction of both detrusor and sphincters
□ Consequence: ↑↑urinary tract pressure → upper tract damage
Compare presentation of acute vs chronic urine retention (AROU vs CROU)
which type is a/w neural damage
□ Acute retention of urine (AROU): sudden onset, painful
→ Occurs when innervation is normal, eg. BPH
□ Chronic retention of urine (CROU): usually painless with vague lower abdominal distension
→ Occurs when innervation is abnormal, eg. DM
Risk factors of urine retention in male
Common causes of urine retention in male
Male: RF
↑age
↑prostate size, ↑BPH symptoms
↓max urine flow rate
Causes: Bladder outlet obstruction most common:
BPH (53%)***** constipation (7.5%), CA prostate (7%), urethral stricture (3.5%), clot retention (3%), bladder/urethral stone (2%), bladder neck stenosis (post-prostate surgery), phimosis, CA bladder
Common causes of urinary retention in female
Causes:
Detrusor underactivity: Detrusor hypocontractility, drug-induced, bladder overdistention (e.g. post-anesthesia)
Obstructive causes (rarer): organ prolapse (eg. cystocele), gynaecological tumours (eg. fibroid)
Neurogenic bladder: neurological deficit e.g. SCI, CVA, PD
2 major pathological processes that cause AROU
Increase resistance to urine flow/ Obstructive:
- Mechanical: strictures, clots, stones
- Dynamic: large prostate, bladder neck tone
- Functional: e.g. neuropathic bladder
Impaired detrusor contraction/ Neurogenic:
- Drug induced
- Bladder overdistension (e.g. post-anesthesia)
- Neuropathic bladder
Combination
Mechanical causes of bladder outlet obstruction
- Mural, intraluminal, extramural
Mural:
Urethral stricture from prev instrumentation or STDs
Bladder neck tumours
Urethritis
Intraluminal:
Stones
Clot retention in haematuria
Foreign bodies
Extramural compression: BPH CA prostate Constipation/ stool impaction Pelvic tumours Prostatitis, pregnancy, pelvic organ prolapse (cystocele, rectocele, uterovaginal prolapse)
