URO - 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)
Drug-induced bladder outlet obstruction
ddx drugs
Drug-induced:
Sympathomimetics: α-agonists (cold medications), β-agonists (bronchodilators), MDMA
Anticholinergics: anticholinergics (bronchodilators), antipsychotics, antispasmodics (opioids), antihistamines, antidepressants, disopyramide (class Ia antiarrhythmic)
Causes of Neurogenic bladder
- Brain, spinal cord, nerves
Brain: stroke, Parkinson’s disease, MS, Normal pressure Hydrocephalus, MSA
Spinal cord: trauma, vertebral metastasis, spinal stenosis, transverse myelitis, spinal cord haematoma/abscess, spinal cord tumour
Nerves: diabetic neuropathy, radical pelvic surgery, Guillain-Barre syndrome
Causes of acute overdistension of bladder
↑urine production: excessive fluid intake (esp alcohol)
↓voiding: post-anaesthesia (GA, epidural), analgesics, painful peri-anal pathologies, prolonged immobility
Common precipitating factors of AROU
Constipation
UTI
Immobility
Painful peri-anal conditions: thrombosed hemorrhoids, perianal abscess
Excessive fluid intake (alcohol)
Drugs: Sympathomimetics, anticholinergics, Anesthesia/ analgesia
Outline history taking questions for urinary retention
5 main parts
Confirm AROU:
- r/o anuria or oliguria by bladder USG/first catheterized urine vol
- painful or painless?
Characterize current episode, ask precipitating factors
Find etiology:
- BOO: obstructive LUTS S/S
- BPH and complications: Gross haematuria, UTI, Stones, Renal impairment (uremic S/S)
- Neurological: LL weakness, Sphincter function, Back pain, CVA, PD…etc
- Drugs
- Iatrogenic strictures: prostate surgery, TURP…etc
- STD, Prostatitis
Screen for malignancy:
Constitutional symptoms, gross painless haematuria
Complications
UTI: fever, dysuria, irritative symptoms, haematuria
Stone disease
Renal failure: vomiting, lethargy, drowsiness, uremic rash
Detail the surgical and medical history for urinary retention
Medications:
BPH medications (eg. α-blockers, 5-α reductase inhibitors) Anticholinergics, antimuscarinics
Surgery: iatrogenic stricture
Prostate surgery
Urethral instrumentation
Outline P/E for urinary retention
- Vitals: Septic, Uraemic?
- urethral catheter output → any gross haematuria?
- Abdominal exam
- Palpable bladder: tender mass upon deep suprapubic palpation
- pelvic masses: fibroid, gravid uterus, ovarian cyst
- Faecal loading
- Bilateral ballotable kidneys due to hydronephrosis
- Phimosis - DRE: ± PV exam if female
□ Signs of cord compression: saddle anaesthesia, anal tone, perianal sensation
□ Painful peri-anal conditions
□ Prostate: size, consistency and tenderness (high-rising prostate → C/I to Foley insertion)
□ Faecal impaction - LL neurological examination:
□ LMN paralysis
□ Sensory level
Bladder outlet obstruction
- S/S
- Complications
S/S:
Weak stream, hesitancy and intermittency, terminal dribbling, incomplete emptying, overflow incontinence, lower abdominal distention Uremic symptoms (obstructive nephropathy)
Complications:
- Urine retention
- Recurrent UTI
- Bladder calculi
- Hydroureter and hydronephrosis
- Renal impairment/ acute-renal failure
Uroflowmetry can diagnose bladder outlet obstruction
True or false
False
Uroflowmetry cannot differentiate Detrusor hypocontraction and BOO
Need Urodynamic studies to dx BOO
First-line diagnostic test and treatment of urinary retention
Bladder scan: ≥300mL in a patient unable to void suggests urinary retention, ≥1L suggests chronic retention of urine
Immediate bladder decompression by
□ Urethral catheterization (first-line) by 14-18Fr Foley’s catheter
□ Suprapubic catheterization (SPC)
Urethral catherization
- equipment
- forms for different pathologies
- C/I
Urethral catheterization (first-line) by 14-18Fr Foley’s catheter
Failure to pass into bladder can be due to
- Enlarged prostate → use thicker (20-22 Fr) catheters
- Urethral stricture → use thinner (10-12 Fr) catheters
C/I: recent urologic surgery, urethral injury, urethral strictures (high-rising prostate, blood at urethral meatus)
Suprapubic catherization (SPC)
- Indications
- C/I
- Complications
Indications: failed urethral catheterization, Hx of urethral trauma (eg. straddle injury), long-term bladder drainage expected (>3w)
C/I: non-distended bladder (higher risk of bowel injury), uncorrected bleeding tendency, known/suspected urothelial CA (seeding)
Complications: bowel perforation, rectal injury (overshooting), haematuria
Urethral cathertization
Procedure, 4 steps
- Aseptic technique: clean patient’s genital area with hibitane, drape surrounding areas
- Intraurethral LA: apply xylocaine jelly around meatal opening → milk jelly down urethra → wait 5min
- Insertion: use forceps to hold 14Fr Foley’s catheter → insert all the way down using no touch technique
- Fixation: inject 10mL of water into balloon → withdraw catheter until resistance encountered
Suprapubic catherization (SPC)
- Process, 2 steps
- LA injected 2FB above pubic symphysis
- Small incision made in skin/fascia → insert trocar-type suprapubic tube → catheter advanced over trocar → sutured in place → look for gush of urine
First-line investigations for urinary retention
Investigations:
□ Blood: CBC (leukocytosis), LFT, RFT (obstructive nephropathy)
□ Catheterized urine: biochemistry, microscopy, C/ST
□ KUB for stones or faecal loading
□ Do NOT take PSA → AROU can cause false elevation (to be done 4-6w later)
Urodynamic study for urinary retention
- Metrics measured
Intravesical and rectal pressure
Detrusor pressure
Uroflow rate
Sphincter function EMG
Bladder volume
Cystogram and reflux (video)
> > > high detrusor pressure, low uroflow is diagnostic of BOO
List 3 complications after relieving AROU and pathophysiology
- Post-obstructive diuresis: >200mL/h urine ×≥2h or >3L urine in 24h
MoA: tubular damage → ↓concentrating ability → rapid fluid and solute loss - Haemorrhage ex-vacuo (transient haematuria):
MoA: bladder mucosal disruption with sudden emptying of greatly distended bladder - Transient hypotension
MoA: vagovagal response or relief of pelvic venous congestion
Management options for AROU due to BPH
Initiate BPH medications
Trial without catheter (TWOC): ≥2 TWOC attempts before considering surgical therapy
→ Involves: removal of catheter after 1-2w → determine whether pt can void spontaneously
- Success (20-40%): perform urodynamic evaluation for confirmation of BOO
- Failure: if cannot void + bladder volume >400mL → recatheterize
Failed TWOC ×2:
→ Long-term catheterization
→ Clean intermittent self-catheterization
→ Elective TURP
