Neurourology

Physiology — Storage & Emptying

Filling (Storage)

1. Accommodation

• Compliance
• Sympathetic stimulation
• Parasympathetic inhibition

2. Closed bladder outlet

• Sympathetic stimulation → increases involuntary smooth sphincter tone
• Onuf's nucleus stimulation → increases voluntary striated sphincter tone

Emptying (Voiding)

1. Open bladder outlet

• Relaxation of the pelvic muscle
• Sympathetic inhibition
• Onuf's nucleus inhibition

2. Detrusor contraction

• Parasympathetic stimulation
• Sympathetic inhibition

Pathways & Receptors

System	Level	Nerve	Receptor
Sympathetic	T10–L2	Hypogastric	β₃
Parasympathetic	S2–S4	Pelvic	M₃
Somatic	S2–S4	Pudendal (Onuf's nucleus)	—

• Central control by the pontine micturition center
• M₂ is the predominant receptor, but M₃ is the primary (functional) receptor

Treatment Options — by Functional Category

Storage

A — Bladder related

• Behavioral → education, bladder training, timed voiding, pelvic floor
• Medication → antimuscarinic, β₃ agonist, Botox (presynaptic)
• Neuromodulation → sacral, posterior tibial
• Augmentation

B — Outlet related (sphincter)

• Behavioral therapy → bladder training, timed/fluid restriction, pelvic floor
• Sling procedure
• Artificial urinary sphincter

Voiding

A — Bladder related

• Credé maneuver
• Neuromodulation

B — Outlet related (sphincter / BPH / stricture)

• α-blocker
• Prostate surgery
• Urethral stricture repair
• Sphincterotomy
• CIC
• Indwelling catheter

EAU 16 (2025) discourages Credé / Valsalva / triggered reflex voiding: they raise intravesical pressure and provoke reflex sphincter contraction → hazardous to the urinary tract unless UDS confirms pressures stay within safe limits. All assisted emptying requires low outlet resistance + close urodynamic surveillance. Triggered voiding can induce AD in lesions at or above T6. The penile clamp is absolutely contraindicated in NDO or low compliance.

Evaluation

• Detailed history — including neurological and bowel history
• Physical exam — including sensory, reflexes, anal tone
• Voiding diary & QoL
• Labs & PVR
• Pad test & uroflow (optional)

→ After this, the patient is categorized as Low risk vs Unknown risk

Risk Stratification

Framework: AUA/SUFU 2021 NLUTD. Not present in EAU 16 (2025), which uses only an informal low- vs high-risk split.

Click the algorithm to open it full size.

Category	Defining features
Low risk (must meet all)	Suprapontine lesion or lesion distal to the spinal cord · spontaneous void · low PVR · no hydronephrosis · normal renal function
Unknown risk	Suprasacral lesion, MS · elevated PVR · recurrent UTI → these need upper tract imaging + UDS
Moderate risk	UDS shows BOO or DO · high PVR · no hydronephrosis · normal renal function
High risk	Poor bladder compliance · elevated detrusor pressure · DSD · hydronephrosis · abnormal renal function

• Low risk → no routine upper tract imaging, renal function testing, or UDS
• Not clearly low risk → unknown risk until worked up, which then reclassifies as moderate or high

Patterns of LUT Following Neurological Disease

Key: I = impaired · OV = overactive · N = normal · S = synergic · D = dyssynergic · OP = open/incompetent · A = areflexia · CNR = competent, non-relaxing · F = fixed tone

Disorder	Detrusor activity	Compliance	Smooth sphincter	Striated sphincter	Comment
CVA	OV	N	S	S	Suprapontine
Cerebral palsy	OV	N	S	S / 25% D	25% have DSD
Parkinson	OV	N	S	S	Bradykinesia
Multiple system atrophy	OV	N	OP	S (denervation)	No TURP — open bladder neck
MS	OV	N	S	S / 30–60% D	30–60% have DSD; ~25% areflexia
Suprasacral cord injury	OV	N	S / D	D	Smooth sphincter DSD if lesion above T6
Autonomic dysreflexia	OV	N	D	D
Sacral SCI	A	N	CNR	F	Compliance may be decreased
Disk	A	N	CNR	S
Pelvic surgery	I or A	↓ or N	OP	F
Diabetes	I or A or OV	N or ↑	S	S

Autonomic Dysreflexia

• Above T6 — spontaneous discharge of α₁ stimulant during bladder filling
• Signs → bradycardia, hypertension, sweating
• Treatment → abort the stimulus, drain the bladder, nitropaste above the level of the lesion, or nifedipine

EAU defines AD as an SBP rise > 20 mmHg from baseline, with headache, blurred vision, flushing/sweating above the lesion and pallor/cold skin below it. Campbell: more common in cervical (60%) than thoracic (20%) SCI; bradycardia typical but only 23% actually bradycardic in one series. Triggers: bladder/bowel distension, cystoscopy, urodynamics, any noxious stimulus (ingrown toenail, pressure sore), sexual stimulation. Drugs: 2% nitroglycerin paste above the lesion is first-line; sublingual nifedipine 10–20 mg works but is prohibited in many centers (rapid, non-reversible BP drop); IV nitroprusside if refractory. Prophylaxis: terazosin 1–10 mg daily. EAU (Strong): BP + HR monitoring is mandatory during UDS and other invasive procedures in at-risk patients; empty the rectal ampulla first.

DSD — Detrusor Sphincter Dyssynergia

• Suprasacral SCI
• MS (30–60%)
• Cerebral palsy (25%)

Management

• CIC
• Sphincterotomy — if patient unable to do CIC
• Botox to the sphincter
• Indwelling catheter

How to decrease the rate of bladder stones in SCI with a Foley catheter

1. Long-term antibiotics
2. Acidify urine
3. Increase fluid intake
4. Routine bladder lavage

Fowler Syndrome

• Urinary retention with no neurological disease in a young female
• Associated with PCOS
• Capacity over 1 L with no urge sensation
• UDS → impaired sphincter relaxation

Impaired sphincter relaxation is the concentric-needle EMG finding (decelerating bursts / complex repetitive discharges). The urodynamic finding is detrusor acontractility.

CIC vs Indwelling Catheter

Benefits of CIC over indwelling catheter

• Improved QoL
• Sexual activity
• Maintenance of bladder compliance — 80% lost with a catheter
• Decreased risk of infection, stone, cancer

Bladder cancer in SCI with chronic catheter

• Incidence 1% → surveillance after 8 years

Underactive Bladder (DUA)

• Difficult to diagnose — overlaps with OAB and is associated with BOO
• Diagnosis by urodynamics → measure BCI

BCI = Pdet@Qmax + 5(Qmax)

• < 100 → underactive / acontractile bladder

Management

• Behavioral, timed voiding, pelvic physiotherapy
• CIC, indwelling catheter, urinary diversion
• Bladder outlet obstruction surgery
• Neuromodulation

Neuromodulation — positive results found in

1. Non-obstructive urinary retention
2. DUA

OAB

OAB = urgency, with or without UUI, usually with increased daytime frequency and nocturia, in the absence of UTI or other obvious pathology.

Evaluation

• Hx + physical exam + UA + PVR + QoL + voiding diary
• Urodynamics should be done if a neurological etiology is suspected
• Urodynamics & cystoscopy should be done when surgery for UUI is considered

Treatment Pathway

1. Behavioral, timed voiding, fluid restriction
2. Pelvic floor muscle therapy
3. OAB medication (antimuscarinic / β₃ agonist)
4. Botox or neuromodulation
5. Urinary diversion / augmentation

Management of MS for LUTS

• Hx + physical exam + voiding diary + QoL + UA + US KUB + PVR + UDS
• High PVR → CIC
• Low PVR → 1st behavioral therapy · 2nd OAB medication · 3rd Botox · 4th neuromodulation · 5th indwelling catheter · 6th augmentation

Antimuscarinics

Divided into tertiary or quaternary.

A — Tertiary (lipophilic)

• Cross BBB → CNS side effects
• Oxybutynin (non-selective)
• Tolterodine
• Darifenacin (highest M3 selectivity)
• Solifenacin

B — Quaternary (lipophobic)

• Safe on CNS
• Trospium (safe, but watch the renal profile)

Contraindications

• Urinary retention
• Closed-angle glaucoma — precisely: untreated narrow-angle; treated narrow-angle is not a contraindication
• Myasthenia gravis
• cognitive impairment

Side effects

• Constipation, dry mouth, blurry vision, headache, retention

β₃ Agonist

• Mirabegron (50 mg PO daily)
• Effect at 4 weeks to 3 months
• Contraindicated → severe uncontrolled hypertension

OnabotulinumtoxinA (Botox)

• MoA → inhibits release of ACh at the presynaptic terminal
• Indications → ① OAB with incontinence · ② decrease DLPP
• Efficacy → 30% complete resolution · 60% have a 50% reduction in symptoms
  • Retreatment often needed after 6 months
  • Do not reinject within 3 months
• Complications → UTI (most common), high PVR, transient retention requiring CIC
• Contraindications → UTI, pregnancy, myasthenia gravis, not accepting catheterization

Steps

1. Map the bladder — except the trigone, don't inject it
2. 100 U / 10 mL → inject 0.5 mL × 20 sites
3. Increase to 200 U / 30 mL → inject 1 mL × 30 sites — for neurogenic overactivity

Sacral Neuromodulation

• MoA → modifies the voiding reflex — stimulation of the S3 afferent nerve

2-stage procedure

1. Stage 1 → insertion of the electrode at the S3 root, test for 2–4 weeks; if symptoms improved →
2. Stage 2 → connection of the electrode to a subcutaneous generator

How to know if placement is accurate

Root	Response
S3 (target)	Bellows of the pelvic floor + plantar flexion of the great toe
S2 (move down)	Anus contraction + plantar flexion of the whole foot
S4 (move up)	Bellows of the pelvic floor without plantar flexion

EAU 16 (2025) Strong: "Consider sacral neuromodulation in selected neuro-urological patients" (LE 1b) — MS with NDO are often good responders. MRI is no longer a barrier — current generators/leads are 1.5-T and 3-T conditional. Campbell notes SNM is not FDA-approved for neurogenic bladder (off-label) despite efficacy: RCT success 76% on vs 42% off.

Percutaneous Tibial Nerve Stimulation

• Insertion 5 cm cephalad to the medial malleolus and 2 cm posterior to the tibia
• Stimulates S3 through the tibial nerve
• Proper placement → patient feels sensation at the bottom of the foot

Polyuria

• Polyuria = > 40 mL/kg
• Nocturnal polyuria = 33% of the volume at night (NPI > 33%)

Evaluation

• Hx (DM, OSA, neuro) + physical + FVC (frequency-volume chart)

Click the algorithm to open it full size.

FVC finding	Next step	Result
Low volume	Look for a urological cause	Treat
Nocturnal polyuria (NPI > 33%)	Look for CHF, DM, OSA, excessive PM fluid intake	Treat the cause
Polyuria (> 40 mL/kg)	Overnight water deprivation	Urine osmolality > 800 → primary polydipsia; Urine osmolality < 800 → renal concentration test
Renal concentration test	Normal → central DI	Abnormal → nephrogenic DI
Mixed	Both patterns

Treatment for nocturnal polyuria (NPI)

• Control the underlying cause
• Desmopressin — watch for hyponatremia

Contraindicated in:

• CrCl < 50
• Hyponatremia
• vWD

Spinal Shock

• Decreased excitability of cord segments at and below the lesion → areflexic, acontractile bladder; urinary retention is the rule
• Duration → 6–12 weeks in complete suprasacral lesions; may last 1–2 years
• Resolution → begins with return of the bulbocavernosus reflex, alongside return of lower-limb DTRs
• First UDS within 3 months of SCI (EAU); repeat after spinal shock resolves
• Do not perform irreversible interventions based on symptoms during this period

Storage Pressure & the Upper Tract

• DLPP = lowest Pdet at which leakage occurs without a detrusor contraction or raised abdominal pressure
• DLPP > 40 cmH₂O → hydronephrosis or VUR in 85%
  • A cut-off of 20 cmH₂O is more sensitive (91.5%) for upper tract damage
  • Aim for as low a pressure as reasonably achievable, well < 40 cmH₂O — the 40 figure is not a validated "safe" line
• Impaired compliance → < 20 mL/cmH₂O (no consistent definition; 10–20 range used)

VUR in neurogenic bladder

• Incidence 17–25% in SCI; more common with suprasacral injury
• Driven by high storage/voiding pressures + infection — no discrete VUR pressure threshold is stated
• Best initial treatment → normalize urodynamics (lower storage pressure, lower outlet resistance) before considering surgical correction
• Upper tract deterioration 51% with urethral catheters vs lower with voiding/CIC

Bladder Augmentation

• Aim → low-pressure reservoir; improves compliance, abolishes/reduces NDO
• EAU (Strong): "Offer bladder augmentation in low bladder compliance and/or refractory neurogenic detrusor overactivity" — only when all less-invasive methods have failed
• Supratrigonal cystectomy → indicated with a severely thick, fibrotic bladder wall; CIC may become necessary
• Caution with pre-operative renal scars → metabolic acidosis
• Auto-augmentation (detrusor myectomy) → low surgical burden, does not preclude further intervention

Long-term complications

Complication	Rate
Bowel dysfunction	15%
Mucus production	12.5%
Stone formation	10%
Metabolic abnormalities	3.35%
Bladder perforation	1.9%

• Lifelong follow-up is essential — stabilizes renal function and prevents anatomical deterioration, but morbidity is significant
• Any bowel-segment reconstruction → annual history, physical, metabolic panel (electrolytes/acid-base), renal function, upper tract imaging (AUA/SUFU)

Follow-up & Surveillance

No high-level evidence; intervals are largely unspecified. Flagged as such rather than invented.

EAU 16 (2025)

• Interval between baseline and control investigations should not exceed 1–2 years; much shorter in high-risk
• High risk → upper tract ultrasound every 6 months
• High risk → physical exam + urine labs yearly
• UDS → mandatory baseline in high-risk, repeated at regular intervals — no numeric interval given
• Any significant clinical change → further specialized investigation (Strong)

AUA/SUFU 2021

• Low risk → no routine yearly surveillance unless symptoms, imaging, or renal function change
• Moderate / high risk → yearly history, physical, symptom check + yearly renal function + upper tract imaging every 1–2 years
• UDS → repeat for a change of symptoms or when clinically indicated — no fixed interval
• Stone history or high stone risk → imaging every 1–2 years