Definition and Overview
Neurogenic bladder is a condition in which normal urinary function is lost due to damage to any part of the nerve pathway that controls bladder storage and discharge (cerebral cortex → pontine micturition center → sacral urination center → peripheral nerves → bladder).
Normal urination requires recognition of bladder fullness, volitional decision on the timing of urination, and coordinated operation of detrusor muscle contraction and external urethral sphincter relaxation. If any of these steps are impaired, neurogenic bladder occurs.
Neural control of urination
autonomic nervous system
- Parasympathetic nerve (S2~S4): Contracts the detrusor muscle and relaxes the internal urethral sphincter through the pelvic nerve. Acetylcholine acts on the M3 receptor.
- Sympathetic nerve (T10~L2): Relaxes the detrusor muscle (β3 receptor) and contracts the internal urethral sphincter (α1 receptor) through the hypogastric nerve. Involved in storing urine.
somatic nerves
- Pudendal nerve (S2~S4): Responsible for voluntary contraction of the external urethral sphincter.
central nervous system
- Barrington nucleus: control center for the micturition reflex
- Cerebral cortex (medial frontal lobe): volitional inhibition of urination
Classification
Overactive bladder — upper motor neuron lesion
In lesions beyond the pons (stroke, multiple sclerosis, Parkinson's disease, etc.), the cerebrum's ability to inhibit urination is lost, causing uninhibited contraction of the detrusor muscle. Bladder capacity decreases, and urinary frequency, urgency, and urge incontinence occur.
Detrusor-sphincter dyssynergia (DSD) — spinal cord lesions
In spinal cord lesions above the sacral cord (cervical and thoracic spine), detrusor-sphincter dyssynergia (DSD) occurs, in which the external urethral sphincter does not relax at the same time as the detrusor muscle contracts. Pressure within the bladder rises dangerously, increasing the risk of hydronephrosis, vesicoureteral reflux, and renal failure.
Underactive bladder — lower motor neuron lesions
In sacral (S2-S4) or peripheral nerve lesions (diabetic autonomic neuropathy, cauda equina syndrome, or after pelvic surgery), detrusor muscle contractility is reduced and urine output is incomplete. The amount of residual urine increases and overflow incontinence occurs.
Characteristics of each cause disease
spinal cord injury
Approximately 80-90% of spinal cord injury patients are accompanied by neurogenic bladder. The type is determined by the level of damage, with DSD mainly appearing in cervical and thoracic spine injuries, and hypoactive bladder appearing in conus and cauda equina injuries.
multiple sclerosis
Urinary symptoms are reported in approximately 75-90% of patients. Detrusor overactivity is the most common (approximately 65%), and DSD is also present in approximately 25% of cases.
Parkinson's disease
Frequent urination, urgency, and nocturia occur in approximately 40-70% of patients, which is caused by overactivity of the detrusor muscle. It is understood that dopamine deficiency in the basal ganglia weakens the micturition inhibitory pathway.
Diabetic autonomic neuropathy
It progresses in the following order: decreased bladder sensation → hyperinflation → decreased detrusor contractility. Bladder sensation becomes dull, so you cannot feel urine, which ultimately leads to underactive bladder and increased residual urine.
diagnosis
urination log
Identify urination patterns by recording urination time, amount, and episodes of urinary incontinence for 3 days.
Residual urine measurement
After urination, the amount of residual urine is measured using ultrasound (bladder scan). Residual urine of more than 100 mL is clinically significant.
Urodynamic study
It is a key test for diagnosing neurogenic bladder.
- Cystometry: Measures bladder capacity, detrusor overactivity, and fullness threshold.
- Uroflowmetry: rate and pattern of urination
- Pressure-flow test: assessment of detrusor contractility and urethral resistance
- External urethral sphincter electromyography: DSD confirmation
imaging test
- Renal ultrasound: screening for hydronephrosis and vesicoureteral reflux
- Voiding cystourethrography (VCUG): Evaluation of reflux and bladder morphology.
- Brain/spinal cord MRI: Identify causative nerve lesions
treatment
overactive bladder
- Drugs: Anticholinergics (oxybutynin, solifenacin, tolterodine) are first-line treatment. β3 agonists (mirabegron) are also an alternative.
- Botulinum toxin: In case of non-compliance with medication, botulinum toxin A injection into the detrusor muscle. It reduces the frequency of urinary incontinence by approximately 50-70%, and the effect lasts for 6-9 months.
- Sacral neuromodulation: Cases that do not respond to conservative treatment
Hypoactive bladder/DSD
- Intermittent self-catheterization (CIC): the gold standard in residual urine management. Performed every 4 to 6 hours to prevent bladder overdistension and infection.
- α-Blockers (tamsulosin): Relax the bladder neck and sphincter muscles.
- Long-term indwelling catheter: Last alternative when self-catheterization is not possible (high risk of infection)
upper urinary tract protection
The most important treatment goal in neurogenic bladder is protection of the upper urinary tract (kidneys). The key is to maintain intravesical pressure below 40 cmH2O, minimize residual urine, and prevent vesicoureteral reflux.
complications
- Recurrent urinary tract infections (UTIs): Frequent due to residual urine and catheter use.
- Vesicoureteral reflux and hydronephrosis: caused by high intravesical pressure in DSD.
- Chronic renal failure: the end result of long-term upper urinary tract damage.
- Autonomic dysreflexia: Dangerous sympathetic hyperreflexia caused by bladder distension in spinal cord injury above T6.