Introduction
The main 2 functions of the urinary bladder are1 storage of urine until it is time to empty and2 Evacuation by passing urine periodically at appropriate times.
These 2 functions are achieved by finely coordinated processes of contraction and relaxation of the detrusor muscle and urethral sphincters of the bladder under the control of centers of micturition in the brain stem with the inhibitory influence of the cerebral cortex which occurs around 3-4 years. By 3-4 years the majority of children stop daytime wetting. This fine balance of detrusor contraction and relaxations of the sphincter is controlled by the innervation of detrusor and sphincter muscles by sympathetic (T10, L1 spinal segment) parasympathetic (S2-S4 spinal segments), and motor/sensory nerves.
Disorders of voiding develop as incontinence or urinary retention if spinal segments of nerves are affected.
The clinical conditions commonly causing disorders of voiding are a variety of congenital and acquired conditions affecting spinal cord segments of dorsal lumbar, sacral regions including cauda equina and Conus medullaris ex. Meningomyelocele, lipomeningocele, diastematomyelia, spina bifida, and sacral agenesis. Traumatic injuries and tumors of the spinal cord are rare but important causes of neurogenic bladder.
Causes of Voiding Dysfunction
Neurogenic causes: Meningomyelocele, lipomeningocele, spina bifida, sacral agenesis, diastematomyelia, tethering of spinal cord, Arnold Chiari malformation, trauma to the spinal cord, and rarely tumors of the spinal cord.
Many of these conditions are associated with abnormal findings on neurological examination of lower extremities, abnormalities of feet, a tuft of hair, nevus, or dimple in the region of the lower back, and bowel dysfunction.
Non-neurogenic causes: Neuropathic or non-neurogenic/neurogenic bladder or Hinman's syndrome, monosymptomatic nocturnal enuresis, psychologic disturbances.
UTI, obstructive uropathy, vesicoureteral reflux, polyuric syndromes can easily be detected by good history, physical examination, urine culture, and radiologic studies.
Neurogenic Bladder - Presentation
A detailed history of the age of bladder and bowel control, type of voiding problems. Daytime and nighttime enuresis should be noted. Incontinence or enuresis denotes hyperactive bladder contraction or small capacity bladder. Incontinence may occur during the daytime, whilst giggling, laughing, etc. Urinary retention may be due to an increased tone of sphincter with poor relaxation ex. Detrusor - sphincter dyssynergia (DSD). Continuous dribbling is due to the continuous relaxation of sphincters, usually caused by spinal cord lesions affecting cauda equina. Daytime incontinence in children above 8 years of age without obvious neurologic cause needs complete workup of neurogenic bladder. A family history of incontinence may be present.
Detailed examination of the back to detect nevus, hair, lump, dimple which indicates abnormalities of spine-like spina bifida, lipomeningocele, sacral agenesis which can be diagnosed by simple x-ray of the spine followed by MRI to detect spinal cord compression and/or tethering requiring surgery. Examination of genitals, neurological examination for paraplegia, hydrocephalus, and tone of anal sphincters are important points.
Neurogenic Bladder - Investigations
Urine examination routine and culture to detect UTI which is a common clinical presentation of neurogenic bladder with functional obstruction, incomplete voiding and residual urine. Longterm chemotherapy is useful to prevent recurrent UTI.
Plain X-Ray of lumbosacral vertebrae for spina bifida, sacral agenesis.
Ultrasonography of kidneys, ureters, and bladder to detect upper tract dilatation like hydronephrosis, hydroureter, hypertrophy of bladder wall in DSD. Due to backpressure transmitted from bladder contractions against a non-relaxing sphincter in DSD; secondary VUR and reflux nephropathy with multiple renal scars occur, chronic renal failure is a consequence of poorly managed neurogenic bladder.
MCU to rule out vesicoureteral reflux/obstructive uropathy
MRI spine in suspected cases to rule out tethering of cord or spinal cord tumors
Kidney function tests to detect azotemia, metabolic acidosis, calcium/phosphorus abnormality, urinary concentrating defects which are due to tubular dysfunction are common metabolic problems.
Urodynamic studies, which measure the activity of detrusor muscle and urethral sphincter, bladder capacity, sensory and motor functions of the bladder are important in the evaluation of the type and severity of bladder dysfunction. This special test helps in the diagnosis of the type of neurogenic bladder so that drug therapy can be decided to control inappropriate detrusor contraction and relaxation of the sphincter. Indication of UDS is1 wetting with neurologic lesions2 day and night time enuresis after the age of 10 years.
Neurogenic Bladder - Treatment
Management of neurogenic bladder is complex and needs a team approach. In a common situation such as meningomyelocele pediatric urologist, nephrologist neuro physician, physiotherapist, a radiologist with dedication are required for the comprehensive treatment.
Management includes:
- Prevention and control of urinary tract infection with appropriate long term drug therapy.
- Clean intermittent catheterization to evacuate the bladder completely is advocated to reduce backpressure and prevent residual urine. Parents can be trained to perform CIC 3-4 times a day at home.
- Use of drugs to relax hypercontractile detrusor muscle ex. Oxybutynin or to increase the contraction of hypocontractile bladder muscle use of cholinergic agents like Bethanachol can help to a certain extent. Relaxation of the urethral sphincter may be different and alpha-blockers like prazosin may be useful. These drugs should be used after urodynamic evaluation by experts.
- Rarely in selected cases, surgery is indicated to augment the bladder capacity and or tighten the urethral sphincter.
- Bladder training programs using bio feed methods should be tried.