Urological management of patients with spinal cord injury

Investigations and urological review

Radiology

Ultrasound (US)

This is the most useful non-invasive technique to monitor bladder emptying and the integrity of the upper tracts. The combination of plain abdominal radiography with US has superseded routine intravenous urography for annual review, and most of the important changes to the upper tracts, especially dilatation, parenchymal scarring, and stone formation, can be diagnosed on US. When abnormalities are detected, other imaging modalities may be required.

 

Video-urodynamics

Although the degree of detrusor activity may be predicted by the level of the SCI, formal baseline studies should be performed at 3–4 months to enable definitive bladder management to be planned. The investigation is in two parts. The cystometrogram relates the filling pressure to bladder volumes, and identifies and quantifies unstable contractions and abnormalities of compliance. The simultaneous contrast radiological study allows screening of the bladder and urethra. This is an important part of the investigation and is video-recorded or the images digitised. In many patients with a suprasacral cord lesion, detrusor contractions are associated with a simultaneous contraction of the distal sphincter mechanism — the void is obstructed due to the "dyssynergic" distal sphincter. Dyssynergic high pressure voiding frequently causes autonomic dysreflexia, a potentially serious and occasionally fatal autonomic disturbance resulting in severe hypertension. It is discussed in detail in chapter 6. Although the distal sphincter eventually relaxes, the unstable "voiding" detrusor contraction usually fades away before the bladder has emptied properly, leaving a significant residual. This encourages infection and stone formation, and ongoing unstable contractions often lead to vesico-ureteric reflux, hydronephrosis, and pyelonephritis. The contrast part of the study helps characterise many aspects of these extremely important complications, and enables appropriate (often surgical) action to be taken before irreparable damage takes place.

Effects of detrusor-distal sphincter dyssynergia:

• High bladder pressures → Vesico-ureteric reflux → Hydronephrosis → Chronic renal failure
• Incomplete bladder emptying → Recurrent urinary tract infections → Pyelonephritis → Chronic renal failure

 

Isotope renography/nuclear medicine

DMSA renography is a sensitive indicator of renal scarring and differential renal function, and is indicated when US studies suggest upper tract damage. DTPA and MAG 3 renography are useful investigations to characterise upper tract obstruction, and also to monitor the progress of the kidney after treatment for vesico-ureteric reflux. Serial estimation of the glomerular filtration rate (GFR) using Cr-EDTA or Tc-DTPA is a sensitive method of determining any decline in renal function, and a reduction in GFR (or creatinine clearance) is observed before changes can be measured in serum creatinine.

Isotope renography in spinal cord injury:

DMSA	Tc-DTPA and MAG3	Cr-EDTA GFR
- Differential renal function - Renal scarring - Accurate and reproducible in long-term follow-up	- Diagnosis and follow-up of uretero-pelvic junction or ureteral obstruction - Indirect cystography for vesico-ureteric reflux - Differential renal function - Indirect measurement of GFR	- Serial assay is a sensitive index of small changes in GFR

 

Biochemistry

Routine baseline serum creatinine, urea and electrolyte estimations are performed, and should be repeated annually until the clinician in charge is certain that the urinary tract is completely stable on definitive management, and with no significant radiological or urodynamic prognostic risk factors.

 

Later management

In many patients the early management of the urinary tract merges with the long-term plan. With the increasing use of suprapubic catheters at an initial stage, many tetraplegic patients are discharged into the community content not to alter this method of bladder management. However, both suprapubic and urethral catheters should be discouraged where safer methods are available, especially in paraplegics. Above all, the merits of ISC should be stressed to the patient. In those men whose penis will retain a condom, sheath drainage is an extremely safe method of bladder management. Where necessary, endoscopic distal sphincterotomy is undertaken to abolish dyssynergia.

Personal choice is now emerging as a major factor in planning, and the individual’s lifestyle preferences must be taken account of, though not at the expense of risk to the upper tracts. Some aspire to continence and freedom from indwelling catheters. Others are unwilling to self-catheterise, and will not relinquish their suprapubic catheters. Tetraplegics with poor hand function have fewer choices available to them, and avoidance of autonomic dysreflexia and freedom from infection may be the dominating influences in their personal choice.

After the first year, many paraplegic and a few incomplete tetraplegic patients wish to explore alternatives that allow freedom from permanent catheterisation, and restoration of continence. Patient awareness and lifestyle aspirations are increasing the demand for complex lower urinary tract reconstruction. Surgical options are tailored for each individual, and the urologist advising spinally damaged patients must balance the potential to improve symptoms against unrealistic patient expectations and the possibility of surgical complications.

Simultaneous faecal incontinence and female pelvic floor disorders (especially following cauda eqina lesions) frequently require a multidisciplinary approach. In particular, the involvement of specialist nurse practitioners and stomatherapists at an early stage in planning treatment is emphasised.

 

Detrusor hyperreflexia

In the presence of DSD, sustained rises in detrusor pressure (Pdet) may result in severe renal damage secondary to obstruction or high pressure vesico-ureteric reflux of (infected) urine. Continence and voiding are secondary considerations in these cases (nearly always males), where renal preservation is of the utmost priority. Recurrent suprapubic catheter blockage is common, even in the absence of calculous debris, and may result from catheter shaft compression by grossly unstable bladder contractions and mucosal plugging. Significant rises in detrusor pressure may occur even in the presence of an indwelling catheter on free drainage, and an association between these unstable contractions and upper tract scarring has recently been confirmed. Suprapubic catheters (SPC) should be cycled on at least two occasions each day, and simultaneous anticholinergic therapy should be used. Some men may opt for distal endoscopic sphincterotomy or stenting and condom drainage rather than SPC. Stents are less reliable in SCI patients than in those with outflow obstruction associated with prostatic enlargement. Others may be obese or suffer penile retraction, and condom sheath drainage may be impossible.

Detrusor hyperreflexia in the presence of DSD — Risks:

• Autonomic dysreflexia in patients with spinal cord lesions above T6
• Renal damage due to obstruction, high pressure vesico-ureteric reflux

The maintenance of continence is of vital importance to personal morale, and for the preservation of intact perineal and buttock skin. We briefly examine some of the many surgical procedures available to restore continence and to facilitate self-catheterisation.

Detrusor hyperreflexia — medical management:

• Anticholinergic treatment: Oxybutynin, Tolterodine, Propiverine HCI, Flavoxate, Propantheline
• Intravesical therapy (experimental): Capsaicin, Resiniferatoxin

Detrusor hyperreflexia — surgical management:

• Augmentation cystoplasty
• Sacral anterior root stimulator (SARS)
• Posterior rhizotomy
• Urinary diversion

 

Augmentation cystoplasty

Where conventional medical treatment with anticholinergic therapy has failed, and if indwelling catheters are to be avoided, the bladder must be deafferentated or bisected and augmented with a patch of bowel to provide a bladder of sufficient compliance and volume to safely accommodate a socially useful volume of urine. In female patients, DSD is very unusual, and severe incontinence rather than upper tract protection is the main indication for augmentation. After augmentation, inability to void is the rule rather than the exception, and the patient must demonstrate the willingness and ability to self-catheterise before surgery can be contemplated.

Even after augmentation, anticholinergic therapy may be required to make the patient completely dry. Cystitis may be a recurrent problem after enterocystoplasty, and there remains a long-term theoretical risk of neoplastic transformation in the enteric patch, especially if this is colon. Nitrosamine production associated with UTI has been implicated in this process.

For those who cannot access their own urethra (wheelchair-bound females being an especially important group), the simultaneous provision of a self-catheterising abdominal stoma (Mitrofanoff) may be an integral part of the initial surgery (see below).

 

Neuromodulation and sacral anterior root stimulation (SARS)

In patients with complete suprasacral cord lesions, functional electrical stimulation of the anterior nerve roots of S2, S3 and S4 is very successful in completely emptying the paralysed bladder. Assisted defaecation, and in the male, implant-induced erections may be coincidental advantages of the implant. The device most commonly in use is the Finetech-Brindley stimulator; the anterior roots of S2, S3 and S4 are stimulated via a receiver block implanted under the skin, and a posterior rhizotomy is performed simultaneously. This cures reflex incontinence, improves bladder compliance and diminishes DSD, and thus ensures that neither the use of the implant nor overfilling of the bladder will trigger autonomic dysreflexia. Reflex erections and ejaculation will be lost with posterior rhizotomy, and simultaneous neuromodulation is under investigation as an alternative to rhizotomy in men.

No comparative or controlled prospective studies between augmentation cystoplasty and SARS are yet available, but despite its cost, the stimulator is amongst the first in a line of options designed to keep this group of patients catheter free.

 

Stress incontinence

Both male and female patients with conus and cauda equina lesions are vulnerable to sphincter weakness incontinence (SWI), as well as older women with pre-existing pelvic floor disorders, prolapse, etc. regardless of the neurological level of injury. This often manifests itself later as the patient becomes more active during rehabilitation, urinary leakage occurring for example on transfer to and from the wheelchair.

Colposuspension, pubo-urethral slings and, recently, tension free vaginal tapes are effective in treating SWI, though sometimes obstructive in patients with acontractile bladders attempting to void by straining or compression. In paraplegic females, urethral closure and SPC is a reliable method of ensuring continence, though where appropriate, permanent suprapubic catheterisation may be avoided by performing a Mitrofanoff procedure. Bladder neck injections with bulking agents have a less reliable record in this difficult group.

Artificial urinary sphincters (AUS) have an excellent record of continence, but there is a higher attrition rate in paraplegics due to infection or cuff erosion, especially if ISC is undertaken regularly. Placement around the bulbar urethra should be avoided in patients confined to a wheelchair, and impotence frequently complicates cuff placement in the membranous position. For both male and female paraplegic patients the bladder neck is therefore the optimal site for AUS cuff placement.

 

The acontractile bladder and assisted voiding

Since the adoption and widespread use of intermittent self-catheterisation (ISC) in detrusor failure the complications of chronic retention and long-term catheterisation have been significantly reduced. Most patients with good hand function manage the technique, though paraplegic females have more difficulty accessing their urethra. This may be sufficient to cause them to abandon attempts in favour of long-term suprapubic catheterisation.

Since Mitrofanoff first described his technique in children, the procedure has been adapted to other circumstances, including stomal intermittent self-catheterisation in the paraplegic wheelchair-bound female patient. Even in tetraplegic patients with limited hand function stomal ISC is sometimes feasible with careful siting of the channel. In those patients who have undergone a Mitrofanoff procedure, stomal ISC is usually regarded as preferable to urethral catheterisation, and females whose native urethra remains in situ and who have a stoma almost never catheterise their own urethra. Complications of the procedure are irritatingly frequent though rarely life-threatening. Minor "plastic" procedures for stomal stenosis are required in up to 30% of cases and complete channel revisions for leakage or failure are necessary in 15%.

The procedure may be undertaken in conjunction with bladder augmentation and/or bladder neck closure for intractable incontinence.

 

Mixed faecal and urinary incontinence

Cauda equina lesions causing sphincter weakness frequently result in mixed faecal and urinary incontinence. This may have a devastating impact on rehabilitation, and the urologist should not consider involuntary urinary loss in isolation. Malone described the effectiveness of the antegrade colonic (continence) enema (ACE) in children with meningomyelocoele, and it may be helpful in managing sphincter weakness faecal incontinence secondary to cauda equina or conus injury. The procedure (like the Mitrofanoff) consists of the construction of a self-catheterising channel from appendix or tapered small bowel between abdominal wall and underlying caecum or colon. Every 48 hours or thereabouts, the bowel is intubated via the stoma, and a large volume enema (e.g. 2 L water) administered to wash the bowel clear of faeces. Continence is achieved until the large bowel refills. The ACE procedure is much less effective in treating the profound constipation frequently encountered in suprasacral SCI. The procedure can be performed simultaneous to a Mitrofanoff, colposuspension, urethral closure, or bladder neck cuff implantation, although the remaining components of the AUS should not be implanted due to the risk of infection.