ETIOLOGY, CLASSIFICATION OF NEUROGENIC BLADDER AND UTI IN SCI

Neurogenic Sphincter

     The primary cause of bladder dysfunction in SCI is an incomplete or complete interruption in the neurocontrol of the external urethral sphincter, which results in an inability of the sphincter to relax, the last of three steps in normal micturition:

1. Awareness of bladder fullness by sensory feedback

2. Voluntary contraction of the detrusor muscle of the bladder to produce necessary pressure in the bladder

3. Synergic relaxation of the external urethral sphincter to produce an opening for the urine and decrease intravesical pressure

     The inability of many patients with SCI to relax the external sphincter and voluntarily contract the detrusor muscle causes problems in both retention and expulsion of urine. Problems such as incontinence or urinary retention can cause other complications, such as urinary infections, vesicoureteral reflux, and/or hydronephrosis. Management of the neurogenic bladder is therefore aimed at preventing high residual urine and lowering high intravesical pressure caused by impaired sphincter function.

Classification

     Following are the three commonly used classifications of neurogenic bladder following SCI:

Level of Motor Neuron Involvement Upper motor neuron (UMN) type Bladder Complete Incomplete	External Urethral Sphincter Control Group C: Cerebral cortical control - voluntary sphincter control through residual intact cerebrospinal pathway; common in patients with incomplete SCI
Lower motor neuron (LMN) type Bladder Complete Incomplete	Group S: Spinal synergic control -inducing synergic reflexic sphincter opening using cutaneous or other stimulation - 10%-15% of patients with complete SCI; use external collector.
Bladder Function Spinal shock bladder Uninhibited bladder Reflex bladder Coordinated Uncoordinated	Group Q: No cortical or spinal synergic sphincter control; also, no normal handfunction for self-catheterization; common in complete quadriplegia; consider surgery
Autonomous bladder Motor paralytic bladder Sensory paralytic bladder Mixed UMN and LMN bladder	Group P: No cortical or spinal synergic sphincter control, but normal hand function to perform intermittent self-catheterization or anal stretch; common in complete paraplegic patients; consider TUR or sphincterectomy.

Urinary Tract Infection in SCI

     Urinary tract infection is a serious complication of neurogenic bladder in SCI, related to high morbidity and mortality rates. With impaired sensation, the classic UTI symptoms of dysuria, frequency, urgency, and suprapubic pain are not reliable in UTI in SCI . UTI is sometimes overlooked and therefore untreated. Bacteriuria, the presence of bacteria in the urine, is very common in patients with an indwelling catheter. The distinction between lower and upper urinary tract bacteriuria is important since upper tract infections pose threats of renal damage. Tissue invasion by organisms in the urinary tract is often accompanied by high WBCs.

     Upper urinary tract surveillance of SCI patients can be performed solely with renal ultrasound, which is noninvasive, widely available, and less costly than renal nuclear scan. Additionally, renal ultrasound provides anatomic information about the upper tracts not shown on renal nuclear scan. By incorporating yearly renal ultrasound study of SCI patients, further upper tract imaging can be reserved for those cases in which the RUS reveals positive findings (Gousse, et al 2003).

      Individuals with SCI should be evaluated with urine culture to ensure proper treatment. Reliance on dipstick testing for NIT and LE in individuals with SCI can lead to high rates of overtreatment for UTI, given the fact that regular catheterization is associated with significant bacteriuria.

     Antibacterial therapy for 1-2 weeks frequently results in relapse. However, repetitive and insufficient antibiotic therapies can cause highly resistant organisms. Antimicrobial resistance in outpatients with SCI is common (Waites, et al 2000). SCI patients with symptomatic UTIs should be treated with the most specific, narrowest spectrum of antibiotics for the shortest period of time; quinolones are recommended (Siroky, 2002). Treatment of acute symptomatic UTI with ciprofloxacin for 14 days can lead to improved clinical and microbiological outcomes, compared with short-course therapy of 3 days (Dow, et al 2004). However, possible benefits of antibiotic prophylaxis must be balanced against possible adverse effects, such as development of antibiotic resistant bacteria (Neil-Weise & van den Broek, 2005).

      Bladder irrigation with normal saline and dip-slide bacterial counting may be considered.  Bladder irrigation with neomycin/polymycin may be effective in changing resistance of most organisms (Linsenmeyer, et al 1999). E coli 83972 may reduce the frequency of UTI's in SCI patients with neurogenic bladder (Hull, et al 2000). A randomized, double-blind comparison showed that bladder irrigation is generally well tolerated for 8 weeks. No advantages were detected for neomycin-polymyxin or acetic acid over saline in terms of reducing the urinary bacterial load and inflammation. Bladder irrigation as a means of treatment for bacteriuria in persons with neurogenic bladder is not recommended (Waites, et al 2006).

     An analysis of the evidence on selected aspects of the prevention and management of urinary tract infections in SCI and multiple sclerosis was performed by the Agency for Health Care Policy and Research and is available as Evidence Report/Technology Assessment No. 6: Prevention and Management of Urinary Tract Infections in Paralyzed Persons. An analysis of the evidence does not support the regular use of antimicrobial prophylaxis for patients with neurogenic bladder caused by spinal cord dysfunction (Morton, et al 2002).