Bacteriuria

The definitions of what represents significant bacteriuria vary. Investigators and clinicians frequently define infection based on bacteriuria levels ranging from 10 ³ to 10 ⁵ colony-forming units (CFU) per milliliter of urine. However, insufficient data exist to recommend a standardized level for the diagnosis of CAUTI. Historically, the medical literature pertaining to urinary catheters has not made clear distinctions between asymptomatic bacteriuria and UTI. Often the term UTI has been used when bacteriuria (with or without symptoms) is present. The key problem, then, is that persons with SCI & D who use urinary catheters commonly have bacteriuria. The standard of care among SCI & D providers is not to treat asymptomatic bacteriuria, which has been defined as 10 ⁵ CFU of 1 or more organisms in an appropriately collected specimen in an asymptomatic person, with antibiotics.

Pyuria

Pyuria, defined as white blood cells (WBC) in the urine, is also commonly seen in individuals with neurogenic bladder dysfunction and especially in catheterized patients. However, in the catheterized patient, pyuria alone is not diagnostic of either asymptomatic bacteriuria or CAUTI. Different researchers have defined significant pyuria variably, with levels as low as 5 WBC per high-powered field being considered clinically significant. However, there is disagreement regarding a threshold for significant pyuria, because many persons with SCI & D have chronic pyuria but no overt signs of illness (eg, fevers, chills, nausea, vomiting).

Bacterial Colonization

Colonization of the bladder with bacteriuria is the norm in persons with SCI & D who use urinary catheters, either indwelling or intermittent. As noted earlier, treatment with antibiotics is not justified based on the presence of bacteriuria alone. Because of the risk of recurrent infections and development of resistant organisms in individuals with SCI & D, urine cultures should be obtained before initiation of antibiotic therapy in symptomatic persons. Empirical therapy may then be initiated with the opportunity of adjusting antimicrobial therapy based on culture results.

UTI Symptoms

The differentiation between asymptomatic bacterial colonization and clinical UTI can be difficult and is compounded by a lack of consensus regarding what constitutes UTI symptoms, the combination of symptoms and laboratory findings necessary for the diagnosis, and the symptoms that require antibiotic treatment (vs being managed with conservative measures, such as increasing fluid intake or catheterizations). UTI symptoms in individuals with SCI & D are diverse in both type and severity. These symptoms may include fever, rigors, chills, nausea and vomiting, abdominal discomfort, sweating, muscular spasms, fatigue, and autonomic dysreflexia (AD). Individuals may also present with cloudy or malodorous urine, increased urinary sediment, and catheter blockage. However, typical presenting symptoms experienced by individuals without SCI & D, such as dysuria, urinary frequency, and urinary urgency, may be absent.

As discussed further later, there is a need for consistency of reporting of various signs and symptoms of UTI. This factor has led to the development of clinical data sets to facilitate this process. Signs and symptoms vary in their usefulness for UTI diagnosis. Massa and colleagues reported that cloudy urine had the highest accuracy (83.1%) and leukocytes in the urine had the highest sensitivity (82.8%) for the presence of UTI. Fever had very high specificity (99%) but very low sensitivity (6.9%). In addition, AD was found to be both insensitive and nonspecific, because AD may be triggered by multiple causes. Other symptoms, including kidney/bladder discomfort, increased spasticity, feeling sick, sense of unease, increased need to perform catheterization, feeling tired, incontinence, and foul-smelling urine, all had high sensitivity (77%–95%) but very low specificity (<50%). Persons with SCI & D are not always able to accurately predict the presence of a UTI based on their symptoms.

UTI Diagnosis

A UTI is characterized by the new onset of symptoms and not merely the presence of bacteria or WBC in the urine. To make the diagnosis, relevant laboratory findings, including bacteriuria (seen on urinalysis, dipstick, or culture), pyuria (leukocyturia), or a positive urine culture, must be accompanied by symptoms (see earlier section). In individuals with neurogenic bladder dysfunction, asymptomatic bacteriuria of varying degrees is the norm. Persons with SCI & D often do not present with similar symptoms to those in the general population, because of impaired or absent pain sensation.

Data Sets and Consensus Statements

Interpretation of UTI signs and symptoms is not standardized across systems of care or in different regions of the world. Led by Biering-Sorenson and colleagues, international data sets for SCI & D have been developed. Recently, a basic data set for UTI was developed to standardize collection and reporting of the minimal amount of information required to define a possible UTI in daily practice. This data set also makes it possible to evaluate and compare the results from various published studies. The importance of the urinary tract in SCI & D is evident in that data sets have been developed not only for UTI but also lower urinary tract function, imaging, and urodynamics. Data sets are incorporated into the National Institute of Neurological Disorders and Stroke common data elements to facilitate sharing of data from different studies.

Neurourology

There is tremendous complexity in the functioning of both the bladder and external urethral sphincter as distinct anatomic and functional units. However, the key to their proper functioning is the process through which these organs work together in a tightly orchestrated and reciprocal fashion. Thus, for effective urine storage to occur, the bladder must be in a state of relaxation while the external urethral sphincter is simultaneously in a state of tight contraction. Alternatively, when the voiding phase is initiated, a specific sequence of events needs to occur: first, the urethral sphincter relaxes, and then, the bladder contracts. This coordinated reciprocal control of the bladder and the external urethral sphincter is mediated by a control center in the brainstem called the pontine micturition center (PMC).

Accordingly, any neurologic injury above the PMC leads to suppression of inhibitory inputs from higher cortical centers and results in neurogenic detrusor overactivity with intact coordination of the external urethral sphincter and bladder. Injuries to the spinal cord below the PMC but above the sacral motor outflow result in neurogenic detrusor overactivity with a lack of external urethral sphincter and bladder coordination, a condition known as detrusor sphincter dyssynergia. This is the situation seen in most individuals who have complete (American Spinal Injury Association Impairment Scale A) suprasacral spinal cord injury. The problem in this situation is that the lack of coordination can lead to sustained high pressures in the bladder, with corresponding increases in complications, including UTIs, vesicoureteral reflux, calculi, hydronephrosis, and kidney damage. Thus, knowing some basic neurourology and the main location of a neurologic injury, the likely form of neurogenic bladder dysfunction can be predicted. Forms of neurogenic bladder dysfunction and descriptions based on location of neurologic injury are presented in Table 1 according to the functional model of voiding dysfunction originally described by Wein.

Bladder Management in Neurogenic Bladder Dysfunction

As described earlier, an understanding of the lower urinary tract pathophysiology in an individual with neurogenic bladder dysfunction is key to developing an optimized plan for long-term bladder management. The goal is to ensure complete bladder emptying before the occurrence of high-pressure, uncoordinated involuntary detrusor contractions. Thus, when patients or clinicians ask about the correct time interval for the performance of CIC, these individuals should be redirected to think about bladder management in terms of appropriate volume intervals. Volume intervals are best determined through the use of a well-performed urodynamics evaluation.

The urodynamic study should be performed in all individuals with neurogenic bladder dysfunction as soon as stable bladder functioning has been achieved, and again, when there is a change in clinical urologic status. For example, an individual who has been performing CIC for 5 years without complications does not specifically need a new urodynamics test, because the risks of testing (stricture formation, infections) do not justify the small anticipated benefit. On the other hand, individuals with neurogenic bladder dysfunction who report increased rates of UTIs, difficulty catheterizing, leakage between catheterizations, development of new urinary calculi, hydronephrosis, or deterioration in renal function would clearly benefit from a repeat urodynamics test, because the cause of many of these conditions may be improper bladder management.

The urodynamics test involves placement of a urinary catheter and a rectal catheter to simultaneously measure bladder and intra-abdominal pressures. The bladder is then infused with sterile saline at a defined rate to rapidly reproduce the filling-voiding cycle. During the filling phase, the compliance (elasticity) of the bladder can be calculated. Several studies have shown that poor compliance (equivalent to high stiffness) is associated with greater rates of upper tract deterioration and other urologic complications. The presence, pressures, and volume at which any involuntary bladder contractions occur are recorded. The voiding phase is analyzed by simultaneously recording the urinary flow rate and the detrusor pressure. These data are then plotted on to various nomograms such as the International Continence Society nomogram. This strategy allows the urodynamicist to determine if the voiding cycle is obstructed (defined as high bladder pressures in the presence of a low urinary flow rate) or unobstructed. The patient’s clinical history, pattern of pressure data, and the simultaneous collection of sphincter electromyographic activity and fluoroscopic images helps the urodynamicist determine the likely cause of neurogenic bladder dysfunction. For example, bladder outlet obstruction in a 25-year-old man with complete suprasacral spinal cord injury is likely caused by detrusor sphincter dyssynergia. Similar obstruction in an elderly man without known neurologic disease is most likely caused by benign prostatic hyperplasia.

Based on the results of the urodynamics test in conjunction with recommended annual studies, including upper tract imaging with a renal/bladder ultrasonography and laboratory tests to evaluate bladder function, a plan for bladder management is developed and implemented. Effective implementation of a bladder management plan likely includes a combination of behavioral modification (fluid restriction), pharmacotherapy, and CIC. Pharmacotherapy can be used to help suppress involuntary bladder contractions, increase bladder capacity, and lower bladder pressures. Second-line therapies, including injection of botulinum toxin, can be tried for refractory cases. Surgical diversions are available for the most severely affected individuals. Use of indwelling urinary catheters should be strongly discouraged because of high rates of infections and other severe complications. However, for some individuals, this option is the only available means to achieve bladder emptying.

Catheterization should be timed such that the bladder is emptied before the volume at which high-pressure involuntary contractions develop. A team approach is required, with necessary involvement from nurse educators, clinicians, occupational therapists, social workers, and family members/caregivers. The bladder management plan is continually adjusted based on evolving patient needs and circumstances.

Recurrent UTIs in Individuals with Neurogenic Bladder Dysfunction

We would like to emphasize that many conditions such as recurrent UTIs are best controlled through the implementation of a well-designed bladder management plan. Therefore, patients with neurogenic bladder dysfunction who present with recurrent UTIs should first be treated by attempting to optimize their bladder management. In addition, a search for treatable sources of infection with imaging studies and cystourethroscopy should be implemented to identify treatable causes, including infected calculi, diverticuli, and strictures. However, after all available attempts have been exhausted, patients can be directed to use various preventive strategies, which is comprehensively reviewed in the following sections.