Bladder dysfunction in persons with spinal cord injury (SCI) has medical, physical, and social consequences. Most people with SCI have some degree of bladder dysfunction. Normally, the bladder stores urine at low pressures within a relaxed detrusor (bladder wall smooth muscle), until it is socially appropriate to void. As the relaxed bladder fills to a threshold of approximately 300-400 mL, progressive distention leads to increasing afferent input to the sacral and pontine micturition centers until detrusor contraction and sphincter relaxation are initiated. The timing and coordination of detrusor contraction and sphincter relaxation is mediated by the pontine micturition centre and leads to voiding in a low pressure environment. The frontal cortex can initiate or suppress voiding volitionally and subsequently contribute to continence by limiting voiding to desired times. The ability to fill and empty the bladder under low pressure is of utmost importance in maintaining the health of the kidneys, ensuring continence and preventing urinary tract infections (UTI).
A SCI disrupts communication between the sacral micturition centre in the spinal cord and the pons and cortex in the brain; resulting in the loss of coordinated bladder filling and emptying. The involuntary functions of the kidney, such as its general metabolism, osmotic regulation, and the filtration and production urine are unaffected by a SCI. In contrast, a SCI can affect bladder function in different ways depending on the level of the injury. This includes an inability to sense a full bladder, overactivity or underactivity of the detrusor muscle and/or internal and external sphincters, and dys-coordination between the detrusor and sphincters during voiding. The latter process is referred to as detrusor sphincter dyssynergy (DSD). A spastic (reflex) bladder usually occurs with a SCI above the conus medullaris (spinal level of T12) while an areflexic (flaccid) bladder usually occurs in injuries at and below T12-L1, including conus medullaris and cauda equina injuries. The spastic bladder is often referred to as an upper motor neuron (UMN) bladder while the flaccid bladder is referred to as a lower motor neuron (LMN) bladder. The functional goal of bladder management following SCI is to tailor a bladder emptying program that is specific to the individual and compatible with his/her lifestyle and activities of daily living. Medical goals include achieving regular bladder emptying and avoiding stasis; avoiding high filling and voiding pressures; maintaining continence while avoiding abnormal frequency and urgency; and preventing and treating complications such as UTI, autonomic dysreflexia (usually only in those with injuries at or above T6), reflux, stones, and strictures.
There is a growing body of research evidence to aid in clinical decision making when managing bladder function following a SCI.While the amount of level 1 and 2 evidence has increased substantially in recent years, it is important to recognize that level 1 and 2 evidence is not available for all aspects of bladder complications, and that level 3, 4 and 5 evidence continues to provided important contributions to this field. The expanding scientific literature, however, presents a challenge when synthesizing and summarizing findings into a chapter of reasonable length. As a result, for sections where several levels of evidence exist and the level 5 evidence studies do not add novel or compelling evidence, level 5 evidence is summarized under the subheading Summarized Level 5 Evidence Studies. The contributions from these studies were not included in the related discussion or conclusions.
The present chapter is organized into sections addressing the type of bladder dysfunction (UMN vs. LMN), therapeutic strategies including the prevention and management of complications, and a final section focused on UTI prevention and treatment.