Voiding Dysfunction

Question 1

What is the role of the normal lower urinary tract?

Answer 1

• Normal lower urinary tract function is essential for proper storing or urine, as well as efficient emptying at an appropriate, socially acceptable time
• Disruptions in neurologic input can result in disruption of either or even both functions of the lower urinary tract and result in inability to void or incontinence of urine
• In addition, low bladder storage pressures are essential to allow the kidneys to deliver urine to the lower urinary tract and maintain normal GFR

Question 2

What are the effects of long-term uncorrected high bladder storage pressures?

Answer 2

• Long-term uncorrected high bladder storage pressures can result in hydronephrosis and loss of renal function.
• Understanding normal function and innervation are key to understanding the anticipated problems which can arise, and in determining follow-up and monitoring patients with a variety of neurologic disease for lower urinary tract issues
• Non neurogenic voiding dysfunction may also result in difficulties in bladder storage, emptying, or both, and can have a huge impact on patient quality of life and social functioning

Question 3

Describe the innervation of the lower urinary tract.

Answer 3

• Normal innervation of the lower urinary tract consists of both autonomic and somatic inputs
• Coordination of these systems is essential for proper functioning
• Bladder storage is the main function of the sympathetic nervous input
  
  • Sympathetic efferent innervation originates from cord level T10-L2 and travel via the hypogastric nerve
  • The bladder body contains beta adrenergic receptors, while the bladder neck has mainly alpha adrenergic receptors
  • Sympathetic stimulation results in relaxation of the bladder body with increased tone at the bladder neck, promoting urine storage
  • The sympathetic system is also thought to inhibit the parasympathetic input, again resulting in urine storage
  • Stimulation of the parasympathetic system results in bladder emptying
• Parasympathetic input arises from the 2nd to 4th sacral segment and travel via the pelvic nerve
  
  • Detrusor contraction is mediated via muscarinic receptors in the bladder body, resulting in a coordinated detrusor contraction.
• Somatic input to the external urethral sphincter, a striated muscle, travels via the pudendal nerve and originate in S 2-3

Question 4

What do the sensory fibers do in the lower urinary tract?

Answer 4

• Sensory afferent input travels via many A-delta fibers and sense fullness, relaying information to higher centers
• Changes in the afferent fibers and input can occur in a variety of neurologic diseases

Question 5

Explain the coordination of normal micturition.

Answer 5

• Normal micturition is a coordinated activity of the nervous system.
• The key coordination center for micturition occurs in the pontine micturition center
• If cortical function is intact, proper timing of micturition and necessary suppression of the micturition reflex occurs and voiding can be delayed to a socially acceptable time
• The pontine micturition center sends excitatory signals results in relaxation of the external sphincter and then detrusor contraction
• The first neurologic change which occurs during micturition is a suppression of external sphincter input, resulting in silencing of signal and relaxation of the external sphincter
• This is followed a coordinated detrusor contraction, which pulls up and opens the bladder neck (also termed the internal sphincter) allowing evacuation of urine

Question 6

Describe the presentation and diagnosis of non-neurogenic voiding dysfunction.

Answer 6

• Non neurogenic voiding dysfunction is a common cause of morbidity, and these symptoms are seen in all age groups but do tend to increase with age
• Overactive bladder is a term used to describe a sense of urinary urgency, usually accompanied by frequency and nocturia, and may also result in urge incontinence
• It is typically idiopathic, but can have a huge impact on patient quality of life, sexual function, and social function
• Other pathology such as bladder cancer must be considered, and should be evaluated for as clinically indicated

Question 7

What are the treatment options for non-neurogenic voiding dysfunction?

Answer 7

• A variety of treatment options are available, and typically overlap with treatment options in patients with neurogenic voiding dysfunction
• Stress urinary incontinence may also result in loss of urine, and is considered a non-neurogenic etiology
• Stress leakage is the leakage which occurs with increases in abdominal pressure, such as during coughing, sneezing, or laughing
• This is typically caused by weakening of the support of the bladder neck and urethra, but may also be seen in the setting of an incompetent sphincter, due to neurologic disease or previous surgery

Question 8

What is the pathophysiology of diseases that involve lesions between the pontine micturition center and the bladder?

Answer 8

• Can result in a variety of impacts on lower urinary tract function
• Supra sacral spinal cord lesions, such as spinal cord injury, tumors, infarcts, etc., can result in a hyper reflexic bladder, with loss of volitional control of urinary storage and emptying
• In addition the bladder wall may thicken and loose its visceo elastic properties which are required for low pressure storage and renal delivery of urine to the bladder
• Because the coordination of the autonomic and somatic systems occurs above the lesions, coordination may be lost resulting in detrusor-sphincter dyssynergia

Question 9

How are lesions between the pontine micturition center and the bladder diagnosed?

Answer 9

• This is diagnosed on bladder urodynamics studies, which evaluate bladder filling pressure, contractions, and sphincteric function
• If the bladder contracts and the sphincter does not relax (typically the external sphincter) high pressures can be sustained in the bladder preventing normal transit of urine from the kidneys to the bladder
  
  • Vesicoureteral reflux can occur as well
• The patient may be unaware this occurring, and may not leak urine as a result
• This is why all patients with spinal cord lesions should be evaluated by a urologist familiar with neurourology and undergo urodynamics testing

Question 10

What is the presentation of spinal cord lesions that affect micturition?

Answer 10

• Sacral spinal cord lesions can result in a variety of findings, most commonly an atonic bladder with loss of contractility, and a sometimes fixed external urinary sphincter
• Volitional voiding ability is typically lost but bladder storage parameters (filling pressures) are usually in the normal range
• In some instances bladder filling pressures may be affected so these patients typically undergo urodynamics testing to ensure safe pressures, but most represent little risk to renal function and normal transit of urine to the bladder can proceed normally

Question 11

What effects do peripheral lesions have on micturition?

Answer 11

• Peripheral lesions, for example pelvic plexus injuries as the result of pelvic surgery or radiation result in similar lower urinary tract issues as sacral cord lesions
  
  • normal bladder storage but loss of ability to volitionally void.

Question 12

What is bladder compliance and how does it affect micturition?

Answer 12

• Bladder compliance is a key concept when evaluating patients with urodynamics testing
• Not only can detrusor-sphincter dyssynergia result in urine transport issues and impact renal function, but sustained bladder pressures during filling can also have a significant negative impact on renal function long-term
• Bladder compliance is defined as the change in bladder volume (ml) over the change in bladder pressure (cm H2O) at bladder capacity
• The normal bladder accommodates mainly as the result of visceoelastic properties and little change in pressure (<10 cm H2O) is seen from full to empty
• With neurologic disease, particularly supra sacral cord lesions, these properties can be adversely affected as the result of bladder wall thickening and collagen deposition
• The bladder compliance is measured during the filling phase of urodynamics testing

Question 13

What are the main concerns of the neurologist when evaluating patients with neurologic disease affecting the urinary system?

Answer 13

• The main concern of the neurourologist when evaluating patients with neurologic disease is to determine if the upper tracts (kidneys) are at risk due the bladder pathology
• A socially acceptable method of bladder storage and emptying is also a priority, and finally minimizing urinary tract infections and hospitalizations is and important
• The management can be broken down by understanding the issues
• The two main issues are either failure to store urine, or failure to empty urine, or both
• The causes can be due to either the bladder, the outlet (urethra, sphincter) or both
• Thinking in these terms can provide clear understanding of treatment options

Question 14

How is failure to store due to bladder problems treated? What about patients with non-neurogenic bladder overactivity?

Answer 14

• Failure to store due to the bladder may be treated by medications (anti cholinergic medications, beta adrenergic agonist), botulinum toxin injection, or surgical enlargement with ileal bladder augmentation
• Patients with non-neurogenic bladder overactivity are treated similarly, though augmentation would rarely be done in this setting.

Question 15

How is failure to empty due to bladder atony treated?

Answer 15

Failure to empty due to the bladder (for example atony) can be treated with catheterization or an indwelling catheter

Question 16

How is failure to store, empty, or both due to urine outlet dysfunction treated?

Answer 16

• Failure to store due to the outlet requires a surgical procedure to close or tighten the outlet
• Failure to empty due to the outlet can be treated with catheterization, or medications to relax the sphincter such as alpha adrenergic agonists
• Often the patient has both failure to store and empty, and treatment will be directed by urodynamics testing