DIAGNOSIS OF NEUROGENIC BLADDER IN SCI

     A comprehensive and systematic evaluation of the bowel  is recommended.

Physical Examination

1. Sacral sensation to pin prick is an indication of incomplete SCI and is often associated with intact sensation of bladder fullness

2. Voluntary toe movement or contraction/relaxation of the anal sphincter are positive indicators for bladder recovery, because they often indicate intact voluntary control of the external urethral sphincter and a coordinated detrusor-sphincter pattern. Patients with incomplete SCI almost always have normal bladder function.  However, voluntary toe movement does not enable differentiation of the types of neuropathic voiding disorders which continue to require urodynamic examination (Schurch, 1999).

3. Sympathetetic skin responses of the right hand and foot are of value in diagnosing bladder neck dyssynergia. Recording perineal sympathetic skin response is also a sensitive diagnostic tool for bladder neck incompetence in SCI (Rodic, et al 2000). Abnormal sympathetic skin responses in patients with bladder neck dyssynergia suggest that the integrity of the descending sympathetic spinal tract is necessary for a synergic function of the vesicourethral complex (Schurch, et al 1997).

4. Ice-water test (IWT) is a useful complement to urodynamic studies in patients with neurological bladder disease and in patients with micturitional disorders that are otherwise difficult to interpret. The IWT can be used to accelerate the appearance of the micturition reflex and to induce micturition during cystography (Ronzoni, et al 1997).

5. Positive anal tone and the presence of the bulbocavernosus reflex during routine rectal examinations do not indicate a coordinated detrusor-sphincter function or bladder recovery.

6. Less than 30mL of residual urine, in patients who urinate freely during bowel movement, is an indication that catheterization is not needed.

Urodynamic Study

     Urodynamic study of the neurogenic bladder records the neurophysiological function of the detrusor and external urethral sphincter. Since urologic complications are a major source of morbidity and mortality among SCI patients, all SCI patients should undergo urodynamic evaluation, and management of urinary tract in SCI should be based on urodynamic principles and findings, rather than on neurologic history (Watanabe, et al 1996; Weld & Dmochowski, 2000). Urodynamic study consists of the following procedures:

1. Bladder fullness documents whether or not the patient has the sensation of bladder fullness and the bladder capacity at which the patient experiences urgency.  Bladder volume can be estimated from sonographic measurements and is most accurate when bladder shape is factored into the measurement (Bih, et al 1998).  Electrical impedance analysis technique is an alternative measure of bladder volume indirectly (Kim, et al 1998).

2. External urethral sphincter EMG documents whether or not the patient can voluntarily contract or expand the external urethral sphincter, upon command and without cutaneous stimulation. Voluntary control is an indication for regaining normal bladder function and is often seen in patients with incomplete SCI. Also look for spontaneous activity and motor action potentials of the external urethral sphincter with a needle electrode.

3. Cystometrogram/sphincter EMG documents the time relationship between the intravesical pressure and the sphincter EMG activity, which demonstrates if the detrusor muscle and the external sphincter muscle are working together (synergia) or against each other (dyssynergia). This study is done by filling the bladder with normal saline to a maximum amount of 500mL, recording the pressure in the bladder and the EMG activity of the external urethral sphincter simultaneously, and observing the patient's response. A sudden rise in intravesical pressure indicates contraction of the detrusor muscle. (This muscle does not contract in patients with spinal shock or low motor neuron lesions.) At the time that the detrusor muscle contracts:
   • The capacity of the bladder is the amount of urine that can be stored in the bladder before incontinence occurs
   • The maximal pressure in the bladder, compared with the pressure at the external urethral sphincter, determines the direction of urine flow
   • The simultaneous sphincter EMG activity demonstrates either synergia or dyssynergia. In patients with dyssynergia and increased sphincter activity, voiding is incomplete and back pressure from high external pressure may be harmful to the upper urinary tract

4. Crede or Valsalva maneuver, abdominal tapping, or anal stretch (frequently used by patients to promote bladder evacuation) can also be used to document whether or not bladder evacuation occurs, i.e. whether or not these procedures produce relaxation of the external urethral sphincter muscle and increased bladder pressure. In patients with complete upper motor neuron lesions, these maneuvers tend to increase both sphincter activity and intravesical pressure. In many patients with complete SCI, anal stretch inhibits both detrusor and urethral sphincter contraction.

5. Urethral pressure profile (UPP) compares the peak pressure in the urethra with the intravesical pressure recorded on the cystometrogram and provides information about bladder emptying. UPP is done by slowly withdrawing a water-filled catheter that is connected to a pressure transducer.

6. Sacral reflex latency study, in which the glans penis is stimulated and the response from the external urethral sphincter is recorded, can indicate whether or not the bublocavernosus reflex is intact. Abnormally prolonged or absent latency of the sacral reflex suggests involvement along the reflex arc.

7. Nuclear scanning, renal ultrasound, and voiding cystourethrography should be performed on all SCI patients with neurogenic bladder to determine if vesicouretheral reflux, stone disease, or impending renal failure is present, all of which contraindicate bladder retraining. Patients with T10-L2 injuries often exhibit vesicoureteral reflux in the early stage of SCI due to the involvement of the sympathetic nervous system (Suzuki & Ushiyama, 2001). Renal damage may be silent, and therefore annual surveillance, such as renal ultrasound and renal scan, are indicated (Bergman, et al 1997). In patients with stone disease, intravenous urography may also be required (Perkash 1993). Radionuclide renograms are also done to monitor renal function and to help formulate the treatment plan (Phillips, et al 1997).  Renal sonography should be performed while the bladder is full to best detect hydronephrosis in asymptomatic spinal cord injured patients (Bih, et al 1998). Sonography and renal scan are safe, sensitive, and specific for detecting hydronephrosis. Combined use of both may be a reliable alternative to intravenous urography in long-term follow-up of neurogenic bladder dynsfunction (Tsai, et al 2001). Renal cortex scintigraphy can be effective in differentiating acute pyelonephritis from fever due to other sources (Kao, et al 2000).