Myelodysplasia and Neurogenic Bladder Dysfunction Workup

Updated: Jul 09, 2019
  • Author: Terry F Favazza, MD; Chief Editor: Marc Cendron, MD  more...
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Workup

Laboratory Studies

Obtain urinalysis, urine culture, and serum electrolytes with blood urea nitrogen (BUN) and creatinine levels before the infant leaves the hospital. BUN and creatinine levels should be tested at least 24 hours after birth to reflect the infant's levels rather than the mother's.

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Imaging Studies

Abdominal ultrasonography

Perform abdominal ultrasonography (US) as soon as possible after birth to detect hydronephrosis or other upper genitourinary (GU) tract pathology. Once the child has recovered from the closure of the spinal defect and is stable for transportation, renal US is performed to evaluate upper GU tract anatomy.

Voiding cystourethrography

After US, voiding cystourethrography (VCUG) is performed to evaluate the lower GU tract. These studies provide a baseline for the appearance of the upper and lower GU tracts, can facilitate the diagnosis of hydronephrosis or vesicoureteral reflux (VUR), and can help identify children at risk for upper GU tract deterioration.

VCUG is the radiographic test of choice to evaluate for VUR. The procedure is as follows:

  • A supine film of the abdomen is obtained first, including the bladder and kidneys
  • A small catheter is placed in the child's bladder, and the bladder is filled with contrast
  • A cystogram is obtained with the patient in the supine and oblique positions; the size, shape, and capacity of the bladder are evaluated, as is the presence of trabeculae or diverticula.
  • The next film is obtained as the child voids or leaks; when VUR is present, the bladder, urethra, and ureters are demonstrated; in higher-grade reflux, the renal collecting system also may be seen
  • A final film is obtained after the bladder has been emptied; the presence of reflux is an indication for starting prophylactic antibiotics

Lateral spine radiography

In suspected sacral agenesis, a lateral spine film is the appropriate imaging study.

Magnetic resonance imaging

Although US of the spinal canal can be useful in infants younger than 5 months, it becomes much less sensitive once the vertebrae begin to ossify. The criterion standard for evaluation of spinal cord anatomy is magnetic resonance imaging (MRI). This is the test of choice when a change in neurologic symptoms causes cord tethering to be suspected.

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Other Tests

Measure of residual urine

As soon as possible, measure the residual urine to determine if intermittent catheterization (IC) is necessary. The normal capacity of the newborn bladder is 10-15 mL, and consistent catheterized residual volumes of 10 mL or more should raise concerns regarding detrusor areflexia.

Urodynamic study

This test provides the most information regarding the impact of myelodysplasia on bladder function and is used to assess bladder function and guide treatment. Because the bony level often does not always correspond with the neurologic defect that is present, and because the effect of the lesion on bladder function cannot be entirely determined by radiographic studies or physical examination, the information gained from a urodynamic study is invaluable.

The urodynamic study provides a measurement of several variables related to bladder function. Bladder capacity, compliance, detrusor and abdominal storage, voiding pressures, urine flow rate, postvoiding residual volume, and the relationship between detrusor contraction and the urinary sphincter can be evaluated. In addition, if contrast is instilled in the bladder, the anatomy can be imaged during voiding.

The core of the urodynamic study is cystometrography (CMG). A small catheter is placed in the bladder, and the bladder is slowly filled with liquid. Pressures within the bladder (intravesical) and the abdominal compartment are measured, and by subtracting the abdominal pressure from the intravesical pressure, the pressure generated by the detrusor muscle can be calculated. Because the child is monitored through a filling and voiding phase, bladder capacity can be quantified, and the urine flow rate, postvoiding residual volume, and the force generated by a bladder contraction can be measured.

Electromyography

If more information is desired, electromyography (EMG) can be used to demonstrate the relation between the detrusor muscle and the external urinary sphincter.

During normal voiding, the sphincter relaxes as the detrusor contracts to allow unobstructed urinary flow. Spinal cord injury can lead to discoordination so that the sphincter is closed when the detrusor contracts, creating high pressures within the bladder but low flow rates. This is known as detrusor-sphincter dyssynergy. In infants with detrusor-sphincter dyssynergy, increased EMG activity occurs during voiding. The presence of this dyssynergy places infants at a much greater risk of upper GU tract deterioration.

Fluoroscopy

Fluoroscopy can be used to perform video-urodynamic imaging with contrast enhancement of the bladder, which allows the bladder to be depicted during voiding. In addition, reflux may be revealed (identical to findings in VCUG), or if a closed sphincter is revealed during voiding, findings strongly suggest the presence of detrusor-sphincter dyssynergy, often obviating the need for EMG studies.

Remember that a great number of artifacts can be introduced into urodynamic studies when they are performed in infants and children.

Comparison of adjunctive data from radiographic studies and voiding or catheterized volume diaries is always advisable during planning of individualized bladder management.

Common findings are as follows:

  • A common diagnosis made using urodynamic studies is detrusor areflexia or a bladder that does not generate a contraction; the result is that the bladder will not empty (stasis); these patients can occasionally void with abdominal straining, but except in rare cases, they need to be managed with IC
  • Another possible diagnosis is detrusor-sphincter dyssynergy, in which increased sphincter activity occurs during detrusor contraction; this finding is important because DSD has been associated with an increased risk of upper GU tract deterioration in as many as 70% of patients; it is typically managed with IC and anticholinergic medications
  • In older patients, sphincterotomy (surgical ablation of the urinary sphincter) can be considered, but this procedure dramatically reduces outlet resistance and usually renders patients incontinent and reliant on an external collection device
  • Detrusor hyperreflexia, defined as the presence of involuntary detrusor contractions (usually at low volumes), can produce symptoms of urgency and urge incontinence; treatment is composed of anticholinergic medications to reduce contractions and timed voiding or use of IC
  • Urodynamic studies can also reveal outflow obstruction; in patients with obstruction, high voiding and/or storage pressures are seen, which have been correlated with increased risk of upper GU tract deterioration; this is managed with IC, surgical resection of the obstructing tissue, or urinary diversion (in extreme cases)

Genetic testing

If multiple anomalies are present, if the sex of the child is in question, or if a specific genetic syndrome is suspected, a karyotype may be of value but is not routinely required.

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