eMedicine Specialties > Pediatrics: Surgery > Urology

Myelodysplasia and Neurogenic Bladder Dysfunction: Differential Diagnoses & Workup

Author: Terry F Favazza, MD, Consulting Staff, Urologic Associates of Southern Arizona
Coauthor(s): Harry P Koo, MD, Chairman of Urology Division and Director of Pediatric Urology, Virginia Commonwealth University; Professor of Surgery, VCU School of Medicine, Medical College of Virginia; Director of Urology, Children's Hospital of Richmond
Contributor Information and Disclosures

Updated: Mar 27, 2008

Differential Diagnoses

Myelodysplasia

Other Problems to Be Considered

Spina bifida occulta
Sacral agenesis
Nonneurogenic/neurogenic bladder
Vesicoureteral reflux

Workup

Laboratory Studies

• Obtain urinalysis, urine culture, and serum electrolytes with 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.

Imaging Studies

• Abdominal ultrasonography: Perform abdominal ultrasonography 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 ultrasonography is performed to evaluate upper GU tract anatomy.
• Voiding cystourethrography
  • Following ultrasonography, 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, and can help identify children at risk for upper GU tract deterioration.
  • VCUG is the radiographic test of choice to evaluate for vesicoureteral reflux. 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 vesicoureteral reflux 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 to start prophylactic antibiotics.
• Lateral spine radiography: In suspected sacral agenesis, a lateral spine film is the appropriate imaging study.
• MRI: Ultrasonography of the spinal canal can be useful in infants younger than 5 months; however, once the vertebrae begin to ossify, ultrasonography becomes much less sensitive. The criterion standard for evaluation of spinal cord anatomy is MRI. This is the test of choice when a change in neurologic symptoms causes cord tethering to be suspected.

Other Tests

• Measure of residual urine: As soon as possible, measure the residual urine to determine if 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 relationship between the detrusor muscle and the external urinary sphincter. During normal voiding, the sphincter relaxes as the detrusor muscle 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 (DSD). In infants with DSD, increased EMG activity occurs during voiding. The presence of DSD 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 DSD, 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 contractions. 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 diagnosis is DSD, in which increased sphincter activity occurs during detrusor contractions. 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. DSD 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 is defined as the presence of involuntary detrusor contractions, usually at low volumes. This 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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