Urodynamic assessment has become a necessary tool for the evaluation of lower urinary tract dysfunction in children. However, there are subtleties that exist when performing these studies in children relative to adults. As a result, certain adaptations must be made in order to achieve results that are both accurate and reproductive when dealing with pediatric patients. The ways in which urodynamics varies between children and adults will be discussed, as well as the differences that occur during testing.
The indications for urodynamics in both children and adults are largely the same: to assess the functionality of the lower urinary tract. However, the causes for testing are oftentimes very different. For instance, children commonly undergo urodynamic testing for birth defects that affect the way the bladder and urethra function.
Neurogenic bladder, which is a condition described as a lack of bladder function due to a brain, spinal cord, or nerve dysfunction, is one common reason for a child to receive these tests. Enuresis – also commonly known as bedwetting – is another reason for a child to undergo urodynamic assessment.
Whereas adults receive urodynamic testing for incontinence disorders that typically develop later in life, children are usually born with these disorders. There are three types of incontinence1 in children: anatomic, neurologic, and functional. In many instances, the cause of pediatric incontinence is congenital.
Special considerations must be made in pediatric urodynamic testing, especially when infants or toddlers are the patients. Due to artifacts that arise in the measurements because of movement, it can be difficult to reliably obtain urodynamic results among this demographic.
Although the initial exam prior to urodynamics testing is generally the same for both pediatric patients and adults, there are subtle differences. For instance, when a child’s history is obtained, included information should involve prenatal history, as well as perinatal complications. The physical exam should look at spinal abnormalities, lower extremity reflexes, muscle mass, gait, handedness, and fine/gross motor coordination.
Like adult testing, a detailed voiding diary should be obtained that includes characterization of incontinence as well as fluid intake, frequency of catheterizations, frequency of voids, and voided volumes. A urinalysis and urine culture should be obtained as well.
A striking difference is that children, particularly those that are less than three months of age, should undergo radiology prior to urodynamic assessment. Here, a spinal sonogram should be performed, as well as a renal sonogram. Information such as bladder wall thickness, hydroenphrosis, dialation of rectum, bladder contour, bladder neck appearance, and urethral anatomy should all be obtained prior to invasive testing.
For practical purposes, physicians must consider the differences in bladder capacity between children and adults. These differences can change the way that the tests are performed, as well as interpretation of the results. For instance, during the bladder filling portion of cystometry, the bladder should be filled at a rate of 5 – 10% of the expected bladder capacity for the child’s age, per minute.
Deviations from this rate can adversely affect measurements regarding the child’s bladder capacity, intravesical pressure, and bladder compliance. To calculate the expected bladder capacity, urologists should utilize Hjalmas equation2, which is: expected capacity (mL) = 30 + (age in years x 30). For children with myelodysplasia3, this value can be calculated as follows: 24.5 x age in years + 62. In children, filling cycles should be performed at least twice.
Due to the invasive nature of urodynamic testing, this procedure can be traumatic for children. It is important that a knowledgeable staff is available to ease the child’s anxiety. To help the patient remain calm, age-appropriate diversions such as feedings, video games or television may be necessary. For older children, full and detailed explanations using catheterizable dolls or visual aids can be useful.
Since crying, movement, and distress can cause artifacts in the measurement, 2% lidocaine jelly can be placed intraurethrally for several minutes prior to catheterization. This technique can minimize discomfort in the child with little effect on the urodynamic tracings. For some children, particularly those who have had prior urethral surgery or have extreme anxiety regarding the procedure, sedation is sometimes necessary.
While electromyography studies in adults commonly utilize patch electrodes, EMG needle electrodes may be more appropriate in children. These electrodes can be employed during cystometry in order to provide the most accurate information. As a general rule of thumb, EMG needle electrodes should be used for children with known or suspected neurologic disorders, or when pelvic sensation is poor.
Lastly, the nurse performing the urodynamics study should be emotionally prepared for the procedure. For most children, crying and screaming should be expected. This can make it difficult for the nurse performing the procedure. It can make it difficult to concentrate. Focus is required to deliver a quality urodynamics test result free of errors and artifacts.
Ultimately, there are subtle differences that must be taken into account when performing urodynamic testing on children, as certain aspects can adversely affect the measurements relative to when the same tests are performed on adults.
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- Schaeffer AJ, Diamond DA. Pediatric urinary incontinence: Classification, evaluation, and management. Afr J Urol 2014;20:1-13. Link
- Nevéus T, Von gontard A, Hoebeke P, et al. The standardization of terminology of lower urinary tract function in children and adolescents: report from the Standardisation Committee of the International Children's Continence Society. J Urol. 2006;176(1):314-24. Link
- Palmer LS, Richards I, Kaplan WE. Age related bladder capacity and bladder capacity growth in children with myelomeningocele. J Urol. 1997;158(3 Pt 2):1261-4. Link