The client has a urinary health problem which procedure is performed using indirect visualization

Vesicoureteral Reflux

VCUG has long been the established gold standard for the detection of VUR. Despite its ability to provide excellent visualization of the entire urethra and to assess the presence and grade of VUR, conventional VCUG involves direct radiation exposure to the gonads. Magnetic resonance voiding cystourethrography (MRVCU) was first described in 1992 but did not become a potential alternative until the advent of near–real-time magnetic resonance fluoroscopy.36 MRVCU is composed of T1-weighted images of the entire genitourinary tract obtained before the transurethral administration of Gd-DTPA, as well as images obtained during and after micturition. Rodriguez and coworkers37 performed MRVCU before excretory MRU and demonstrated reflux in four of five children with known VUR. In another study38 using conventional VCUG as the standard reference, MRVCU was found to have a sensitivity of 76% and a specificity of 90% in the detection of VUR. In addition, renal scarring was detected in 13 of 17 kidneys confirmed by nuclear scintigraphy. Therefore, MRVCU allows for an accurate determination of VUR and reflux nephropathy. Limitations may include difficulty voiding in the supine position for some patients and incomplete voiding in some infants and young children due to sedation. Although the procedure is technically feasible, it seems unlikely that MRVCU will gain widespread acceptance.

Voiding Cystourethrography

VCU is the primary diagnostic modality for identification of VUR. It requires catheterization, which can lead to significant distress among both children and parents. The grading of VUR is based on radiographic appearance by VCU (see Fig. 61.1). In children with UTI, VCU should be performed as soon as the child has completed the course of antibiotic therapy. Evaluation with VCU has been suggested after the first febrile infection in children younger than 5 years.

The results of VCU can be affected by size, type, and position of the catheter; rate of bladder filling; height of the column of contrast media; state of hydration of the patient; and volume, temperature, and concentration of the contrast medium.

Nuclear cystography has been used to reduce the radiation exposure for children during follow-up of VUR. Nuclear cystography, although it is more sensitive, does not permit specific grading of VUR or reveal anatomic defects, such as ureterocele and diverticulum. Nevertheless, it is useful in determining resolution of reflux during follow-up or after surgical correction.

8 When should VCUG be performed?

VCUG should be performed after a first UTI in boys and girls and generally after the bladder infection is treated.

In boys, routine fluoroscopic VCUG is recommended as the initial examination, particularly to study the urethral anatomy (e.g., to look for valves in the posterior urethra, a common cause of lower urinary tract obstruction in young boys).

In girls, either routine VCUG can be done or a voiding urethrogram can be performed by instilling a radionuclide into the bladder. The latter procedure is performed in the nuclear medicine department; images are obtained with a gamma camera, and reflux is detected when the radionuclide (which is diluted in the sterile saline that is placed in the bladder via a catheter) reaches the ureter during the instillation of contrast agent or during voiding.

Voiding Cystourethrography.

Voiding cystourethrography (VCUG), an important complement to ultrasonography, can identify anatomic and/or functional abnormalities in lower urinary tract disorders. It is particularly important in the evaluation of urinary tract infection for the detection and assessment of vesicoureteral reflux.

Radionuclide cystography is associated with significantly decreased radiation exposure to the patient compared to VCUG and has gained acceptance for use in the pediatric population, especially for follow-up evaluation of vesicoureteral reflux in children. However, it has considerable technical limitations in the newborn, and it has not been widely used in this patient population.

Voiding Cystourethrography

Voiding cystourethrography (VCUG) is mainly used for demonstrating a cystocele, evaluating bladder neck hypermobility, and demonstrating an open bladder neck at rest (sphincteric incompetence). Dynamic lateral cystography at rest and during straining is an important adjunct to the urodynamic evaluation; it is useful for demonstrating the presence of and degree of urethra-vesical hypermobility and cystocele formation (Fig. 56-1).11 In additional, dynamic fluoroscopy has been shown to be more accurate than physical examination in demonstrating an enterocele.12,13 Other pathologic conditions detected by VCUG include vesicoureteral reflux, vesicovaginal fistula, and urethral diverticular disease.

Voiding Cystourethrography

The VCUG is the most important examination in assessing VUR in children. The VCUG may be performed either with fluoroscopy and iodinated contrast or with nuclear imaging agents (usually Tc99m-pertechnetate) using similar techniques (direct radionuclide cystography, or RNC). Fluoroscopic and nuclear VCUG provide different information and, as such, have different indications. The traditional fluoroscopic VCUG can show urethral and bladder abnormalities as well as VUR. The RNC may be more sensitive for reflux detection, but it poorly evaluates the urethra and does not allow grading of reflux. Detection of VUR by either fluoroscopic or radionuclide VCUG may rely on the child’s ability to void and the proper performance of certain technical aspects of the study, such as filling the bladder to capacity.207-209 The radionuclide VCUG should not be used to evaluate first infections in infants or young boys in whom risk of genitourinary abnormality is high and urethral visualization important, nor in any child in whom imaging resolution of the lower urinary tract is important. The radionuclide VCUG may be most useful for VUR screening, for evaluation of the UTI in older children who have a lower risk of reflux, or for follow-up reflux evaluation.210

The main advantage of RNC has been the lower radiation exposure: 1 to 5 mrad (ovarian dose) instead of 27 to 1000 mrad (previously reported ovarian exposure depending on equipment).210,211 With modern imaging technology and a tailored examination, however, the fluoroscopic VCUG has been done with exposures of 1.7 to 5.2 mrad.212 Indirect radionuclide VCUG has been proposed as part of a renal imaging study and avoids catheterization by allowing the bladder to fill with tracer cleared by the kidneys. However, because it detects only about 60% of the reflux cases, compared with direct VCUG, this is not recommended.177

The VCUG may be performed as soon as the urine is sterile and bladder irritability is absent with return to normal capacity. Studies have shown that UTIs do not cause reflux.210 Whether the VCUG is done during treatment or a few weeks after the UTI is unimportant, so long as the child has normal renal function, responds rapidly to antimicrobial treatment, and is maintained on prophylactic antimicrobial treatment to keep urine sterile in the interval between the herald infection and the radiologic evaluation.

Subsequent imaging should be tailored to the results of the VCUG.213 In most cases, a kidney and bladder ultrasound study complements the VCUG well, detecting other urinary tract structural abnormalities such as dysplasia or obstruction.207,214-217 However, some argue that the widespread use of antenatal ultrasound detects many of these abnormalities, and ultrasound should be used selectively rather than routinely in the initial evaluation of a febrile UTI.69 Further prospective study in a large, varied patient population is necessary to clarify this issue. Finally, if VUR appears to be the primary diagnosis, DMSA scintigraphy with single-photon emission computed tomography (SPECT) or three-dimensional renal magnetic resonance imaging (MRI) may be the most useful studies with which to detect renal scars.

Voiding Cystourethrography

VCUG is indicated in children with recurrent UTIs to detect reflux and in children with an abnormal flow pattern to detect bladder outlet abnormalities (e.g., valves, strictures). In children with non-neurogenic detrusor-sphincter dysfunction and in children with the same dysfunction but of neurogenic origin, the proximal urethra may show a “spinning top” configuration during filling or voiding. With detrusor and pelvic floor muscles contracting at the same time, the detrusor contraction dilates the proximal urethra down to the level of the forcefully closed external sphincter.15

Voiding Cystourethrography

Voiding cystourethrography is essential when evaluating the megaureter to rule out vesicoureteral reflux. A conventional fluoroscopic cystogram is preferred over a nuclear cystogram in that the anatomic appearance of the bladder, bladder neck, urethra, and ureters is necessary for precise diagnosis and treatment. The cyclical voiding cystourethrogram is beneficial when an ectopic, sphincteric ureter is suspected. In this scenario, the ureter can be obstructed when the bladder is at rest and refluxing only during the voiding phase. Cyclical evaluation may be required to document the refluxing phase. Blickman and Lebowitz44 characterize the refluxing obstructed megaureter as having the appearance of a markedly enlarged proximal ureter associated with a normal-appearing ureterovesical segment.

VOIDING CYSTOURETHROGRAPHY

Voiding cystourethrography (VCUG) is the study of choice for diagnosing vesicoureteral reflux and assessing the anatomy of the bladder and urethra. Indications for this investigation include urinary tract infection,13 antenatally or postnatally diagnosed hydronephrosis, and suspected posterior urethral valves, among others. A catheter is placed into the bladder using aseptic technique. At most institutions sedation is not administered. In our experience, the examination can be performed without sedation in the vast majority of children, given proper explanation and reassurance. Water-soluble contrast is instilled into the bladder under the pressure of gravity until pressure within the bladder induces micturition. The amount of contrast used will vary according to the patient's age and bladder capacity. At some institutions a single cycle of filling and voiding is performed. At others, two or three cycles are the routine.27 This method, termed cyclic VCUG, has demonstrated greater sensitivity in detecting reflux but results in a higher radiation dose than does the single-cycle method.

Exact views obtained will vary from institution to institution but all will include images of the bladder that will allow for assessment of its wall characteristics and structural abnormalities such as diverticula, ureteroceles, or urachal abnormalities. These images should also show if there is any reflux into the ureters. Images of the urethra are obtained during voiding either with the catheter in place or after its removal. Whether the urethra is imaged with a catheter in place or not depends on the institution and the individual radiologist. At our institution an image of the urethra is obtained with the catheter in place as well as after its removal, thus giving an image of the urethra in cases where the child stops voiding just as the catheter is removed. An image of the renal fossae will assess for any reflux to the level of the kidney, characterize the collecting system anatomy (duplex or not), and assign a grade to that reflux.28

Here, as with the other modalities, the study is tailored to the individual child. The bladder can be filled via a suprapubic catheter or a Mitrofanoff if present. If a child is unable to void naturally, the bladder can be drained via the catheter in situ. If the child is reticent to void, warm water applied to the perineum can induce voiding. Despite a variety of maneuvers, there are children who will not void on the fluoroscopy table. In these cases the micturition phase of the study is not possible and the sensitivity of the study to detect reflux is diminished. In some institutions an image is taken after the child has been permitted to void in the bathroom.

Complications related to the study can occur and are similar to those encountered in any catheterization of the bladder, with infection and trauma being the most common. We have encountered cases of urinary retention postprocedure.

Diagnosis

VUR is diagnosed by VCUG (see Fig. 148-3) or radionuclide cystography (RNC). Often, reflux will not occur during filling of the bladder but may be seen only during voiding, thus illustrating the importance of the voiding phase of the cystogram. It is preferable that all boys and infant girls undergo VCUG as their initial study, whereas in older girls with their first UTI, RNC may be used. RNC is used for serial studies. VCUG provides more anatomic detail than RNC does. RNC is being used with increasing frequency, particularly in females with infection, in siblings as screening for reflux, and in children with VUR as annual follow-up. RNC is not good at delineating anatomic abnormalities such as bladder diverticula or PUV. Ultrasound and IVP are poor screening tests for VUR. Patients with known VUR will have normal IVP and renal ultrasound findings in more than 50% of cases.