Vesicoureteral Reflux Workup

Updated: Dec 14, 2018
  • Author: Carlos Roberto Estrada, Jr, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Workup

Approach Considerations

Different imaging strategies have been proposed for children presenting with febrile urinary tract infection (UTI) to identify significant vesicoureteral reflux (VUR) while minimizing patient morbidity, radiation exposure, and financial burden. None of these imaging strategies is universally accepted. 

Because VUR and UTI may affect renal structure and function, performing renal ultrasound to assess the upper urinary tract is recommended by the American Urological Association (AUA), with optional dimercaptosuccinic acid (DMSA) renal scanning to assess the status of the kidneys for scarring and function. [9]

The American Academy of Pediatrics (AAP) recommends that all febrile infants with UTIs undergo renal and bladder ultrasonography (RBUS). Voiding cystourethrography (VCUG) should not be performed routinely after the first febrile UTI; VCUG is indicated if RBUS reveals hydronephrosis, scarring, or other findings that would suggest either high-grade VUR or obstructive uropathy, as well as in other atypical or complex clinical circumstances. [10]  

The “top-down approach” (TDA) aims at restricting the number of VCUGs and its associated morbidity while identifying patients with clinically significant reflux. In this approach, children presenting with febrile UTIs are acutely investigated with DMSA renal scans to identify renal parenchymal inflammation. Those with evidence of renal involvement are offered VCUG and late DMSA scan to identify VUR and permanent renal scarring, respectively.

Although TDA can identify clinically significant VUR with high sensitivity, some lesions seen on DMSA scans are attributed to congenital dysplasia and unrelated to UTI. Ionizing radiation exposure, financial costs, limited availability of DMSA scans in the acute setting, variability in interpreting the results, and low yield of actionable findings on DMSA scans are other limitations. [4]  

 

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Laboratory Studies

Perform urinalysis and urine culture in all neonates born with antenatal or postnatal hydronephrosis to rule out UTI. More than 90% of newborns void within the first 24 hours.

The serum creatinine level of a neonate reflects that of maternal creatinine (ie, 1 mg/dL) in the first 24 hours of life; thus, repeat the serum creatinine assessment after at least 24 hours. The average serum creatinine level in a healthy neonate is approximately 0.4 mg/dL.

Obtain serum electrolytes in neonates with antenatal hydronephrosis due to VUR because they may have a dysplastic kidney on the affected side. Check for acidosis.

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Imaging Studies

The recommended radiographic evaluation for VUR includes a voiding cystourethrography (VCUG),  a renal-bladder ultrasonography, and a nuclear renal technetium-99m–labeled dimercaptosuccinic acid (DMSA) scan. [11]

In sexually active adolescent girls, renal-bladder ultrasonography may be used to screen for renal abnormalities following a febrile UTI. If any abnormality is seen, conduct further workup studies with VCUG to rule out VUR.

VCUG, which provides clear anatomic detail and allows accurate grading of the degree of reflux, remains the gold standard tool to identify VUR. However, the test is usually a traumatic experience to both patients and their families due to the need for catheterization. Additionally, it carries a risk of introducing infection into the urinary tract. More importantly, it identifies a population with clinically-insignificant VUR that may never come to clinical attention, leading to potential overtreatment. 

Voiding cystourethrography/radionuclear cystourethrography technique

Perform the VCUG while the patient is awake and include a voiding phase. Appearance of the urethra is important to determine if the child has some degree of voiding dysfunction or, in males, if the child has posterior urethral valves. VUR is graded based on appearance of contrast in the ureter and upper collecting system during the voiding phase of the cystography. The VCUG also helps to evaluate the bony structures such as the lower spine and the pelvic architecture. It may also show whether the child has excessive feces in the colon.

In a neonate or small child, place a pediatric feeding tube rather than a Foley catheter in the urinary bladder. The Foley balloon may lead to a false diagnosis of a ureterocele or evoke an involuntary bladder spasm, complicating the test.

After filling the bladder with contrast, remove the feeding tube and allow the child to void.

The voiding phase of the cystography is considered the most important part of the test for assessing reflux. Perform the VCUG, rather than nuclear cystography, during the initial evaluation of a patient with suspected reflux; this provides good anatomic information about the lower urinary tract.

Allowing the bladder to fill and to empty several times (cycling) increases the sensitivity of the study. See the image below.

A voiding cystourethrogram (VCUG) of a patient wit A voiding cystourethrogram (VCUG) of a patient with grade III vesicoureteral reflux (VUR). Note that the contrast flows up the ureter and into the renal pelvis. The calyces are sharp, and no evidence of hydronephrosis exists.

Renal and bladder ultrasonography

Obtain renal ultrasonography to evaluate the presence and degree of hydronephrosis. If hydronephrosis is present, inspect the ureters for dilatation. A dilated ureter in the presence of hydronephrosis may indicate VUR; however, hydronephrosis with an undilated ureter implies ureteropelvic junction obstruction.

Evaluate the appearance of the renal parenchyma and size of the kidneys. Abnormal or dysplastic kidneys are smaller and appear brighter or more echogenic. The presence of the corticomedullary junction indicates a normal kidney.

Ultrasonography is also a good modality to monitor kidney growth over time.

Evaluation of the bladder (prevoid and postvoid, measurement of bladder thickness) provides additional information about the lower urinary tract and bladder function. Bladder ultrasonography helps to reveal bladder-wall thickness, a dilated ureter, and the presence of a ureterocele or ectopic ureter. It also gives information about incomplete bladder emptying due to voiding dysfunction.

Compare renal size over time to assess renal growth.

Renal ultrasonography has not been demonstrated to be a reliable modality for revealing renal lesions, but obvious renal scarring can be seen in more severe cases.

Nuclear renal scan

DMSA is considered the best nuclear agent for visualizing the cortical tissue, evaluating renal function, and revealing the presence of renal scars. To detect pyelonephritis and renal scarring associated with reflux, use Tc-99m–labeled DMSA renal scintigraphy. Pyelonephritis impairs renal tubular uptake of a radionuclide isotope, causing cortical photon defects on the DMSA scan. Persistent photopenic defects on the DMSA scan represent renal scarring and irreversible renal damage.

The DMSA scan is used to confirm suspected pyelonephritis and to evaluate the effectiveness of VUR medical management. Patterns of abnormal radionuclide may also help to differentiate between renal lesions caused by infections (focal areas of low uptake, usually upper and lower poles of the kidney) from diffuse decreased uptake seen in renal dysplasia due to abnormal renal development.

The presence of photopenic areas within the kidney reflects a history of previous pyelonephritis.

Development of new photopenic areas within the renal cortex, especially in the polar regions, indicates new scar formation.

Diffuse decreased uptake of the radionuclide may indicate renal dysplasia.

Several authors have advocated DMSA renal scan as the first study following a febrile UTI. Patients found to have renal lesions on DMSA were found to have a higher incidence of UTIs and VUR, thus preselecting patients who needed to undergo VCUG (top-to-bottom approach to the evaluation of VUR).

Timing of DMSA scanning is critically important. To assess for resultant kidney scarring following an episode of pyelonephritis, wait at least 6 months to obtain the DMSA because of the strong potential for false-positive results due to residual effects of the infection.

 

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Procedures

Cystoscopy 

Cystoscopy plays a very limited role in VUR diagnosis. Conduct this study when the anatomy of the urethra, bladder, or upper tracts is incompletely defined with radiographic evaluation and when ureterocele is suspected.

Perform a video urodynamic evaluation with filling cystometrography and a pressure-flow study with electromyography in any child with a suspected secondary cause of VUR.

Filling cystometrography entails filling the bladder with a feeding tube and monitoring bladder pressures during filling and voiding. Normal bladder pressures should be less than 40 cm of water; however, the bladder pressure increases transiently to 60-80 cm of water during voiding.

Perform filling cystometrography to evaluate for overactive detrusor contractions, bladder compliance, and detrusor leak point pressure, which are significant risk factors for VUR.

High detrusor pressure and low urinary flow rate during voiding cystometrography indicates bladder outlet obstruction. This may be due to posterior urethral valves in boys, detrusor sphincter dyssynergia, or Hinman syndrome in children. Bladder outlet obstruction is another secondary cause of VUR.

Urodynamics

Perform urodynamics in patients with secondary VUR caused by lower urinary tract dysfunction. Lower urinary tract dysfunction, which may cause secondary VUR, includes overactive bladder, spinal cord injury, and bladder outlet obstruction.

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Staging

The International Reflux Grading system classifies VUR into 5 grades, depending on the degree of retrograde filling and dilatation of the renal collecting system. This system is based on the radiographic appearance of the renal pelvis and calyces on a voiding cystogram, as follows:

  • Grade I: Urine backs up into the ureter only, and the renal pelvis appears healthy, with sharp calyces.

  • Grade II: Urine backs up into the ureter, renal pelvis, and calyces. The renal pelvis appears healthy and has sharp calyces.

  • Grade III: Urine backs up into the ureter and collecting system. The ureter and pelvis appear mildly dilated, and the calyces are mildly blunted.

  • Grade IV: Urine backs up into the ureter and collecting system. The ureter and pelvis appear moderately dilated, and the calyces are moderately blunted.

  • Grade V: Urine backs up into the ureter and collecting system. The pelvis is severely dilated, the ureter appears tortuous, and the calyces are severely blunted.

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