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PEDIATRICS Vol. 113 No. 3 March 2004, pp. 548-550

Utility of Follow-up Renal Sonography in Children With Vesicoureteral Reflux and Normal Initial Sonogram

Lisa H. Lowe, MD*, Manish N. Patel, DO*, John M. Gatti, MD{ddagger} and Uri S. Alon, MD§

* Department of Radiology, Children’s Mercy Hospital and University of Missouri, Kansas City, Missouri
{ddagger} Department of Pediatric Urologic Surgery, Children’s Mercy Hospital and University of Missouri, Kansas City, Missouri
§ Department of Nephrology, Children’s Mercy Hospital and University of Missouri, Kansas City, Missouri


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
Objective. The purpose of this study was to determine the value of follow-up renal sonography in children who presented with urinary tract infection and were found to have a voiding cystogram diagnosis of vesicoureteral reflux while having a normal initial renal sonogram.

Methods. We retrospectively reviewed the medical records of 64 consecutive children who presented for follow-up renal sonography with a voiding cystogram diagnosis of vesicoureteral reflux and a normal initial sonogram conducted as part of the routine evaluation after urinary tract infection. Data recorded included gender, age, initial grade of reflux, time to follow-up sonogram, and abnormalities on follow-up sonogram. Children with conditions that may predispose to vesicoureteral reflux were excluded.

Results. Children who were studied (7 boys, 57 girls) ranged in age from 1 month to 10 years, 10 months (mean: 35.6 months; median: 24 months). Ninety-four (73.4%) of 128 renal units demonstrated vesicoureteral reflux on voiding cystogram; 89 (94.7%) of 94 of them were grade 1 to 3. The mean time to follow-up was 22 months (range: 4 months to 5 years, 2 months; median: 18 months). All 128 (95% confidence interval: 0%–2.8%) renal units were normal on follow-up sonography.

Conclusion. Routine performance of repeat sonography seems unnecessary among children, particularly girls, with low- to medium-grade vesicoureteral reflux, who have had a previous normal sonogram and no conditions that predispose to vesicoureteral reflux.

Key Words: vesicoureteral reflux • sonography • urinary tract infection • kidneys • prophylactic antimicrobials

The initial uroradiologic approach to infants and young children with febrile urinary tract infections, including voiding cystourethrography and renal sonography, is unequivocally recommended by such organizations as the American Academy of Pediatrics, the American Academy of Family Practice, the American College of Emergency Physicians, the American Urological Association, and the American College of Radiology.1,2 The goal of these imaging studies is to identify anatomic and functional abnormalities that may place patients at risk for recurrent infection and kidney damage. Ultrasound is used as an adjunct to voiding cystography to detect abnormal renal size, thinning of the parenchyma (scarring), obstruction, and hydronephrosis. Because children with vesicoureteral reflux are at risk for renal scarring, which, if severe, can be associated with significant morbidity, renal sonography is often periodically repeated, often with each subsequent voiding cystourethrogram. However, there is little guidance regarding follow-up imaging beyond periodic voiding cystography until vesicoureteral reflux has resolved spontaneously or persisted significantly enough to warrant surgical correction.3

It has been our impression that if a renal ultrasound is initially normal in a child with history of urinary tract infections, then repeat ultrasounds rarely deteriorate in the setting of primary vesicoureteric reflux. The purpose of this study was to determine the utility of follow-up renal ultrasound in the setting of known vesicoureteral reflux and a normal initial sonogram.


   METHODS
TOP
 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
A departmental computerized scheduling database identified 64 consecutive children from May 2001 to March 2002 (11 months) who were scheduled for follow-up renal sonography after having a normal initial sonogram and diagnosis of vesicoureteral reflux based on fluoroscopic voiding cystogram. Demographic data (age and gender) were recorded in addition to grade of reflux on initial voiding cystogram, renal size on initial and last follow-up sonogram, time between initial and last follow-up sonogram, abnormal findings on last follow-up sonogram, use of prophylactic antimicrobials, spontaneous resolution of reflux on cystogram during the study period, surgical intervention, and presence of recurrent infection.

Only children with primary reflux were included in the study. Specifically, children with known conditions that may predispose to vesicoureteral reflux, such as neurogenic bladder, ureteroceles, obstructive uropathy, renal duplication, and dysplasia, were excluded from the study. In children who had multiple follow-up sonograms, only the last sonogram result was used for data analysis.

All sonograms were performed using HDI 5000 ultrasound machines (Phillips Medical Systems, Bothell, WA). Sonograms and fluoroscopic voiding cystograms were initially interpreted by 1 of 6 pediatric radiologists. Follow-up sonograms were also reviewed retrospectively a second time by another pediatric radiologist to confirm the normal initial result. Renal size was measured in a longitudinal plane and compared with published standards.4 Grading of vesicoureteral reflux was based on the criteria of the International Reflux Study in Children.5

For the purpose of data analysis, each kidney was considered a "renal unit," and all patients had 2 kidneys. StatXact 3.0 software (Cytel Software, Cambridge, MA) was used to calculate the confidence interval based on the binomial distribution.


   RESULTS
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 ABSTRACT
 METHODS
 RESULTS
DISCUSSION
 CONCLUSION
 REFERENCES
 
The study group included 128 renal units in 7 male and 57 female children ranging in age from 1 month to 10 years, 10 months (mean: 35.6 months; median: 24 months) at presentation. Ninety-four renal units had vesicoureteral reflux on voiding cystogram (Table 1). All 128 renal units were normal on initial and follow-up sonography (95% confidence interval: 0%–2.8%). The time from the initial normal sonogram to the last follow-up sonogram ranged from 4 months to 5 years, 2 months (mean: 22 months; median: 18 months).


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  		TABLE 1. Initial Grades of Vesicoureteral Reflux

 
Fifty-two (81.25%) of 64 children received prophylactic antibiotics, 10 did not, and in 2 this information could not be obtained. Vesicoureteral reflux resolved during the study period in 64 renal units (42 children). In 42 (65.63%) of 64 renal units (28 children; average age: 4 years, 10 months), reflux resolved spontaneously (4 grade 1, 27 grade 2, 10 grade 3, 1 grade 4). In 14 children (mean age: 6 years, 9 months). reflux resolved in 22 (34.38%) of 64 renal units as a result of surgical intervention (3 grade 1, 10 grade 2, 7 grade 3, and 2 grade 4). Recurrent infection was documented in 14 (21.88%) of 64 children, with 9 (64.28%) of the 14 being managed surgically.


   DISCUSSION
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 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
CONCLUSION
 REFERENCES
 
Urinary tract infection is the most common occult bacterial infection in febrile infants and young children. In 25% to 35% of this population, vesicoureteral reflux is detected.1,2 Children with vesicoureteral reflux and upper urinary tract infection are at increased risk of pyelonephritis, which may lead to parenchymal scarring.2,6–9 Moderate to severe parenchymal scarring can be associated with hypertension and, although rare, renal insufficiency.8,10,11 It is the current recommendation to keep infants and young children with vesicoureteral reflux on long-term protective antibiotics.10,11

Ninety-five percent of our population had grade 3 reflux or lower, with none having grade 5 vesicoureteral reflux. By selecting a cohort of patients with reflux but no initial ultrasound abnormality, children with higher grades of vesicoureteral reflux, namely grades 4 and 5, may have been eliminated, by definition, from our study. Because it has been shown that higher grades of reflux are more commonly associated with renal scarring and reflux nephropathy, it is not surprising that renal scars were not seen on follow-up in our study population. Furthermore, although the results of our study apply more to children with lower grades of reflux, others have also noted a low likelihood of developing renal scarring while on antibiotic suppression, as is the routine in our institution, despite the grade of reflux.12–16 Indeed, recent studies from Sweden17 and our own institution18 demonstrated the drastic decline of recurrent urinary tract infections as cause of pediatric chronic renal failure. This phenomenon has been attributed to early diagnosis and treatment of urinary tract infection with potent antibiotics by community pediatricians and family physicians, thus decreasing the risk of scar development.19,20 We were able to confirm implementation of prophylactic antimicrobials in 81.25% of our patients. However, the number of patients who did not receive antimicrobials was too small to conclude that they may not be needed.

Although reflux resolved spontaneously in 42 (44.7%) of 94 renal units (28 children) during the mean 22-month study period, we cannot determine the potential number that may have resolved spontaneously beyond this point. Reflux resolved as a result of surgical intervention in another 22 (23%) of 94 renal units (14 children). This group of children who were treated by surgery was composed of older children with an average age at the time of surgery of 6 years, 9 months, as compared with 28 children who were not treated surgically with spontaneous resolution of reflux documented on voiding cystogram (average age: 4 years, 10 months). In addition, recurrent infection was documented in 14 (21.88%) of 64 children, and in 9 (64%) of these 14 children, surgery was performed. Renal sonography, nonetheless, remained normal in all of the above subgroups of spontaneous resolution of reflux, surgical intervention, and recurrent infection.

Our study found that the yield of follow-up ultrasound in children with urinary tract infection, vesicoureteral reflux of low to medium grade, and initial normal sonogram is negligible. It is possible that minimal scarring would have been detected by other, more sensitive means, such as cortical renal scintigraphy, computed tomography, or magnetic resonance imaging.21,22 However, the clinical relevance of such mild scarring has never been proved.22

This study is limited by its retrospective nature and reflects the experience of a single children’s tertiary referral institution. The majority of our patients were female, reflecting the prevalence of reflux as a whole. These results are more compelling when considering sonographic imaging follow-up in younger girls with vesicoureteral reflux of low to medium grade and a normal initial sonogram. The mean time to follow-up was 22 months, and we cannot determine possible findings that may have occurred beyond this period. Nevertheless, in some cases, clinical judgment, in particular history of recurrent infection, persistent reflux in older children, or presence of voiding dysfunction, may still indicate the need for repeat follow-up sonograms.


   CONCLUSION
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
REFERENCES
 
Routine performance of repeat sonography seems unnecessary among children, particularly girls, with low- to medium-grade vesicoureteral reflux, who have had a previous normal sonogram and no conditions that predispose to vesicoureteral reflux.


   FOOTNOTES
 
Received for publication Dec 6, 2002; Accepted Jul 14, 2003.

Reprint requests to (L.H.L.) Department of Radiology, Children’s Mercy Hospital, 2401 Gillham Rd, Kansas City, MO 64108. E-mail: lhlowe{at}cmh.edu


   REFERENCES
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 

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PEDIATRICS (ISSN 1098-4275). ©2004 by the American Academy of Pediatrics

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Do Children with UTIs Need Repeat Ultrasound?
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