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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE  
Year : 2013  |  Volume : 24  |  Issue : 2  |  Page : 297-302
Value of sonography in the diagnosis of mild, moderate and severe vesicoureteral reflux in children


Department of Radiology and Pediatric Nephrology, Isfahan University of Medical Sciences, Isfahan, Iran

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Date of Web Publication26-Mar-2013
 

   Abstract 

This study was conducted to determine the positive predictive value (PPV) of gray scale sonography in the diagnosis of mild, moderate and severe vesicoureteral reflux (VUR). This cross-sectional descriptive analytic study was conducted in the University Clinic of Isfahan University of Medical Sciences in 2008. The study was performed on children aged two to 12 years; female children with febrile urinary tract infection (UTI) and clinical suspicion of VUR and males with history of UTI and VUR who attended follow-up during the six months study period were selected. Non-cooperative patients were excluded from the study. A total of 90 patients were studied. The data gathering method was sequential. The following sonographic parameters were assessed in all the study patients: antero-posterior pelvic diameter, distal ureteric diameter and stasis of urinary system, which were measured at rest and during and after the Valsalva maneuver. Also, the vesicoureteral junction distance and distance of vesicoureteral junction to the midline were measured on both sides at rest. We then referred them for radionuclide cystography (RNC) and the results of the two methods were compared. Data were analyzed with SPSS program and t-test and chi square formulas were used. The sensitivity of ultrasound in the diagnosis of VUR was 70.9% and the specificity was 51.4%. Thus, the PPV was 69.64% and the negative predictive value was 52.94%. Although the most definite diagnosis of VUR is made with micrurating cystoureterography or RNC, sonography may be used as the first step in evaluation for VUR, especially in high-grade VUR.

How to cite this article:
Adibi A, Gheysari A, Azhir A, Merikhi A, Khami S, Tayari N. Value of sonography in the diagnosis of mild, moderate and severe vesicoureteral reflux in children. Saudi J Kidney Dis Transpl 2013;24:297-302

How to cite this URL:
Adibi A, Gheysari A, Azhir A, Merikhi A, Khami S, Tayari N. Value of sonography in the diagnosis of mild, moderate and severe vesicoureteral reflux in children. Saudi J Kidney Dis Transpl [serial online] 2013 [cited 2014 Jul 29];24:297-302. Available from: http://www.sjkdt.org/text.asp?2013/24/2/297/109582

   Introduction Top


Urinary tract infection (UTI) is a major source of pediatric bacterial infections. Vesicoureteral reflux (VUR) is one of the leading causes of UTI in children and is a common pediatric urologic disorder that can cause renal scarring. [1] The presence of VUR is documented in 25-40% of children presenting with UTI. Among children who have febrile UTI, 50-91% are found to have defects on renal cortical scintigraphy, indicating acute pyelonephritis (APN). [2] Up to 25% of the causes of end-stage renal failure (ESRD) in children is VUR. [3] The reflux may be an isolated occurrence or may be seen in association with other congenital anomalies of the kidney/urinary tract or as part of syndromal entities. [4] The majority of cases of VUR (90%) in children is due to a primary congenital failure of the ureterovesical junction (UVJ), resulting in retrograde flow of urine from the bladder into the kidneys. [3] Among children with APN diagnosed by scintigraphy, 38-57% will develop permanent renal damage. [5]

The occurrence of VUR and renal scarring in children with UTI has been well documented. [6] About 75% of siblings of patients with VUR are asymptomatic, while 20% of siblings of patients with dysfunctional voiding have reflux. [7] The sensitivity of ultrasound in detecting VUR and renal scarring is inferior to that of voiding cystourethrogram (VCUG) and dimethyl succinic acid (DMSA) renal cortical scintigraphy. Nevertheless, ultrasound remains part of the routine evaluation of first-time UTI because it can assist in depicting structural abnormalities such as asymmetric renal size, hydronephrosis and duplex kidneys. [8] Ultra-sonography (USG) is ideally suited for the evaluation of children with a suspected urinary tract abnormality because it is painless, involves no radiation exposure and provides excellent anatomic imaging of the urinary system. USG has replaced intravenous urogram (IVU) as the initial examination, and the results of USG usually determine what further evaluation is required. In children older than three to four years who have signs only of lower UTI, VCUG is not recommended if renal sonogram is normal. Nuclear imaging and sonography have replaced excretory urography (EU) as the preferred radiologic examination of the upper urinary tract. [2],[7]

Computerized tomography (CT) scan and magnetic resonance imaging (MRI) do not currently have a role in the usual diagnostic algorithm or follow-up of children with UTI. Generally speaking, USG is an unreliable modality for the detection of VUR. It cannot therefore be used as the only test to exclude clinically significant VUR. Nevertheless, clues to the presence of VUR can be inferred from certain sonographic findings, namely complete duplication, peristaltic ureteral dilatation and calyceal dilatation. An abnormally small kidney in a child suggests parenchymal thinning, even in the absence of visible scarring. [7],[8]

Ultrasonography is best used in conjunction with screening VCUG to assess for renal size, upper tract abnormalities such as hydronephrosis and ureteral dilatation, obvious scarring, ureteral ectopia or bladder abnormalities such as ureterocele and bladder wall thickening. Obtaining reproducible sonograms is highly operator dependent. [2],[7] Sonography has been proposed for the follow-up of patients with reflux or for detecting reflux in siblings.

Approximately 74% of kidneys with reflux on VCUG were normal on USG obtained on the same day, and approximately 25% of the refluxing kidneys that are missed have reflux of grade III or worse. Patients with VUR are typically followed-up with serial radionuclide cystography every 12-24 months. The International Classification of Reflux is not commonly applied to radionuclide studies, but the amount of activity that appears in the upper urinary tracts can be quantified into one of three levels of severity and used as a basis of comparison in serial follow-up examinations.

Presently, there are two gold standards to diagnose VUR: VCUG and renal nuclear cystography (RNC). Because of the difficulty in performing both VCUG and RNC, and the danger of exposure to ionizing rays, finding a safe and satisfying method is necessary. According to the current guidelines, we must perform both USG and VCUG or RNC for all patients with a high suspicion of VUR. [7],[8]

Ultrasonography now plays a valuable role in the diagnosis of VUR. Thus, our major goal is to determine the positive predictive value (PPV) of USG in the diagnosis of mild, moderate and severe VUR by means of different sonographic parameters.


   Methods and Materials Top


This study was a cross-sectional descriptive analytic study performed at the University Clinic of Isfahan University of Medical Sciences

in 2008, and the research protocol was approved by the local ethics committee. Subjects were selected from children aged between two and 12 years coming to the nephrology clinic. Girls with febrile UTI and clinical suspicion of VUR and boys with history of UTI and VUR attending follow-up were selected.

After parents gave written informed consent, the children were referred for sonography. All ultrasounds were performed by one radiologist with good expertise in pediatric sonography. The ultrasound equipment was a Toshiba Just Vision model with 3.5-5 MHZ curvilinear probe. Ultrasounds were performed after the subjects were adequately hydrated. Urinary tract ultrasound was performed to determine the following parameters: renal size, bladder volume and wall thickness, distance between vesicoureteral junction and the midline, distal ureteral diameter (if any) and antero-posterior diameter of the renal pelvis, which was measured at rest as well as during and after performing the Valsalva maneuver. The ultrasonographer's view of presence or absence of VUR as a whole and its grade according to distal ureteral and renal pelvis diameters were also recorded.

To measure the vesicoureteral junction distance bilaterally, the probe was placed in the axial plan on the suprapubic area and the distance between the two points was determined. To determine the distance between the vesico-ureteral junction and midline bilaterally, we placed the probe in the sagittal oblique plan and the distance from the neck of bladder to the vesicoureteral junction on each side was measured. If stasis was observed in the pelvicalyceal system without any obstruction, VUR was suggested.

Patients were then referred to the nuclear medicine department for performing RNC. Initially, the bladder after catheterization was filled with a solution that consisted of about 500 mL normal saline and 1-2 milicurri 99-technetium and DTPA. Following this, 20 pictures were taken over 20 s. Subsequently, in the voiding phase, 120 pictures were taken over 2 s. Post-voiding, one picture was taken over 100-120 s after complete bladder emptying. The amount of bladder filling was recorded as bladder volume; the presence as well as grade of VUR, classified as mild, moderate and severe, was noted. All RNCs were performed by a single person with one gamma camera set, ADAC, dual head and jinx model, made in the USA.

The data were analyzed with the SPSS program and t-test and chi square formula. P-values less than 0.05 were considered as significant.


   Results Top


In this cross-sectional study, 90 patients were evaluated. The results of RNC showed that 55 had VUR (61%) and 35 did not have VUR (39%). The sensitivity of ultrasound in the diagnosis of VUR was 70.9% and the specificity was 51.4%, with a PPV of 69.64% and negative predictive value (NPV) of 52.94% when considering final sonographer comment.

[Table 1] shows the comparison between USG and RNC in the diagnosis of VUR. On USG, false negative reports were seen in 47.8%, 38.9% and 0% of mild, moderate and severe VUR, respectively. [Table 2] compares the isolated sonographic criteria with RNC results.
Table 1: Comparison of sonography and radionuclide cystography in patients with and without vesicoureteral reflux in our study patients.

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Table 2: Comparison of means and SD of different sonographic parameters in comparison with the radionuclide cystography results.

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There was a significant difference in the following parameters between subjects with positive and negative RNC with VUR at rest and during and after performing the valsalva maneuver (P-values <0.05):

  • antero-posterior renal pelvis diameters
  • distal ureteral diameters
There was no significant difference in the distance of the vesicoureteral junction from the midline between the two groups.

In reporter-observer curve analysis, the cut-off points for the AP diameter of the renal pelvis were 3 mm for all three situations: rest, during Valsalva and after Valsalva maneuver. The cut-off points of distal ureteral diameters were 1.8, 2.3 and 2.5 mm at rest during the valsalva and after the valsalva maneuver, respectively.


   Discussion Top


The results show that parameters of system stasis at rest, during the valsalva maneuver and after the valsalva maneuver have equal values in the diagnosis of VUR. The pelvis diameter at rest, at the cut-off point 3.0 mm with the sensitivity of 63.6% and specificity of 80%, is the best point of sensitivity and specificity in the diagnosis of VUR.

In our study, the sensitivity of USG in the diagnosis of VUR was 70.9% and the specificity was 51.4%. Thus, the PPV was 69.64% and NPV was 52.94%. Our report is similar to that of Kenney et al who reported sensitivity and specificity rates of USG of 63% and 78%, respectively, in the diagnosis of VUR. They suggested that absence of distal ureteral dilation on USG, on its own, cannot reliably exclude VUR, and another method like VCUG is needed to diagnose VUR. [9]

Mahant et al reported the sensitivity and specificity of USG in the diagnosis of VUR of 40% and 76%, respectively. The PPV of USG was 32% and the NPV was 82%, which is comparable to our results. They concluded that renal ultrasound was neither sensitive nor specific for VUR in children with a first UTI. [10]

Muensterer et al concluded that we should not diagnose VUR based only on kidney morphology on USG, and accurate diagnosis needs consideration of age adjustment in kidney length. In their study, they measured certain other parameters that were not studied by us. [11]

Darge in his study showed that voiding USG has a sensitivity of 57-100% and specificity of 85-100%, with a PPV of 58-100% and an NPV of 87-100%, and 73% complete accordance with VCUG. [12] He also showed in another study that harmonic voiding USG has a sensitivity of 86% and specificity of 92% and PPV of 73% and NPV of 96%. [13] Teresa Berrocal et al showed that voiding USG correlates with VCUG grading in 83% of the patients. Hence, these methods can potentially be substituted for gray scale sonography (low sensitivity and low specificity), and even VCUG. [14]

The equal values of system stasis at rest and during and after the valsalva maneuver show that system stasis is a phenomenon independent of these variables. The comparison of RNC and sonography shows that there is a correlation between the final results and the severity of VUR.

Our study shows a higher prevalence of VUR in patients younger than 48 months, as shown in previous reports. However, this has to be viewed with caution as we did not screen all girls with UTI with VCUG or RNC. The mean age of the affected patients in our study was 5.5 years. Similarly, in another study from Iran, the mean age at diagnosis of VUR was 4.1 years. [15] In that study, they determined the prevalence of each grade of VUR, which was mild in 10%, moderate in 65% and severe in 25% of the patients. In comparison, our data showed mild VUR in 45%, moderate in 44% and severe in 11% of the study subjects. The higher prevalence of mild VUR in our study is probably because of earlier referral for RNC or imprecise technique of RNC.

In our study, the specificity of USG was acceptable. In mild VUR, sonography is not a valuable device because 47.8% of patients with mild VUR were reported as normal. Even in moderate VUR, USG is not a valuable device because 40% of the patients with moderate VUR were reported as normal. In patients with severe VUR, USG was positive in 80% of the patients.

In one study, they used USG and pelvic diameter at rest to diagnose VUR. They determined that pelvic size over 8 mm is associated with VUR. [15] According to our study, at the cut-off point of 3 mm, USG diagnoses VUR with sensitivity of 63.6% and specificity of 80%. Also, performing the valsalva maneuver did not offer any benefit in the diagnosis of VUR. This may be because the renal pelvis does not receive the pressure effect of the valsalva maneuver.

In conclusion, our data suggest that USG is a sensitive but not specific device in the diagnosis of VUR, and diameter of the renal pelvis at rest is the most sensitive and specific parameter that aids in diagnosis. The accuracy of USG in the diagnosis of VUR is higher in normal children and in those with severe VUR. Thus, although VCUG or RNC is required for a definitive diagnosis of VUR, USG may be the first step to assess patients with suspected VUR, thereby reducing the exposure to radiation. Our ultrasound device was gray scale sonography, but other kinds of sonography are available such as Doppler sonography with or without contrast and gray scale sonography with contrast. We suggest that the sensitivity and specificity of these devices should be assessed and compared with VCUG and RNC.

 
   References Top

1.Bell LE, Mattoo TK. Update on childhood urinary tract infection and vesicoureteral reflux. Semin Nephrol 2009;29:349-59.  Back to cited text no. 1
[PUBMED]    
2.Lim R. Vesicoureteral reflux and urinary tract infection: Evolving practices and current controversies in pediatric imaging. AJR Am J Roentgenol 2009;192:1197-208.  Back to cited text no. 2
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3.Tsiouris S, Sioka C, Marinarou A, Al-Bokharhli J, Sionti I, Fotopoulos A. VU reflux deterioration in monozygotic twins. Indian J Pediatr 2008;75:285-7.  Back to cited text no. 3
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4.Conte ML, Bertoli-Avella AM, de Graaf BM, et al. A genome search for primary vesicoureteral reflux shows further evidence for genetic heterogeneity. Pediatr Nephrol 2008;23: 587-95.  Back to cited text no. 4
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5.Lin KY, Chiu NT, Chen MJ, et al. Acute pyelonephritis and sequelae of renal scar in pediatric first febrile urinary tract infection. Pediatr Nephrol 2003;18:362-5.  Back to cited text no. 5
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6.Howard RG, Roebuck DJ, Yeung PA, Chan KW, Metreweli C. Vesicoureteric reflux and renal scarring in Chinese children. Br J Radiol 2001;74:331-4.   Back to cited text no. 6
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7.Belman BA, Lowell RK, Kramer SA. Clinical Pediatric Urology. 4 th ed. 2002. London, Universitas Sumatra utara. Martin Dutiz   Back to cited text no. 7
    
8.Kenney IJ, Negus AS, Miller FN. Is sonographically demonstrated mild distal ureteric dilatation predictive of vesicoureteric reflux as seen on micturating cystoureterography. Pediatr Radiol 2002;32:175-8.  Back to cited text no. 8
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9.Mahant S, Friedman J, Mac Arthur C. Renal ultrasound findings and vesicoureteral reflux in children hospitalized with urinary tract infection. Arch Dis Child 2002;86:419- 20.  Back to cited text no. 9
    
10.Muensterer OJ. Conprehensive ultrasound versus voiding systurethtogtaphy in the diagnosis of vesicourereral reflux. Eur Pediatr 2002;161: 435-7.   Back to cited text no. 10
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11.Darge K. Voiding urosonography with ultrasound contrast agents for the diagnosis of vesicoureteric reflux in children. I. Procedure. Pediatr Radiol 2008;38:40-53.  Back to cited text no. 11
    
12.Darge K. Voiding urosonography with US contrast agents for the diagnosis of vesicoureteric reflux in children Comparison with radiological examinations. Pediatr Radiol 2008;36:54- 63.   Back to cited text no. 12
    
13.Berrocal T, Gay F, Arjonilla A. Vesicoureteral reflux: Can the urethra be adequately assessed by using contrast- enhanced voiding US of the bladder? Radiology 2002;234:235-41.  Back to cited text no. 13
    
14.Sharbaf FG, Fallahzadeh MH, Modarresi AR, Esmaeili M. Primary vesicoureteral reflux in Iranian Children. Indian Pediatr 2007;44:128- 30.  Back to cited text no. 14
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15.Tsai YC, Hsu CY, Lin GJ, et al. Vesicoureteral reflux in hospitalized children with urinary tract infection: the clinical value of pelvic ectasia on renal ultrasound, inflammatory responses and demographic data. Chang Gung Med J 2004;27:436-42.  Back to cited text no. 15
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Correspondence Address:
Atoosa Adibi
Department of Radiology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan
Iran
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DOI: 10.4103/1319-2442.109582

PMID: 23538353

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