ULTRASOUND
EVALUATION OF RENAL SCARRING IN CHILDREN WITH VESICOURETRAL REFLUX
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ADRIANO A. CALADO, UBIRAJARA BARROSO JR., VIVIAN A.BARROSO, ANTONIO S. SOUZA, MIGUEL ZERATI FILHO
Institute of Urology and Nephrology, São José do Rio Preto, São Paulo, Brazil
ABSTRACT
Introduction:
Renal damage and subsequent scarring constitute a significant problem
in children with vesicoureteral reflux (VUR). Most studies have shown
99mTc dimercaptosuccinic acid (DMSA) scintigraphy to be the most sensitive
method of detecting renal scarring. It has been widely accepted that ultrasound
should be the initial investigation of urinary tract infection. The noninvasive
nature of ultrasound, its lack of ionizing radiation and the ease with
which investigations can be repeated are advantages of this method. Until
now there are relatively few studies comparing DMSA scintigraphy and ultrasound.
This study compares directly the ability of DMSA scintigraphy and ultrasound
to detect renal scarring.
Material and Methods: We evaluated the charts
of 88 patients who had undergone both ultrasound and DMSA scintigraphy
for primary VUR. The ultrasounds were reviewed by one consultant radiologist
and renal scars were deemed diffuse or focal. The data were analyzed to
determine the sensitivity, specificity, positive and negative predictive
value of the renal ultrasound in detecting focal and diffuse renal scars.
Results: Renal ultrasound detected focal
or diffuse renal scarring in 41 patients. Ultrasound examination correlated
with the DMSA study in 36 patients. On the other hand, of the 47 patients
with normal ultrasonography, the DMSA study showed renal scars in 14 patients.
The sensitivity, specificity, positive and negative predictive value were
66%, 84%, 87.5% and 61%, respectively. Of the focal scars, ultrasound
examination correlated in only 8 patients (32%). On the other hand, of
the 29 patients with diffuse scarring, ultrasound scanning demonstrated
scars in 28 (96.5%).
Conclusion: This study suggests that a high-resolution
ultrasound performed by experienced ultrasound technicians is able to
accurately detect diffuse renal scarring. When focal scarring was present,
the correlation was poor.
Key words:
vesico-ureteral reflux; kidney; ultrasonography; DMSA renal scanning
Braz J Urol, 28: 250-253, 2002
INTRODUCTION
The
reflux nephropathy is one of the few causes of terminal renal disease
which can be prevented through its diagnosis and adequate treatment of
the vesicoureteral reflux (VUR). Renal scarring are the main lesions associated
to VUR and they occur due to an association of reflux and urinary infection
(1). At the moment of the diagnosis 30 to 50% of the children presented
renal scarring (2). The present treatment for VUR has the objective of
preventing infectious episodes through clinical watchful and antibiotic
prophylaxis, as the surgery is indicated just to selected cases (3,4).
The evaluation of the renal parenchyma through
a scintigraphic study (dimercaptosuccinic acid – DMSA) proved to
be better than excretory urography and renal ultrasound for detection
of renal scarring (5). Due to its low cost and feasibility, some authors
have suggested the use of renal ultrasound as the examination of choice
in children who have VUR, being excretory urography and DMSA performed
only in selected cases.
The objective of this study is to analyze
the accuracy of renal ultrasound in detecting renal scarring in patients
who had VUR in our institution.
MATERIAL AND METHODS
The
charts of 814 patients who had VUR treated in our institution in the period
from July of 1968 to December 1999 were retrospectively evaluated. From
these patients, 88 underwent renal ultrasound and DMSA at the moment of
the diagnosis. The patients’ age varied from 6 months to 12 years
old (mean = 4.6 years). All patients were first submitted to clinical
management with antibiotic prophylaxis.
All patients whose ultrasound and scintigraphic
examinations were available to revision were included in this study. All
patients included in the study had their exams reevaluated, and the images
and reports revised by only one examiner (pediatric radiologist). The
presence of renal scarring and their posterior classification in focal
or diffuse was determined through the scintigraphic exam (DMSA). When
the renal parenchyma presented more than 2 focal scarring, global lesions
and/or differential function lower than 40%, the scarring was classified
as diffuse (6).
The ultrasonographic findings were compared
to the DMSA ones and it was determined the sensibility, specificity, positive
and negative predictive value in detecting focal and diffuse renal scarring.
RESULTS
Considering
the 88 studied patients, the VUR was grade I in 7 (7.9%), grade II in
14 (15.9%), grade III in 26 (29.5%), grade IV in 27 (30.7%) and grade
V in 14 (15.9%). The VUR was unilateral in 34 patients (51%) and bilateral
in 43 (49%); consequently, 131 renal units with reflux were studied. It
was evident in the scintilographic examination (DMSA), 54 renal scarring
(41.2%), being 25 focal and 29 diffuse. Table-1 demonstrates the presence
of renal scarring according to the grade of VUR. Among the patients who
presented focal scarring, we noticed correlation with the ultrasound examinations
in only 8 cases (32%). On the other hand, from the 29 renal cases who
presented diffuse scarring, there was a correlation with the ultrasound
examination in 28 cases (96.5%).
From the 41 patients who presented high
evidences of renal scarring in the ultrasound examination, there was confirmation
of this finding through DMSA in 36 cases. On the other hand, DMSA examination
detected renal scarring in 18 patients out of 47 patients who presented
normal ultrasound examination. These results demonstrate that the ultrasound
examination presents 66% of sensibility and 85.2% of specificity to detect
renal scarring. The positive and negative predictive values of this examination
are 87.8% and 61.7%, respectively.
DISCUSSION
Renal
ultrasound examination has been playing an important role in the evaluation
of urinary tract pathologies, mainly due to its feasibility, low cost,
absence of morbidity, besides the high resolution of the most modern equipment.
It is well known that the evaluation of renal parenchyma plays a fundamental
role in patients with vesicouretral reflux, as the presence of renal scarring
is determinant of worse prognosis and in more severe cases may lead to
chronic renal failure. Excretory urogram for evaluating the renal parenchyma
has been replaced in the last years by the scintilographic study (DMSA).
Several studies have stated the superiority of the DMSA in detection of
renal scarring, and nowadays this method is considered the “gold
standard” (7).
In our study we observed that ultrasound
examination was not able to detect small scars, since for focal scars
detected with the DMSA, there was correlation with ultrasound examination
in only 32% of the cases. However, when the kidney presented scars classified
as diffuse with DMSA, the ultrasound was able to detect 96.5% of the cases.
Tasker et al. (8), in a study performed in 100 children with VUR, found
scars in 19 cases. When these findings were correlated with the ultrasound
examination, it was shown that this procedure was able to diagnose only
1 out of 12 patients with segmental scars, while it was able to diagnose
all patients with diffuse scars (100%).
Examining the data related to sensibility,
specificity, positive and negative predictive values of the ultrasound
examination, we observed that they present high positive predictive values
and specificity, while their negative predictive values and sensibility
were low. That is, when the ultrasound shows a scar, it will probably
be confirmed by the DMSA. On the other hand, when the ultrasound examination
is normal, we can infer that probably it does not exist diffuse scars.
In spite of some limitations of this method,
ultrasound examination plays an important role for patients with VUR.
The current treatment for VUR consists of prevention of renal lesions,
which in severe cases could lead to reflux nephropathy. Several studies
have suggested that clinical treatment with antibiotic prophylaxis presents
high rates of spontaneous resolution, depending mainly on the grade of
VUR and on the patient’s age at the time of the diagnosis (9).When
these patients presented favorable evolution according to clinical treatment,
the occurrence of new scars or even progression of the previous ones is
rather rare. For this reason, some authors have shown that scintigraphic
evaluation must be performed only in selected cases, and they suggest
that the findings of this examination have presented less impact in the
patients’ treatment, when compared to treatments that were initially
considered (10). Despite the fact that the DMSA is the most accurate method
to detect renal scars, these studies have stated that the detection of
these lesions did not play a fundamental role in determining the procedures
(10). Bellinger (11) observed that DMSA scanning would be better indicated
for cases in which the ultrasound shows renal lesion, dysplasia, severe
hydronephrosis or VUR of high grade level, before deciding between ureteral
reimplantation or nephrectomy.
CONCLUSION
When the ultrasound examination is performed by an experienced operator with high resolution equipment, it presents good accuracy in detecting diffuse scars; however, it is not accurate to detect focal scars. Patients who have primary VUR of low level and with no recurrent infections, usually present no renal scars or only focal scars, not leading to progression. Consequently, in this group, ultrasound can be used for evaluation and follow up. Scintigraphic examination would be indicated for patients with alterations in ultrasound examination or when there is a higher possibility of detecting new renal scars, as for those patients with VUR of high grade, associated voiding disorders and recurrent urinary infections.
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- Merguerian PA, Jamal MA, Agarwal SK, McLorie GA, Bagli DJ, Shuckett B et al.: Utility of DMSA renal scanning in the evaluation of children with primary vesicoureteral reflux. Urology, 53: 1024-1028, 1999.
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____________________
Received: April 19, 2001
Accepted after revision: April 3, 2002
______________________
Correpondence address:
Dr. Miguel Zerati Filho
Instituto de Urologia e Nefrologia
Rua Voluntários de São Paulo, 382
São José do Rio Preto, SP, 15015-200, Brazil
Fax: + + (55) (17) 232-2230
E-mail: iunsjrp@zaz.com.br