Year : 1998 | Volume
: 9 | Issue : 2 | Page : 134--138
Radionuclide Assessment of Patients with Urinary Tract Infection and Vesico-Ureteric Reflux Using Tc-99m-Dimercaptosuccinic Acid
Department of Diagnostic Radiology, King Hussein Medical Center, Amman, Jordan
Department of Diagnostic Radiology, King Hussein Medical Center, P.O. Box 13311, Amman 11942
The purpose of this study was to evaluate pediatric patients with urinary tract infection and to identify the risk of developing renal scarring and its relationship to the presence of vesico-ureteric reflux. The subjects in this study were 29 pediatric patients between two months and 11 years of age with a history of urinary tract infection among which 69% were females. All the patients underwent radio-isotope scanning using Technetium-99-m-dimercaptosuccinic acid, 4-6 weeks after the eradication of the acute infection. Micturating cysto-urethrography and renal ultrasound examinations were performed before the radio-isotope scanning. Isotope scanning showed evidence of scarring in 34% of the kidneys, while ultrasound scanning was positive in only 29% of the kidneys. The agreement between the results of the two examinations was in 88% of the kidneys. Reflux was noted in 53% of the kidneys of which 62% showed scarring by isotope scanning. Only 11% of the kidneys with no reflux showed evidence of scarring, while 92% of kidneys with severe reflux had renal scarring. In patients with reflux, 57% of the kidneys in female patients and 50% of the kidneys in male patients developed renal scarring evident on DMSA scanning. Absence of reflux had a high predictive value for absence of renal scarring, while the presence of reflux did not necessarily imply the presence of renal scarring but the possibility increased with the severity of reflux.
|How to cite this article:|
Al-Kaylani H. Radionuclide Assessment of Patients with Urinary Tract Infection and Vesico-Ureteric Reflux Using Tc-99m-Dimercaptosuccinic Acid.Saudi J Kidney Dis Transpl 1998;9:134-138
|How to cite this URL:|
Al-Kaylani H. Radionuclide Assessment of Patients with Urinary Tract Infection and Vesico-Ureteric Reflux Using Tc-99m-Dimercaptosuccinic Acid. Saudi J Kidney Dis Transpl [serial online] 1998 [cited 2020 Sep 26 ];9:134-138
Available from: http://www.sjkdt.org/text.asp?1998/9/2/134/39285
Urinary tract infection (UTI) in childhood can be an important cause of morbidity and of end-stage renal failure. Moreover, the association of UTI with vesico-ureteral reflux, which occurs m 1% to 2% of the pediatric population, increases the risk for renal scarring , . However, renal involvement is also common in the absence of reflux  , and a low correlation with the presence of reflux was observed by some investigators, especially in children over one year of age  . Therefore, when UTI is documented, it is of primary importance to differentiate between a disease limited to the lower urinary collecting system and one that involves the renal parenchyma. An accurate differential diagnosis is often difficult because symptoms, clinical signs, and laboratory finding are frequently non-specific, especially in neonates and infants  .
Several imaging techniques have been proposed to detect the presence of renal parenchymal involvement in children with UTI, but renal scintigraphy with technetium99-m-dimercaptosuccinic acid (DMSA) has now become a standard technique in detecting cortical lesions in subjects with UTI  ; as it has been shown to have a better sensitivity and specificity than other techniques ,, . The aim of this study was to evaluate pediatric patients with urinary tract infection (UTI) and to assess the development of renal scarring and its relationship to the presence of vesicoureteric reflux.
Material and Method
Twenty nine children were studied (58 kidneys), with a mean age of three years and four months, (range 2 months to 11 years). There were 20 (69%) female patients and 9 (31%) male patients, (M: F ratio 1:2.2). The mean age of female was 3 years and 9 months (70% were below the age of 4 years) and that of males was 2 years and 2 months (88% were below the age of 3 years).
Patients referred to us had been diagnosed clinically and microbiologically as having UTI with high suspicion of pyelonephritis.
Materials and Methods
Dimercaptosuccinic acid (DMSA) was used. Patients were injected between 1 - 5 mCi (37-185 MBq) of Tc-99- m-DMSA calculated according to their ages and weights. After two hours they were imaged, and three views [Figure 1] were taken: posterior (post), left posterior oblique (LPO) and right posterior oblique (RPO). Three hundred thousand counts were taken for each view.
The examinations were performed 4-6 weeks after eradication of the last attack of infection. Each kidney was analyzed separately. Patients with abnormality of kidney shape or position or those with obstruction due to any cause were excluded from the study.
A kidney was considered abnormal when one or more scars were seen in that kidney [Figure 2], or when the kidney appeared to be atrophic with reduction in its function.
MCU was performed on all patients. Grading of reflux was done according to the classification as described by Sutton . The classification includes; Grade 0: no reflux; Grade 1: reflux confined to the lower pelvic portion of a normal-size ureter; Grade II: reflux extending up to the kidney only on micturation without ureteral dilatation; Grade III: reflux extending up to the kidney in the resting state and also during voiding without ureteral dilatation; Grade IV: reflux up to the kidney with dilatation of the upper tract.
Ultrasound (US) was performed on all the patients. The kidney was considered abnormal when a cortical defect, or loss of renal cortex thickness was observed, or when the kidney appeared distorted and small.
Intravenous urography was performed on all the patients in order to exclude those with evidence of obstruction along the urinary tract including those with suspicion of pelvi-ureteric junction obstruction.
DMSA was positive in 20 kidneys (34%). The upper and lower portions were equally affected by scars (44% and 43% respectively). Middle portion were affected in 13% only. Of the total number of the affected kidneys 50% were on the night and 50% on the left. Ultrasound revealed pathology in 29% of the kidneys.
Among the 20 kidneys which showed positive results with DMSA, 15 (75%) were positive with US; while in the 38 kidneys which showed negative results with DMSA, 36 (95%) were negative with US and only 2 (5%) were positive. Thus there was an agreement between the results of DMSA and US in 15 positives and 36 negatives constituting 51 kidneys out of 58 amounting to 88%. Disagreement in the results of the two examinations was in 7 kidneys only amounting to 12%. The significance of agreement between US and DMSA in the positive and negative cases was statistically examined using chi squared test. The resulting (observed value) of x2 was 30.77 while the critical (expected value) at a ,, . We excluded obstruction or other congenital pathology in our study. DMSA as well as MCU findings revealed equal involvement by the right and left kidney. This meant that the side at which the kidney is located had no effect on the development of reflux or the development of renal scarring following UTI. For those kidneys with negative reflux, DMSA scan was negative in 89% of the cases, which meant that there was a rather strong relationship between absence or reflux and absence of scarring. While the presence of reflux carries a risk of about 55% for the presence of scarring [Table 2]. From [Table 1], we can see that renal damage and scarring correlated to the degree of reflux, especially in grades 0 and IV. But in patients with grades I to III, the results were variable and this might be explained partially by the fact that the number of cases in our study was relatively small.
These findings were similar in both males and females [Table 1],[Table 2]. This meant that once the child had a urinary tract infection, the development of further complication such as renal scarring was independent of his sex and was more related to the presence of reflux and to its degree. This sounded reasonable because once the patient had UTI, the protective effect of the long urethra in male is eliminated. Thus the chance of further sequelae of UTI will depend on other factors (e.g. VUR).
Our results suggest, for pediatric patients with UTI, that absence of reflux has a high predictive value for low likelihood of renal scarring and that the presence of reflux is not always associated with scarring, but the chances of scarring increases with the grade of reflux.
Sex of the child with reflux has no influence in the development of scarring. The scarring mainly affects the upper and lower part of the kidney.
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