|Year : 2017 | Volume
| Issue : 1 | Page : 76-80
|The role of dynamic renal scintigraphy on clinical decision making in hydronephrotic children
Seçil Arslansoyu Çamlar1, Nazlı Deveci1, Alper Soylu1, Mehmet Atilla Türkmen1, Derya Özmen1, Gamze Çapakaya2, Salih Kavukçu1
1 Department of Pediatrics, Division of Nephrology, Medical Faculty, Dokuz Eylul University, Izmir, Turkey
2 Department of Nuclear Medicine, Medical Faculty, Dokuz Eylul University, Izmir, Turkey
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|Date of Web Publication||12-Jan-2017|
| Abstract|| |
Hydronephrosis may be related to an obstructive cause, ureteropelvic/uretero-vesical junction obstruction or nonobstructive [vesicoureteral reflux (VUR)]. When an obstructive pathology is considered, dynamic renal scintigraphy may help to predict whether it is a true obstruction or not. In this study, we aimed to determine the contribution of dynamic renal scintigraphy with  mTc-MAG-3 to the clinical decision-making for surgery in hydronephrotic children. Files of the patients evaluated by MAG-3 scintigraphy for antenatal (AH)/postnatal (PH) hydronephrosis between 1992 and 2014 were reviewed. Gender, age, hydronephrosis (HN) grade by ultrasound (US), presence of VUR, MAG-3 result (obstructive vs. nonobstructive), ultimate diagnosis, and need for surgery were assessed. Cases with double collecting system and neurogenic bladder were excluded from the study. All of the patients had normal serum creatinine and eGFR. There were a total of 178 patients with 218 hydronephrotic renal units (mean age 34.7 ± 52.7 months; male/ female = 121/57, AH of 62%). MAG-3 was nonobstructive in 134 and obstructive in 84 hydronephrotic renal units. MAG-3 was obstructive in 47 of 121 (39%) males and 30 of 57 (53%) females (P = 0.058, odds ratio (OR) for obstruction was 1.9 for girls). MAG-3 was obstructive in 47 of 135 (35%) units with AH and 37 of 83 (45%) units with PH (P = 0.137). In 81 units with the society of fetal urology-4 HN by US, MAG-3 was obstructive in 55 (68%), and surgery was required in 52 of 55 (95%). Surgery was required for only two (7%) of the remaining 26 units with nonobstructive dilatation (P <0.001, sensitivity 96%, specificity 89%, OR 208). Antero-posterior diameter >16.5 mm was the best cutoff level for predicting obstruction by MAG-3 (sensitivity 75.2%; specificity 71%; OR 3.8). MAG-3 significantly affects clinical decision for surgery in HN. Hydronephrotic girls have more risk in terms of true obstruction. Combining MAG-3 with US improves the discrimination of true obstruction during follow-up.
|How to cite this article:|
Çamlar SA, Deveci N, Soylu A, Türkmen MA, Özmen D, Çapakaya G, Kavukçu S. The role of dynamic renal scintigraphy on clinical decision making in hydronephrotic children. Saudi J Kidney Dis Transpl 2017;28:76-80
|How to cite this URL:|
Çamlar SA, Deveci N, Soylu A, Türkmen MA, Özmen D, Çapakaya G, Kavukçu S. The role of dynamic renal scintigraphy on clinical decision making in hydronephrotic children. Saudi J Kidney Dis Transpl [serial online] 2017 [cited 2017 Mar 27];28:76-80. Available from: http://www.sjkdt.org/text.asp?2017/28/1/76/198146
| Introduction|| |
Hydronephrosis (HN) is defined as a significant increase in the diameters of the collecting system on ultrasonography (US). Although HN is seen in every 1/100 pregnancy, important urinary disorders are seen only in 1/500.
The majority of antenatal hydronephrosis (AH) does not represent a real obstruction. However, in other cases, the underlying causes are vesicoureteral reflux (VUR) or obstructive uropathies like ureteropelvic junction obstruction (UPJO), ureterovesical junction obstruction (UVJO), and posterior urethral valve (PUV). , The definition of HN based on US and other imaging tools is required to elucidate the etiology.
Scintigraphy, as in many other areas, is a diagnostic tool used in imaging of the urinary tract for many years. While useful in the representation of renal function and demonstration of renal scarring, its use is limited in cystic diseaseor stones. While static scintigraphy shows formation of scar, dynamic scintigraphy is helpful in evaluation of obstruction. Dynamic scintigraphy is a structural and functional imaging modalities used in all age groups including neonatal period.Especially when an obstructive pathology is considered, dynamic renal scintigraphy may help to predict whether there is a drainage congestion in the transition or not. , ,
In this study, we aimed to determine the contribution of dynamic renal scintigraphy with 99mTc-MAG-3 (mercaptoacethyltriglycine) to the clinical decision-making for surgery in hydronephrotic children.
| Patients and Methods|| |
Files of the patients evaluated by MAG-3 scintigraphy for antenatal (AH)/postnatal (PH) hydronephrosis between 1992 and 2014 in the Dokuz Eylul University Pediatric Nephrology clinic were reviewed. Gender, age, HN grade by US, presence of VUR, MAG-3 result (obstructive vs. nonobstructive), ultimate diagnosis, and need for surgery were assessed. Cases with double collecting system and neurogenic bladder were excluded from the study. All of the patients had normal serum creatinine and eGFR. Renal units with HN was specified as the right, left, and bilateral. Grading of HN by US was done in accordance with the classification of the society of fetal urology (SFU) grade. Anteroposterior (AP) pelvic diameter was noted if it was stated on US report.
VUR was diagnosed by voiding cystourethrography and graded by the International Reflux Study Committee Classification. 
Dynamic scintigraphy was performed in well hydrated patients in the supine position. 2.59 MBq of 99mTc-MAG3/kg body weight was administered intravenously to children. Serial images were taken rapidly at short intervals following administration of parenteral radiopharmaceutical substance by gamma cameras. Diuretic was administered in 12th min (F20+ protocol). Results were categorized as obstructive and nonobstructive. Differential uptake ≤40% in a renal unit was considered as abnormal. 
Final diagnosis and surgery requirement were based on serial clinical, US, and radionuclide study results. In some cases, cystoscopy was needed. Antireflux surgeries were not included in the surgery group. Patients with obstructive versus nonobstructive AH with respect to MAG- 3 were compared for age, gender, US findings, ultimate diagnosis, and surgical approach.
| Statistical analyses|| |
Categorical data are given in proportions and expressed as percentages. Continuous data were shown as mean ± standard deviation and com-pared using Student's t-test. The P <0.05 was considered as statistically significant. The study has been approved by the Local Ethical Committee.
| Results|| |
There were a total of 198 patients with a diagnosis of AH/PH. Patients without followup (n = 10) or having double collecting system (n = 7), and neurogenic bladder (n = 3) were excluded from the study. Thus the final study population included 178 patients with 218 hydronephrotic units (mean age 34.7 ± 52.7 months; male/female = 121/57, AH of 62%).
The ratio of AH was higher in boys (82/121, 68%) compared to girls (28/57, 49%). MAG-3 was nonobstructive in 134 and obstructive in 84 hydronephrotic renal units. Comparison of the final diagnoses and surgical intervention rates with respect to MAG-3 result are seen in [Table 1].
|Table 1. Comparison of the final diagnosis and surgical intervention rate with respect to MAG3 results.|
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MAG-3 was obstructive in 47 of 121 (39%) males and 30 of 57 (53%) females (P = 0.058, OR for obstruction was 1.9 for girls). MAG-3 was obstructive in 47 of 135(35%) units with AH and 37 of 83 (45%) units with PH (P = 0.137). In 81 units with SFU-4 AH by US, MAG-3 was obstructive in 55 (68%), and surgery was required in 52 of 55 (95%). Surgery is required for only 2 (7%) of the remaining 26 units with nonobstructive dilatation [P <0.001, sensitivity 96%, specificity 89%, odds ratio (OR) 208]. Sensitivity and specificity of MAG- 3 for obstructive AH with respect to AP pelvis diameter in US is shown in [Table 2]. AP diameter >16.5 mm was the best cutoff level for predicting obstruction by MAG-3 (sensitivity 75.2%; specificity 71%; OR 3.8).
|Table 2. Sensitivity and specifity of AP diameter for predicting obstruction by MAG-3 renal scintigraphy.|
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| Discussion|| |
AH may be associated with an obstructive or nonobstructive cause.2 With the extensive use of prenatal US, AH can be detected in the antenatal period. In the absence of antenatal US, AH can be diagnosed based on findings such as urinary tract infection, loin pain, voiding dysfunction, or pain. Furthermore, with increasing experiences, an algorithm is being set for diagnosis and monitoring of these patients.
Diuretic renogram can be performed with diethylentriamine pentaacetic acid, MAG3, and ethylendisistein. In this study, all patients underwent MAG3 scintigraphy. There are various ongoing studies evaluating the accuracy of results by modifying the examination (diuretic timing or using other medications) in the field of nuclear medicine and using different parameters (tissue tracer transit, response to furosemide stimulation, single kidney function <40%, transit cortical time, and differential renal function). , , When evaluating a child with HN, it is important to pay attention to the necessity and timing of the imaging modalities since it requires need of intravenous cannulation and low-dose irradiation. Even though the AP diameter higher than 7 and 10 mm in neonatal period is accepted as a limit for advanced imaging for obstruction, the consensus is that a diameter higher than 15 mm is a predictive for obstruction. In this study, AP diameter >16.5 mm was the best cutoff level for predicting obstruction by MAG-3. Several studies have determined the values of 16-24 mm. ,
In the literature, several homogenous groups within the age, unilateral, or UPJO were studied. , , The purpose of this study was to compare different groups for age, uni/bilaterally, AH/PH who were diagnosed as obstructive/nonobstructive. We found no difference in the diagnosis of obstruction in the neonatal period compared to the older age-groups once dynamic scintigraphy was compared based on age. When comparing gender and MAG3 results, it was observed that MAG3 results showed obstructive findings, which were more significant among females. The probability of hydronephrotic girls to be obstructive is almost two times higher than the boys. This may be related to high rate of transient AH among males.
AH can resolve spontaneously. Even some patients with obstructive renogram have been found to improve without surgery. On the other hand diuretic renogram may be falsely interpreted as obstructive in the presence of VUR due to reverse flow of urine or presence of dilated and tortuous ureters results in kinks. We couldn't find a correlation between VUR grade and obstructive findings in MAG-3 scintigraphy.
Diuretic renography delivers important parameters to determine the need for surgical intervention. Although being diagnosed obstructive according to scintigraphy results is helpful in determining whether the patient has any need for surgical intervention, it is not enough to make an ultimate decision of an absolute need for such an operation. Therefore, the age of the patient, symptoms, and the grade of the obstruction are among the factors in decision-making process of a surgeon; however, there might be differences from one clinic to another. Some authors also suggest conservative management for some obstructive cases. In their study, including patients with unilateral AH detected in the prenatal period, Ozcan et al, indicated that among the patients with decreased drainage function, the drainage increased at later periods even in the group which was not surgically operated. Grade of AH and even thinned out parenchyma in US and decreased function in one kidney compared to the other might be more enlightening regarding the prognosis of longterm renal functions. , The question of benefiting from a surgical intervention in this patient group is another controversial issue. This study did not include the indications with which the patients were surgically operated. Of the cases who were also obstructive at the ultimate diagnosis (according to MAG3 results), MAG3 sensitivity is 82% and specificity 92%; however, among the nonobstructive cases, error margin is higher. It could be concluded that one can trust the obstruction detecting capacity of MAG3; but if there is any nonobstructive result, the patient should be assessed again with other data.
This study has its own limitations. Although US was performed in the same clinic, it was not conducted by the same physician. In some of the US reports, AP diameter of renal pelvis was not recorded. Parenchymal thickness was not evaluated in detail; therefore, this parameter was not included in the study. In this study, reasons for surgical intervention did not involve indications, timing of surgery, or time to perform the operation.
| Conclusion|| |
MAG-3 significantly affects clinical decision for surgery in AH. Hydronephrotic girls have more risk in terms of true obstruction. Combining MAG-3 with US improves the discrimination of true obstruction during follow-up.
Conflict of interest: None declared.
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Seçil Arslansoyu Çamlar
Department of Pediatrics, Division of Nephrology, Medical Faculty, Dokuz Eylul University, Izmir
[Table 1], [Table 2]
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