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Renal Doppler ultrasound resistive index vs. renal scintigraphy with 99mTc-DTPA as diagnostic test for ureteropelvic junction obstruction in children
Actas Urol Esp. 2019;43(8):419---424
Actas Urol´ ogicas Espa˜ nolas www.elsevier.es/actasuro
ORIGINAL ARTICLE
Renal Doppler ultrasound resistive index vs. renal scintigraphy with 99m Tc-DTPA as diagnostic test for ureteropelvic junction obstruction in children夽 A. Ruiz-Martínez a , E. Sierra-Díaz b,∗ , A.J. Celis-de la Rosa c , M.Á. Valenzuela Hernández d , M.G. González Flores e , M.V. Belmonte Hernández b a
Departamento de Cirugía Pediátrica, Hospital general de Zona 67, Instituto Mexicano del Seguro Social (IMSS), Apodaca, Nuevo León, Mexico b Departamento de Urología, Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social (IMSS), Guadalajara, Jalisco, Mexico c Departamento de Salud Pública, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico d Departamento de Medicina Nuclear, Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social (IMSS), Guadalajara, Jalisco, Mexico e Departamento de Radiología e Imagen, Centro Médico Puerta de Hierro, Guadalajara, Jalisco, Mexico Received 6 November 2018; accepted 13 February 2019 Available online 20 September 2019
KEYWORDS Ureteropelvic junction obstruction in children; Doppler ultrasound; Resistive index; Renal scintigraphy with 99m Tc-DTPA
Abstract Objective: A cross-sectional study was carried out with the objective of evaluating the usefulness of Doppler ultrasound with resistive index (RI) measure compared with renal scintigraphy with 99m Tc-DTPA in children with unilateral ureteropelvic junction obstruction. Methods: The study included children under 15 years with a diagnosis of unilateral ureteropelvic junction obstruction, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. The selected patients were sent to the Nuclear Medicine Department to carry out a renal scintigraphy with 99m Tc-DTPA and days later were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with RI. Results: A total of 21 patients were included in the study, 15 males and 6 females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years. Only 3 had an antecedent of ureteropyeloplasty in the affected kidney. The scintigraphy reported data of unilateral obstruction in 18 patients, including the 3 patients with previous surgery. The average glomerular filtration rate (GFR) obtained with the scintigraphy was 100.28 ml/min. The average GFR in affected
夽 Please cite this article as: Ruiz-Martínez A, Sierra-Díaz E, Celis-de la Rosa AJ, Valenzuela Hernández MÁ, González Flores MG, Belmonte Hernández MV. Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99m Tc-DTPA para el diagnóstico de nos. Actas Urol Esp. 2019;43:419---424. estenosis ureteropiélica en ni˜ ∗ Corresponding author. E-mail address: [email protected] (E. Sierra-Díaz).
2173-5786/© 2019 AEU. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
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A. Ruiz-Martínez et al. kidneys was 43.03 ml/min and 57.24 ml/min in healthy kidneys (p < .001). Doppler ultrasound with RI reported ectasia in 100% of the affected kidneys and one normal contralateral kidney. The average RI in affected kidneys was 0.69 mm/s and 0.50 mm/s in healthy kidneys (p < .001). Conclusions: With the results obtained, we can suggest that ultrasound Doppler with measurement of RI can be an alternative tool to renal scintigraphy with 99m Tc-DTPA in some cases. © 2019 AEU. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE Estenosis ureteropiélica en ni˜ nos; Ecografía Doppler; Índices de resistencia; Gammagrafía renal con 99m Tc-DTPA
Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99m Tc-DTPA para el diagnóstico de estenosis ureteropiélica en ni˜ nos Resumen Objetivo: Se llevó a cabo un estudio de corte transversal con el objetivo de evaluar la utilidad de la ecografía Doppler con índice de resistencia (IR) en comparación con la gammagrafía renal con 99m Tc-DTPA en ni˜ nos con estenosis ureteropiélica unilateral. Métodos: El estudio incluyó ni˜ nos menores de 15 a˜ nos con diagnóstico de estenosis ureteropiélica unilateral, ri˜ nón contralateral sano con o sin antecedente de plastia ureteropiélica. Los pacientes seleccionados se derivaron al Departamento de Medicina Nuclear para llevar a cabo la gammagrafía renal y días más tarde se derivaron al Departamento de Radiología para la realización de la ecografía Doppler renal con IR. Resultados: Un total de 21 pacientes fueron incluidos en el estudio, 15 hombres y 6 mujeres, que representan el 71,4% y el 28,6%, respectivamente. La edad promedio fue de 5,3 a˜ nos. Solo 3 tuvieron un antecedente de plastia ureteropiélica en el ri˜ nón afectado. La gammagrafía renal informó datos de obstrucción unilateral en 18 pacientes, incluidos los 3 pacientes con cirugía previa. La tasa promedio de filtración glomerular (TFG) en general obtenida con la gammagrafía fue de 100,28 ml/min. El promedio de TFG fue de 43,03 ml/min en los ri˜ nones afectados y de 57,24 ml/min en los ri˜ nones sanos (p < 0,001). La ecografía Doppler con IR reportó ectasia en el 100% de los ri˜ nones afectados y en un ri˜ nón contralateral normal. El IR promedio fue de 0,69 mm/s en los ri˜ nones afectados y de 0,50 mm/s en los ri˜ nones sanos (p < 0,001). Conclusiones: Con los resultados obtenidos, podemos sugerir que la ecografía Doppler renal con medición del IR puede ser una herramienta alternativa a la gammagrafía renal con 99m Tc-DTPA en algunos casos. © 2019 AEU. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
Introduction UreteroPelvic Junction Obstruction (UPJO) is defined as a blockage of urine flow from the kidney into the proximal ureter. This blockage may result in progressive damage to the kidney function secondary to backpressure and hydronephrosis. This is why it is of great importance to understand how to diagnose and treat this pathology.1 Incidence of UPJO has been estimated in 1 in 1000---1500 newborns and is the first cause of antenatal hydronephrosis. UPJO is 3 times more common in males and 20---25% of cases may be bilateral. Intrinsic stenosis, insertion anomaly of the ureters, peripelvic fibrosis, peristaltic abnormalities, and blood vessels crossing the ureter have been studied as causes of UPJO.2 Renal scintigraphy with 99m Tc-DTPA (RS) is the most widely used noninvasive test to determine the degree and dynamics of ureteropelvic urine-transport problems in children. During last years, several protocols and techniques have been developed; this has produced significant variability in interpretive criteria and results among different nuclear medicine laboratories. Correlation with other techniques, such as pressure flow studies, also has been poor.3
In order to promote standardization of the technique and protocols, three consensus papers have been published as follows: from the Society Fetal Urology; the Pediatric Nuclear Medicine Council, and the Ninth International Symposium on Radionuclides in Nephrourology.3---6 In clinical practice, one of the main points before defining UPJO management is to differentiate between obstructive and nonobstructive dilatation. As mentioned previously, RS is the most widely used test. The sensitivity and specificity reported for this test are 88---100% and 73---79, respectively.7,8 In Mexico, the availability of nuclear medicine is limited to some Medical Centers of the Government Health System and in some private hospitals. UltraSonography (US) has been utilized as first modality in the evaluation of congenital renal obstruction. Although renal US is an ideal noninvasive method for detecting infant hydronephrosis, the significance of the upper tract dilation is more difficult to assess because it does not reveal renal function. Investigations with Doppler Ultrasound (DU) have yielded advances in some areas. Resistive Index (RI) is a measure of resistance to blood flow through the kidney and is defined as peak systolic frequency shift minus end diastolic frequency shift divided by peak systolic frequency shift. Any
Renal Doppler ultrasound vs renal scintigraphy in ureteropelvic junction obstruction condition that raises impedance to blood flow through the kidney may raise the RI.9 We designed this cross-sectional study with the objective of evaluating the usefulness of DU with RI measure compared with RS in children with unilateral UPJO.
Materials and methods Our study universe comprised patients seen as outpatients during a 1-year time period at the Pediatric Urology Department of the Pediatric Hospital of the Western National Medical Center of the National Institute of Social Security (IMSS) in the state of Jalisco, Mexico. The institutional ethics committee authorized the study protocol with the registration number R-2012-1302-25. Patients and parents were informed about the study. We included in the study patients of both sexes aged between 8 months and 15 years with a diagnosis of unilateral ureteropelvic stenosis, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. Patients were not included if they had a sole kidney, lithiasis, VesicoUreteral Reflux (VUR), or other congenital urinary-tract malformations. The selected patients were to the Nuclear Medicine Department to carry out a renal scintigraphy with 99m TcDTPA. Two to 4 weeks after the scintigraphy, the patients were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with the measurement of Resistive Index (RI). The affected kidney was treated as the case and the normal kidney as the control. An experienced pediatric Radiologist and a Nuclear Medicine Physician carried out the DU and RS, respectively. The Radiologist was not informed of the result of the scintigraphy prior to performing the Doppler ultrasound.
Renal scintigraphy with
99m Tc-DTPA
Radiopharmaceutical and patient preparation for study To prepare the radiopharmaceutical (99m Tc-DTPA), the kit ® Pentacis was used and adjusted by weight and age according by the European Association of Nuclear Medicine. Labeling control was defined as a labeling efficiency of ≥90%.10 Patients drank 250---500 ml of water 1 h before to start of the test. Patients were also asked to empty the bladder before the study. Protocol for renal scintigraphy with 99m Tc-DTPA A scintillation camera (Phillips System Precedence 16, ® SPECT/CT ) equipped with low-energy general-use collimators was used to perform the tests. Acquisition of dynamic image started after administration of the 99m Tc-DTPA as an intravenous bolus injection. For the blood flow phase one image was obtained every 2 s for 60 s and for the functional phase one image was obtained every 60 s for 30 min. Sequential phase were acquired over a 30-min with the patient in the supine position, with posterior projection with a 64 × 64 matrix, for the kidneys and bladder included in the field of view. After urination, the diuretic Furosemide (1 mg/kg) was administered intravenously.11
421
Processing Analyses were performed by delineating Regions of Interest (ROI) around each kidney and in the aorta in the dynamic images obtained during the vascular phase, calculating timeactivity curves for each kidney vs. the time in seconds. The dynamic images obtained every 1 min during functional phase, and ROI were drawn around each kidney and their collecting systems. The background was subtracted utilizing defined ROI around the outer perimeter for each kidney. Evaluation of 99m Tc-DTPA eliminated was adapted from the T½ method, indicative of an obstructive kidney if the proportional elimination was <50% at 20 min, corresponding to a T½ of >20 min, indicative of an unobstructed kidney if the proportional elimination was ≥60% at 20 min, corresponding to a T½ of <15 min, or undetermined if the proportional elimination was 50---60% at 20 min.11 The complete protocol performing Renal scintigraphy with 99m TcDTPA may be consulted on cited references.10,11 Renal Doppler ultrasound and resistive index measure Renal Doppler ultrasound was carried out with a highfrequency linear transducer (iSTYLE Toshiba Medical Systems Corporation) as well as convex multifrequency, depending on patient’s age group. We evaluated the morphological aspects, dimensions, and degree of renal ectasia. This was assessed in Mode B as well as in Doppler, pulsated Doppler assessing renal artery, segmental, interlobar and arcuate arteries in both kidneys, with a minimum of three cycles to obtain systolic peak, diastolic peak, and an RI of 3. The value of the RI reported was defined based on minimal and maximal values (average). For data analysis, we employed descriptive statistics, Student t test for mean difference, Fisher exact test for correlation, and tests to calculate sensitivity and specificity. Calculations were performed with Excel tables and the OpenEpi ver. 3 statistical software programs.
Results During the study period, we detected 77 patients with renal ectasic data at different grades. With the use of imaging studies, we discarded for the study patients with vesicoureteral reflux, posterior ureteral valves, congenital mega-ureter, lithiasis, ureteroceles, and bilateral UPJO. A total of 21 (n = 21) patients were included in the study, 15 males and six females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years, with a range of 1---14 years. Of the 21 patients, only three had an antecedent of ureteropyeloplasty in the affected kidney; the remainder of the 21 patients had no surgical antecedent. Of the kidneys affected, 16 were right-side and five were left-side, corresponding to 76.2% and 23.8%, respectively. The scintigraphy conducted reported data of unilateral obstruction in 18 of patients, included the 3 patients with previous of surgery. The remaining three patients only showed ectasia of the renal pelvis with delay of elimination and good response to application of diuretic. The average glomerular filtration rate (GFR) in general obtained with the scintigraphy was 100.28 ml/min. The average GFR in affected kidneys was 43.03 ml/min (27---59) and 57.24 ml/min (45---62) in healthy kidneys (p < 0.001).
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A. Ruiz-Martínez et al.
Table 1
RI results (mm/s) and the GFR (ml/min).
Age 7 2 *9 O 14 1 1 O 13 4 1 1 *9 10 1 4 *2 1 1 10 1 O 15 5 5.33
Ectasic kidney RI 0.7 0.5 0.36 0.9 0.75 0.72 0.65 0.51 0.76 0.71 0.52 0.8 0.86 0.56 0.68 0.86 0.78 0.76 0.75 0.77 0.63 0.69
Normal kidney RI 0.25 0.43 0.42 0.5 0.43 0.45 0.54 0.37 0.45 0.5 0.56 0.48 0.63 0.52 0.45 0.75 0.45 0.6 0.53 0.62 0.62 0.50
GFR ectasic kidney
GFR normal kidney
41 45 50 45 42 51 43 45 40 42 45 39 43 48 59 42 40 42 44 27 31 43.04
58 61 56 54 58 60 61 57 58 59 45 50 62 56 56 54 61 60 58 62 56 57.23
GFR 99 106 106 99 100 111 104 102 98 101 90 89 105 104 115 96 101 102 102 89 87 100.29
RI: resistive Index; GFR: glomerular filtration rate; *NonObstructive Diuretic Renogram. OPrevious surgery. Average mean in blacks.
Table 2
Glomerural Filtration Rate
65
Coefficients.
60
Model
55
Unstandardized coefficients
50
B
Std. error
70.888 −34.741
4.525 7.340
Sig.
45
(Constant) DU
40 35
.000 .000
30 25 0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
Table 3 tables.
Calculation of sensitivity and specificity with 2-x-2
Resistive index
Figure 1 In this graph we are able to observe the inverse relation between the RI and the GFR on utilizing a paired analysis.
The carrying out of Doppler Ultrasound (DU) with measurement of the RI (Restive Index) reported ectasia in 100% of the affected kidneys and a normal contralateral kidney. The average RI in affected kidneys was 0.69 mm/s (0.3---0.9) and 0.50 mm/s (0.2---0.75) in healthy kidneys (p < 0.001). Based on what has been described in then literature,11 probable obstruction is considered in kidneys with a RI greater than 0.7 mm/s. Table 1 and Fig. 1 demonstrate the relationship of patients with RI values obtained on the DU and the GFR for each of the kidneys and the total. As a cross-sectional data analysis, the regression coefficient for the predictor is the difference in response per unit difference in the predictor. Output produced from linear regression is shown in Table 2. On relating the results of the scintigraphy with those obtained in the Doppler Ultrasound (DU), we obtained the following results: obstructed patients with elevated RI, 12; obstructed patients with normal RI, six; nonobstructed
Measure
%
Sensitivity Specificity
66.67 96
95%CI (43.75---83.72) (43.85---100)
patients with elevated IR, none; and nonobstructed patients with normal RI, three. On analyzing these values in a 2-x-2 table for sensitivity and specificity, we obtained the results presented in Table 3. We also performed a ROC curve that is shown in Fig. 2. Analysis of the curve indicates to us that the sensitivity and specificity of the US is 67 and 96%, respectively, if we take a cut-off point of 0.70. We are also able to observe that, on taking a cut-off point with a value of 0.63, sensitivity increases to 78% and specificity decreases to 88%.
Discussion To date, renal scintigraphy with 99m Tc-DTPA (RS) continues to be the most sensitive and specific method to determine whether obstructive uropathy exists. However, the
Renal Doppler ultrasound vs renal scintigraphy in ureteropelvic junction obstruction 1,00 0,90 0,80
Sensitivity
0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00 0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
1 - Specificity
Figure 2
ROC curve.
availability of equipment to perform the RS continues to be a problem in many places. The results obtained in this work might suggest that the use of Doppler Ultrasound (DU) with RI measurement can comprise an alternative tool to suspect whether or not there is renal obstruction. This study shows that sensitivity can be of 67 up to 78%, and specificity, nearly 100%, depending on the cut-off point utilized. Our study, in addition to analyzing healthy kidneys, compared RI values with those of ectatic kidneys in the same patients, finding a statistically significant difference (p < 0.001). A study in 2004 reported that RI values in undilated kidneys of children vary significantly.12 Another study carried out in children aged less than 7 years conducted by Bude reported that the RI is age-dependent and that there is an inversely proportional relationship, that is, the RI diminishes as age increases.13 A research that included a group of 29 children with unilateral hydronephrosis, 10 patients showed acute obstruction caused by ureteral stone and 7 had UPJO. Twelve patients had nonobstructive hydronephrosis. From a control group (n = 32), the mean RI was 0.61. In children with acute obstruction and UPJO, RIs were 0.69 and 0.631 respectively. In nonobstructive dilatation, RI was 0.61. RI differences were statistically significant between groups (p < 0.01) and also in patients with obstructive and nonobstructive hydronephrosis (p < 0.01). With regards to identification of acute obstruction, RI ≥ 0.70 was found to have 70% sensitivity and 92% specificity.14 In 1992, Tublin et al. reported a study with the objective of determining the sensitivity of renal duplex Doppler sonography in the detection of patients with acute renal colic. Patients underwent gray scale and duplex Doppler sonography followed by IntraVenous Urography (IVG) or Retrograde Pyelography (RP). The 59% of patients were found to have obstruction based on IVP and on RP. Of the 19 patients with urinary obstruction, 15 had sonographic evidence of hydronephrosis. The mean RI of obstructed and nonobstructed was 0.67 ± 0.09 (0.52---0.8) and 0.6 ± 0.07 (0.47---0.76), respectively (p < 0.004). It is noteworthy that 12 of the obstructed kidneys had mean RI values of less than 0.7, and that the seven nonobstructed kidneys had mean RI values greater than 0.7. Based on an RI value of 0.7, sensitivity and specificity of DU for the diagnosis of acute renal colic were 37 and 84%, respectively.15 One year later, Platt and colleagues measured the RI in patients with symptoms of acute renal colic. After DU, confirmation of obstruction was obtained with IVU
423
in 23 patients. The mean RI for 23 obstructed kidneys was 0.77 ± 0.07, which was significantly higher than the mean RI for the contralateral normal kidneys (0.60 ± 0.04) (p < 0.001). RI elevation occurred before collecting-system dilatation in four of the 23 patients with obstructed kidney.16 Mileti´ c et al. evaluated the reliability of Doppler waveform alterations in diagnosis acute unilateral renal obstruction vs non nonrenal abdominal problems as control group. The mean RI in control group was 0.64 vs. 0.72 in the acute renal-obstruction group (p < 0.01). Reported sensitivity and specificity was 94 and 99%, respectively.17 Shokeir in 1999 reported the role of DU in patients with diagnosis of acute unilateral renal obstruction in 117 patients. Patients were evaluated with IVU and DU with the determination RI. IVU reported normal kidneys in 49 patients and unilateral ureteral obstruction in 68. The last group had a normal contralateral kidney. For the 68 obstructed kidneys the mean RI was 0.73, higher than the mean RI of 0.64 in 166 normal kidneys (p < 0.001). For all of the patients, RI was sensitive in 77% and specific in 83%.18 Other studies have shown differences between RI of hydronephrotic kidneys before nephrostomy and the normal contralateral kidney in 229 cases with a threshold of 0.70. The sensitivity and specificity of the Doppler diagnosis of obstruction were 92 and 88%, respectively.19,20 The previously mentioned studies were conducted mainly in adult patients. However, the scarce information related with minors coincides with various aspects, especially that of demonstrating that IR is found elevated in children and adults with unilateral obstructive uropathy. The information also reveals sensitivity values ranging from 37 to 94% and specificity, from 83 to 99%. Our study demonstrates 68---78% sensitivity and 88---96% specificity depending on the cut-off point established based on the Receiver Operating Characteristic (ROC) curve. Riahinezhad et al. reported a study, which included 39 children aged 2 months to 13 years with unilateral hydronephrosis. Only 5 children showed a complete obstructive pattern after renal scintigraphy. The classic indices of doppler duplex (resistive index and pulsatility index) did not show the ability to make a difference between the obstructive and non-obstructive patterns. However, the delta RI between two kidneys of each patient could differentiate the non-obstructive condition (p 0.006). A cutoff value of 0.055 has a sensitivity of 60% and a specificity of 82.2%.21 Their results are very similar to our results. However, our work included 18 patients with an obstructive pattern after renal scintigraphy, which is, and advantage regarding the sample and statistics. An important contribution of this work is that sensitivity and specificity values are obtained based on the results of the renal scintigraphy with 99m Tc-DTPA which can be considered as one of the most sensitive (88---100%) and specific (73---79%) studies available.
Conclusion Clearly the RS is a diagnostic tool that contributes definitive information for decision-making in the diagnosis and treatment of minors with UPJO. However, the results of our work coincide with the sensitivity and specificity values of other
424 authors. Taken together, these data can define DU as a reliable tool and more accessible, fast, and cost-effective than RS, in addition to its being able to be applied in patients of any age. With the results obtained, we can suggest that ultrasound Doppler with measurement of Resistive Index can be an alternative tool to the Renal scintigraphy with 99m Tc-DTPA in some cases. This does not imply that it should be substituted for the scintigraphy, in that the data that can be obtained from the latter are much broader and of great usefulness in determining diagnosis and definitive treatment.
References 1. Hashim H, Woodhouse C. Ureteropelvic junction obstruction. Eur Urol Suppl. 2012;11:25---32. 2. Becker AM. Postnatal evaluation of infants with an abnormal antenatal renal sonogram. Curr Opin Pediatr. 2009;21:207---13. 3. Bernard M, Waldo C. Ureteropelvic junction anomalies: congenital ureteropelvic junction problems in children. In: Gearhart J, Rink R, Mouriquand P, editors. Pediatric urology. Philadelphia: Saunders Elsevier; 2010. p. 248---82. 4. Conway JJ, Maizels M. The ‘well tempered’ diuretic renogram: a standard method to examine the asymptomatic neonate with hydronephrosis or hydroureteronephrosis. A report from combined meetings of The Society for Fetal Urology and members of The Pediatric Nuclear Medicine Council --- The Society of Nuclear Medicine. J Nucl Med. 1992;33:2047---51. 5. Sty JR, Pan CG. Genitourinary imaging techniques. Pediatr Clin North Am. 2006;53:339---61. 6. O’Reilly P, Aurell M, Britton K, Kletter K, Rosenthal L, Testa T. Consensus on diuresis renography for investigating the dilated upper urinary tract Radionuclides in Nephrourology Group. Consensus Committee on Diuresis Renography. J Nucl Med. 1996;37:1872---6. 7. Wong DC, Rossleigh MA, Farnsworth RH. Diuretic renography with the addition of quantitative gravity-assisted drainage in infants and children. J Nucl Med. 2000;41:1030---6. 8. Tripathi M, Chandrashekar N, Phom H, Gupta DK, Bajpai M, Bal C, et al. Evaluation of dilated upper renal tracts by technetium99m ethylenedicysteine F+O diuresis renography in infants and children. Ann Nucl Med. 2004;18:681---7.
A. Ruiz-Martínez et al. 9. Lee B, O’Reilly P, Roy C. Urinary obstruction. In: Pollack H, McClennan B, editors. Clinical urography. Philadelphia: WB Saunders Company; 2000. p. 1846---50. 10. European Association of Nuclear Medicine. Dosage card (Version 5.7.2016). Available from: http://www.eanm.org/docs/EANM Dosage Card 040214.pdf [accessed 29.06.16]. 11. Cosenza NN, Lau F, Lima MCL, Amorim BJ, Mosci C, Lima ML, et al. Influence of bladder fullness on the detection of urinary tract obstruction by dynamic renal scintigraphy. Radiol Bras. 2017;50:237---43, http://dx.doi.org/10.1590/ 0100-3984.2016-0061. 12. Gill B, Palmer LS, Koenigsberg M, Laor E. Distribution and variability of resistive index values in undilated kidneys in children. Urology. 1994;44:897---901. 13. Bude RO, DiPietro MA, Platt JF, Rubin JM, Miesowicz S, Lundquist C. Age dependency of the renal resistive index in healthy children. Radiology. 1992;184:469---73. 14. Brkljaci´ c B, Kuzmi´ c AC, Dmitrovi´ c R, Rados M, Vidjak V. Doppler sonographic renal resistance index and resistance index ratio in children and adolescents with unilateral hydronephrosis. Eur Radiol. 2002;12:2747---51. 15. Tublin ME, Dodd GD 3rd, Verdile VP. Acute renal colic: diagnosis with duplex Doppler US. Radiology. 1994;193:697---701. 16. Platt JF, Rubin JM, Ellis JH. Acute renal obstruction: evaluation with intrarenal duplex Doppler and conventional US. Radiology. 1993;186:685---8. 17. Mileti´ c D, Fuckar Z, Susti´ c A, Mozetic V, Smokvina A, Stanci´ c M. Resistance and pulsatility indices in acute renal obstruction. J Clin Ultrasound. 1998;26:79---84. 18. Shokeir AA, Abdulmaaboud M. Resistive index in renal colic: a prospective study. BJU Int. 1999;83:378---82. 19. Tublin ME, Bude RO, Platt JF. The resistive index in renal Doppler sonography: where do we stand? AJR Am J Roentgenol. 2003;180:885---92. 20. Platt J, Rubin J, Ellis J. Distinction between obstructive and nonobstructive pyelocaliectasis duplex Doppler sonography. AJR Am J Roentgenol. 1989;153:997---1000. 21. Riahinezhad M, Sarrami A, Gheisari A, Shafaat O, Merikhi A, Karami M, et al. How may Doppler indices help in the differentiation of obstructive from nonobstructive hydronephrosis? J Res Med Sci. 2018;23:76, http://dx.doi.org/10.4103/ jrms.JRMS 627 17.
Actas Urol´ ogicas Espa˜ nolas www.elsevier.es/actasuro
ORIGINAL ARTICLE
Renal Doppler ultrasound resistive index vs. renal scintigraphy with 99m Tc-DTPA as diagnostic test for ureteropelvic junction obstruction in children夽 A. Ruiz-Martínez a , E. Sierra-Díaz b,∗ , A.J. Celis-de la Rosa c , M.Á. Valenzuela Hernández d , M.G. González Flores e , M.V. Belmonte Hernández b a
Departamento de Cirugía Pediátrica, Hospital general de Zona 67, Instituto Mexicano del Seguro Social (IMSS), Apodaca, Nuevo León, Mexico b Departamento de Urología, Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social (IMSS), Guadalajara, Jalisco, Mexico c Departamento de Salud Pública, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico d Departamento de Medicina Nuclear, Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social (IMSS), Guadalajara, Jalisco, Mexico e Departamento de Radiología e Imagen, Centro Médico Puerta de Hierro, Guadalajara, Jalisco, Mexico Received 6 November 2018; accepted 13 February 2019 Available online 20 September 2019
KEYWORDS Ureteropelvic junction obstruction in children; Doppler ultrasound; Resistive index; Renal scintigraphy with 99m Tc-DTPA
Abstract Objective: A cross-sectional study was carried out with the objective of evaluating the usefulness of Doppler ultrasound with resistive index (RI) measure compared with renal scintigraphy with 99m Tc-DTPA in children with unilateral ureteropelvic junction obstruction. Methods: The study included children under 15 years with a diagnosis of unilateral ureteropelvic junction obstruction, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. The selected patients were sent to the Nuclear Medicine Department to carry out a renal scintigraphy with 99m Tc-DTPA and days later were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with RI. Results: A total of 21 patients were included in the study, 15 males and 6 females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years. Only 3 had an antecedent of ureteropyeloplasty in the affected kidney. The scintigraphy reported data of unilateral obstruction in 18 patients, including the 3 patients with previous surgery. The average glomerular filtration rate (GFR) obtained with the scintigraphy was 100.28 ml/min. The average GFR in affected
夽 Please cite this article as: Ruiz-Martínez A, Sierra-Díaz E, Celis-de la Rosa AJ, Valenzuela Hernández MÁ, González Flores MG, Belmonte Hernández MV. Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99m Tc-DTPA para el diagnóstico de nos. Actas Urol Esp. 2019;43:419---424. estenosis ureteropiélica en ni˜ ∗ Corresponding author. E-mail address: [email protected] (E. Sierra-Díaz).
2173-5786/© 2019 AEU. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
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A. Ruiz-Martínez et al. kidneys was 43.03 ml/min and 57.24 ml/min in healthy kidneys (p < .001). Doppler ultrasound with RI reported ectasia in 100% of the affected kidneys and one normal contralateral kidney. The average RI in affected kidneys was 0.69 mm/s and 0.50 mm/s in healthy kidneys (p < .001). Conclusions: With the results obtained, we can suggest that ultrasound Doppler with measurement of RI can be an alternative tool to renal scintigraphy with 99m Tc-DTPA in some cases. © 2019 AEU. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE Estenosis ureteropiélica en ni˜ nos; Ecografía Doppler; Índices de resistencia; Gammagrafía renal con 99m Tc-DTPA
Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99m Tc-DTPA para el diagnóstico de estenosis ureteropiélica en ni˜ nos Resumen Objetivo: Se llevó a cabo un estudio de corte transversal con el objetivo de evaluar la utilidad de la ecografía Doppler con índice de resistencia (IR) en comparación con la gammagrafía renal con 99m Tc-DTPA en ni˜ nos con estenosis ureteropiélica unilateral. Métodos: El estudio incluyó ni˜ nos menores de 15 a˜ nos con diagnóstico de estenosis ureteropiélica unilateral, ri˜ nón contralateral sano con o sin antecedente de plastia ureteropiélica. Los pacientes seleccionados se derivaron al Departamento de Medicina Nuclear para llevar a cabo la gammagrafía renal y días más tarde se derivaron al Departamento de Radiología para la realización de la ecografía Doppler renal con IR. Resultados: Un total de 21 pacientes fueron incluidos en el estudio, 15 hombres y 6 mujeres, que representan el 71,4% y el 28,6%, respectivamente. La edad promedio fue de 5,3 a˜ nos. Solo 3 tuvieron un antecedente de plastia ureteropiélica en el ri˜ nón afectado. La gammagrafía renal informó datos de obstrucción unilateral en 18 pacientes, incluidos los 3 pacientes con cirugía previa. La tasa promedio de filtración glomerular (TFG) en general obtenida con la gammagrafía fue de 100,28 ml/min. El promedio de TFG fue de 43,03 ml/min en los ri˜ nones afectados y de 57,24 ml/min en los ri˜ nones sanos (p < 0,001). La ecografía Doppler con IR reportó ectasia en el 100% de los ri˜ nones afectados y en un ri˜ nón contralateral normal. El IR promedio fue de 0,69 mm/s en los ri˜ nones afectados y de 0,50 mm/s en los ri˜ nones sanos (p < 0,001). Conclusiones: Con los resultados obtenidos, podemos sugerir que la ecografía Doppler renal con medición del IR puede ser una herramienta alternativa a la gammagrafía renal con 99m Tc-DTPA en algunos casos. © 2019 AEU. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
Introduction UreteroPelvic Junction Obstruction (UPJO) is defined as a blockage of urine flow from the kidney into the proximal ureter. This blockage may result in progressive damage to the kidney function secondary to backpressure and hydronephrosis. This is why it is of great importance to understand how to diagnose and treat this pathology.1 Incidence of UPJO has been estimated in 1 in 1000---1500 newborns and is the first cause of antenatal hydronephrosis. UPJO is 3 times more common in males and 20---25% of cases may be bilateral. Intrinsic stenosis, insertion anomaly of the ureters, peripelvic fibrosis, peristaltic abnormalities, and blood vessels crossing the ureter have been studied as causes of UPJO.2 Renal scintigraphy with 99m Tc-DTPA (RS) is the most widely used noninvasive test to determine the degree and dynamics of ureteropelvic urine-transport problems in children. During last years, several protocols and techniques have been developed; this has produced significant variability in interpretive criteria and results among different nuclear medicine laboratories. Correlation with other techniques, such as pressure flow studies, also has been poor.3
In order to promote standardization of the technique and protocols, three consensus papers have been published as follows: from the Society Fetal Urology; the Pediatric Nuclear Medicine Council, and the Ninth International Symposium on Radionuclides in Nephrourology.3---6 In clinical practice, one of the main points before defining UPJO management is to differentiate between obstructive and nonobstructive dilatation. As mentioned previously, RS is the most widely used test. The sensitivity and specificity reported for this test are 88---100% and 73---79, respectively.7,8 In Mexico, the availability of nuclear medicine is limited to some Medical Centers of the Government Health System and in some private hospitals. UltraSonography (US) has been utilized as first modality in the evaluation of congenital renal obstruction. Although renal US is an ideal noninvasive method for detecting infant hydronephrosis, the significance of the upper tract dilation is more difficult to assess because it does not reveal renal function. Investigations with Doppler Ultrasound (DU) have yielded advances in some areas. Resistive Index (RI) is a measure of resistance to blood flow through the kidney and is defined as peak systolic frequency shift minus end diastolic frequency shift divided by peak systolic frequency shift. Any
Renal Doppler ultrasound vs renal scintigraphy in ureteropelvic junction obstruction condition that raises impedance to blood flow through the kidney may raise the RI.9 We designed this cross-sectional study with the objective of evaluating the usefulness of DU with RI measure compared with RS in children with unilateral UPJO.
Materials and methods Our study universe comprised patients seen as outpatients during a 1-year time period at the Pediatric Urology Department of the Pediatric Hospital of the Western National Medical Center of the National Institute of Social Security (IMSS) in the state of Jalisco, Mexico. The institutional ethics committee authorized the study protocol with the registration number R-2012-1302-25. Patients and parents were informed about the study. We included in the study patients of both sexes aged between 8 months and 15 years with a diagnosis of unilateral ureteropelvic stenosis, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. Patients were not included if they had a sole kidney, lithiasis, VesicoUreteral Reflux (VUR), or other congenital urinary-tract malformations. The selected patients were to the Nuclear Medicine Department to carry out a renal scintigraphy with 99m TcDTPA. Two to 4 weeks after the scintigraphy, the patients were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with the measurement of Resistive Index (RI). The affected kidney was treated as the case and the normal kidney as the control. An experienced pediatric Radiologist and a Nuclear Medicine Physician carried out the DU and RS, respectively. The Radiologist was not informed of the result of the scintigraphy prior to performing the Doppler ultrasound.
Renal scintigraphy with
99m Tc-DTPA
Radiopharmaceutical and patient preparation for study To prepare the radiopharmaceutical (99m Tc-DTPA), the kit ® Pentacis was used and adjusted by weight and age according by the European Association of Nuclear Medicine. Labeling control was defined as a labeling efficiency of ≥90%.10 Patients drank 250---500 ml of water 1 h before to start of the test. Patients were also asked to empty the bladder before the study. Protocol for renal scintigraphy with 99m Tc-DTPA A scintillation camera (Phillips System Precedence 16, ® SPECT/CT ) equipped with low-energy general-use collimators was used to perform the tests. Acquisition of dynamic image started after administration of the 99m Tc-DTPA as an intravenous bolus injection. For the blood flow phase one image was obtained every 2 s for 60 s and for the functional phase one image was obtained every 60 s for 30 min. Sequential phase were acquired over a 30-min with the patient in the supine position, with posterior projection with a 64 × 64 matrix, for the kidneys and bladder included in the field of view. After urination, the diuretic Furosemide (1 mg/kg) was administered intravenously.11
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Processing Analyses were performed by delineating Regions of Interest (ROI) around each kidney and in the aorta in the dynamic images obtained during the vascular phase, calculating timeactivity curves for each kidney vs. the time in seconds. The dynamic images obtained every 1 min during functional phase, and ROI were drawn around each kidney and their collecting systems. The background was subtracted utilizing defined ROI around the outer perimeter for each kidney. Evaluation of 99m Tc-DTPA eliminated was adapted from the T½ method, indicative of an obstructive kidney if the proportional elimination was <50% at 20 min, corresponding to a T½ of >20 min, indicative of an unobstructed kidney if the proportional elimination was ≥60% at 20 min, corresponding to a T½ of <15 min, or undetermined if the proportional elimination was 50---60% at 20 min.11 The complete protocol performing Renal scintigraphy with 99m TcDTPA may be consulted on cited references.10,11 Renal Doppler ultrasound and resistive index measure Renal Doppler ultrasound was carried out with a highfrequency linear transducer (iSTYLE Toshiba Medical Systems Corporation) as well as convex multifrequency, depending on patient’s age group. We evaluated the morphological aspects, dimensions, and degree of renal ectasia. This was assessed in Mode B as well as in Doppler, pulsated Doppler assessing renal artery, segmental, interlobar and arcuate arteries in both kidneys, with a minimum of three cycles to obtain systolic peak, diastolic peak, and an RI of 3. The value of the RI reported was defined based on minimal and maximal values (average). For data analysis, we employed descriptive statistics, Student t test for mean difference, Fisher exact test for correlation, and tests to calculate sensitivity and specificity. Calculations were performed with Excel tables and the OpenEpi ver. 3 statistical software programs.
Results During the study period, we detected 77 patients with renal ectasic data at different grades. With the use of imaging studies, we discarded for the study patients with vesicoureteral reflux, posterior ureteral valves, congenital mega-ureter, lithiasis, ureteroceles, and bilateral UPJO. A total of 21 (n = 21) patients were included in the study, 15 males and six females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years, with a range of 1---14 years. Of the 21 patients, only three had an antecedent of ureteropyeloplasty in the affected kidney; the remainder of the 21 patients had no surgical antecedent. Of the kidneys affected, 16 were right-side and five were left-side, corresponding to 76.2% and 23.8%, respectively. The scintigraphy conducted reported data of unilateral obstruction in 18 of patients, included the 3 patients with previous of surgery. The remaining three patients only showed ectasia of the renal pelvis with delay of elimination and good response to application of diuretic. The average glomerular filtration rate (GFR) in general obtained with the scintigraphy was 100.28 ml/min. The average GFR in affected kidneys was 43.03 ml/min (27---59) and 57.24 ml/min (45---62) in healthy kidneys (p < 0.001).
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Table 1
RI results (mm/s) and the GFR (ml/min).
Age 7 2 *9 O 14 1 1 O 13 4 1 1 *9 10 1 4 *2 1 1 10 1 O 15 5 5.33
Ectasic kidney RI 0.7 0.5 0.36 0.9 0.75 0.72 0.65 0.51 0.76 0.71 0.52 0.8 0.86 0.56 0.68 0.86 0.78 0.76 0.75 0.77 0.63 0.69
Normal kidney RI 0.25 0.43 0.42 0.5 0.43 0.45 0.54 0.37 0.45 0.5 0.56 0.48 0.63 0.52 0.45 0.75 0.45 0.6 0.53 0.62 0.62 0.50
GFR ectasic kidney
GFR normal kidney
41 45 50 45 42 51 43 45 40 42 45 39 43 48 59 42 40 42 44 27 31 43.04
58 61 56 54 58 60 61 57 58 59 45 50 62 56 56 54 61 60 58 62 56 57.23
GFR 99 106 106 99 100 111 104 102 98 101 90 89 105 104 115 96 101 102 102 89 87 100.29
RI: resistive Index; GFR: glomerular filtration rate; *NonObstructive Diuretic Renogram. OPrevious surgery. Average mean in blacks.
Table 2
Glomerural Filtration Rate
65
Coefficients.
60
Model
55
Unstandardized coefficients
50
B
Std. error
70.888 −34.741
4.525 7.340
Sig.
45
(Constant) DU
40 35
.000 .000
30 25 0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
Table 3 tables.
Calculation of sensitivity and specificity with 2-x-2
Resistive index
Figure 1 In this graph we are able to observe the inverse relation between the RI and the GFR on utilizing a paired analysis.
The carrying out of Doppler Ultrasound (DU) with measurement of the RI (Restive Index) reported ectasia in 100% of the affected kidneys and a normal contralateral kidney. The average RI in affected kidneys was 0.69 mm/s (0.3---0.9) and 0.50 mm/s (0.2---0.75) in healthy kidneys (p < 0.001). Based on what has been described in then literature,11 probable obstruction is considered in kidneys with a RI greater than 0.7 mm/s. Table 1 and Fig. 1 demonstrate the relationship of patients with RI values obtained on the DU and the GFR for each of the kidneys and the total. As a cross-sectional data analysis, the regression coefficient for the predictor is the difference in response per unit difference in the predictor. Output produced from linear regression is shown in Table 2. On relating the results of the scintigraphy with those obtained in the Doppler Ultrasound (DU), we obtained the following results: obstructed patients with elevated RI, 12; obstructed patients with normal RI, six; nonobstructed
Measure
%
Sensitivity Specificity
66.67 96
95%CI (43.75---83.72) (43.85---100)
patients with elevated IR, none; and nonobstructed patients with normal RI, three. On analyzing these values in a 2-x-2 table for sensitivity and specificity, we obtained the results presented in Table 3. We also performed a ROC curve that is shown in Fig. 2. Analysis of the curve indicates to us that the sensitivity and specificity of the US is 67 and 96%, respectively, if we take a cut-off point of 0.70. We are also able to observe that, on taking a cut-off point with a value of 0.63, sensitivity increases to 78% and specificity decreases to 88%.
Discussion To date, renal scintigraphy with 99m Tc-DTPA (RS) continues to be the most sensitive and specific method to determine whether obstructive uropathy exists. However, the
Renal Doppler ultrasound vs renal scintigraphy in ureteropelvic junction obstruction 1,00 0,90 0,80
Sensitivity
0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00 0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
1 - Specificity
Figure 2
ROC curve.
availability of equipment to perform the RS continues to be a problem in many places. The results obtained in this work might suggest that the use of Doppler Ultrasound (DU) with RI measurement can comprise an alternative tool to suspect whether or not there is renal obstruction. This study shows that sensitivity can be of 67 up to 78%, and specificity, nearly 100%, depending on the cut-off point utilized. Our study, in addition to analyzing healthy kidneys, compared RI values with those of ectatic kidneys in the same patients, finding a statistically significant difference (p < 0.001). A study in 2004 reported that RI values in undilated kidneys of children vary significantly.12 Another study carried out in children aged less than 7 years conducted by Bude reported that the RI is age-dependent and that there is an inversely proportional relationship, that is, the RI diminishes as age increases.13 A research that included a group of 29 children with unilateral hydronephrosis, 10 patients showed acute obstruction caused by ureteral stone and 7 had UPJO. Twelve patients had nonobstructive hydronephrosis. From a control group (n = 32), the mean RI was 0.61. In children with acute obstruction and UPJO, RIs were 0.69 and 0.631 respectively. In nonobstructive dilatation, RI was 0.61. RI differences were statistically significant between groups (p < 0.01) and also in patients with obstructive and nonobstructive hydronephrosis (p < 0.01). With regards to identification of acute obstruction, RI ≥ 0.70 was found to have 70% sensitivity and 92% specificity.14 In 1992, Tublin et al. reported a study with the objective of determining the sensitivity of renal duplex Doppler sonography in the detection of patients with acute renal colic. Patients underwent gray scale and duplex Doppler sonography followed by IntraVenous Urography (IVG) or Retrograde Pyelography (RP). The 59% of patients were found to have obstruction based on IVP and on RP. Of the 19 patients with urinary obstruction, 15 had sonographic evidence of hydronephrosis. The mean RI of obstructed and nonobstructed was 0.67 ± 0.09 (0.52---0.8) and 0.6 ± 0.07 (0.47---0.76), respectively (p < 0.004). It is noteworthy that 12 of the obstructed kidneys had mean RI values of less than 0.7, and that the seven nonobstructed kidneys had mean RI values greater than 0.7. Based on an RI value of 0.7, sensitivity and specificity of DU for the diagnosis of acute renal colic were 37 and 84%, respectively.15 One year later, Platt and colleagues measured the RI in patients with symptoms of acute renal colic. After DU, confirmation of obstruction was obtained with IVU
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in 23 patients. The mean RI for 23 obstructed kidneys was 0.77 ± 0.07, which was significantly higher than the mean RI for the contralateral normal kidneys (0.60 ± 0.04) (p < 0.001). RI elevation occurred before collecting-system dilatation in four of the 23 patients with obstructed kidney.16 Mileti´ c et al. evaluated the reliability of Doppler waveform alterations in diagnosis acute unilateral renal obstruction vs non nonrenal abdominal problems as control group. The mean RI in control group was 0.64 vs. 0.72 in the acute renal-obstruction group (p < 0.01). Reported sensitivity and specificity was 94 and 99%, respectively.17 Shokeir in 1999 reported the role of DU in patients with diagnosis of acute unilateral renal obstruction in 117 patients. Patients were evaluated with IVU and DU with the determination RI. IVU reported normal kidneys in 49 patients and unilateral ureteral obstruction in 68. The last group had a normal contralateral kidney. For the 68 obstructed kidneys the mean RI was 0.73, higher than the mean RI of 0.64 in 166 normal kidneys (p < 0.001). For all of the patients, RI was sensitive in 77% and specific in 83%.18 Other studies have shown differences between RI of hydronephrotic kidneys before nephrostomy and the normal contralateral kidney in 229 cases with a threshold of 0.70. The sensitivity and specificity of the Doppler diagnosis of obstruction were 92 and 88%, respectively.19,20 The previously mentioned studies were conducted mainly in adult patients. However, the scarce information related with minors coincides with various aspects, especially that of demonstrating that IR is found elevated in children and adults with unilateral obstructive uropathy. The information also reveals sensitivity values ranging from 37 to 94% and specificity, from 83 to 99%. Our study demonstrates 68---78% sensitivity and 88---96% specificity depending on the cut-off point established based on the Receiver Operating Characteristic (ROC) curve. Riahinezhad et al. reported a study, which included 39 children aged 2 months to 13 years with unilateral hydronephrosis. Only 5 children showed a complete obstructive pattern after renal scintigraphy. The classic indices of doppler duplex (resistive index and pulsatility index) did not show the ability to make a difference between the obstructive and non-obstructive patterns. However, the delta RI between two kidneys of each patient could differentiate the non-obstructive condition (p 0.006). A cutoff value of 0.055 has a sensitivity of 60% and a specificity of 82.2%.21 Their results are very similar to our results. However, our work included 18 patients with an obstructive pattern after renal scintigraphy, which is, and advantage regarding the sample and statistics. An important contribution of this work is that sensitivity and specificity values are obtained based on the results of the renal scintigraphy with 99m Tc-DTPA which can be considered as one of the most sensitive (88---100%) and specific (73---79%) studies available.
Conclusion Clearly the RS is a diagnostic tool that contributes definitive information for decision-making in the diagnosis and treatment of minors with UPJO. However, the results of our work coincide with the sensitivity and specificity values of other
424 authors. Taken together, these data can define DU as a reliable tool and more accessible, fast, and cost-effective than RS, in addition to its being able to be applied in patients of any age. With the results obtained, we can suggest that ultrasound Doppler with measurement of Resistive Index can be an alternative tool to the Renal scintigraphy with 99m Tc-DTPA in some cases. This does not imply that it should be substituted for the scintigraphy, in that the data that can be obtained from the latter are much broader and of great usefulness in determining diagnosis and definitive treatment.
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