Abstract
Background
Pyeloplasty currently stands as the standard treatment for UPJO. Our study aimed to assess the diagnostic value of sonographic parameters following Lasix administration in patients who underwent pyeloplasty to predict the recurrence of obstruction and the need for reoperation.
Methods
The study included 70 children with UPJO who underwent pyeloplasty. Renal ultrasound was performed on patients three to six months after pyeloplasty. Following the Lasix administration, the changes in ultrasound parameters at the 18th and 30th minute were documented. Within two weeks, patients underwent radioisotope renography. Diuretic ultrasound's diagnostic value in predicting the need for reoperation was assessed through a comparison with radioisotope renography.
Results
The average age of the patients was 3.94 ± 3.52 years. Anteroposterior diameter of the renal pelvis (APD) changes at 18 and 30 min, and the average APD after surgery at 18 and 30 min was significantly higher in patients requiring reoperation. The best cutoff point of APD changes in the 18th minute was 9.50 (sensitivity = 91.7%, specificity = 82.8%). The best cutoff point of APD after surgery in the 18th minute was 25.90 (sensitivity = 91.7%, specificity = 81.0%). The best cutoff points of the resistive index (RI) in the 18th and 30th minutes were reported as 0.70 (sensitivity = 41.7%, specificity = 50.0%) and 0.71 (sensitivity = 41.7%, specificity = 37.9%), respectively.
Conclusions
The assessment of ultrasound findings following pyeloplasty has revealed that changes in APD can serve as a reliable means for assessing the efficacy of the operation.
Similar content being viewed by others
Explore related subjects
Find the latest articles, discoveries, and news in related topics.1 Background
Hydronephrosis is a medical condition characterized by the dilation of the renal pelvis and calyces that occur because of urine retention or reflux. Prenatal hydronephrosis is found in approximately 1–5% of all pregnancies [1]. Ureteropelvic junction obstruction(UPJO) occurs in every 1:750–1500 live births and is known as the third most common cause of antenatal hydronephrosis, following transient and physiological hydronephrosis [2].
The reduction in urine flow from the renal pelvis to the ureter by UPJO leads to the dilation of the renal pelvis and calyces, subsequently causing hydronephrosis. UPJO is a multifactorial condition, with pathologic factors such as the hypoperistaltic ureteral segment, fetal folds of the upper ureter, or intrinsic strictures causing most cases of UPJO in children [3,4,5]. Ultrasound is a safe, noninvasive, and inexpensive tool for postnatal evaluation of children with antenatal hydronephrosis, posing no radiation exposure risk [6].
Pyeloplasty, as a standard procedure for surgical treatment of UPJO, has a success rate of 95–100% [7, 8]. Laparoscopic or retroperitoneoscopic procedures have been proposed as an alternative to the standard open procedure, with encouraging outcomes. All pyeloplasty approaches have advantages and disadvantages, and no definitive evidence exists to determine the best approach [9]. Following up the child after pyeloplasty is recommended to identify recurrent obstruction or loss of kidney function. Reoperation is needed for up to 5% of children after pyeloplasty [2]. The aim of pyeloplasty is to conserve renal function. After the operation, the success of pyeloplasty is evaluated with renal ultrasounds and radioisotope renography. There has yet to be a consensus regarding the follow-up plan. Some surgeons opt for an early ultrasound in the third month after surgery and diuretic renography between the third and sixth month [10]. Other researchers have asserted that follow-up should last up to two years, including when the first signs of recurrence (infection and pain) are most likely to occur [11]. The most common method to assess obstruction after surgery is radioisotope renography. However, ultrasound has recently been proposed as a feasible option and has gradually gained popularity among physicians [10, 12, 13].
The aim of this study was to determine the diagnostic value of ultrasound parameters following the administration of Lasix in patients who underwent pyeloplasty. Ultrasound results were compared to DMSA renography to assess the ability of ultrasound to predict obstruction recurrence and reoperation necessity.
2 Methods
This research was conducted from 2021 through 2022 in the pediatric ultrasound department of Akbar and Dr. Sheikh Mashhad hospitals. The current study includes children between 3 months and 12 years of age who were diagnosed with severe hydronephrosis in radioisotope renography and underwent pyeloplasty for UPJO. The study excluded patients with anatomical abnormalities such as horseshoe kidney, duplex kidney, ectopia, and single kidney, as well as those with contraindications to Lasix intake.
Following three to six months of pyeloplasty, all patients underwent renal ultrasound. An experienced pediatric radiologist, using the same device, performed an ultrasound on all patients with an empty bladder.
Initially, an ultrasound was conducted to determine the APD of the renal pelvis, the resistive index of intraparenchymal arteries, and the minimum and maximum thickness of the kidney parenchyma. A blinded expert radiologist did all renal ultrasounds. The APD diameter for all patients was measured as the maximal diameter of the intrarenal pelvis in the mid renal transverse plane in supine position [14, 15]. Then, Lasix was administered to all patients at a dose of 1 mg/kg. Ultrasound was then conducted after 18 and 30 min, and the same parameters were assessed. The ultrasound parameters changes following the Lasix administration were recorded. Following the ultrasound, all patients underwent radioisotope renography within a maximum of two weeks. The aim was to assess obstruction and recurrence of hydronephrosis (surgical failure). Patients who showed obstruction in the renography required reoperation. The diagnostic value of ultrasound to predict the need for reoperation and recurrence of obstruction was determined by comparing the ultrasound results and changes following the administration of Lasix with radioisotope renography. We used 18 min post diuretic timing because Lasix maximum effect occurs approximately 18 min following intravenous injection and we used 30 min post diuretic timing because we wanted to have two measurement intervals to increase the analysis accuracy [16, 17].
After completing the checklist forms, the results were described as tables, figures, and central and dispersion indexes.
To calculate the sample size, the findings of Kiblawi et al.'s study were used [18]. Since the specificity of 89% provides a higher number compared to the sensitivity of 100%, we used the specificity parameter as the basis for calculating the sample size. We calculate the sample size as 66 people, considering the type 1 error of 0.05 and including 10% attrition. The normality of the data distribution was checked using the Kolmogorov–Smirnov test. The t-test and Mann–Whitney U test were conducted to identify the relationships among quantitative variables for data with normal and non-normal distributions, respectively. The chi-square and Fisher exact tests were used to determine the relationship among qualitative variables. Correlations were examined through the Pearson test for normally distributed data and the Spearman test for data with a non-normal distribution. Sensitivity, specificity, positive and negative predictive value, and accuracy were calculated based on standard formulas. The statistical analysis was conducted using SPSS version 10 (SPSS Inc., Chicago, IL, USA), and a P value < 0.05 was considered indicating statistical significance.
This study was approved by the medical ethics committee of the Mashhad University of Medical Sciences (Ethics code: IR.MUMS.MEDICAL.REC.1400.837). Informed consent was obtained from all participants’ parents to enter the study and they could withdraw from it whenever they did not want to continue the study. Patient data were entered anonymously to remain confidential.
3 Results
This study was conducted on 70 patients. The average age of the patients was 3.94 ± 3.52 years and 58 (82.9%) were girls, and 12 (17.1%) were boys. The left kidney was affected in 41 cases (58.6%) while the right kidney was affected in 29 cases (49.4%), and none of the UPJO cases were bilateral. According to the results of the DMSA renography, the patients were divided into two groups: 12 patients requiring reoperation and 58 patients not requiring reoperation.
The results of the ultrasound parameters examined in two categories of patients who required reoperation and those who did not are presented in Table 1.
The results show APD changes in 18 and 30 min after Lasix administration are significantly higher in patients requiring reoperation compared to the other group (P < 0.001 and 0.003, respectively). Additionally, the average post-surgery APD before Lasix administration and post-surgery APD at 18 and 30 min was significantly higher in the group requiring reoperation (P = 0.004, P < 0.001, P < 0.001, respectively). No significant difference was observed in the other parameters in the two groups.
Figure 1 shows the ROC curve of parameters related to the APD index.
Based on the analysis of APD changes at the 18th minute, the best cutoff point was 9.50, with a sensitivity of 91.7% and a specificity of 82.8%. In the analysis of the APD index after surgery in the 18th minute, the best cutoff point was 25.90, with a sensitivity of 91.7% and a specificity of 81.0%.
The analysis of other parameters relevant to APD is documented in Table 2.
Additional information concerning cutoff points, sensitivity, and specificity of parameters related to APD can be found in Table 2.
Figure 2 shows the ROC curve of parameters related to the resistive index.
In the analysis of RI parameters in the 18th and 30th minutes, the best cutoff points were reported as 0.70 (sensitivity 41.7% and specificity 50.0%) and 0.71 (sensitivity 41.7% and specificity 37.9%), respectively.
Other cutoff points, sensitivity, and specificity of parameters related to RI are reported in Table 3
Figure 3 shows the ROC curve of parameters related to parenchymal thickness.
The cutoff points, sensitivity, and specificity of parameters related to parenchymal thickness are displayed in Table 4. The results show that for the post-surgery parenchymal thickness index, both at the 18th and 30th minutes, the best cutoff point was 5.25, with a sensitivity of 41.7% and a specificity of 15.5%.
4 Discussion
In the last decade, the management of UPJO has become progressively observational despite the need for precise predictors of outcomes. Although the resolution of hydronephrosis and healthy kidneys is possible in many children, it is apparent that some are at risk of compromised renal functional development [19,20,21]. Due to our current knowledge, pyeloplasty is a surgical method that will maintain kidney function in patients; however, there is no approved method or protocol to indicate the procedure's success accurately [10]. The present study investigated the diagnostic value of the diuretic ultrasound for needing reoperation in infants undergoing pyeloplasty. The present study revealed that the diuretic ultrasound evaluation presents more eligible individuals for the reoperation pyeloplasty in comparison with the renal DMSA scan. We observed the best APD (18th minute after the surgery) sensitivity as 91.70% and specificity as 81.00%, while in the 30th minute after surgery, it was 75.00% and 82.80%, respectively. Moreover, APD changes at the 18th and 30th minutes after surgery revealed 91.70% and 83.30% sensitivity and 82.80% and 74.10% specificity, respectively.
According to previous studies, UPJO is known as a prevalent cause of unilateral hydronephrosis in infants and children; hence, pyeloplasty is the standard therapeutic approach, and its success will be indicated by clinical and imaging criteria [22]. Based on the findings of the study and by determining the cutoff and sensitivity and specificity for the variables, this study showed that some of these variables can help differentiate between memorial hydronephrosis after pyeloplasty and hydronephrosis that indicates the need for reoperation. Despite the high success rate of pyeloplasty, developing strong parameters for accurate follow-up of infants undergoing the procedure is still necessary. Based on the side effects associated with the DMSA scan, ultrasound approaches are predicted to become a prevalent feature in pyeloplasty follow-up protocols [13]. Several studies have indicated the APD changes before and after the surgery as a valuable follow-up marker. While Rickard et al. revealed over 40% reduces in APD as a valuable marker [13], Kiblawi et al. determined the 100% sensitivity and 89% specificity for APD changes in ultrasound investigations. Studies have found a significant increase in APD and its changes at the 18th and 30th minutes in cases that require reoperation based on the DMSA [18]. Although their study showed greater sensitivity and specificity, even indicating that APD reduction in ultrasound after pyeloplasty eliminates the need for reoperation, our findings did not yield the same high values they reported. These differences could be because of the variability in the APD calculation method and the studied population.
Similarly, Mohajerzadeh et al. [23] compared the ultrasound and DMSA scan outcomes as the follow-up instrument in infants and children who underwent pyeloplasty surgery. Despite our study, they evaluated the pelvic-cortex ratio and the percentage of pelvic improvement in APD six months after the surgery. However, they observed both sensitivity and specificity as 100% in the studied population; these revealed that APD evaluation in 3 and 6 months after the surgery could indicate higher accuracy values, while our reports showed 91.7% sensitivity and 82.8% specificity at the optimal level. On the other hand, Wickramasekara et al. [24] reported a low sensitivity and specificity of the APD reduction to predict the necessity of the pyeloplasty re-surgery. They have observed that a 25% reduction in the APD revealed 87% of sensitivity and 75% of specificity for the necessity of the pyeloplasty reoperation. Additionally, pelvic-cortex ratio and cortex thickness before and after the surgery were not determined as significant factors for the reoperation; however, the parenchymal thickness in the 18th and 30th minutes after surgery has been reported to be significantly lower in patients who need reoperation.
Moreover, Maria et al. reported that a 15% APD decrease could be significantly associated with pyeloplasty success; hence, a DMSA scan will be necessary if the ultrasound parameters do not improve 6 months after surgery [25]. However, Kiblawi et al. stated that any improvement in APD makes the DMSA scan unnecessary, and the DMSA scan should be used if the APD increase after the pyeloplasty surgery [18]. The findings and controversial reports on the diagnostic value of ultrasound parameters and the necessity of reoperation in infants undergoing pyeloplasty show the need to promote current knowledge. Ultrasound is a low-cost and noninvasive method compared to the standard method of evaluating the success of pyeloplasty. The results of the present study can be used to better understand and manage the complication of UPJO, its treatment, and follow-up. Our study evaluated the diagnostic value of ultrasound in infants and children undergoing pyeloplasty to determine the need for reoperation along with others, which can be used in designing guidelines for management and follow-up after pyeloplasty surgery using ultrasound. Given that ultrasound is an operator-dependent investigation, to reduce ultrasound interobserver variations we recommend that variables be measured by pediatric radiology experts.
Although the present study can be known as a novel study that determined the role of different parameters of the ultrasound, especially APD, in pyeloplasty reopration, it was limited in some aspects, including the retrospective design of the study, limited evaluated parameters, and the few studied population. Future studies should be conducted in the form of cohort and prospective studies, considering a larger sample size and multiple follow-ups with longer intervals. It is also recommended to evaluate different indicators, such as clinical manifestations, their progress, and the reduction percentage, to design appropriate guidelines.
5 Conclusions
The present study was designed and conducted to investigate the diagnostic value of diuretic ultrasound in infants and children undergoing pyeloplasty to determine the need for reoperation. Evaluation of the ultrasound findings after pyeloplasty, compared with renal DMSA scan to check successful operation in patients after pyeloplasty, shows that the changes in APD after surgery in 3- to 6-month follow-up can verify the operation's success. Considering multiple DMSA scans' potentially harmful side effects, performing ultrasound scans at regular intervals and reviewing their parameters would be advantageous in decision-making and patient management. However, further studies are required to determine more aspects of ultrasound efficacy in these terms.
Availability of data and materials
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
Abbreviations
- ADP:
-
Anteroposterior diameter of the renal pelvis
- UPJO:
-
Ureteropelvic junction obstruction
References
Nguyen HT, Herndon CA, Cooper C, Gatti J, Kirsch A, Kokorowski P et al (2010) The Society for Fetal Urology consensus statement on the evaluation and management of antenatal hydronephrosis. J Pediatr Urol 6(3):212–231
Värelä S, Omling E, Börjesson A, Salö M (2021) Resolution of hydronephrosis after pyeloplasty in children. J Pediat Urol 17(1):102
Maizels M, Stephens F (1980) Valves of the ureter as a cause of primary obstruction of the ureter: anatomic, embryologic and clinical aspects. J Urol 123(5):742–747
Adey GS, Vargas SO, Retik AB, Borer JG, Mandell J, Hendren WH et al (2003) Fibroepithelial polyps causing ureteropelvic junction obstruction in children. J Urol 169(5):1834–1836
Abbasi B, Seyed Hosseini M, Moodi Ghalibaf A, Akhavan R, Emadzadeh M, Bolvardi E (2022) Evaluating anemia on non-contrast thoracic computed tomography. Sci Rep 12(1):21380
Gharpure KV, Jindal B, Naredi BK, Krishnamurthy S, Dhanapathi H, Adithan S et al (2021) Calyx to parenchymal ratio (CPR): an unexplored tool and its utility in the follow-up of pyeloplasty. J Pediatr Urol 17(2):2344
Lee YS, Lee CN, Kim MU, Jang WS, Lee H, Im YJ et al (2014) The risk factors and clinical significance of acute postoperative complications after unstented pediatric pyeloplasty: a single surgeon’s experience. J Pediatr Surg 49(7):1166–1170
Kohno M, Ogawa T, Kojima Y, Sakoda A, Johnin K, Sugita Y et al (2020) Pediatric congenital hydronephrosis (ureteropelvic junction obstruction): Medical management guide. Int J Urol 27(5):369–376
Fedelini P, Verze P, Meccariello C, Arcaniolo D, Taglialatela D, Mirone VG (2013) Intraoperative and postoperative complications of laparoscopic pyeloplasty: a single surgical team experience with 236 cases. J Endourol 27(10):1224–1229
Fernández-Ibieta M, Nortes-Cano L, Guirao-Piñera MJ, Zambudio-Carmona G, Ruiz-Jiménez JI (2016) Radiation-free monitoring in the long-term follow-up of pyeloplasty: Are ultrasound new parameters good enough to evaluate a successful procedure? J Pediatr Urol 12(4):230
Nirmal T, Singh J (2008) Follow-up after pyeloplasty: How long? Indian J Urol 24(3):429–430
Cost NG, Prieto JC, Wilcox DT (2010) Screening ultrasound in follow-up after pediatric pyeloplasty. Urology 76(1):175–179
Rickard M, Braga L, Oliveria J-P, Romao R, Demaria J, Lorenzo A (2016) Percent improvement in renal pelvis antero-posterior diameter (PI-APD): prospective validation and further exploration of cut-off values that predict success after pediatric pyeloplasty supporting safe monitoring with ultrasound alone. J Pediatr Urol 12(4):228
Nguyen HT, Benson CB, Bromley B, Campbell JB, Chow J, Coleman B et al (2014) Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system). J Pediatr Urol 10(6):982–998
Hodhod A, Eid H, Capolicchio J-P, Petrella F, Sadri I, El-Sherbiny M et al (2023) How can we measure the renal pelvic anteroposterior diameter in postnatal isolated hydronephrosis? J Pediatr Urol 19(1):75–82
Sarkar SD (1992) Diuretic renography: concepts and controversies. Urol Radiol 14:79–84
Fine EJ (2001) Diuretic renography and angiotensin converting enzyne inhibitor renography. Radiol Clin North Am 39(5):979–995
Kiblawi R, Kuebler JF, Petersen C, Ure BM, Hofmann AD (2020) Ultrasound monitoring after pelvis-sparing dismembered pyeloplasty: high sensitivity and low specificity for the success of operation. Eur J Pediatr Surg 30(01):021–026
Passoni NM, Peters CA (2020) Managing ureteropelvic junction obstruction in the young infant. Front Pediatr 8:242
Tabari AK, Atqiaee K, Mohajerzadeh L, Rouzrokh M, Ghoroubi J, Alam A et al (2020) Early pyeloplasty versus conservative management of severe ureteropelvic junction obstruction in asymptomatic infants. J Pediatr Surg 55(9):1936–1940
Rickard M, Chua M, Kim JK, Keefe DT, Milford K, Hannick JH et al (2021) Evolving trends in peri-operative management of pediatric ureteropelvic junction obstruction: working towards quicker recovery and day surgery pyeloplasty. World J Urol 1:1–8
Hsi RS, Holt SK, Gore JL, Lendvay TS, Harper JD (2015) National trends in followup imaging after pyeloplasty in children in the United States. J Urol 194(3):777–782
Mohajerzadeh L, Khalili M, Shirvani A, Sarafi M, Hajesmaeili A, Ebrahimi G, et al (2022) Comparison of reliability of kidney ultrasound findings after pyeloplasty versus kidney isotope scans for success in patients with ureteropelvic junction obstruction. Iran J Pediatr (in press)
Wickramasekara N, Ignatius J, Lamahewage A (2023) Sonographic follow-up after pyeloplasty: a large, retrospective cohort analysis. Pediatr Surg Int 39(1):1–7
Arbeláez MCS, Nassau DE, Valencia IC, Blachman-Braun R, Alam A, Castellan M (2022) Ultrasonographic stabilization of hydronephrosis after pyeloplasty: Key determinant of postoperative follow-up? J Pediatr Urol 18(5):662
Acknowledgments
Not applicable.
Funding
The study is funded by Mashhad University of Medical Sciences, Mashhad, Iran.
Author information
Authors and Affiliations
Contributions
MMR, RA, AA, and HM conducted the main idea of the study. MMR and RA contributed to supervision. EH, AP, and NK contributed to data gathering. HM contributed to data analysis. EH, AP, NK contributed to drafting of the manuscript. All authors reviewed and accepted the manuscript.
Corresponding author
Ethics declarations
Ethics approval and consent to participate
This study was approved by the medical ethics committee of Mashhad University of Medical Sciences (Ethics code: IR.MUMS.MEDICAL.REC.1400.837). Informed consent was obtained from all patients to enter the study and they could withdraw from it whenever they did not want to continue the study. Patient data were entered anonymously to remain confidential.
Consent for publication
Not applicable.
Competing interests
The authors have no competing interests to declare.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
This article is published under an open access license. Please check the 'Copyright Information' section either on this page or in the PDF for details of this license and what re-use is permitted. If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and re-use information, please contact the Rights and Permissions team.
About this article
Cite this article
Rashed, M.M., Abbasioun, R., Aghaee, A. et al. Diagnostic value of diuretic ultrasound in evaluating the need for reoperation in children undergoing pyeloplasty. Afr J Urol 29, 49 (2023). https://doi.org/10.1186/s12301-023-00381-3
Received:
Accepted:
Published:
DOI: https://doi.org/10.1186/s12301-023-00381-3