A prospective comparative study conducted at a tertiary-care pediatric hospital in Cairo, Egypt, has identified a significant disparity in surgical outcomes for children undergoing pyeloplasty for pelvi-ureteric junction obstruction (PUJO). The research, published in the African Journal of Urology, demonstrates that pediatric patients presenting with an excessively dilated renal pelvis, defined by an anteroposterior diameter (APD) exceeding 50 millimeters, experience a higher rate of postoperative complications and a greater need for secondary surgical interventions compared to those with non-excessively dilated kidneys. This finding suggests that the degree of preoperative dilation serves as a critical marker for surgical risk, necessitating a modified surgical approach for the most severely affected patients.
The study enrolled 43 pediatric cases involving 46 renal units over a three-year period at the Abulreesh Pediatric Urology Unit of Cairo University Hospitals. The participants were divided into two distinct groups based on their preoperative ultrasound measurements. Group 1 consisted of 23 renal units with non-excessively dilated renal pelvises, where the APD ranged from 25 to 50 millimeters. Group 2 included 23 renal units with excessively dilated renal pelvises, characterized by an APD greater than 50 millimeters. The cohort had a male-to-female ratio of 3.8 to 1, with a mean age at presentation of 11.8 months for Group 1 and 16.5 months for Group 2, a difference that was not statistically significant.
Pelvi-ureteric junction obstruction is a congenital condition where the flow of urine from the renal pelvis to the proximal ureter is blocked, often leading to hydronephrosis and progressive renal deterioration if left untreated. While the Anderson-Hynes dismembered pyeloplasty is widely regarded as the gold standard for treating this obstruction with success rates typically reported between 90 and 100 percent, the specific outcomes for children with massively dilated kidneys had remained insufficiently defined in clinical literature. The researchers aimed to evaluate the functional and anatomical outcomes of this standard procedure in the context of extreme dilation, comparing it against standard cases to determine if a different surgical strategy was required.
The surgical technique employed was a standardized Anderson-Hynes dismembered pyeloplasty, performed or directly supervised by senior pediatric urologists. For patients in Group 1, the procedure involved the standard removal of only the stenotic or atretic segment of the pelvic wall. In contrast, for all patients in Group 2, the surgeons systematically performed a formal reduction of the redundant renal pelvis. This excisional reduction involved trimming and excising the aperistaltic, redundant pelvic wall tissue along its dependent border to fashion a funneled renal pelvis, thereby optimizing gravity-dependent clearance and preventing postoperative urinary stasis. This modification was applied in 100 percent of the excessively dilated cases, whereas it was only required in 52.2 percent of the non-excessively dilated cases.
Preoperative assessments revealed that the mean APD for Group 1 was 36.1 millimeters, significantly lower than the 65.5 millimeters observed in Group 2. The mean parenchymal thickness was 6.7 millimeters in Group 1 and 5.56 millimeters in Group 2, while the mean glomerular filtration rate (GFR) was 35.6 milliliters per minute in Group 1 and 31.4 milliliters per minute in Group 2. The operative time was significantly longer for the excessively dilated group, averaging 92.74 minutes compared to 77.45 minutes for the non-excessively dilated group. These baseline differences highlight the increased technical complexity and tissue volume associated with managing giant hydronephrosis in pediatric patients.
Postoperative follow-up was conducted at 3, 6, and 12 months using ultrasonography to measure changes in APD and parenchymal thickness. At 12 months, Group 1 showed a marked reduction in APD, dropping from a preoperative mean of 36.1 millimeters to 5.3 millimeters. In Group 2, the APD also decreased significantly from 65.5 millimeters to 29.1 millimeters, although the postoperative diameter remained significantly higher than that of Group 1. Parenchymal thickness improved in both groups, increasing from 6.7 millimeters to 9.8 millimeters in Group 1 and from 5.56 millimeters to 9.5 millimeters in Group 2, indicating a recovery of renal tissue health in both cohorts despite the initial severity of dilation.
Despite the anatomical improvements, the success rates and complication profiles diverged sharply between the two groups. Group 1 achieved a 100 percent success rate with no recorded postoperative complications. In contrast, Group 2 exhibited a significantly lower success rate and a higher incidence of adverse events. Transient postoperative fever, classified as Clavien-Dindo Grade I, occurred in 30.4 percent of patients in Group 2 and resolved with conservative management. More critically, 21.7 percent of patients in the excessively dilated group required secondary surgical intervention under general anesthesia, classified as Clavien-Dindo Grade IIIb. This included three cases of redo pyeloplasty due to progressive obstruction and two cases of secondary nephrectomy due to severe parenchymal loss and recurrent urinary tract infections.
Statistical analysis indicated that preoperative APD, age at presentation, and preoperative isolated GFR were significantly associated with surgical success, while age at surgery, preoperative creatinine levels, and parenchymal thickness were not. The researchers noted that a baseline APD exceeding 50 millimeters identifies a high-risk cohort susceptible to postoperative complications. The study suggests that simple relief of the anatomical obstruction at the ureteropelvic junction is often insufficient for massively dilated systems, as the floppy renal pelvis can act as a low-pressure reservoir leading to persistent stasis. Integrating extensive excisional reduction into the surgical protocol for these units helps restore upper tract anatomy and yields high overall success, although the risk of failure remains elevated compared to standard cases.
The authors acknowledge several limitations in their study, primarily the 12-month follow-up period, which may be insufficient to detect late failures, as 85 percent of failed pediatric pyeloplasties are reported within three years. Additionally, standardized diuretic renography was not available at all follow-up points, meaning functional criteria such as T-half or differential function were not uniformly applied. The success criteria were therefore mainly anatomical, relying on APD reduction and improved parenchymal thickness. The authors emphasize that longer follow-up and larger sample sizes are needed to accurately detect success rates and complication rates in excessively dilated PUJO. Nevertheless, the study provides valuable insights into the specific challenges of managing giant hydronephrosis in children, highlighting the importance of accurate risk stratification based on preoperative imaging for appropriate surgical planning and parent counseling.
Congenital urinary tract obstruction represents the most frequent fetal abnormality identified on prenatal ultrasound screening, occurring in up to one percent of all pregnancies. Among these conditions, unilateral pelvi-ureteric junction obstruction is the most prevalent obstructive uropathy, arising in approximately one in every 750 to 2,000 live births. Although roughly three-quarters of prenatally identified cases resolve spontaneously after birth, approximately 25 percent require surgical intervention to preserve renal function. When obstruction persists uncorrected, elevated intrarenal pressure impairs local renal blood flow, triggering glomerular and tubular atrophy that progresses to parenchymal fibrosis. The authors differentiated their practical radiologic threshold of an anteroposterior pelvic diameter exceeding 50 millimeters from true giant hydronephrosis, which is defined by volumetric criteria such as containing over one liter of fluid or occupying half of the abdominal cavity. Unlike classic giant hydronephrosis where the kidney becomes a fluid-filled sac with severely attenuated tissue, the children in this trial retained identifiable renal parenchyma suitable for reconstructive pyeloplasty.
Clinical indications for surgery included split renal function between 10 percent and 40 percent, an initial or progressive pelvic diameter exceeding 25 millimeters during conservative monitoring, or clinical symptoms such as loin pain, fever, and urinary stones. Across the total cohort, prenatal ultrasound detected the condition in 31 children, comprising 17 patients in Group 1 and 14 in Group 2, while six patients presented with febrile urinary tract infections. Children presenting with an initial split renal function below 10 percent, a glomerular filtration rate under 10 milliliters per minute, vesicoureteral reflux, urinary tract duplication, recurrent cases, or other urological anomalies were strictly excluded. To confirm statistical reliability, the investigators conducted an a priori power calculation using G*Power software based on anticipated differences in pelvic diameter reduction from published literature. Anticipating an effect size of Cohen’s d equal to 0.85, the team determined that a minimum of 20 renal units per arm was necessary to achieve 80 percent statistical power at a significance level of 0.05, ultimately enrolling 23 units in each arm.
Surgical reconstruction included mucosal-to-mucosal ureteropelvic anastomoses utilizing absorbable sutures, supported by internal stenting across the majority of procedures. Overall, 42 patients received internal Double-J stents, two received nephrostomy stents, and two units were managed without stents, with all stents remaining in place for four to six weeks before outpatient removal. Perinephric tube drains were placed in all patients and removed prior to hospital discharge on the second or third postoperative day, alongside 24 hours of bladder drainage. In evaluating longitudinal recovery, serial ultrasound demonstrated distinct anatomical recovery trajectories between the cohorts. Non-excessively dilated renal units displayed continuous pelvic caliber reduction throughout the follow-up period, whereas excessively dilated kidneys achieved marked decompression within six months before plateauing at twelve months. Furthermore, stratified analyses confirmed that baseline clearance capacity did not hinder structural decompression, as postoperative reductions in pelvic diameter and gains in parenchymal thickness did not differ significantly between patients presenting with low versus high baseline glomerular filtration rates.
Subject of Research: Surgical outcomes of pyeloplasty in pediatric patients with excessively dilated renal pelvises
Article Title: Comparing outcome of pyeloplasty in excessively and non excessively dilated renal pelvis in pediatric population: a prospective comparative study
Article References: Salah, M., Samir, A., shouman, A., Abdel Azim, M. S., Orban, T., & Assem, A. (2026). Comparing outcome of pyeloplasty in excessively and non excessively dilated renal pelvis in pediatric population: a prospective comparative study. African Journal of Urology, 32(1), Article 84. https://doi.org/10.1186/s12301-026-00632-z
Image Credits: AI Generated
DOI: 10.1186/s12301-026-00632-z
Keywords: pyeloplasty, pediatric urology, hydronephrosis, pelvi-ureteric junction obstruction, renal pelvis dilation, surgical complications, Anderson-Hynes technique, reduction pyeloplasty, Comparing, outcome, excessively, dilated
