Ultrasonographic stabilization of hydronephrosis after pyeloplasty: Key determinant of postoperative follow-up?

Although more than 1500 pediatric pyeloplasties are performed in the United States per year, there is a lack of consensus on the adequate imaging modality and timing of follow-up after surgery. The aim of this study is to evaluate if ultrasonographic stabilization in the grade of hydronephrosis after pyeloplasty is an adequate parameter to define the optimal length of follow-up after surgery and to detect failed procedures. Secondarily, we want to analyze clinical variables that could impact ultrasonographic stabilization. This is a retrospective chart review of patients who underwent pyeloplasty between 2012 and 2020. Patients were included if they were ≤21 years-old at the time of surgery, had pre and postoperative renal-ultrasounds, had ≥3 months of postoperative follow-up, and had met the criteria for ultrasonographic stabilization after surgery. Ultrasonographic stabilization was defined as 2 consecutive ultrasounds after pyeloplasty, a minimum of 1-month apart, with the same degree of hydronephrosis according to the Society for Fetal Urology (SFU) grading system. Data concerning clinical, surgical, and postoperative variables were collected. A total of 143 pyeloplasties met the inclusion criteria. Median age at surgery was 10.5 months with a median post-operative follow-up time of 29 months. Ultrasonographic stabilization was achieved in a mean time of 14.5 months post-operatively. Compared to the preoperative US SFU grade, at ultrasonographic stabilization 127 (88.9%) patients had an improvement of ≥1 grades of hydronephrosis. There were 9 pyeloplasty failures that were diagnosed and surgically corrected in a median of 7.5 months after the initial surgery. No clinical or surgical variables were associated with time to achieve ultrasonographic stabilization. There is great variability in the length of follow-up after pyeloplasty, ranging from 3-months to 7-years. In our cohort, the bast majority of patients had achieved ultrasonographic stabilization and displayed improvement in their initial grade of hydronephrosis by 14.5 months after surgery. Timeframe in which surgical failures were diagnosed and corrected. There were not clinical or surgical variables associated to time to achieve stabilization. Similar results have been reported in the literature; however, most of them have evaluated as their main outcome resolution and not stabilization of hydronephrosis. Ultrasonographic stabilization is a suitable and non-invasive parameter for determining the length of follow-up after unilateral pyeloplasty, as it is an adequate timeframe for identifying failed pyeloplasties, observing improvement or stabilization of hydronephrosis, and performing any additional procedure required after the primary repair. Summary table Clinical characteristics and its association with ultrasonographic stabilization. Summary table Variables US Stabilization time (mean) p -value Preoperative grade of hydronephrosis SFU 3 14.33 0.98 SFU 4 14.28 Diagnosis of hydronephrosis Prenatal 13.3 0.038 Postnatal 17.8 Vesicoureteral reflux Yes 10.8 0.22 No 14.7 Age at surgery < 6 months 13.2 0.57 ≥6 months to <1 year 16.7 ≥1 to <2 years 16.7 ≥2 to <6 years 12.1 ≥ 6 years 14.5 Surgical approach Open 14 0.91 Robotic-assisted 14.2 No 14.2 0.83 Yes 13.5 Redo pyeloplasty No 14.2 0.74 Yes 15.7 Complications (<90 days after surgery) No 14.2 0.09 Yes 8 ∗Only 141 renal units had preoperative MAG3% renal scan. [ABSTRACT FROM AUTHOR]