Diuretic renography in hydronephrosis: renal tissue tracer transit predicts functional course and thereby need for surgery

We attempted to define predictive factors for surgery in children with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of ureteropelvic junction (UPJ) obstruction. We retrospectively evaluated our 16-yr experience (1988-2003) with 343 children (260 male and 83 female) with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of UPJ obstruction and who were followed conservatively. Right-sided hydronephrosis was present in 110 and left-sided in 233 children. According to the Society for Fetal Urology (SFU) classification none had grade 0 of postnatal hydronephrosis, 20 had grade 1, 118 grade 2, 147 grade 3, and the remaining 58 children grade 4 postnatal hydronephrosis. Relative renal function (RRF) on radionuclide scans revealed 235 children with RRF>40%, 68 with RRF between 30% and 40%, and 40 patients with RRF 5% was the main indication for surgery. Commercially available software GraphPad Prism 4.0 (GraphPad prism, Prism 4 for Windows, version 4) using the Fisher exact test was used for statistical evaluation. Surgical correction was needed in 179 children (52.2%) during the course of conservative management. The average age at surgery was 10.6 mo (range, 1 mo to 7 yr). Of those, 50% underwent surgery during the first 2 yr of life and the majority of the remaining patients underwent surgery between the 2 and 4 yr of age; only two patients required surgery later on. Univariate analysis revealed that child sex, side of hydronephrosis, and SFU grade of prenatal hydronephrosis were not significant predictive factors for surgery. However, SFU grade 3-4 of postnatal hydronephrosis (p 50% of children with antenatal diagnosis of UPJ obstruction in this series required surgical correction while on conservative protocol. SFU grade 3-4 of postnatal hydronephrosis and RRF<40% are significant independent predictive factors for surgery.

We retrospectively reviewed a consecutive series of patients who underwent pyeloplasty. In all cases preoperative and postoperative isotope renal scans were performed to assess the surgical outcome with particular emphasis on the change in renal function postoperatively. The clinical records of 108 consecutive children with ureteropelvic junction obstruction were reviewed. Individual renal function was evaluated and obstruction was confirmed by diuretic assisted 99mtechnetium diethylenetriaminepentaacetic acid or mercaptoacetyltriglycine renography. A total of 100 pyeloplasties in 98 children between 5 days and 16 years old was included. Results were analyzed by groups according to patient age and symptoms at presentation. Drainage half-times improved in 98% of patients and only 1 required reoperation. Improved renal function greater than 5% was noted in about a third of each age group. Function remained stable in 68% of the kidneys and decreased in only 1. Of the improved kidneys 77% had impaired function preoperatively (40% or less of the total contribution). Those presenting with a renal mass had the greatest improvement in function. There was no statistically significant difference in improvement in renal function by age group or patient presentation. Regression analysis revealed that preoperative differential renal function was the only statistically significant predictor of improvement in renal function after pyeloplasty. Pyeloplasty in children is safe and renal functional improvement can be expected in the majority of kidneys with impaired function at presentation. However, there was no indication that early pyeloplasty in infants is more likely to result in improved function than in older children.

This report is the conclusion of the international consensus committee on renal transit time (subcommittee of the International Scientific Committee of Radionuclides in Nephrourology) and provides recommendations on measurement, normal values, and analysis of clinical utility. Transit time is the time that a tracer remains within the kidney or within a part of the kidney (eg, parenchymal transit time). It can be obtained from a dynamic renogram and a vascular input acquired in standardized conditions by a deconvolution process. Alternatively to transit time measurement, simpler indices were proposed, such as time of maximum, normalized residual activity or renal output efficiency. Transit time has been mainly used in urinary obstruction, renal artery stenosis, or renovascular hypertension and renal transplant. Despite a large amount of published data on obstruction, only the value of normal transit is established. The value of delayed transit remains controversial, probably due to lack of a gold standard for obstruction. Transit time measurements are useful to diagnose renovascular hypertension, as are some of the simpler indices. The committee recommends further collaborative trials.