Radiation-free monitoring in the long-term follow-up of pyeloplasty: Are ultrasound new parameters good enough to evaluate a successful procedure?

INTRODUCTION: Long-term evolution of residual hydronephrosis after successful pyeloplasty is not common. In this report, we have studied new ultrasound parameters, and have investigated the frequency of residual hydronephrosis. We highlight alternative radiation-free monitoring of pediatric pyeloplasties with ultrasound alone.

PATIENTS AND METHODS: Children who had undergone successful open Anderson-Hynes pyeloplasties in the period 2001-2010 were followed up. Exclusion criteria included non-clearly obstructed renography scans (tracer clearance half-time < 20 min), crossing vessels, failed pyeloplasty, bilateral disease, other renal concomitant anomaly, absence of ultrasound measurements, and loss to follow up (<1 year). Postoperative (postoperative) ultrasound parameters were anteroposterior (AP) diameter, pelvis-cortex (P/C) ratio, a proportion that takes in account these two values, enhancing sensitivity to evaluate minimal evolutive changes), and percentage of improvement (PI) in AP diameter (which reflects in relative means the evolution of each AP diameter, being 0% no change, and 100% absence of hydronephrosis) (Figure). Echographic checks were made at 3 and 6 months postoperatively and then yearly afterwards. SPSS software (v. 17.0 IBM, College Station, TX, USA) was used.

RESULTS: Out of 80 pyeloplasties performed in the above-mentioned period, 44 patients (i.e., 44 renal units) fulfilled the inclusion criteria for the main study. The median age at time of operation was 15 months (range 2 months-10.3 years). The median follow-up was 4.5 years (range 1-12 years). The mean preoperative anteroposterior diameter was 26 mm (range 16-54 mm). At the third postoperative check, the mean the PI was 29%, and rose to 53% at 6 months (p=0.027). Posterior controls showed a stable yearly PI during follow-up, without statistically significant variations (40-59% in subsequent years, p>0.5). The P/C ratio had already downgraded significantly at the third postoperative check (4.6 preoperative vs. 1.8 postoperative; p=0.03). A subgroup analysis of failed pyeloplasty (4 renal units) showed all PI < 15% at the third postoperative month (sensitivity 100%, specificity 86%). Complete resolution of hydronephrosis occurred in nine patients (20%).

DISCUSSION: The P/C ratio and PI are new feasible ultrasound parameters in pyeloplasty follow-up. Early improvement in the P/C ratio can be expected and might avoid repeated ionizing scans. A PI>15% in subsequent postoperative checks might be enough for safe monitoring with ultrasound alone. Thus, renograms may be solicited only in these cases where ultrasound parameters do not improve in the first 6 postoperative months. Afterwards, ultrasound parameters often remain stable in the long term. Absence of hydronephrosis could only be documented in the long term in one out of every five patients.