Increasing thickness of the renal medullary pyramid following intervention in children with posterior urethral valves.

INTRODUCTION: Posterior urethral valves (PUV) are a leading cause of pediatric chronic kidney disease and end-stage renal disease. Existing prognostic tools like postoperative nadir serum creatinine are delayed in availability, prompting investigation into earlier indicators of renal prognosis. Renal pyramidal thickness (PT) has emerged as a promising ultrasonographic measure in congenital hydronephrosis, but its prognostic value in PUV is poorly defined.

OBJECTIVE: To characterize PT and renal parenchymal thickness (ParT) before and after surgical intervention for PUV and to evaluate the relationship with renal function postoperatively over 2 years.

STUDY DESIGN: Medical records of 58 patients with PUV who had both preoperative and serial postoperative renal ultrasounds were reviewed. PT, ParT, and anteroposterior diameter (APD) were measured bilaterally, and bilateral measurements were summed to generate composite measures (i.e., combined PT, combined ParT, and combined APD). Changes in PT and ParT over a 2-year postoperative time period were analyzed using linear mixed models and correlated with final serum creatinine.

DISCUSSION AND CONCLUSIONS: Following PUV surgery, PT increased significantly in both kidneys, most prominently in the early (i.e., first 6 months) postoperative period. The PT size increase for both kidneys over the 2-year follow-up duration was found to be nearly identical to the "catch up" rate in unilateral hydronephrotic kidneys following pyeloplasty for congenital hydronephrosis. Final PT measurements were inversely correlated with final serum creatinine. However, none of the preoperative or early postoperative renal ultrasound measurements were predictive of final serum creatinine. Initial creatinine was found to be the strongest predictor of renal function at 2 years.