Three-Dimensional Renal Parenchymal Volume as a Surrogate for Renal Function Estimation in Obstructed Kidneys Undergoing Surgical Repair.

Purpose: To investigate the relationship between renal parenchymal volume (RPV) and renal function in obstructed kidneys using a novel three-dimensional (3D) volume-rendering technique.

Materials And Methods: Forty-seven consecutive patients who underwent pyeloplasty, ureteroureterostomy, or ureteroneocystostomy at a single institution between 2007 and 2013 were reviewed. Patients with preoperative CT scan and split differential functional (SDF) assessment by diuretic renography were included. Those with solitary kidneys and bilateral obstruction were excluded. Baseline serum creatinine (Cr) and estimated glomerular filtration rate (eGFR) as calculated by the modification of diet in renal disease equation were determined. Percent of total RPV for the obstructed kidney was determined using 3D reconstruction software by drawing regions of interest around the borders of the kidney on CT. The renal pelvis, hilar vessels, and hilar fat were excluded. Percent of total RPV was then correlated with SDF.

Results: Nineteen patients with both preoperative CT and diuretic renal scans were included. Two underwent ureteroneocystostomy, 1 underwent ureteroureterostomy, and 16 underwent pyeloplasty. Mean serum Cr was 1.07±0.26 mg/dL with a mean eGFR of 69.43±18.90 mL/minute. Mean SDF was 37.32%±11.66% in the obstructed kidneys. There was a statistically significant correlation between percent of total RPV and SDF (R(2)=0.28, p=0.02).

Conclusions: There is a significant correlation between percent total RPV determined by 3D reconstruction of CT scan images and SDF as determined by diuretic renography in obstructed kidneys. CT-based percent RPV has potential as a functional assessment tool in obstructed kidneys. With further validation, it may be used to counsel patients considering surgical repair of ureteral or ureteropelvic junction obstruction.