Simplified approach to estimating renal function based on computerized tomography.

Abstract

INTRODUCTION: To determine whether a simplified approach to estimate renal function based on preoperative computerized tomography (CT) imaging correlates with nuclear renography (NR) following surgical treatment of ureteropelvic junction obstruction (UPJO). MATERIALS AND METHODS: We reviewed the charts of 47 patients who underwent robotic assisted laparoscopic pyeloplasty (RALP) for UPJO who had performed preoperative and postoperative NR and preoperative CT imaging. Twenty patients satisfied our inclusion criteria. We calculated differential renal function by measuring parenchymal thickness at the upper pole, midpole and lower pole regions of the kidney on the preoperative CT. Distances were measured from the edge of the collecting system to the capsule at the midpoint of the kidney in the coronal plane. After parenchymal thickness measurements were calculated bilaterally, a differential parenchymal thickness was obtained, and the ratio of parenchymal area was compared to the observed function on NR. Measurements were taken by three blinded observers and compared to preop and postop differential renal function as measured by NR to assess if preoperative CT renal parenchymal thickness correlates well with differential function of the affected and contralateral kidneys. RESULTS: Estimated renal function was predicted with excellent accuracy and minimal interobserver variability. Pearson correlation coefficients for Observers 1, 2 and 3 were 0.89, 0.88 and 0.91, respectively when compared to the postoperative differential function on NR. The interclass correlation coefficient between the three observers was 0.957, which indicates an almost perfect correlation and reproducibility of the formula. CONCLUSIONS: Estimating differential renal function based on renal parenchymal thickness on preoperative CT imaging correlates very well with observed postoperative differential renal function on NR following RALP.