Temporal Study of Renal Volume Losses in Patients with Robotic Partial Nephrectomies

Robotic partial nephrectomies (RPNs) by their nature are associated with renal volume loss. Our goal of this study is to examine renal volume loss over time post partial nephrectomy. Fifty patients were followed for 1-year post-RPN with two-layer renorrhaphy and the sliding clip technique. This was done with a preoperative CT scan to assess renal mass and location. Patients post-RPN were imaged at time points 3 days, 6 months, and 12 months. Patient demographics were 82% men with a median (interquartile range [IQR]) age of 57 (45-67) years and all were of Japanese descent. The medians (IQR) for warm ischemia time were 18 minutes (14-22), total operative time was 181.5 minutes (169.3-218.5), and estimated blood loss was 20 mL (10-50). The tumor characteristics had a median (IQR) diameter of 2.8 cm (2.5-3.4) with a RENAL score of 7 (6-8). The renal CT showed median (IQR) volume losses at 3 days of -1% (-7.1, 1.8), at 6 months of -15.3% (-20.6, -11.2), and at 12 months of -16.3% (-19.0, -12.8). Significance was seen at the 3 days to 6 months comparison for volume loss (p < 0.0001). Mean (standard deviation) estimated glomerular filtration rate (GFR) losses were as follows: at discharge 0.5% (12.9), 1 month -6.4% (11.8), 6 months -4.6% (9.8), and 12 months -3.6% (11.9). Statistical analysis showed significance for GFR loss at the comparison between discharge to 1 and 6 months (p = 0.01, p = 0.04). The initial volume loss seen postsurgery from resected healthy tissue was not significant and only became relevant at longer time points, suggesting that loss could be from atrophy. Volume loss over time supports the hypothesis that suture renorrhaphy is a primary cause of volume loss when warm ischemia time is <25 minutes.