Changes in renal parenchymal volume and renal function after minimally invasive partial nephrectomy for renal cell carcinoma at median 47.4-month follow-up

Partial nephrectomy (PN) is the standard treatment for localized renal cell carcinoma (RCC). The long-term trajectory of renal parenchymal volume (RPV) and its relationship with renal function remain poorly understood. This study aimed to evaluate the long-term changes in RPV and estimated glomerular filtration rate (eGFR) after minimally invasive PN for RCC and to identify the factors influencing these changes. Among 1,947 patients who underwent minimally invasive PN (laparoscopic or robot-assisted PN) for renal tumors between January 2015 and December 2021, 149 patients with RCC and complete serial imaging and clinical follow-up data were included in the final analysis. Ipsilateral, contralateral, and total RPV were measured using three-dimensional CT volumetry preoperatively, at the first postoperative follow-up (1–6 months), and at the last follow-up (≥ 36 months). eGFR was calculated using the CKD-EPI equation. The primary endpoints were the annualized change rates of ipsilateral RPV, contralateral RPV, total RPV, and eGFR from the first postoperative follow-up to the last follow-up. Secondary endpoints were the corresponding absolute values of ipsilateral RPV, contralateral RPV, total RPV, and eGFR at the last follow-up. Univariate and multivariate linear regression models were employed to identify the predictors of RPV and eGFR changes, including patient demographics, comorbidities, tumor characteristics, and surgical parameters. The median follow-up duration was 47.4 months (IQR: 36.0-60.4). The interval from PN to the first follow-up was 2.8 months (IQR:1.2–3.5). The ipsilateral RPV declined progressively from 172.57 cm³ preoperatively to 156.66 cm³ at the first follow-up and to 136.04 cm³ at the last follow-up, indicating an annualized decline of -3.00%. The contralateral RPV remained stable measuring 175.02 cm³ preoperatively, 179.92 cm³ at the first follow-up, 178.80 cm³ at the last follow-up, with no significant evidence of compensatory hypertrophy observed. The total RPV and eGFR exhibited annual declines of -1.08% (IQR: -2.70%-0.10%) and − 0.65% (IQR: -3.11-0.83%), respectively. Multivariate analysis showed that tumor composition (cystic vs. solid, p = 0.028), surgical method (robot vs. laparoscopy, p = 0.048), and ischemia type (non-warm vs. warm, p = 0.023) were associated with the annualized ipsilateral RPV change rate. Meanwhile, no independent predictors were identified for the annualized change rates of contralateral RPV, total RPV, or eGFR. Final total RPV was independently associated with age and preoperative RPV measurements, whereas final eGFR was independently associated with age, preoperative contralateral RPV, and preoperative eGFR. Ipsilateral renal parenchyma progressively atrophies during long-term follow-up after minimally invasive PN, with limited contralateral compensation. Annualized ipsilateral RPV change was associated with tumor composition and surgical method, while ischemia type showed an exploratory adjusted association. CT-based volumetry provides a practical tool for assessing split renal function and should be integrated into long-term postoperative surveillance.