Ischemia and Functional Recovery from Partial Nephrectomy: Refined Perspectives

Background: Nephron mass preservation is a key determinant of functional outcomes after partial nephrectomy (PN), while ischemia plays a secondary role. Analyses focused specifically on recovery of the operated kidney appear to be most informative, yet have only included limited numbers of patients. Objective: To evaluate the relative impact of parenchymal preservation and ischemia on functional recovery after PN using a more robust cohort allowing for more refined perspectives about ischemia. Design, setting, and participants: A total of 401 patients managed with PN with necessary studies were analyzed for function and nephron mass preserved specifically within the kidney exposed to ischemia. Intervention: PN. Outcome measurements and statistical analysis: The nephron mass preserved was measured from computed tomography scans <2 mo before and 3–12 mo after PN. Patients with two kidneys were required to have nuclear renal scans within the same timeframes. Recovery from ischemia was defined as the percent function preserved normalized by the percent nephron mass preserved. Pearson correlation was used to evaluate relationships between functional recovery and nephron mass preservation or ischemia time. Multivariable linear regression assessed predictors for recovery from ischemia. Results and limitations: The median tumor size was 3.5 cm and the median RENAL score was 8. Cold and warm ischemia were utilized in 151 and 250 patients, and the median ischemia time was 27 and 21 min, respectively. The function preserved was strongly correlated with nephron mass preserved(r = 0.63; p < 0.001). Median recovery from ischemia was significantly higher for hypothermia (99% vs 92%; p < 0.001) and remained consistently strong even with longer duration. Multivariable analysis demonstrated that recovery from ischemia, which normalizes for nephron mass preservation, was significantly associated with ischemia type and duration (both p < 0.05). However, each additional 10 min of warm ischemia was associated with only a 2.5% decline in recovery from ischemia. Limitations include the retrospective design. Conclusions: Our data suggest that functional recovery from clamped PN is most reliable with hypothermia. Longer intervals of warm ischemia are associates with reduced recovery; however, incremental changes are modest and may not be clinically significant in patients with a normal contralateral kidney. Patient summary: Functional recovery after clamped partial nephrectomy is primarily dependent on preservation of nephron mass. Recovery is most reliable when hypothermia is applied. Longer intervals of warm ischemia are associated with reduced recovery; however, the incremental changes are modest. The impact of ischemia on functional recovery after clamped partial nephrectomy cannot be accurately evaluated unless nephron mass loss is accounted for. Functional recovery is most reliable with hypothermia. Longer duration of warm ischemia was associated with poorer recovery, although the incremental changes were modest.