Warm Ischemia Time: How Much of It Matters and Markers for Renal Functional Loss

Summary Partial nephrectomy (PN) is the standard of care for small renal masses, offering oncologic control with maximal renal preservation. A central concern in PN is warm ischemia time (WIT), traditionally capped at 30 minutes to prevent irreversible nephron loss. However, emerging evidence challenges this rigid threshold, emphasizing that preserved nephron volume, baseline renal function, and surgical technique are more predictive of long-term renal outcomes. This chapter reviews the evolving role of WIT, highlighting that while minimizing ischemia is still important—especially in high-risk patients—individualized strategies, such as selective or zero ischemia, early unclamping, and advanced imaging, provide better outcomes. Moreover, biomarkers like cystatin C, NGAL, and KIM-1 offer earlier detection of renal injury, though their application in PN remains under investigation. A multimodal and patient-specific approach, rather than adherence to strict ischemia cut-offs, is essential for optimizing postoperative renal function.