Editorial Comment to Different methods of hilar clamping during partial nephrectomy: Impact on renal function

Abstract

Partial nephrectomy (PN) has gained in popularity since current scientific evidence has suggested that renal function preservation should be increasingly prioritized.1-3 Renal ischemia related to hilar clamping is deleterious to the remaining renal parenchyma. Many studies have investigated ischemia time limits and altering factors in relation to subsequent renal function.4-6 Ischemia time is the strongest modifiable surgical risk factor for postoperative chronic kidney disease.7 However, the safe duration of ischemia remains controversial. The great merit of the study by Lee et al. is that it reported renal function data in a large and homogeneous series of 369 patients managed by open PN for a single localized unilateral pT1a renal tumor; 10.6% of whom had no vascular clamping, 54.4% had warm ischemia and 35.0% had cold ischemia.8 They concluded that the impact of warm and cold ischemia seems to be comparable with a significant decrease of estimated glomerular filtration rate (eGFR) in the early postoperative period, but without significant impact on 1-year eGFR. As expected, ultimate renal function decreases proportionally with increasing ischemia time, in both hilar clamping groups. The authors' conclusions underscore the importance of minimization of ischemia time whenever hilar clamping is required. As the vast majority of prior studies assessing the impact of ischemia, this series included patients with a normal contralateral kidney. It should be noted that, in this case, the effect on serum creatinine is blunted and, therefore, the effect on total GFR is minimized, although there might be a significant reduction in the GFR of the operated kidney. Renal reserve serves to protect the organism, maintaining a near normal GFR, and ischemic damage is potentially masked by the compensatory role of the normal contralateral kidney. Therefore, analysing renal function consequences of various technical scenarios during PN on a solitary kidney could be particularly informative. In a series of PN on solitary kidneys, Thompson et al. concluded that whenever pedicle clamping was expected, warm ischemia should be completed within 20 min, and cold ischemia within 35 min. They also showed that warm ischemia patients are significantly more likely to develop acute renal failure in the postoperative period and chronic kidney disease during follow up compared with patients managed without hilar clamping.9 Nguyen and Gill found a similar benefit in limiting warm ischemia to less than 20–25 min when renal function decreases at a faster rate with additional minutes of ischemia.10 This accumulated data should prompt us to preferentially choose PN with no clamping whenever technically feasible, especially in patients with a solitary kidney or preoperative renal function impairment. It is noteworthy that the absence of significant differences in eGFR decrease at 1 year in the present study could be due to the short ischemia time in this series, probably as a result of the small size of the tumors (<4 cm). These results are probably not transposable to patients with more complex tumors where vascular clamping is often necessary for allowing good hemostasis and obtaining a bloodless field, which is essential for successful tumor removal, with negative surgical margins and accurate surgical collecting system closure. Finally, it is obvious that a certain number of small renal tumors are indolent and not life-threatening. We should therefore integrate information, such as age, comorbidities, baseline renal function and technical difficulty of PN, in our decision algorithm. This is particularly true because increased alternative options exist for small renal tumor management, including active surveillance or ablative techniques, which are less deleterious options in regard to renal function. None declared.