The Impact Of Ischemia Time During Open Nephron Sparing Surgery On Solitary Kidneys: A Multi-Institutional Study

Traditionally, partial nephrectomy for moderate and large renal tumors has been performed with hilar clamping and cold ischemia. With the advent of laparoscopic partial nephrectomy, prolonged periods of hilar clamping with warm ischemia have been increasingly tolerated.

While most urologists would agree that up to 30 minutes of warm ischemia may be tolerated, the exact impact of prolonged warm ischemia on renal function after partial nephrectomy is largely unknown.In the Journal of Urology, Thompson, Novick, and colleagues report the results of a retrospective, multi-institutional study designed to evaluate the association between the lengths of cold or warm ischemia on renal function in patients undergoing partial nephrectomy. The cohort consisted of 537 patients who underwent nephron sparing surgery in patients with a solitary kidney at the Cleveland (n= 363) and Mayo Clinics (n= 174).The cohorts consisted of 85 patients who required no renal ischemia, 174 who underwent warm ischemia, and 278 patients that required cold ischemia. Median tumor sizes for each group were 2.5 cm, 3.5 cm, and 4.0 cm, respectively.Both warm and cold ischemia were associated with an increased risk of temporary dialysis, urine leak, and chronic renal failure compared with patients who did not require ischemia at all. Permanent dialysis was required in 9.6% of patients requiring warm ischemia longer than 20 minutes, compared with 3.9% for patients requiring less than 20 minutes of warm ischemia. Cold renal ischemia longer than 35 minutes was also associated with an increased incidence of acute renal failure. Of course, these data are confounded by the fact that prolonged ischemia was directly proportional to tumor size and indirectly proportional to the renal remnant.This study comprised from the largest cohort of patients undergoing partial nephrectomy in the setting of a solitary kidney suggest that long-term renal complications are best avoided if the warm ischemia time is kept under 20 minutes cold ischemia time is limited to 35 minutes. These data have important implications for surgeons performing complex laparoscopic nephron-sparing surgery where warm ischemic times may exceed 20 minutes.(Source: Journal of Urology : Cleveland Clinic and Mayo Clinic : April 2007.)