Interrupting the blood flow for more than 20 to 25 minutes during kidney cancer surgery leads to a greater risk for patients developing chronic kidney disease, a Mayo Clinic and Cleveland Clinic collaborative research team has found. The study was published today in the journal European Urology. For the retrospective study, researchers analyzed outcomes of 362 patients with only one kidney who underwent surgery for renal cortical tumors at Mayo Clinic and Cleveland Clinic between 1990 and 2008. Using a technique called warm ischemia, surgeons kept the patient’s kidneys at body temperature during the partial nephrectomy. Ischemia involves cutting off the blood supply to the kidney with clamps in order to control bleeding and to keep blood from obscuring the surgeon’s view of the kidney. It also allows for precise closure of the urine collecting system and the surgical opening. The median ischemia time was 21 minutes in the study and the median age of patients was 62 years. Ischemia can cause tissue damage from a lack of oxygen and nutrients. Researchers found that each additional minute of warm ischemia is associated with a 5 to 6 percent increase in the odds of developing acute renal failure or reduced kidney functioning and is associated with a 6 percent increased risk of new onset Stage IV chronic kidney disease during long-term follow-up. “This is the largest evaluation of warm ischemia time in patients with a single kidney who are undergoing a partial nephrectomy …