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 in the journal European Urology.
For the retrospective study, researchers analysed outcomes of 362 patients with only one kidney who underwent surgery for renal cortical tumours at Mayo Clinic and Cleveland Clinic between 1990 and 2008. Using a technique called warm ischaemia, surgeons kept the patient’s kidneys at body temperature during the partial nephrectomy. Ischaemia 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 ischaemia time was 21 minutes in the study and the median age of patients was 62 years.
Ischaemia can cause tissue damage from a lack of oxygen and nutrients. Researchers found that each additional minute of warm ischaemia 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 ischaemia time in patients with a single kidney who are undergoing a partial nephrectomy, combining the experiences of the Mayo Clinic and Cleveland Clinic, both leaders in the field of kidney cancer," says R. Houston Thompson, MD, Mayo Clinic urologist and the study’s primary investigator. "These results suggest that every minute counts when the renal arteries and veins are clamped. When planning for the surgery, surgeons should make efforts to minimise ischaemia time, especially in situations where a person only has one kidney."
"Historically, 30 minutes was considered the maximum safe duration of warm ischaemia during partial nephrectomy, and other retrospective clinical studies have suggested that warm ischaemia for 40 to 55 minutes is safe," says Dr Thompson. "However, these studies included patients with two kidneys, which could mask the true effects of ischaemia on renal function.
"Because each additional minute of warm ischaemia invites the risk for chronic kidney problems, if longer ischaemic times are unavoidable, techniques such as ice slush (cold ischaemia) should be considered." The researchers stress that the study’s results do not have implications for patients treated with cold ischaemia.
(Source: Mayo Clinic: European Urology: June 2010)