Impact of renal cryoablation on urine composition

To examine prospectively serial urine biochemical parameters in 14 patients (9 men, 5 women) undergoing laparoscopic cryoablation of a small, exophytic solid renal mass. Prior studies have shown that various types of renal injury may predispose to the formation of urinary calculi. The metabolic effects of cryoenergy on the surrounding normal renal parenchyma are unknown.

Timed 24-hour urine collections were obtained preoperatively and postoperatively on days 1, 30, and 60 to evaluate the following parameters: light microscopic findings, volume, pH, creatinine, protein, beta(2)-microglobulin, calcium, citrate, oxalate, phosphate, uric acid, sodium, and potassium.

Urinary beta(2)-microglobulin excretion increased from a preoperative baseline value of 114.8 to 1931.2 microg/L on postoperative day 1, an increase of more than 15-fold (P = 0.05), thus confirming major renal injury. These values sharply decreased at 30 days and returned to near-baseline levels at 60 days postoperatively (P = 0.76). Nevertheless, all lithogenic parameters remained within the normal range throughout the follow-up period, with no significant change in any value.

Our findings suggest that renal cryoablation does not adversely alter urine composition with respect to lithogenic parameters for up to 2 months after surgery. Elevated beta(2)-microglobulin levels indicating significant renal injury immediately postoperatively spontaneously revert to baseline levels within 2 months.