Does involvement of the collecting system by energy ablation techniques used to treat small renal masses increase the risk of complications

Energy ablative strategies (percutaneous and laparoscopic) are being increasingly employed in the treatment of small renal masses.

The concern with the treatment of centrally located tumors is that contact of energy used for tumor ablation may result in an increased risk of post-procedural complications such as urine leak, fistula, UPJ obstruction, or ureteral stricture. In this report by Warlick and colleagues, the effect of percutaneous cryotherapy in contact with the collecting system is examined.

Of 32 patients treated with percutaneous cryotherapy for 41 renal tumors over a 15 month period, 6 patients were thought to have "involvement" of the collecting system by the evolving iceball, defined as being within 5 mm of the collecting system during intraprocedural imaging. Mean tumor size was 2.4 cm (range 0.5-5.2) and mean follow-up was 167.7 days (range 90-288). Probe size was 2.4 mm and 2 freeze/thaw cycles were used. Four patients had direct contact of the iceball with the collecting system, whereas in 2 patients, the iceball came within 5 mm. None of these patients developed gross hematuria, or clinical signs, symptoms, or imaging features consistent with urine leak, fistula, UPJ obstruction, or ureteral stricture. The authors conclude that contact of the collecting system by the evolving iceball does not seem to associated with increase complication rates, although obviously should still be avoided whenever possible.

The authors noted that in animal studies, the collateral damage of radiofrequency ablation (RFA) seems to be significantly greater than that of cryotherapy and that the complication rate associated with RFA of central lesions may be significantly greater. They noted that the 3 mm outer rim of the iceball that develops with cryotherapy does not reach the "critical temperature" necessary for tissue destruction and therefore may allow contact of this front with adjacent normal structures without undo sequelae.

Written by Christopher G. Wood, MD - UroToday

Urology 67: 079-1083, May 200