Persistent Contrast Enhancement Several Months after Laparoscopic Cryoablation of the Small Renal Mass May Not Indicate Recurrent Tumor

Purpose: We evaluated the clinical implication of persistent contrast enhancement demonstrated several months after laparoscopic renal cryoablation of a small renal mass. Patients and Methods: Between September 2000 and May 2007, 30 patients underwent laparoscopic cryosurgery for an organ-confined renal tumor measuring <= 3.5 cm in diameter. A pure laparoscopic approach was used with third generation cryotechnology-17-gauge cryoprobes and argon-helium gas. The patients were followed by serial CT or MRI every 3 months after cryotherapy or until radiographic resolution of contrast enhancement at the site of ablation. Results: Of 30 patients (comprising 32 cases), by 3 months after cryosurgery, 27 (84.4%) treated renal masses demonstrated no contrast enhancement at the ablation site. However, 5 (15.6%) ablation sites showed enhancement at 3 months; three of those persisted by 6 months, but only one displayed enhancement by 9 months. The patient with persistent enhancement by 9 months underwent partial nephrectomy that demonstrated no recurrent cancer. All other enhancing ablation sites showed no enhancement by 10 months after cryotherapy without recurrence. No tumor, including those that demonstrated persistent enhancement after cryotherapy, showed enlargement at the ablation site. Conclusions: This study demonstrates that persistent contrast enhancement at the cryoablation site is uncommon but may be detected by cross-sectional imaging up to 9 months after the procedure. The cause of persistent enhancement remains uncertain but may not be necessarily because of malignancy. These data suggest a benign etiology not necessitating further therapy and should be taken into account during post-treatment radiologic surveillance.