CardioVascular and Interventional Radiology | 2019
Six Cases of Radiographic Ice Ball Involvement of the Ureter During Percutaneous Cryoablation for Renal Cancers
Abstract
To the Editor, Image-guided percutaneous renal cryoablation (PRC)associated ureteral injury is rare, but may cause severe clinical sequelae, including hydronephrosis and chronic renal failure. If the ice ball involves the ureter during PRC, careful post-procedural observation is required to prevent such sequelae. However, clinical consequences of radiographic ice ball involvement of the ureter have not been extensively studied. Herein, we report six cases of unavoidable ice ball involvement of the ureter during PRC with follow-up outcomes. This case series study was approved by the institutional review board. Ice ball involvement of the ureter was identified on procedural computed tomography (CT) in six men (age range 55–88 years) among 297 patients who underwent PRC for renal tumors, from May 2012 to December 2017. Tumor sizes ranged from 12 mm to 40 mm. The shortest distance from the ureter to the nearest tumor edge was 1–6 mm on pre-procedural CT. PRC was performed under local anesthesia using an argon-based cryoablation system (CryoHit, Galil Medical, Yokneam, Israel) with CT fluoroscopy guidance in all patients. Depending on the tumor size, one to four 17-gauge cryoprobes (IceRod or IceSeed, Galil Medical) were inserted. Two 10or 15-min freezing cycles were separately performed with at least 2 min of passive thawing. The procedure was completed after confirming the coverage of the tumor by the ice ball with a sufficient margin (C 6 mm). To protect the ureter from cryoinjury, retrograde warm (38–40 C) saline perfusion at a speed of 120–180 mL/h, via a 6-Fr single J ureteral stent, was administered in four patients. Hydrodissection was performed in four patients through injection of a mixture of contrast media and saline using a 21-gauge Chiba needle resulting in a slight increase in the distance between the ureter and the tumor in two patients. The ice ball involved the ureter totally and partially in four and two patients, respectively. Figure 1 illustrates total involvement of the ureter. All patients experienced transient hematuria postoperatively. CT or magnetic resonance imaging performed on postoperative days 1–3 depicted thickening of the ureteral wall. The ureteral stent was removed on the 1st or 2nd postoperative day. The ureteral wall thickening improved over time in all patients. In the median follow-up period of 41 months (range 7–59 months), no radiological findings suggesting ureter strictures (e.g., hydronephrosis and hydroureter) or other adverse events were observed in any patient. Multiple new renal tumors developed postoperatively in a patient, thus requiring hemodialysis due to renal impairment secondary to molecular-target drugs administered for the treatment of the tumors. No severe renal function deterioration was found in any other patient. Recent large studies reported that ureter strictures developed at an incidence rate of less than 1% after PRC [1, 2]. Cryoinjury of the ureter was first reported in 1976 in a canine animal model [3]. Although no loss of ureteral integrity was found, fibrosis of the lamina propria, loss of the ureteral smooth muscle, and regeneration of the transitional epithelium were noted on histopathologic examination [3]. Another animal-model study using porcine demonstrated no severe injuries by intentional cryoablation & Yusuke Matsui [email protected]