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Probe Retraction during Renal Tumor Cryoablation: A Technique to Minimize Direct Ureteral Injury
Probe Retraction during Renal Tumor Cryoablation: A Technique to Minimize Direct Ureteral Injury Adam Froemming, MD, Thomas Atwell, MD, Michael Farrell, MD, Matthew Callstrom, MD, PhD, Bradley Leibovich, MD, and William Charboneau, MD
Ureteral injury is a well-known complication of radiofrequency ablation of renal tumors. Ureteral injury with cryoablation seems to be less common, but has been reported. Herein, the authors describe a technique that can be used to avoid direct ureteral injury during cryoablation of renal masses. Initial ice ball formation serves to fix the probe in the target. The mass and kidney can then be retracted away from the ureter to avoid direct involvement with the subsequent ice ball. The authors report three successful example cases, with no significant complications. J Vasc Interv Radiol 2010; 21:148 –151 Abbreviation:
RF ⫽ radiofrequency
PERCUTANEOUS cryoablation has been successfully used as a treatment of renal tumors (1). It has qualities that make it an attractive alternative to radical or partial nephrectomy and percutaneous radiofrequency (RF) ablation in selected patients, including its limited invasiveness (vs surgery) and potential to treat larger tumors and monitor ablation (vs RF ablation). Most applications of percutaneous cryoablation have been targeted toward small, posterior renal tumors (2,3), although larger tumors can be successfully treated as well (4). Although ureteral complications following RF ablation are well-recognized (5–7), the risks of direct ureteral injury with percutaneous cryoablation From the Department of Radiology, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905. Received December 10, 2008; final revision received August 9, 2009; accepted September 21, 2009. Address correspondence to A.F.; E-mail: froemming.adam@ mayo.edu None of the authors have identified a conflict of interest. © SIR, 2010 DOI: 10.1016/j.jvir.2009.09.014
148
have not been defined. It has been shown that direct cryoablation of the ureter can cause ureteral strictures and urinary obstruction in dogs (8). A single case of ureteral stricture following direct cryoablation of the ureter in humans has been reported (9). An additional ureteral stricture due to contraction of a cryoablation defect has been previously described (10). Herein, we present three example cases of a technique that may help avoid direct extension of the cryoablation ice ball to important structures such as the ureter, thereby minimizing potential risks.
CASE 1 A 66-year-old woman presented with an incidentally discovered 2.4-cm mass in the mid-lower pole of the left kidney. Due to advanced medical comorbidities, including leukemia and chronic anticoagulation, and tumor location, percutaneous cryoablation was chosen as the best treatment option. Our method of percutaneous cryoablation has been previously described (4). With the patient under general anesthesia and by using combined
ultrasonographic (US) and computed tomographic (CT) guidance, two percutaneous cryoprobes (Endocare, Irvine, California) were placed into the left renal mass. The ureter was identified in an unexpectedly proximal location, only 2 mm from the probe tips (Fig 1a). Initial activation of the probes generated a small ice ball extending back from the probe tips, effectively fixing them in the lesion. Gentle retraction using two fingers was then applied, with approximately 1–2-cm displacement measured at the skin surface. Repeat imaging showed the probes to be 19 mm removed from the ureter and still in the desired locations in the mass (Fig 1b). Cryoablation was then performed with a 10 minute-5 minute6 minute freeze-thaw-freeze cycle while maintaining retraction on the probes throughout the freezing and stick-thaw cycles. The resulting ice ball was seen to encompass the entire mass and extend 8 mm beyond the tip of the probes but was well short of the ureter. Magnetic resonance (MR) imaging performed the next day helped confirm the cryoablation defect that
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Figure 1. Axial CT images without intravenous contrast obtained during cryoablation of a left renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 2 mm. (b) Image obtained after retraction shows that there is 19 mm of separation between the ureter (arrow) and probe tip.
Figure 2. Axial CT images without intravenous contrast obtained during cryoablation of a right renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 8 mm. (b) Image obtained after retraction shows that there is 18 mm of separation between the ureter (arrow) and probe tip.
entirely encompassed the tumor. A moderate hematoma was observed, with no clinical significance. Follow-up CT at 11 weeks and again at 23 weeks helped confirm the absence of any residual tumor and no ureteral injury.
CASE 2 A 74-year-old woman with a history of left nephrectomy for clear cell renal cell carcinoma presented with a 1.8-cm mass in the lower pole of her solitary right kidney.
With use of our standard technique, two percutaneous cryoprobes were placed into the right lower pole renal mass with a combination of US and CT guidance. Initial images demonstrated probe tips to be 8 mm away from the ureter (Fig 2a). After 2 minutes of
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Probe Retraction during Renal Tumor Cryoablation
January 2010
JVIR
Figure 3. Axial CT images without intravenous contrast obtained during cryoablation of a left renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 14 mm. (b) Image obtained after retraction shows that there is 24 mm of separation between the ureter (arrow) and probe tip.
probe activation and initial ice ball formation, gentle retraction using similar technique was applied. Repeat imaging demonstrated the ureter located 18 mm from the probe tips (Fig 2b). Cryoablation was then performed with a 9 minute-4 minute-6 minute freeze-thaw-freeze cycle while maintaining retraction. The resulting ice ball was seen to extend 9 mm beyond the probe tips, which was still 9 mm short of the ureter. Intravenous contrast medium-enhanced CT performed afterward cryoablation helped confirm the presence of a cryoablation defect that entirely encompassed the tumor. There were no complications.
cutaneous cryoprobe was placed under US and CT guidance. Initial imaging demonstrated the ureter located 14 mm from the probe tip (Fig 3a). After initial ice ball formation, gentle retraction by using the same technique was applied. Subsequent imaging demonstrated an increased interval of 24 mm between the cryoprobe and ureter (Fig 3b). Cryoablation was then performed with a 6 minute-5 minute-4 minute freeze-thawfreeze cycle, maintaining retraction. The resulting ice ball was seen to encompass the entire mass and spare the ureter. MR imaging performed the same day helped confirm the cryoablation defect that entirely encompassed the tumor. There were no complications.
CASE 3 A 77-year-old man with a history of renal cell carcinoma treated with right radical nephrectomy in 1985 developed a 2.4-cm mass in the lower pole of his solitary left kidney. Interestingly, this patient had undergone percutaneous ablation of a left upper pole renal mass 2 years before this presentation. With use of our standard percutaneous cryoablation technique, a single per-
DISCUSSION We present three representative cases of successful percutaneous cryoablation using a technique to achieve maximal separation of critical structures from the ablation ice ball, thereby minimizing potential complications. This technique can allow for the successful treatment of renal lesions in close proximity to the ureter with less risk of injury.
After probe placement, the proximity of important structures is assessed by using CT. Activation of the probe(s) creates an initial small ice ball, which primarily extends back from the probe tip. This initial ice ball serves both to fix the probe(s) in relation to the tumor and as a point of fixation for manipulation. Gentle manipulation can then be used to retract the tumor and kidney away from structures to be avoided, such as the ureter. Such manipulation can be performed with only a few fingers, resulting in approximately 1–2 cm of retraction measured at the skin surface, allowing for some tenting of the skin. Cryoablation can then be continued with standard freeze-thaw cycles, as the ice ball then extends distal to the probe tip. In the case of multiple cryoprobes, all probes are placed before freezing and retraction. Although experience with this technique is limited, it is promising. Cases 1 and 2 are examples of application of this technique to percutaneous cryoablation of lower pole renal tumors, resulting in complete tumor treatment and sparing of a ureter that would
Volume 21
Number 1
have otherwise been directly involved by the ice ball. Furthermore, cases 1 and 2 are examples of use with multiple probes. Although the resulting ice ball in case 3 would not have involved the ureter in retrospect, the ability to gain a greater margin by retraction of the kidney further away allowed the confidence to aggressively treat the entire lesion and achieve total coverage. In our cases, imaging guidance and monitoring was done with a combination of US and CT. However, the use of this technique would not be restricted to these modalities and could be combined with MR monitoring as well. We did not experience any significant event with our patients by using gentle probe and ice ball manipulation. However, it is uncertain if retraction and manipulation during cryoablation would increase the risk of hemorrhage. Hemorrhage is a recognized complication of cryoablation, including risk of renal ice ball fracture during surgical cryoablation (10). In our own experience in the treatment of more than 230 renal tumors with percutaneous cryoablation, we have grown to appreciate that some degree of bleeding is evident by imaging after most ablations. Although we have not observed any significant bleeding with use of gentle retraction in this technique, awareness of
Froemming et al
the potential for hemorrhage should emphasize the need for caution. One of the drawbacks of this technique is that the radiologist must maintain retraction throughout the limited monitoring CT scans obtained during the ablation. This requires the radiologist to keep his or her hand in the gantry during the scan, with subsequent radiation exposure. Although lead protection is used, this is still suboptimal and we are currently working on creating a device that will manually maintain required traction without direct user involvement. In conclusion, we describe a technique to minimize injury to important structures near a cryoablation site by increasing separation distance. Initial activation of cryoprobes can serve to fix them in the tumor and allow subsequent gentle manipulation to achieve greater separation from critical adjacent structures, such as the ureter, and minimize the risk of complications. Application of this technique may allow for successful treatment of tumors that would otherwise not be amenable to percutaneous therapy. References 1. Stein R, Kaouk J. Renal cryotherapy: a detailed review including a 5-year follow-up. BJU Int 2007; 99:1265–1270. 2. Aron M, Gill I. Minimally invasive nephron-sparing surgery (MINSS) for
3.
4.
5.
6.
7.
8. 9.
10.
•
151
renal tumors. II. Probe ablative therapy. Eur Urol 2007; 51:348 –357. Mouraviev V, Joniau S, Van Poppel H, Polascik T. Current status of minimally invasive ablative techniques in the treatment of small renal tumours. Eur Urol 2007; 51:328 –336. Atwell T, Farrell M, Callstrom M, et al. Percutaneous cryoablation of large renal masses: technical feasibility and short-term outcome. AJR Am J Roentgenol 2007; 188:1195–2000. Rhim H, Dodd G III, Chintapalli K, et al. Radiofrequency thermal ablation of abdominal tumors: lessons learned from complications. Radiographics 2004; 24: 41–52. Gervais D, McGovern J, Arellano R, McDougal W, Mueller PR. Radiofrequency ablation of renal cell carcinoma. I. Indications, results, and role in patient management over a 6-year period and ablation of 100 tumors. AJR Am J Roentgenol 2005; 185:64 –71. Weizer A, Raj G, O’Connell M, Robertson C, Nelson R, Polascik T. Complications after percutaneous radiofrequency ablation of renal tumors. Urology 2005; 66:1176 –1180. Bagley D, Terrill R, Javadpour N, Beazley R. Cryosurgery of the ureter in dogs. Invest Urol 1976; 14:241–245. Littrup P, Ahmed A, Aoun H, et al. CT-guided percutaneous cryotherapy of renal masses. J Vasc Interv Radiol 2007; 18:383–392. Cestari A, Guazzoni G, dell’Acqua V, et al. Laparoscopic cryoablation of solid renal masses: intermediate term followup. J Urol 2004; 172:1267–1270.
Ureteral injury is a well-known complication of radiofrequency ablation of renal tumors. Ureteral injury with cryoablation seems to be less common, but has been reported. Herein, the authors describe a technique that can be used to avoid direct ureteral injury during cryoablation of renal masses. Initial ice ball formation serves to fix the probe in the target. The mass and kidney can then be retracted away from the ureter to avoid direct involvement with the subsequent ice ball. The authors report three successful example cases, with no significant complications. J Vasc Interv Radiol 2010; 21:148 –151 Abbreviation:
RF ⫽ radiofrequency
PERCUTANEOUS cryoablation has been successfully used as a treatment of renal tumors (1). It has qualities that make it an attractive alternative to radical or partial nephrectomy and percutaneous radiofrequency (RF) ablation in selected patients, including its limited invasiveness (vs surgery) and potential to treat larger tumors and monitor ablation (vs RF ablation). Most applications of percutaneous cryoablation have been targeted toward small, posterior renal tumors (2,3), although larger tumors can be successfully treated as well (4). Although ureteral complications following RF ablation are well-recognized (5–7), the risks of direct ureteral injury with percutaneous cryoablation From the Department of Radiology, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905. Received December 10, 2008; final revision received August 9, 2009; accepted September 21, 2009. Address correspondence to A.F.; E-mail: froemming.adam@ mayo.edu None of the authors have identified a conflict of interest. © SIR, 2010 DOI: 10.1016/j.jvir.2009.09.014
148
have not been defined. It has been shown that direct cryoablation of the ureter can cause ureteral strictures and urinary obstruction in dogs (8). A single case of ureteral stricture following direct cryoablation of the ureter in humans has been reported (9). An additional ureteral stricture due to contraction of a cryoablation defect has been previously described (10). Herein, we present three example cases of a technique that may help avoid direct extension of the cryoablation ice ball to important structures such as the ureter, thereby minimizing potential risks.
CASE 1 A 66-year-old woman presented with an incidentally discovered 2.4-cm mass in the mid-lower pole of the left kidney. Due to advanced medical comorbidities, including leukemia and chronic anticoagulation, and tumor location, percutaneous cryoablation was chosen as the best treatment option. Our method of percutaneous cryoablation has been previously described (4). With the patient under general anesthesia and by using combined
ultrasonographic (US) and computed tomographic (CT) guidance, two percutaneous cryoprobes (Endocare, Irvine, California) were placed into the left renal mass. The ureter was identified in an unexpectedly proximal location, only 2 mm from the probe tips (Fig 1a). Initial activation of the probes generated a small ice ball extending back from the probe tips, effectively fixing them in the lesion. Gentle retraction using two fingers was then applied, with approximately 1–2-cm displacement measured at the skin surface. Repeat imaging showed the probes to be 19 mm removed from the ureter and still in the desired locations in the mass (Fig 1b). Cryoablation was then performed with a 10 minute-5 minute6 minute freeze-thaw-freeze cycle while maintaining retraction on the probes throughout the freezing and stick-thaw cycles. The resulting ice ball was seen to encompass the entire mass and extend 8 mm beyond the tip of the probes but was well short of the ureter. Magnetic resonance (MR) imaging performed the next day helped confirm the cryoablation defect that
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Figure 1. Axial CT images without intravenous contrast obtained during cryoablation of a left renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 2 mm. (b) Image obtained after retraction shows that there is 19 mm of separation between the ureter (arrow) and probe tip.
Figure 2. Axial CT images without intravenous contrast obtained during cryoablation of a right renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 8 mm. (b) Image obtained after retraction shows that there is 18 mm of separation between the ureter (arrow) and probe tip.
entirely encompassed the tumor. A moderate hematoma was observed, with no clinical significance. Follow-up CT at 11 weeks and again at 23 weeks helped confirm the absence of any residual tumor and no ureteral injury.
CASE 2 A 74-year-old woman with a history of left nephrectomy for clear cell renal cell carcinoma presented with a 1.8-cm mass in the lower pole of her solitary right kidney.
With use of our standard technique, two percutaneous cryoprobes were placed into the right lower pole renal mass with a combination of US and CT guidance. Initial images demonstrated probe tips to be 8 mm away from the ureter (Fig 2a). After 2 minutes of
150
•
Probe Retraction during Renal Tumor Cryoablation
January 2010
JVIR
Figure 3. Axial CT images without intravenous contrast obtained during cryoablation of a left renal mass. (a) Initial image. The distance between the ureter (arrow) and probe tip is 14 mm. (b) Image obtained after retraction shows that there is 24 mm of separation between the ureter (arrow) and probe tip.
probe activation and initial ice ball formation, gentle retraction using similar technique was applied. Repeat imaging demonstrated the ureter located 18 mm from the probe tips (Fig 2b). Cryoablation was then performed with a 9 minute-4 minute-6 minute freeze-thaw-freeze cycle while maintaining retraction. The resulting ice ball was seen to extend 9 mm beyond the probe tips, which was still 9 mm short of the ureter. Intravenous contrast medium-enhanced CT performed afterward cryoablation helped confirm the presence of a cryoablation defect that entirely encompassed the tumor. There were no complications.
cutaneous cryoprobe was placed under US and CT guidance. Initial imaging demonstrated the ureter located 14 mm from the probe tip (Fig 3a). After initial ice ball formation, gentle retraction by using the same technique was applied. Subsequent imaging demonstrated an increased interval of 24 mm between the cryoprobe and ureter (Fig 3b). Cryoablation was then performed with a 6 minute-5 minute-4 minute freeze-thawfreeze cycle, maintaining retraction. The resulting ice ball was seen to encompass the entire mass and spare the ureter. MR imaging performed the same day helped confirm the cryoablation defect that entirely encompassed the tumor. There were no complications.
CASE 3 A 77-year-old man with a history of renal cell carcinoma treated with right radical nephrectomy in 1985 developed a 2.4-cm mass in the lower pole of his solitary left kidney. Interestingly, this patient had undergone percutaneous ablation of a left upper pole renal mass 2 years before this presentation. With use of our standard percutaneous cryoablation technique, a single per-
DISCUSSION We present three representative cases of successful percutaneous cryoablation using a technique to achieve maximal separation of critical structures from the ablation ice ball, thereby minimizing potential complications. This technique can allow for the successful treatment of renal lesions in close proximity to the ureter with less risk of injury.
After probe placement, the proximity of important structures is assessed by using CT. Activation of the probe(s) creates an initial small ice ball, which primarily extends back from the probe tip. This initial ice ball serves both to fix the probe(s) in relation to the tumor and as a point of fixation for manipulation. Gentle manipulation can then be used to retract the tumor and kidney away from structures to be avoided, such as the ureter. Such manipulation can be performed with only a few fingers, resulting in approximately 1–2 cm of retraction measured at the skin surface, allowing for some tenting of the skin. Cryoablation can then be continued with standard freeze-thaw cycles, as the ice ball then extends distal to the probe tip. In the case of multiple cryoprobes, all probes are placed before freezing and retraction. Although experience with this technique is limited, it is promising. Cases 1 and 2 are examples of application of this technique to percutaneous cryoablation of lower pole renal tumors, resulting in complete tumor treatment and sparing of a ureter that would
Volume 21
Number 1
have otherwise been directly involved by the ice ball. Furthermore, cases 1 and 2 are examples of use with multiple probes. Although the resulting ice ball in case 3 would not have involved the ureter in retrospect, the ability to gain a greater margin by retraction of the kidney further away allowed the confidence to aggressively treat the entire lesion and achieve total coverage. In our cases, imaging guidance and monitoring was done with a combination of US and CT. However, the use of this technique would not be restricted to these modalities and could be combined with MR monitoring as well. We did not experience any significant event with our patients by using gentle probe and ice ball manipulation. However, it is uncertain if retraction and manipulation during cryoablation would increase the risk of hemorrhage. Hemorrhage is a recognized complication of cryoablation, including risk of renal ice ball fracture during surgical cryoablation (10). In our own experience in the treatment of more than 230 renal tumors with percutaneous cryoablation, we have grown to appreciate that some degree of bleeding is evident by imaging after most ablations. Although we have not observed any significant bleeding with use of gentle retraction in this technique, awareness of
Froemming et al
the potential for hemorrhage should emphasize the need for caution. One of the drawbacks of this technique is that the radiologist must maintain retraction throughout the limited monitoring CT scans obtained during the ablation. This requires the radiologist to keep his or her hand in the gantry during the scan, with subsequent radiation exposure. Although lead protection is used, this is still suboptimal and we are currently working on creating a device that will manually maintain required traction without direct user involvement. In conclusion, we describe a technique to minimize injury to important structures near a cryoablation site by increasing separation distance. Initial activation of cryoprobes can serve to fix them in the tumor and allow subsequent gentle manipulation to achieve greater separation from critical adjacent structures, such as the ureter, and minimize the risk of complications. Application of this technique may allow for successful treatment of tumors that would otherwise not be amenable to percutaneous therapy. References 1. Stein R, Kaouk J. Renal cryotherapy: a detailed review including a 5-year follow-up. BJU Int 2007; 99:1265–1270. 2. Aron M, Gill I. Minimally invasive nephron-sparing surgery (MINSS) for
3.
4.
5.
6.
7.
8. 9.
10.
•
151
renal tumors. II. Probe ablative therapy. Eur Urol 2007; 51:348 –357. Mouraviev V, Joniau S, Van Poppel H, Polascik T. Current status of minimally invasive ablative techniques in the treatment of small renal tumours. Eur Urol 2007; 51:328 –336. Atwell T, Farrell M, Callstrom M, et al. Percutaneous cryoablation of large renal masses: technical feasibility and short-term outcome. AJR Am J Roentgenol 2007; 188:1195–2000. Rhim H, Dodd G III, Chintapalli K, et al. Radiofrequency thermal ablation of abdominal tumors: lessons learned from complications. Radiographics 2004; 24: 41–52. Gervais D, McGovern J, Arellano R, McDougal W, Mueller PR. Radiofrequency ablation of renal cell carcinoma. I. Indications, results, and role in patient management over a 6-year period and ablation of 100 tumors. AJR Am J Roentgenol 2005; 185:64 –71. Weizer A, Raj G, O’Connell M, Robertson C, Nelson R, Polascik T. Complications after percutaneous radiofrequency ablation of renal tumors. Urology 2005; 66:1176 –1180. Bagley D, Terrill R, Javadpour N, Beazley R. Cryosurgery of the ureter in dogs. Invest Urol 1976; 14:241–245. Littrup P, Ahmed A, Aoun H, et al. CT-guided percutaneous cryotherapy of renal masses. J Vasc Interv Radiol 2007; 18:383–392. Cestari A, Guazzoni G, dell’Acqua V, et al. Laparoscopic cryoablation of solid renal masses: intermediate term followup. J Urol 2004; 172:1267–1270.