Thermal Damage of the Genitofemoral Nerve Due to Radiofrequency Ablation of Renal Cell Carcinoma: A Potentially Avoidable Complication

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1 Avoidable Nerve Damage in Radiofrequency Ablation Interventional Radiology Technical Innovation Andreas Boss 1,2 Stephan Clasen 1 Markus Kuczyk 3 Aristotelis Anastasiadis 3 Diethard Schmidt 1 Claus D. Claussen 1 Fritz Schick 2 Philippe L. Pereira 1 Boss A, Clasen S, Kuczyk M, et al. DOI: /AJR Received December 22, 2004; accepted after revision February 15, Supported by the German Ministry for Education and Research (BMBF) (Contract No. 16SV1351), the AKF program of the University of Hospital of Tübingen (AKF No ), Siemens Medical Solutions, and Radionics Europe. 1 Department of Diagnostic Radiology, University Hospital of Tübingen, Hoppe Seyler Strasse 3, Tübingen, Germany Address Correspondence to A. Boss (andreas.boss@med.uni-tuebingen.de). 2 Section on Experimental Radiology, University Hospital of Tübingen, Tübingen, Germany Department of Urology, University Hospital of Tübingen, Tübingen, Germany AJR 2005; 185: X/05/ American Roentgen Ray Society Thermal Damage of the Genitofemoral Nerve Due to Radiofrequency Ablation of Renal Cell Carcinoma: A Potentially Avoidable Complication OBJECTIVE. A technique is presented that may prevent damage to the genitofemoral nerve during percutaneous radiofrequency ablation of renal cell carcinomas. The genitofemoral nerve originates from the upper part of the lumbar plexus and descends laterally along the psoas major muscle, which is anatomically close to the kidney. During radiofrequency ablation, nearby healthy nerve tissue could be damaged by heat conductance. In the described technique, the radiofrequency applicator within the renal tumor is used as a lever to displace the kidney away from the psoas muscle. CONCLUSION. Three clinical cases are presented in this study. In one case, the technique was not applied, leading to coagulation of the genitofemoral nerve. In the other two cases, hazard to the genitofemoral nerve was averted by using the mentioned technique. ercutaneous radiofrequency ablation can be applied as minimally in- P vasive treatment of deep-seated malignant tumors. In this method of interventional radiology, thermal energy is focused on the targeted tumor after imagingguided percutaneous placement of a radiofrequency applicator. The uses of radiofrequency ablation have been extended within recent years from the treatment of primary and secondary liver tumors to the treatment of renal, lung, and bone tumors. The most commonly applied imaging techniques are sonography and CT. Compared with surgical resection, the complication rate in radiofrequency ablation of renal cell carcinomas is low. However, with increasing numbers of treated patients the possible complications may also increase. The most common complication is the destruction of nearby healthy organ parenchyma by heat conductance [1 3]. In this study, we report on a case of a medially situated renal cell carcinoma close to the psoas muscle in which the genitofemoral nerve was affected by tissue heating resulting in chronic pain and diminished sensitivity in the ipsilateral groin. In two further cases, we applied a technique to prevent damage to the genitofemoral nerve located close to the renal tumor. Materials and Methods An open 0.2-T scanner (Magnetom Concerto, Siemens Medical Solutions) with a single-loop body coil was used. Radiofrequency ablation treatments were performed with MR-compatible internally perfused cluster applicators (active needle tip 2.5 cm) in combination with an impedance-controlled 200-W generator (Cooltip System, ValleyLab). Patients were placed in the prone position on the MR table, and IV sedation was administered using mg of pethidine (Dolantin, Aventis Pharma) and mg of midazolam (Dormicum, Roche). Skin and the adjacent subcutaneous region were anesthetized with 10 ml of 1% xylocaine solution. The electrode was navigated into the tumor using fast gradient-echo sequences (acquisition time 2.5 sec; TR/TE 45/13). Correct placement of the applicator was visualized with T1- and T2-weighted spin-echo sequences. After correct positioning of the radiofrequency applicator within the tumor in two patients, the heating zone was displaced from the psoas muscle by using the applicator as a lever for moving the kidney. The site of skin entry was used as a fixed point for torquing the handle of the applicator medially leading to a lateral displacement of the renal tumor. The exact position of the tumor was repeatedly visualized by T2-weighted sequences during breath-hold until a suitable distance from the active tip to the psoas muscle of at least 1.5 cm was reached, which is larger than the typical coagulation extent of the cluster applicators that were used. The distance between the active tip and the surface of the psoas muscle was assessed in a transverse cut. AJR:185, December

2 A C Fig year-old man presenting with cm renal cell carcinoma. A, T2-weighted fast spin-echo image at 0.2 T shows renal cell carcinoma (arrow) close to major psoas muscle (arrowheads). Patient placed in prone position. B, After first cycle of radiofrequency treatment (12 min), T2-weighted imaging shows coagulation necrosis within tumor exhibiting signal loss (white arrow) and edema in residual tumor tissue (black arrowhead). Radiofrequency cluster applicator still situated within tumor (black arrow). Psoas major muscle shows area of edema (white arrowhead). C, After second ablation cycle, coagulation necrosis was induced in psoas muscle (arrowhead) by heat conduction. B Results In the first case, a 63-year-old man presenting with a cm heterogeneous enhancing renal tumor in the left kidney close to the major psoas muscle was treated (Fig. 1A). After the first ablation cycle of 12 min, residual tumor tissue was visible medially to the coagulation necrosis. Within the psoas muscle next to the coagulation lesion, edema was induced showing hyperintense signal behavior in T2-weighted imaging (Fig. 1B). After repositioning the electrode, another ablation 1628 AJR:185, December 2005

3 Avoidable Nerve Damage in Radiofrequency Ablation Fig. 2 Genitofemoral nerve derives from first and second lumbar nerve carrying sensory and motor nerve fibers. Nerve (black line) passes through major psoas muscle (light red band) to emerge on its anterior surface and runs laterally downward to divide into genital and femoral branches. Genital branch passes through inguinal canal and supplies cremaster muscle and small area of overlying skin. Femoral branch supplies skin over femoral triangle. Renal parenchyma is shown in dark red. In described technique, applicator is used as lever to displace kidney from psoas muscle using site of skin entry (black X) as center of rotation. After torquing handle in medial direction, kidney moves laterally, enlarging distance from muscle. cycle of 8 min was performed in which the residual tumor tissue was ablated. In T2-weighted imaging, coagulation within the psoas muscle was found exhibiting signal loss (Fig. 1C). After the intervention, the patient experienced chronic pain in the skin area of the ipsilateral groin and diminished sensitivity. The pain corresponded to the skin area supplied by the femoral branch of the genitofemoral nerve (Fig. 2), which was affected by the coagulation of the psoas muscle. During the 4 months after treatment, the patient reported decreasing pain intensity due to spontaneous healing; however, the diminished sensitivity in the skin area of the femoral triangle persisted. The next two patients a 66-year-old man with a cm renal tumor (Fig. 3A) and a 75-year-old woman with a cm renal tumor presented with solitary renal tumors located in the medial part of the kidney close to the psoas muscle. These patients were treated not only using the same radiofrequency ablation system as the previous patient, but, in addition, with the mentioned technique for preventing thermal damage to the genitofemoral nerve despite the proximity of the tumors to the psoas muscle. In the 66-year-old patient, the distance of the applicator from the psoas muscle could be increased from 0.4 cm to 1.5 cm by this technique (Fig. 3B); in the case of the 75-year-old patient, from 0.4 cm to a distance of 1.8 cm. Both patients were treated with one ablation cycle of 12 min while manually securing the position of the needle applicator. After the treatment, both patients showed edema in the psoas muscle (Fig. 3C) but no signs of tissue necrosis. Although they experienced acute pain in the skin area of the ipsilateral groin after the analgesia faded, they showed no lack of skin sensitivity. Both patients were completely free of pain after 12 hr, and no chronic damage to the genitofemoral nerve occurred. No complications followed in either of these patients. In all three patients, no residual tumor tissue was found on follow-up MRI 6 weeks after treatment. Discussion The number of reports on radiofrequency ablation of renal cell carcinomas is still low [4, 5]. However, in these studies radiofrequency ablation of renal tumors showed markedly lower complications rates compared with radical or partial nephrectomy, with postoperative complication rates ranging from 14 26% [6, 7]. The most commonly reported complications of radiofrequency ablation of renal tumors are regional hemorrhage, infection, abscess formation, hematuria, urethral stricture, bowel perforation, damage to healthy nearby tissue by heat conductance, and skin burn, with complications occurring in 2 7% of treatments [1 3]. For radiofrequency ablation treatment of renal tumors, the generally accepted protocols from primary and secondary liver tumors have been adapted. To prevent undesired heating hazards, exact monitoring of the ablation procedure has to be performed to protect healthy tissue. In addition, special precaution is necessary to preserve the genitofemoral nerve. In particular, MR guidance allows for immediate assessment of the treated area by visualizing the extent of coagulation necrosis and surrounding tissue edema, which cannot be accomplished by sonography or CT. Our study draws attention to the danger of damaging the genitofemoral nerve by radiofrequency ablation of renal cell carcinomas resulting in chronic pain, tenderness, and diminished sensitivity within the skin area of the ipsilateral groin. We have proposed an effective technique to avoid this complication: The radiofrequency applicator can be used as a lever to move the heating area so as to obtain a distance of about 1.5 cm from the psoas muscle, which is further than the typical size AJR:185, December

4 A C Fig year-old man presenting with cm renal cell carcinoma. A, T2-weighted transverse fast spin-echo image (acquisition time 4 min 50 sec) shows radiofrequency applicator (arrow) positioned in center of renal tumor (black arrowhead) 4 cm from psoas muscle (white arrowheads). B, Needle and kidney were moved away from psoas muscle using radiofrequency applicator as lever to distance of 1.5 cm. Applicator position was visualized with T2- weighted fast spin-echo imaging during breath-hold (18 sec). C, After radiofrequency ablation, T2-weighted imaging (acquisition time 4 min 50 sec) shows coagulation necrosis of tumor tissue (black arrowhead). In psoas muscle, edema (white arrowhead) was induced that resolved completely within 12 hr. B of the coagulation zone of a cluster electrode [8]. However, the sensitivity of nerve tissue to heat conductance during radiofrequency ablation has so far not been tested. We recommend increasing the distance from applicator to psoas muscle to the largest amount possible. Although slight edema could not be completely avoided in the psoas muscle, induced pain persisted for less than 12 hr in two pa AJR:185, December 2005

5 Avoidable Nerve Damage in Radiofrequency Ablation tients with critical tumors positioned in close proximity to the nerve. Acknowledgments We would like to acknowledge the German Ministry for Education and Research (BMBF) (Contract No. 16SV1351) and the AKF program of the University Hospital of Tübingen (AKF No ) who supported this project. We also thank Siemens Medical Solutions and Radionics Europe for their continuous support. References 1. Mulier S, Mulier P, Ni Y, et al. Complications of radiofrequency coagulation of liver tumours. Br J Surg 2002; 89: Livraghi T, Solbiati L, Meloni MF, Gazelle GS, Halpern EF, Goldberg SN. Treatment of focal liver tumors with percutaneous radio-frequency ablation: complications encountered in a multicenter study. Radiology 2003; 226: Liddell RP, Solomon SB. Thermal protection during radiofrequency ablation. AJR 2004; 182: Gervais DA, McGovern FJ, Arellano RS, McDougal WS, Mueller PR. Renal cell carcinoma: clinical experience and technical success with radio-frequency ablation of 42 tumors. Radiology 2003; 226: Farrell MA, Charboneau WJ, DiMarco DS, et al. Imaging-guided radiofrequency ablation of solid renal tumors. AJR 2003; 180: Beisland C, Medby PC, Sander S, Beisland HO. Nephrectomy: indications, complications and postoperative mortality in 646 consecutive patients. Eur Urol 2000; 37: Butler BP, Novick AC, Miller DP, Campbell SA, Licht MR. Management of small unilateral renal cell carcinomas: radical versus nephron-sparing surgery. Urology 1995; 45: Pereira PL, Trubenbach J, Schenk M, et al. Radiofrequency ablation: in vivo comparison of four commercially available devices in pig livers. Radiology 2004; 232: AJR:185, December