DOI:10.2214/AJR.04.1946
AJR 2005; 185:1627-1631
© American Roentgen Ray Society
Thermal Damage of the Genitofemoral Nerve Due to Radiofrequency Ablation of Renal Cell Carcinoma: A Potentially Avoidable Complication
Andreas Boss1,2,
Stephan Clasen1,
Markus Kuczyk3,
Aristotelis Anastasiadis3,
Diethard Schmidt1,
Claus D. Claussen1,
Fritz Schick2 and
Philippe L. Pereira1
1 Department of Diagnostic Radiology, University Hospital of Tübingen,
Hoppe Seyler Strasse 3, Tübingen, Germany 72076.
2 Section on Experimental Radiology, University Hospital of Tübingen,
Tübingen, Germany 72076.
3 Department of Urology, University Hospital of Tübingen, Tübingen,
Germany 72076.
Received December 22, 2004;
accepted after revision February 15, 2005.
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. 134-0-0), Siemens Medical Solutions, and Radionics
Europe.
Address Correspondence to A. Boss
(andreas.boss{at}med.uni-tuebingen.de).
Abstract
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.
Introduction
Percutaneous radiofrequency ablation can be applied as minimally
invasive treatment of deep-seated malignant tumors. In this method of
interventional radiology, thermal energy is focused on the targeted tumor
after imaging-guided 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 100-150 mg of pethidine
(Dolantin, Aventis Pharma) and 2.5-5 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.
Results
In the first case, a 63-year-old man presenting with a 2.1 x 2.3 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 cycle of 8 min was performed in which the
residual tumor tissue was ablated.
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Fig. 1A —63-year-old man presenting with 2.1 x 2.3 cm renal cell
carcinoma. 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.
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Fig. 1B —63-year-old man presenting with 2.1 x 2.3 cm renal cell
carcinoma. 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).
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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.
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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.
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The next two patients—a 66-year-old man with a 3.1 x 2.5 cm
renal tumor (Fig. 3A) and a
75-year-old woman with a 1.5 x 1.8 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.
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Fig. 3A —66-year-old man presenting with 3.1 x 2.5 cm renal cell
carcinoma. 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).
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Fig. 3B —66-year-old man presenting with 3.1 x 2.5 cm renal cell
carcinoma. 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).
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Fig. 3C —66-year-old man presenting with 3.1 x 2.5 cm renal cell
carcinoma. 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.
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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 radio-frequency 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 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 patients 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. 134-0-0) who supported this project. We also thank
Siemens Medical Solutions and Radionics Europe for their continuous
support.
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Abstract
Introduction
