DOI:10.2214/AJR.05.0176
AJR 2006; 186:S311-S315
© American Roentgen Ray Society
Efficacy of Transhepatic Radiofrequency Ablation of Renal Cell Carcinoma
John P. McGahan1,
Kyung Mee Ro1,
Christopher P. Evans1 and
Lars M. Ellison1
1 All authors: Department of Radiology, University of California, Davis, Medical
Center, 4860 Y St., Suite 3100, Sacramento, CA 95817.
Received February 1, 2005;
accepted after revision April 18, 2005.
Address correspondence to J. P. McGahan.
Abstract
OBJECTIVE. The purpose of this report is to describe an alternative,
using a transhepatic route, to CT guidance of radiofrequency ablation of renal
masses.
CONCLUSION. In four supine patients, radiofrequency ablation of a
right renal mass was performed under sonographic guidance. The radiofrequency
ablation needle was placed transhepatically into the mass. Color sonography
was useful in guiding needle placement and avoiding intervening vessels in the
liver and kidney. This technique may be used in selected patients as an
alternative to CT guidance of radiofrequency ablation.
Keywords: abdomen • abdominal imaging • ablation • radiofrequency • radiofrequency ablation • renal disease
Introduction
Radiofrequency ablation has found widespread use since first described in
1990 for ex vivo coagulation of liver tissue
[1,
2]. Radiofrequency ablation was
originally used most commonly in clinical practice to treat hepatic neoplasms.
Not until 1997 was radiofrequency ablation reported to provide extensive
necrosis of renal tumors both ex vivo and in vivo
[3]. Initial case reports of
treatment of renal cell carcinoma (RCC) with radiofrequency ablation described
the use of sonography for guidance
[4,
5]. However, most recent
publications and larger series describe the almost exclusive use of CT for
guidance
[6-8].
We report four patients in whom sonography was used to guide radiofrequency
ablation of right RCC using a transhepatic approach.
Subjects and Methods
Four patients with enlarging right renal masses were considered candidates
for radiofrequency ablation. All had solid incidental masses that had been
detected and followed on CT. Lesion sizes averaged 2.6 cm (range, 2-3 cm), and
all were in the upper pole or anterior aspect of the mid pole of the right
kidney (Table 1). In one
patient, renal biopsy revealed RCC. In the other three patients, biopsy was
not performed, but the masses were considered likely to be RCC because they
were solid, without fat, and enlarging. This study was approved by our
institutional review board. All patients gave informed consent to undergo the
procedure.
Because of underlying medical conditions or advanced age, none of the
patients was considered a surgical candidate. The demographic data are
included in Table 1. Conscious
sedation was not used in any of the patients. An anesthesia consultation was
obtained for all four patients. Patient 3 was considered such a high surgical
risk and anesthesia risk that the consulted anesthesiologist would provide
anesthesia only in the main operating room. The other three patients received
general anesthesia in the radiology department. In all patients, anesthesia
was induced with IV propofol, 1% (Baxter Healthcare), and maintained with
inhaled isoflurane (Baxter Healthcare). All patients had a platelet count
greater than 75,000, a partial thromboplastin time within 25% of the reference
range, and a prothrombin time within 2 sec of the reference range.
Radiofrequency ablation was considered the best treatment option for the
patients' renal malignancies. Before treatment, the optimal route of access to
these four presumed RCC tumors was planned. In all four patients, a
transhepatic route was selected. The supine position was believed to be the
best option. Access to the lesions in the upper pole of the kidney by CT using
prone positioning would have required an angulated technique but with possible
probe placement over the 12th rib. In two patients, the mass was in the
anterior mid pole of the right kidney, which would have required a needle
puncture through the renal hilum if the posterior approach had been used. In
two patients, prone positioning was not possible because of the patients'
weight (214 lb [97 kg] and 302 lb [137 kg]) and possible respiratory
compromise. All patients were scanned with sonography in the supine position,
and all tumors were seen well.
At the time of the procedure, sonography was used to identify and avoid
vascular structures within the intervening liver during needle placement
(Figs. 1A,
1B,
1C,
1D,
2A,
2B,
2C,
2D, and
2E). The radiofrequency
ablation needle was placed via the transhepatic route. In three patients, a
17-gauge Cool-tip needle (Valleylab) was used, and in the other patient, a
17-gauge Cool-tip cluster electrode (Valleylab) was placed. Sonography guided
the radiofrequency ablation in all four patients. In one patient (patient 3),
the consulting physician from the department of anesthesia believed the
patient would be treated best in the operating room rather than in the CT or
sonography suite. Therefore, sonography was used portably in the operating
room.
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Fig. 1A —Radiofrequency ablation of right renal mass in 86-year-old man
(patient 2). Real-time sonogram shows renal mass marked by electronic calipers
in upper pole of right kidney (RK). 1 = first diameter, 2 = second
diameter.
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Fig. 1B —Radiofrequency ablation of right renal mass in 86-year-old man
(patient 2). Color Doppler sonogram shows that few large vessels surround mass
(M). Vessels are more central in kidney (arrow).
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Fig. 1C —Radiofrequency ablation of right renal mass in 86-year-old man
(patient 2). Needle (straight arrow) has been placed transhepatically
into renal mass (curved arrow), which appears echogenic during
radiofrequency ablation treatment. RT = right.
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Fig. 1D —Radiofrequency ablation of right renal mass in 86-year-old man
(patient 2). CT scan obtained after radiofrequency ablation shows avascular
renal mass (arrow) and left kidney with renal cyst (C).
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Fig. 2A —Radiofrequency ablation of renal cell carcinoma in 80-year-old man
(patient 4). Sonogram obtained before radiofrequency ablation shows right
renal mass marked with electronic calipers. L = liver, K = kidney, 1 = first
diameter, 2 = second diameter.
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Fig. 2B —Radiofrequency ablation of renal cell carcinoma in 80-year-old man
(patient 4). Color Doppler sonogram shows hepatic vessels (arrowhead)
that were in needle path of possible ablation of renal mass (M).
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Fig. 2D —Radiofrequency ablation of renal cell carcinoma in 80-year-old man
(patient 4). Needle was passed transhepatically (straight arrow)
under sonographic guidance, thus avoiding hepatic vessels. Sonogram obtained
during treatment shows increased echogenicity of mass (curved arrow).
L = liver.
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In all four patients, the radiofrequency needle was placed through the
liver into the far border of the solid renal mass under sonographic guidance.
The lesions were identified well with sonography using the transhepatic route
with the patient supine. Use of sonography and color flow sonography allowed
vessels within the liver to be identified and avoided during needle placement
(Figs. 1A,
1B,
1C,
1D,
2A,
2B,
2C,
2D, and
2E). Sonography was used to
guide precise needle placement in the renal mass. Color flow sonography was
then used to avoid larger vessels within the kidney during needle placement.
Biopsy was not performed on three patients because of the characteristic CT
appearance of an enlarging renal mass. In one patient, preprocedural biopsy
revealed RCC. Radiofrequency ablation was performed using a pulsed current
with automated impedance control and an internally cooled electrode. The
wattage was increased in increments of 10 W/min, from 40 W to a maximum of 180
W. The end point of treatment was based on repeated impedance interruption and
simultaneous observation of an echogenic response on sonography. Needles were
repositioned in all patients, and one or two additional radiofrequency
ablation treatments were performed (Table
1). After radiofrequency ablation, the needle was removed with a
pullback technique through the liver at a power setting of 30 W, without use
of internally cooled saline. The patients were allowed to recover, and
dedicated contrast-enhanced (150 mL of iohexol [Omnipaque 300], GE Healthcare)
CT (LightSpeed, GE Healthcare) of the kidney was performed within 12 hr of the
treatment. All procedures were performed in the afternoon; the patients were
watched overnight and discharged the next morning. They were followed with
dedicated contrast-enhanced renal CT every 3 months for the first year and
annually after that.
Results
In all four patients, radiofrequency ablation of the renal tumors was
successful, as noted on contrast-enhanced CT afterward. All patients had a
zone of surrounding ablated renal tissue. No complications were encountered.
Review of the postoperative CT scans showed an area of lesion ablation
approximately 5 mm to 1 cm greater than the area of the tumor. Follow-up has
been from 3 mo to 4 yr 6 mo, without evidence of recurrence in any
patient.
Discussion
Radiofrequency ablation has become an accepted method of treating RCC in
patients who cannot undergo definitive nephrectomy for a renal mass. A number
of series have shown the efficacy of radiofrequency ablation for RCC. In a
series by Gervais et al. [6],
radiofrequency ablation of 42 RCCs was performed on 34 patients. In 29 RCCs
that were exophytic, no detectable disease remained after radiofrequency
ablation. Of 11 RCCs that were greater than 3 cm in diameter and contacted the
renal sinus, six contained detectable tumor even after repeated ablation.
Mayo-Smith et al. [7]
documented successful treatment of 31 of 32 RCCs after one or two
radiofrequency ablation sessions. All 26 smaller tumors, with a mean diameter
of 2.4 cm, were successfully treated with a single session of radiofrequency
ablation. Five of the six larger tumors, with a mean diameter of 3.5 cm,
needed a second radiofrequency ablation for complete eradication. In most of
these series, CT was used for guidance of radiofrequency ablation treatment of
RCCs. Exclusive CT guidance of radiofrequency ablation was performed in a
series by Zagoria et al. [8],
in which 22 of 24 RCCs were treated successfully. Most of these patients were
placed in the prone or decubitus position, and a posterior approach was
applied under CT guidance. In a review of renal radiofrequency ablation,
Zagoria [9] concluded that CT
guidance had several advantages over sonography in that it can show small
RCCs; lacks the obscuring artifacts that occur with sonography; and, in most
patients, allows the administration of IV contrast material before the
procedure to determine the adequacy of ablation.
We used an alternative guidance method and a different route of needle
placement in these four patients. For all four, the supine position was chosen
over the prone position, because of several factors. In addition, the size of
two of the patients (214 and 302 lb [97 and 137 kg, respectively]) would have
made prone positioning difficult although possible. Furthermore, the
consulting anesthesiologist thought that respiratory compromise might have
occurred with prone positioning in the larger of the two patients. Even
without those considerations, prone positioning would have required steep
needle angulation, perhaps over the 12th rib in two patients, to avoid the
lung pleura. The risk of complications using an intercostal approach is quite
low, and the intercostal approach may be appropriate in some patients. In two
patients, use of the prone position would have required placing the needle
posteriorly through the vascular renal hilum and into the anterior midpole
mass. Therefore, we decided to perform the procedure with all four patients
supine rather than prone.
We used sonography in our four patients for various reasons. One patient
(patient 3), after a preoperative anesthesia consultation, was believed to
have too many medical problems to undergo deep conscious sedation or general
anesthesia in the radiology suite. Therefore, radiofrequency ablation had to
be performed in the operating room, and only sonography could be used for
guidance because we do not have a CT scanner in the operating room.
A second reason for the use of sonography in all patients was that the
renal tumors were visualized well by that method with the patients supine. In
fact, for a transhepatic route, sonography may have advantages over CT, such
as the ability of color Doppler sonography to identify intervening vessels
within the hepatic parenchyma and thus avoid vessels in the needle path (Figs.
1A,
1B,
1C,
1D,
2A,
2B,
2C,
2D, and
2E). Furthermore, we found
sonography to be helpful in identifying and avoiding vessels within the
kidney.
We did not perform a biopsy on some patients before radiofrequency
ablation. Many urologists do not perform a biopsy before removal of renal
masses because of the potential risk of bleeding, the risk of tract seeding,
and the inaccuracies of biopsy
[10]. For three renal masses
that had the typical demographics and imaging characteristics of RCC, we did
not perform a biopsy. However, tract cauterization with radiofrequency
ablation would decrease the occurrence of tract seeding and bleeding with
percutaneous biopsy. For instance, Pritchard et al.
[11] performed renal biopsies
on animals with and without radiofrequency cauterization of the biopsy tract
using a biopsy introducer needle. Radiofrequency ablation of the biopsy needle
tract in the kidney reduced bleeding by 97%, compared with biopsies performed
without radiofrequency ablation. In none of our patients did we see recurrence
along the needle tract through the liver during follow-up. Newer coaxial
needle systems allow biopsy and radiofrequency ablation through a single
needle puncture, thus avoiding the need for one puncture for biopsy followed
by a second puncture for placement of the radiofrequency ablation needle.
Furthermore, in some series, tract seeding of RCC has not been considered as a
problem [12]. However, we
opted not to perform biopsy on three of our four patients.
One disadvantage of the transhepatic route is that it violates the
peritoneum, increasing the risk of seeding, which is mitigated but not
obviated by tract ablation. The 3- to 6-month follow-up in two of our patients
is not adequate for evaluation of this possibility.
In summary, in certain patients, prone positioning for radiofrequency
ablation may be impractical. Patients presenting with significant comorbidity
or an unfavorable tumor location may not be able to undergo radiofrequency
ablation in the prone position. Furthermore, in certain patients, sonography
may be chosen over CT for needle placement. We have reported four patients in
whom the tumor was shown well by sonography when the patients were supine.
Needle placement was visualized well using sonographic guidance and a
transhepatic route. This can be a consideration for certain superior or
anterior masses in the right kidney that require an alternative route of
access or method of treatment.
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Abstract
Introduction
