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Technical Innovation |
1 Interventional Radiology, The University of Texas M. D. Anderson Cancer
Center, 1515 Holcombe Blvd., Box 325, Houston, TX 77030.
2 Urology, The University of Texas M. D. Anderson Cancer Center, Houston, TX
77030.
Received August 30, 2004;
accepted after revision October 8, 2004.
Address correspondence to K. Ahrar
(kahrar{at}mdanderson.org).
Abstract
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CONCLUSION. Percutaneous radiofrequency ablation of tumors in the upper pole of kidneys with intervening lung parenchyma can be accomplished successfully using a transthoracic approach through an iatrogenic pneumothorax. This technique allows for precise placement and repositioning of the radiofrequency electrode under CT guidance without repeated puncture of the visceral pleura.
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We retrospectively reviewed the records of 29 patients with renal cell carcinoma who were treated at our institution with percutaneous radiofrequency ablation from September 2001 to March 2004. We identified four patients who had tumors involving the upper pole of the kidney. There were three men and one woman with a mean age of 74 years (range, 69-83 years). Indications for radiofrequency ablation included one or more of the following: high surgical risk (n = 2), concurrent treatment for other malignancies (n = 3), or a solitary kidney (n = 1). The mean tumor size was 3.5 cm in the largest diameter (range, 2.5-5.3 cm). In all four patients, the tumor was located in the right kidney (Figs. 1A, 1B, 1C, and 1D).
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All radiofrequency ablation procedures were technically successful without any complications related to pneumothorax. All four patients were easily ventilated during the procedure. At the end of the procedure, a moderate pneumothorax was identified in three patients. In these patients, an 8.5-French pneumothorax evacuation tube (Cook) was placed under CT guidance. Tubes were placed by standard Seldinger technique from a posterior approach without repositioning the patients. Each tube was connected to a Heimlich Chest Drain Valve (Cook). The pneumothorax in the fourth patient was small and did not require treatment. All four patients were successfully extubated after the procedure. Expiratory chest radiograms were obtained in all patients the next morning at a mean interval of 18 hr (range, 17-19 hr). In three patients with chest tubes, the lungs were fully expanded. The chest tubes were clamped for 2 hr, and a repeat chest radiogram showed no recurrent pneumothorax. All tubes were successfully removed, and patients were discharged home in stable condition without any further sequelae. The fourth patient with a small pneumothorax that was not treated was found to have a small, stable pneumothorax on the follow-up examination but required no further treatment. Follow-up imaging at a mean of 2.5 months (range, 1-4 months) showed no recurrent pneumothorax or pleural effusion in any of the patients.
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To avoid puncturing the lung with the radiofrequency electrode, one can start the puncture site inferior in relation to the tumor and pleural reflection and triangulate the placement of the electrode into an upper pole tumor. One also can angulate the CT gantry to monitor the path of the needle. Both of these techniques are used for biopsy of abdominal and retroperitoneal masses [6, 7]. While triangulation is effective for performing biopsies, it may not be optimal for radiofrequency ablation of renal tumors. Treatment of larger renal tumors with radiofrequency ablation requires precise positioning of the electrode and creation of multiple overlapping ablations so that the whole tumor is treated. Currently, there are no computer software programs to facilitate this task, and the whole analysis takes place in the mind of the operator. When triangulation techniques or angling of the gantry is used, it becomes increasingly difficult to picture the tumor and the overlapping ablations three-dimensionally, resulting in unnecessary overablation in some areas and underablation in other areas of the tumor.
In our technique, we circumvented these problems by a transthoracic approach to the kidney. In this case, an intentional pneumothorax is created, as has been described in the literature for the biopsy of mediastinal masses [8]. With the lung retracted from the base of the pleural cavity, a clear path becomes available for placement of the electrode in a nearly axial plane. In this fashion, a treatment plan, consisting of the number and location of overlapping ablations, can be formulated in the mind of the operator. The electrode can be retracted and repositioned without puncturing the visceral pleura, minimizing the risk of prolonged air leak or formation of bronchopleural fistulas. When the ablation is completed, one can use an 18-gauge needle or a small catheter to evacuate the pneumothorax. Alternatively, a small (8.5-French) pneumothorax evacuation tube can be inserted posteriorly in the base of the pleural cavity without repositioning the patient. The tube can be connected to suction or a Heimlich Chest Drain Valve. Patients even can be discharged with the chest tube connected to the Heimlich valve. The patient then returns in approximately 24 hr for evaluation of the pneumothorax and chest tube removal. In our patients, initial needle placement could have resulted in the puncture of the visceral pleura. Furthermore, we performed all radiofrequency ablations with the patient under general anesthesia and admitted all of our patients for overnight observation. For these reasons, we chose to treat our patients with pneumothorax evacuation tubes rather than simple evacuation of the pneumothorax using a needle.
Although we did not encounter a tension pneumothorax in any of our patients, it is a potentially life-threatening complication resulting from this technique. One must be cognizant of the size of the pneumothorax and early signs of developing tension pneumothorax. A rapidly enlarging pneumothorax or a tension pneumothorax can be readily treated with placement of a chest tube under CT guidance. Another potential complication is seeding of the tract with neoplastic cells. Of the 213 treated tumors reported in the literature, only one case of seeding has been encountered (0.47%). This risk, albeit small, is present regardless of whether a transpleural or retroperitoneal approach is selected. Early detection and prompt treatment remain the only viable options to manage this potential complication.
In our experience, the intentional pneumothorax can be treated easily, and the chest tubes can be removed successfully fewer than 24 hr following the procedure. We have not encountered any other adverse sequelae from puncturing the parietal pleura or the diaphragm with the radiofrequency ablation electrodes.
In conclusion, we have found that CT-guided, transthoracic radiofrequency ablation of tumors in the upper pole of the kidneys through an intentionally created pneumothorax is feasible and allows for the percutaneous treatment of patients who may be at high surgical risk.
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