Renal Radiofrequency Ablation Research Articles

V470 VIDEO: HYBRID REAL-TIME US SYSTEM FUSED WITH VIRTUAL 3D CT/MRI FOR IMAGE-GUIDED SURGERY

You have accessJournal of UrologyProstate Oncology1 Apr 2010V470 VIDEO: HYBRID REAL-TIME US SYSTEM FUSED WITH VIRTUAL 3D CT/MRI FOR IMAGE-GUIDED SURGERY Naoki Hirahara, Osamu Ukimura, Atsuko Fujihara, Tsuyoshi Iwata, Koji Okihara, Satoru Ishikawa, and Tsuneharu Miki Naoki HiraharaNaoki Hirahara Kyoto, Japan More articles by this author , Osamu UkimuraOsamu Ukimura Kyoto, Japan More articles by this author , Atsuko FujiharaAtsuko Fujihara Kyoto, Japan More articles by this author , Tsuyoshi IwataTsuyoshi Iwata Kyoto, Japan More articles by this author , Koji OkiharaKoji Okihara Kyoto, Japan More articles by this author , Satoru IshikawaSatoru Ishikawa Hitachi, Japan More articles by this author , and Tsuneharu MikiTsuneharu Miki Kyoto, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.544AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES In percutaneous interventional surgery for the renal and prostatic pathology, reliable intra-operative needle guidance is under investigation to increase the precision and safety of the targeting. This video demonstrates the clinical technique and usefulness of the hybrid navigation system (Real-time Virtual Sonography, RVS, Hitachi Medical Co., Kashiwa, Japan) as guidance for renal intervention and lesion-targeted prostate biopsy. METHODS During percutaneous intervention in renal radiofrequency ablation (RFA) for renal tumor, percutaneous nephrostomy for renal lithotripsy (PCNL), as well as MRI-detected lesion-targeted prostatic biopsy, we applied the hybrid system of real-time US with preoperative CT/MRI, which have been first introduced by us for renal intervention (BJU Int. 101:707. 2008). After the registration between pre-operative CT/MRI volume data and real surgical space, the workstation reconstructs and displays new tomograms of the virtual CT/MRI to be synchronized with real-time US image. RESULTS In 10 cases for RFA, 3 cases for PCNL, and 52 cases with MRI-suspicious cancerous lesions in the prostate, the hybrid system allowed real-time US visualization of the area of the surgical targets, that corresponded with the lesions to be detected by pre-operative CT/MRI, which were synchronized and displayed in parallel in the same screen of the US. Synchronized CT image increase the safety of renal intervention because of enhanced anatomical understanding of the vital anatomies surrounding the kidney. Using TRUS-MRI fusion guidance, cancer was revealed in 26 of the 52 patients, which improve up to 50% positive rate. The hybrid system guided biopsy enhanced identifying of cancer in 14 of the 26 cancer patients, which implicated 61% increase of positive rate compared to systematic biopsy technique alone. These data suggested that this system improve prostate cancer detection, especially on the lesions which can be identified by MRI alone. CONCLUSIONS The hybrid US-guidance system with CT for the kidney and with MRI for the prostate intervention allowed excellent anatomical visualization and precise navigation, in which anatomical understanding of the targets and surrounding organs can be enhanced by the synchronized CT or MRI. This system provides potentially effective guidance for the focal targeted therapy. This system involves only minimal additional time and costs, to use clinically available equipments of US, CT and MRI machines. © 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e185-e186 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Naoki Hirahara Kyoto, Japan More articles by this author Osamu Ukimura Kyoto, Japan More articles by this author Atsuko Fujihara Kyoto, Japan More articles by this author Tsuyoshi Iwata Kyoto, Japan More articles by this author Koji Okihara Kyoto, Japan More articles by this author Satoru Ishikawa Hitachi, Japan More articles by this author Tsuneharu Miki Kyoto, Japan More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Radiofrequency ablation of renal tumours: diagnostic accuracy of contrast-enhanced ultrasound for early detection of residual tumour

To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in the early detection of residual tumour after radiofrequency ablation (RFA) of renal tumours. Patients referred to our institution for RFA of renal tumours prospectively underwent CEUS and computed tomography (CT) or magnetic resonance imaging (MRI) before, within 1 day and 6 weeks after treatment. Identification of residual tumour was assessed by three blinded radiologists. Reference standard was CT/MRI performed at least 1 year after RFA. A total of 66 renal tumours in 43 patients (median age 62 years; range 44-71.5) were studied. Inter-reader agreement (kappa value) was 0.84 for CEUS. Prevalence of residual disease was 19%. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), respectively, were as follows: 64% [confidence interval (CI) 39-84], 98% [CI 91-100], 82% [CI 52-95] and 92% [CI 83-97] on 24-h CEUS; 79% [CI 52-92], 100% [CI 94-100], 100% [CI 74-100] and 95% [CI 87-100] on 6-week CEUS; 79% [CI 52-92], 95% [CI 86-98], 79% [CI 52-92] and 95% [CI 86-98] on 24-h CT/MRI; and 100% [CI 72-100], 98% [CI 90-100], 91% [CI 62-98] and 100% [CI 93-100] on 6-week CT/MRI. CEUS has high specificity for the early diagnosis of residual tumour after renal RFA.

The effect of radiofrequency ablation on different organs: Ex vivo and in vivo comparative studies

Objective The purposes of this study are to evaluate the ex vivo and in vivo efficacy of radiofrequency ablation (RFA) on different porcine tissues by the ablation of three different sites simultaneously. Materials and methods A multichannel RFA system, enables three separate tumors to be ablated simultaneously, was used. RFA procedures were applied to normal porcine liver, kidney, and muscle together ex vivo ( n = 12) and in vivo ( n = 17). Pre-impedances, defined as baseline systemic impedances of tissues before beginning RFA, and the areas of ablation zones were measured and compared. Results The areas of ablation zones among three organs had a significant difference in decreasing order as follows: liver, muscle, and kidney in the ex vivo study ( p = 0.001); muscle, liver, and kidney in the in vivo study ( p < 0.0001). The areas of ablation zones between ex vivo and in vivo had a significant difference in the liver and muscle (each p < 0.05). There was no significant correlation between the areas of ablation zones and pre-impedances in both studies. Conclusions Renal RFA produced the smallest ablation zone in both in vivo and ex vivo studies. Muscular RFA demonstrated the largest ablation zone in the in vivo study, and hepatic RFA showed the largest ablation zone in the ex vivo study. This variability in the tissues should be considered for performing an optimized RFA for each organ site.

Differences in Patterns of Care: Reablation and Nephrectomy Rates After Needle Ablative Therapy for Renal Masses Stratified by Medical Specialty

We aimed to study differences in reablation rates, modality utilization, and outcomes after renal tumor cryoablation (CA) and radiofrequency ablation (RFA), stratified by medical specialty. A literature review was performed to identify papers reporting renal RFA and CA results. Patient demographics and clinical and pathological variables were collected, as were ablation success and salvage treatment rates. Interventional radiologists (IR) reported more experience with renal RFA than with CA (31.4% v 11.3% of all reported cases, p < 0.001). However, the majority of renal RFA and CA are performed by urologists. The percutaneous approach was used far more often with RFA than with CA, reflecting this preference by radiologists (80.9% v 23.4%, p < 0.01). The mean tumor size, cancer-specific survival rates, mean follow-up duration, and salvage nephrectomy rates were not statistically different between CA and RFA. Tumor reablation rates were significantly higher for RFA than for CA (7.4% v 0.9%, p = 0.009). RFA reablation rate correlated closely to surgeon specialty, such that 72% of reablations were reported by IR, while only 28% were performed primarily by urologists (p < 0.0001). This was despite IR being primary surgeons in only 31.4% of first tumor ablations. Salvage nephrectomy was performed more after CA than after renal RFA, probably because 89% of CA were done by urologists. There were no reablations in the laparoscopically approached cases. Cancer-specific outcomes after renal tumor CA and RFA are similar. However, RFA has required more reablations to achieve 95% cancer-specific survival rates. IR reported more experience with RFA, and urologists reported more experience with CA. Overall, RFA and CA reablation rates are significantly higher when a percutaneous approach is used and seemed to correlate with surgeon specialty.

Current status of renal radiofrequency ablation

To provide an overview of the current literature addressing the role of radiofrequency ablation (RFA) for the management of renal cortical tumors. As the renal RFA experience continues to mature, longer-term data addressing the oncologic efficacy of this ablative modality are now available. Furthermore, the impact of RFA on secondary clinical endpoints, such as renal function outcomes, has now been addressed in several series. With the stage migration toward diagnosis of smaller renal masses, energy ablative techniques are being increasingly utilized as primary surgical modalities. Here, we review the role of RFA for the management of such masses and comment on technical considerations for this particular ablative technique. In addition, we provide a summary of contemporary longer-term oncologic outcomes and review the impact of RFA on renal function. As more renal masses are diagnosed in the elderly or comorbid patients, it is likely that ablative approaches will assume an increasingly central role in management strategies. In this regard, continued studies are necessary, particularly in regards to oncologic outcomes.

Ablación del cáncer renal por radiofrecuencia

IntroductionThe standard treatment of small renal masses is partial nephrectomy, which has showed similar oncologic results when compared with radical nephrectomy. Recently, ablative techniques, including radiofrequency and cryotherapy ablation, has been developed, with the purpose of minimizing adverse effects of standard surgical excision. In this article we review the technique of radiofrequency ablation. Material and methodsFor this review we conducted a search in the Medline database using the terms “renal radiofrequency ablation”. ResultsThe different currently marketed systems for the delivery of radiofrequency energy are examined. The different techniques of delivery (open, laparoscopic and percutaneous) are described; we observe a trend towards the use of the percutaneous method. Among the published clinical studies there are series of patients with midterm follow-up (3 years) that show oncologic outcomes similar to traditional resection techniques, with fewer complications. ConclusionsRenal tumor radiofrequency ablation has proved an effective therapy with minimal complications. However, it should be used only in selected patients until longer follow-up studies are available.

Ablación del cáncer renal por radiofrecuencia

IntroductionStandard treatment for small renal masses is partial nephrectomy, which has shown oncological results similar to radical nephrectomy. Ablation procedures such as radiofrequency and cryotherapy have recently been developed in order to minimize the side effects of conventional surgical excision. This article reviews radiofrequency ablation. Materials and methodsFor this review, a search was made in the Medline database using the term “renal radiofrequency ablation”. ResultsThe different currently marketed systems for delivery of radiofrequency energy are examined. The different delivery approaches (open, laparoscopic, and percutaneous) are described. A trend towards use of the percutaneous approach was seen. Published clinical studies already include patient series with mid-term follow-ups (3 years) showing oncological outcomes similar to conventional resection procedures with fewer complications. ConclusionsRenal tumor radiofrequency ablation has proved to be an effective treatment with minimal complications. However, it should only be used in selected patients until longer follow-up studies are available.

Is radiofrequency ablation more cost-effective than nephron-sparing surgery for small unilateral renal cell carcinoma?

A recent report suggesting significant cost-effectiveness advantage for renal radiofrequency ablation (RFA) over partial nephrectomy makes assumptions about rates of local cancer recurrence, estimates of which are inexact at this point in time. Uncertainty regarding the oncologic efficacy of RFA technology and the expense and challenges of adequate post-treatment surveillance further confound this comparison. Partial nephrectomy remains the standard of care for nephron-sparing surgery, and should remain the preferred treatment in patients with an acceptable risk profile. Until longer-term follow-up data are available, RFA should be reserved for elderly patients and those with multiple comorbidities who have only a small renal mass.

Infectious Complications after Percutaneous Radiofrequency Ablation of Renal Cell Carcinoma in Patients with Ileal Conduit

Percutaneous renal radiofrequency (RF) ablation is a safe and minimally invasive treatment for renal cell carcinoma. The most common minor complications are pain, self-limiting hematuria, and postablation syndrome. Major complications are rare and include significant hemorrhage and thermal injury to the ureter. Reports of infectious complications after ablation are uncommon, but increased risks in patients with ileal conduits have been reported. The present report describes two patients with ileal conduits who underwent percutaneous renal RF ablation and developed infectious complications (a renal abscess and a calyceal-cutaneous fistula) despite prophylactic antibiotic treatment.

CT-guided Instillation of 5% Dextrose in Water into the Anterior Pararenal Space before Renal Radiofrequency Ablation in a Porcine Model: Positive and Negative Effects

To assess the positive and negative effects of computed tomographic (CT)-guided instillation of 5% dextrose in water (D5W) into the anterior pararenal space before renal radiofrequency (RF) ablation in a porcine model. Under CT guidance, D5W was instilled into the right anterior pararenal space of 10 pigs and RF ablation performed in the right kidney. For the control lesions, RF ablation was performed in the left kidney of the same pigs without pretreatment with D5W. Approximately 1 week after RF ablation, bowel adhesion to both kidneys was compared by using a 5-point scale at open laparotomy, as follows: grade 0=no adhesion, grade 1=detachable adhesion, grade 2=grade 1 adhesion plus other adhesion to organs, grade 3=undetachable adhesion, and grade 4=bowel perforation. The areas of coagulation necrosis in both kidneys were compared at pathologic examination. Bowel adhesions to the right kidneys were classified as grade 0 in nine pigs and as grade 1 in one pig, whereas those to the left kidneys were classified as grade 2 in two pigs and as grade 3 in eight (P<.05). The mean areas of coagulation necrosis in right and left kidneys were 0.58 cm2+/-0.5 and 1.53 cm2+/-1.3, respectively (P<.05). CT-guided D5W instillation has a positive effect in reducing the amount of bowel adhesion injury during RF ablation. However, this technique may limit the area of coagulation necrosis in a swine model. Longer term pathologic evaluation is necessary to fully understand the effects of D5W instillation.

Interventional oncology in urology

Partly because of its rising incidence, but mostly because of the availability of modern examination techniques, the detection rate of small renal-cell carcinomas is increasing more and more. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that arouse the suspicion of malignancy should be treated. Operative treatment techniques such as radical and partial nephrectomy are increasingly carried out as laparoscopic procedures and are regarded as the gold standard. Modern thermal ablation techniques may be a helpful treatment option for patients who are unfit for a surgical resection or refuse it. Radiofrequency ablation (RFA) is the most frequently applied of these methods. Modern probes allow ablation of lesions between 2 and 5 cm in diameter. In the vast majority of cases RFA is carried out percutaneously and monitored by ultrasound or CT; it is deemed safe and the complication rate is low. While randomized comparative studies against open resection are yet available, the preliminary results obtained with renal RFA are promising and suggest that RFA may be superior to other thermal ablation techniques. Clinical success rates are over 90% for radiofrequency, and also for cryotherapy, which is performed less often. Local relapse is very uncommon.

Outcomes of Radiofrequency Ablation for Kidney Cancer

The incidence of small (< 4 cm) solid enhancing renal masses has been rising, and the majority (60% to 80%) of these tumors are renal cell carcinomas (RCCs) when pathologic analysis is performed. Needle ablation for small incidental renal masses is an attractive therapeutic option. Reasons include its decreased morbidity, shorter convalescence, and the ability to avert the higher risk of extirpative surgery in an aging patient population. Radiofrequency ablation (RFA) is a thoroughly studied needle ablative method used for RCC. The current published literature on renal tumor RFA was reviewed. The in vitro experiments, animal studies and clinical experience with RFA for treatment of small RCCs were analyzed and various controversies in renal RFA are presented for discussion. Percutaneous and laparoscopic renal RFA can be safely performed and can eradicate small RCCs with cancer specific survival rates over 90% to 95% in many series. While long-term (5 years or greater) cancer control data are not yet available, these intermediate-term results are similar to those achieved with traditional nephron-sparing surgical options. However, the optimal method to perform RFA for renal masses is still evolving. While long-term cancer control data are not yet available, the current literature suggests that RFA can effectively eradicate small RCCs. Further research is needed to elucidate the influence of various treatment variables, including impedance vs temperature-controlled RFA, sonographic vs computed tomographic guidance, general anesthetic vs conscious sedation, and radiologist vs urologist delivery of renal RFA.

Time Course of Nicotinamide Adenine Dinucleotide Diaphorase Staining after Renal Radiofrequency Ablation Influences Viability Assessment

Nicotinamide adenine dinucleotide (NADH) diaphorase staining has been used to confirm cell viability or death after radiofrequency ablation (RFA) of renal tissue. The time course over which NADH staining status converts from viable to non-viable after a lethal insult has not been defined for renal RFA, but the change may not be immediate. Our objective was to assess porcine renal tissue for viability using NADH diaphorase staining at various times after RFA. Seven pigs underwent monopolar RFA of both kidneys followed by needle biopsy of the ablation zone before and immediately after ablation and at 15-minute intervals thereafter. Initially, a single kidney was treated, and the contralateral kidney was treated 2 weeks later. Biopsies were taken from untreated renal parenchyma in a similar time course after nephrectomy to examine the effect of ischemia. All biopsy specimens, as well as representative sections of the ablation zone, were subjected to NADH staining and reviewed by a pathologist who was blinded to the tissue treatment. Most of the post-RFA biopsy specimens (86%) showed non-viable tissue. However, 14% of the specimens revealed viable tissue as late as 150 minutes after RFA. Therefore, none were positive. In the nephrectomy parenchyma, 92% of the biopsy specimens showed viable tissue as late as 4 hours after the onset of ischemia. Staining for NADH can establish tissue non-viability after RFA, but the timing of staining after treatment must be considered when interpreting results to avoid false positive tests. Tissue that is apparently viable by NADH staining within 2.5 hours of RFA may in fact have been ablated.

550: Time Course of Nicotinamide Adenine Dinucleotide Diaphorase Staining Following Renal Radiofrequency Ablation Influences Viability Assessment

You have accessJournal of UrologyPodium, Sunday, May 21, 2006, 3:30 - 5:30 pm1 Apr 2006550: Time Course of Nicotinamide Adenine Dinucleotide Diaphorase Staining Following Renal Radiofrequency Ablation Influences Viability Assessment J. Kyle Anderson, Meredith R. Baker, Omar Jaffer, Margaret S. Pearle, and Jeffrey A. Cadeddu J. Kyle AndersonJ. Kyle Anderson More articles by this author , Meredith R. BakerMeredith R. Baker More articles by this author , Omar JafferOmar Jaffer More articles by this author , Margaret S. PearleMargaret S. Pearle More articles by this author , and Jeffrey A. CadedduJeffrey A. Cadeddu More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(18)32796-4AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "550: Time Course of Nicotinamide Adenine Dinucleotide Diaphorase Staining Following Renal Radiofrequency Ablation Influences Viability Assessment." The Journal of Urology, 175(4S), pp. 178–179 © 2016 by American Urological AssociationFiguresReferencesRelatedDetails Volume 175Issue 4SApril 2006Page: 178-179 Advertisement Copyright & Permissions© 2016 by American Urological AssociationMetricsAuthor Information J. Kyle Anderson More articles by this author Meredith R. Baker More articles by this author Omar Jaffer More articles by this author Margaret S. Pearle More articles by this author Jeffrey A. Cadeddu More articles by this author Expand All Advertisement PDF DownloadLoading ...

Effects of radiofrequency ablation on individual renal function: assessment by technetium-99m mercaptoacetyltriglycine renal scintigraphy.

We quantitatively evaluated total and individual renal function by technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3) renal scintigraphy before and after radiofrequency ablation (RFA) of renal tumors. Eleven patients who underwent Tc-99m MAG3 renal scintigraphy 1 week before and after RFA were evaluated (7 men and 4 women; age range: 23-83 years; mean age: 60.6 years). Five patients had solitary kidneys, and five had normally or minimally functioning contralateral kidneys. One patient had a renal cell carcinoma in the contralateral kidney. One patient with a solitary kidney underwent RFA a second time for a residual tumor. In patients with a solitary kidney, MAG3 clearance decreased after 5 of 6 RFAs, and in patients with a normally functioning contralateral kidney, MAG3 clearance decreased after 4 of 5 RFAs, but no significant differences were observed between before and after treatments. In addition to the total MAG3 clearance, the split MAG3 clearance was evaluated in patients with a normally functioning contralateral kidney. MAG3 clearance decreased in 4 of 5 treated kidneys, while it adversely increased in the contralateral kidneys after 4 of 5 RFAs. No significant differences, however, were observed between before and after treatments. The results of our study revealed no significant differences in sCr, BUN, CCr, or MAG3 clearance between pre- and post-RFA values. These results support data regarding the functional impact and safety of renal RFA in published reports. We evaluated total and individual renal function quantitatively using Tc-99m MAG3 renal scintigraphy before and after treatment. This scintigraphy was very useful in assessing the effects of RFA on renal function.

Magnetic resonance imaging characteristics of renal tumors after radiofrequency ablation

Objectives The interpretation of radiographic findings in renal tumors treated with minimally invasive modalities, such as radiofrequency ablation (RFA), is critical for assessing treatment adequacy. Magnetic resonance imaging (MRI) is commonly used for patients with renal insufficiency or contrast allergy. Because the MRI experience with renal RFA is limited, we reviewed our experience and report the unique MRI characteristics of RFA-treated renal tumors. Methods A single-institution database of renal RFA was reviewed to identify patients followed up with MRI. A radiologist and urologist retrospectively reviewed all MRI scans to identify the characteristic lesion findings after RFA. Results Eleven patients (12 tumors) treated by RFA were followed up with MRI examinations. The mean follow-up was 10 months. The mean tumor size at ablation was 2.4 cm, with minimal reduction over time. Ablated lesions were characterized by high signal intensity on T 1-weighted images, low signal intensity on T 2-weighted images, and an absence of contrast enhancement. Of the patients treated by percutaneous RFA, 71% developed a characteristic peritumor halo, seen as a rim of low signal intensity on T 1-weighted and T 2-weighted images, surrounding a zone of perinephric fat just external to the ablated area. Two lesions demonstrated enhancement on the initial postablation MRI scan, indicating incomplete ablation. Conclusions The MRI characteristics of successfully ablated renal tumors include the absence of enhancement, minimal size reduction over time, and high and low signal intensity on T 1-weighted and T 2-weighted imaging, respectively. Knowledge of these findings can aid radiologists and urologists in correctly assessing the success of RFA for kidney lesions.

Radiofrequency Ablation of a Central Renal Tumor: Protection of the Collecting System with a Retrograde Cold Dextrose Pyeloperfusion Technique

Renal radiofrequency (RF) ablation therapy is a safe and effective therapy for small renal cell carcinoma. Although the risk of complications is low, the potential for ureteral or calyceal injury does increase in the case of a centrally located lesion. A retrograde cold dextrose pyeloperfusion technique was designed to protect the collecting system in a patient who underwent percutaneous RF ablation of a central tumor of the left kidney.

RETROGRADE RENAL COOLING DURING RADIO FREQUENCY ABLATION TO PROTECT FROM RENAL COLLECTING SYSTEM INJURY

We evaluated the protective effect of continuous retrograde irrigation of ice-cold saline on the renal collecting system during central parenchymal temperature based radio frequency ablation (RFA). In 10 domestic pigs bilateral, centrally located renal parenchymal RFA lesions (intended 2 cm in diameter) were created that intentionally involved the collecting system. RFA probe placement was guided by fluoroscopy with retrograde collecting system opacification and simultaneous direct laparoscopic visualization. In 1 renal unit RFA was performed while infusing ice-cold saline through a previously placed ureteral access sheath and pigtail stent. RFA without renal cooling was performed in the contralateral renal unit. Kidneys were harvested at 7 days. The renal collecting system was inspected for injury by performing retrograde pyelograms and by histological examination of the collecting system adjacent to the ablation zone. The size of RFA lesions was measured. In retrograde cooling procedures the temperature of saline irrigant was -1.0C and the mean temperature of the effluent was 13C. One of 10 cooled renal units demonstrated contrast material extravasation from the collecting system involved by the ablation zone compared with 7 of 10 noncooled renal units (p = 0.025). Lesion size was comparable between cooled kidneys and controls (2.67 and 2.72 cm, respectively, p = 0.629). Retrograde renal cooling helps protect the renal collecting system from injury during RFA without a decrease in expected lesion size. Clinically retrograde renal cooling may decrease the risk of collecting system injury and subsequent complications during RFA.

Radiofrequency ablation of renal tumors

Percutaneous thermal ablation is increasingly applied in the therapy of renal tumors. Various techniques are available, allowing a safe and accurate therapy of renal tumors either using hyperthermia such as radiofrequency ablation (RFA), laser-induced thermotherapy (LITT) and microwave ablation (MW) or by hypothermia (cryoablation). As thermal ablation is a minimally invasive and nephron-sparing procedure, it is ideally suited for patients with a single kidney, multiple tumors or contraindications for resective surgery. Although cryotherapy is the most extensively studied technique, RFA has become the most accepted thermal ablation technique over the last years. Modern RFA probes allow ablation volumes between 2 and 5 cm in diameter. A major advantage of RFA is the ability to avoid tract bleeding and tumor seeding by coagulating the puncture channel during RF probe withdrawal. The increasing number of clinical reports on RFA of the kidney show the promising potential of renal RFA for minimally invasive tumor treatment. Due to its technical benefits, RFA seems to be advantageous when compared to cryoablation or laser ablation. However, there are no long-term follow-up or comparative data proving an equal effectiveness to surgery.

Renal radiofrequency ablation: clinical status 2003.

Energy-based tumor ablative techniques are under development for the minimally invasive treatment of renal cell carcinoma. Radiofrequency ablation has recently entered phase II clinical trials for the treatment of small renal tumors. The authors review the status of these clinical trials. Radiofrequency ablation has shown reproducible tumor destruction in both animal models and recent clinical trials. Radiographic follow-up of radiofrequency ablated small renal tumors demonstrates little or no residual contrast enhancement depending on tumor size, location within the kidney, and mode of delivering radiofrequency energy. Pathologic evaluation of ablated tumors shows more variability in outcome, with many tumors demonstrating small areas of viable residual tumor. Radiofrequency ablation shows promise for the minimally invasive treatment of small renal tumors but will remain experimental until the resolution of certain technical issues.