Image guided radiofrequency ablation for small renal masses

Abstract

The diagnosis of incidental small renal masses (SRM) has increased during the past two decades secondary to the increased use of various abdominal imaging modalities. In the past decade there has been a shift from radical nephrectomy to nephron sparing surgery techniques where partial nephrectomy has become the standard of care. Thermal ablation (TA) modalities such as freezing or heating delivered percutaneously for the treatment of small renal masses (SRM) is now offered in many Institutions as a treatment option. Clinical guidelines have indicated that TA is appropriate for select patients that are medically high risk or elderly. In our institution and in select centers, TA is discussed and often offered for all patients with SRM as equivalent treatment without respect to age or co-morbidities. As provider experience improves and long-term outcome studies become available, TA is becoming increasingly accepted as a potential new standard of care for solid SRM. This review will highlight the role of image guided radiofrequency ablation (RFA) techniques and their application focusing on the different imaging modalities for RFA application which, most commonly, include percutaneous (Magnetic Resonance Imaging (MRI) and computerized tomographic (CT). Our aim is to summarize those studies along with long term follow up.

Ablation Therapies in Small Renal Masses

“…RFA is based on the generation of heat by means of an alternating electric current used at different frequencies and consequently cell death occurs in the exposed area (9). This alternating electric current is transferred to the tissue with the aid of a probe placed in the center of the target tissue, and these systems are generally monopolar.…”

“…RFA-induced cellular damage is based on a time-temperature curve where less time is required at higher temperatures (9). In a study, cellular damage was shown to develop after 60 minutes exposure to 45°C, 5 minutes exposure to 55°C, and 1-minute exposure to 70°C (10).…”

“…At temperatures of 50-80°C, coagulation and cellular damage due to protein denaturation develops within seconds or minutes. Tissue ablation is observed with dehydration and vacuolization at temperatures above 100°C, while carbonization and melting are finally observed in the tissue when 150-300°C is reached (9).…”

Tips and tricks for a safe and effective image-guided percutaneous renal tumour ablation

“…With radiofrequency an alternating current determines ionic friction that leads to slow heat generation, with subsequent protein denaturation, blood coagulation, and coagulative necrosis [33, 34]. RFA determines also blood coagulation, thus reducing the bleeding risk in comparison with cryoablation [35].…”

US-guided percutaneous laser ablation of refractory metastatic retroperitoneal lesions

“…[1–5] Recently, many ablation therapies for abdominal metastatic tumors were used such as radiofrequency ablation (RFA), [6,7] microwave ablation (MWA), [8,9] cryoablation, [10] irreversible electroporation (IRE), [11] and high-intensity focused ultrasound (HIFU). [12,13] Retroperitoneal deep tumors from hepatic, colorectal, renal, prostate, and ovarian carcinomas have important structures like the gastrointestinal tract and large blood vessels around, which may challenge excision, and easily induce serious complications like hemorrhage, intestinal adhesion, and even death after injury.…”