Complications of Radiofrequency Ablation
Reported morbidity and mortality rates associated with RFA (Table 85C.5) can be difficult to interpret, in part because technical approaches vary. Some investigators combine RFA with other treatments, such as liver resection, but addition of a second procedure may inflate the complication rate. Ablation of multiple tumors also increases the risk of complications such as bleeding or bile leak. Early studies often used multiple sequential RFAs for treatment of a single hepatic tumor, because the monopolar electrode gave a smaller thermal ablation field than the current cluster electrodes. The multiple ablations required to destroy larger tumors increased the potential for complications.
Unfortunately, the reporting of morbidities is not standardized. Some authors regard low-grade fevers, transient liver function test elevations, small pleural effusions, and right upper quadrant pain as minor complications, whereas others believe these are expected events that should not be reported. As expected, studies undertaken at institutions with skilled interventionalists or surgeons report fewer complications. Variations in patient selection and disease type also confound interpretation of results: for example, patients with HCC have different comorbid factors than those with colorectal metastases, and a patient's preprocedural state may influence the outcome of RFA.
Direct complications of RFA include biloma, biliary fistula, ascites, hepatic insufficiency, arteriovenous fistula, symptomatic pleural effusion, abscess, pain, hemorrhage, hydropneumothorax, pneumothorax, and thermal injury to surrounding structures. Burns related to grounding pads have also been reported, but these can be avoided by proper positioning of the pads, by using more pads for longer ablations, and by carefully following the manufacturer's directions. Other potential complications are those related to an operative procedure, such as myocardial infarction, cardiac arrhythmias, and pneumonia.
As illustrated by the following two cases, RFA should be undertaken only by skilled physicians able to identify and manage its complications and only at centers equipped with appropriate staff and equipment for acute care. Figure 85C.9 shows a bile duct injury caused by RFA of a colorectal cancer metastasis near the porta hepatis. The injury was treated with endoscopic retrograde cholangiopancreatography (ERCP) and biliary stenting. Figure 85C.10 shows a hepatic artery pseudoaneurysm attributed to RFA of liver metastases. This was successfully treated with embolization by a skilled interventionalist.
The best way to avoid potential complications of percutaneous RFA is to understand its technical limitations. A large multicenter study reported morbidity and mortality rates of 0.3% and 2.2%, respectively (Livraghi, 2003b). In this study, about 33% of all deaths and 10% of morbidities were associated with gastrointestinal thermal injury and perforation. Patients with prior abdominal surgeries resulting in adhesions and those with peripheral liver tumors had an increased risk for gastrointestinal injury during percutaneous ablation. The authors recommended consideration of open or laparoscopic RFA, instead of percutaneous RFA, for tumors within 1 cm of the liver edge adjacent to bowel.
Injury to the diaphragm is also a potential complication during percutaneous RFA, especially when tumors at the dome of the liver are treated. In an animal model, carbon monoxide was introduced into the peritoneal cavity to separate the diaphragm and the liver; although this reduced severe diaphragmatic injury during superficial hepatic RFA (Raman et al, 2004), the technique needs further clinical testing.
Abscess, one of the most frequent complications of RFA, typically occurs 1 week after ablation and requires percutaneous or surgical drainage (de Baere et al, 2003; Wood et al, 2000). Patients with bilioenteric anastomosis or biliary stenting appear to have a higher rate of abscess formation. All patients undergoing RFA should receive periprocedural antibiotics that cover coliforms as well as skin flora, and temperature and leukocyte counts should be followed after the procedure. Normally, low-grade fever and fatigue may occur immediately after RFA for up to 7 to 10 days, a so-called postablation syndrome; however, any persistent significant fever or elevation of white blood cell count should prompt CT imaging for possible hepatic abscess.
Reports of tumor seeding vary from 0.5% to 12% (de Baere et al, 2003; de Sio et al, 2001; Llovet et al, 2001), possibly reflecting differences in follow-up. Llovet and colleagues (2001) found that tumor seeding during RFA was related to subcapsular tumor location and poor tumor differentiation. Recent tumor biopsy, multiple needle insertions, and tumor hemorrhage during treatment may also increase the risk of needle-tract seeding. This complication can be avoided by limiting the number of needle insertions, angling the needle to traverse normal hepatic parenchyma prior to entering the tumor, and cauterizing the tract upon withdrawal of the needle. Nicoli and colleagues (2004) reported rapid diffusion of neoplastic cells after the creation of an arteriovenous fistula following RFA. The authors attributed seeding of tumor cells to the pressure gradient between the high-pressure tumor arteries and the low-pressure portal system; however, this is the only report of this complication in several thousand RFAs to date.
Injury to bile ducts during RFA can result in stenosis and proximal biliary dilation (see Chapter 42Chapter 42AChapter 42B). Most physicians agree that tumors within 15 to 20 mm of a major bile duct should not be treated by RFA (Mulier et al, 2002); however, Elias and colleagues (2001) introduced intraductal cooling to prevent RFA-associated biliary stenosis. They infused cooled (4° C) Ringer's lactate through a catheter after choledochotomy. Intraductal cooling was undertaken in 13 patients undergoing RFA of tumors within 6 mm of a central bile duct; one patient had a local recurrence, and one developed biliary stenosis (Elias et al, 2004). Biliary stenting also can prevent biliary injury during ablation of tumors near the bile ducts (Wood et al, 2000).