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Major Complications after Radio-frequency Thermal Ablation of Hepatic Tumors: Spectrum of Imaging Findings¹

¹ From the Korean Study Group of Radiofrequency Ablation (H.R., K.H.Y., J.M.L., Y.C., J.S.C., S.H.K., W.J.L., H.K.L., G.J.N., S.S.H., Y.H.K., C.M.P., P.N.K., J.Y.B.); the Department of Diagnostic Radiology, Hanyang University Hospital, 17 Haengdang-Dong, Sungdong-Ku, Seoul 133-792, Korea (H.R.); the Department of Radiology, Wonkwang University Hospital, Iksan, Korea (K.H.Y.); the Department of Diagnostic Radiology, Chunbuk University Hospital, Jeonju, Korea (J.M.L.); the Department of Diagnostic Radiology, Korean Veterans Hospital, Seoul (Y.C.); the Department of Diagnostic Radiology, Chungnam University Hospital, Daejon, Korea (J.S.C.); the Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea (S.H.K., W.J.L., H.K.L.); the Department of Diagnostic Radiology, Dong-A University Hospital, Busan, Korea (G.J.N.); the Department of Diagnostic Radiology, Inje University Busan Paik Hospital, Busan, Korea (S.S.H.); the Department of Diagnostic Radiology, Korea University Hospital, Seoul (Y.H.K., C.M.P.); the Department of Diagnostic Radiology, Asan Medical Center, Seoul, Korea (P.N.K.); and the Department of Diagnostic Radiology, Catholic University Hospital of Korea, Seoul (J.Y.B.). Recipient of a Cum Laude award for an education exhibit at the 2001 RSNA scientific assembly. Received March 12, 2002; revision requested April 29 and received June 20; accepted June 21. Address correspondence to H.R. (e-mail: rhimhc@hanyang.ac.kr).

	Abstract

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 
Although radio-frequency (RF) ablation has been accepted as a promising and safe technique for treatment of unresectable hepatic tumors, investigation of its complications has been limited. According to the multicenter (1,139 patients in 11 institutions) survey data of the Korean Study Group of Radiofrequency Ablation, a spectrum of complications occurred after RF ablation of hepatic tumors. The prevalence of major complications was 2.43%. The most common complications were hepatic abscess (0.66%), peritoneal hemorrhage (0.46%), biloma (0.20%), ground pad burn (0.20%), pneumothorax (0.20%), and vasovagal reflex (0.13%). Other complications were biliary stricture, diaphragmatic injury, gastric ulcer, hemothorax, hepatic failure, hepatic infarction, renal infarction, sepsis, and transient ischemic attack. One procedure-related death (0.09%) occurred (due to peritoneal hemorrhage). Three important strategies for decreasing the rate of complications are prevention, early detection, and proper management. A physician who performs RF ablation of hepatic malignancies should be aware of the broad spectrum of major complications so that these strategies can be used.

© RSNA, 2003

Index Terms: Interventional procedures, complications, 761.1269 • Liver, interventional procedures, 761.1269 • Liver neoplasms, therapy, 761.1269, 761.30 • Radiofrequency (RF) ablation, 761.1269

	LEARNING OBJECTIVES

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 
After reading this article and taking the test, the reader will be able to:

• Recognize the imaging features of major complications that occur after RF ablation of hepatic tumors.
  
• Discuss the importance of early detection and proper management of major complications after RF ablation of hepatic tumors.
  
• List the risk factors for the complications encountered after RF ablation of hepatic tumors.
  

	Introduction

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 
Despite having excellent therapeutic effect, any interventional procedure should be performed only after it has been proved safe with minimal morbidity and mortality. Although radio-frequency (RF) thermal ablation has been accepted as a promising technique for treating unresectable hepatic tumors (1–17), there have been few systematic analyses of complications in large series (18–25). Early detection and proper management of complications are possible only if the physician performing RF ablation understands the broad spectrum of complications encountered after ablation. Furthermore, knowledge about such complications enables the operator to minimize complications after ablation as well as exclude high-risk patients during preablation assessment.

The purpose of this article is to present the various imaging features of complications that occur after RF ablation of hepatic tumors according to the survey data of the Korean Study Group of Radiofrequency Ablation. Representative cases of each complication as well as technical tips for avoiding the complication are presented.

	Materials and Methods

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 
In May 2001, the Korean Study Group of Radiofrequency Ablation surveyed 11 institutions about the major complications that occurred after RF ablation of hepatic tumors. A major complication was defined as any symptom that developed after RF ablation and persisted for more than 1 week or required any type of management. Thus, transient postablation syndrome including mild and transient pain and fever was excluded from the survey.

Answers to the detailed questionnaire about the complications after RF ablation were collected. The questions were divided into two categories: basic information and information related to complications. Basic information included date of RF ablation of the first patient, total number of patients, total number of ablation sessions, total number of ablated tumors, guidance modality, inclusion and exclusion criteria, and anesthesia method. Information related to each complication included age and sex of the patient, tumor type, maximum diameter and number of tumors, date of the procedure, date the complication was identified, modality used to diagnose the complication, RF equipment used, procedure time, anesthesia method, guidance modality, method of approach (percutaneous vs open), management of the complication, final result of the complication, and lessons learned from the complication. The types of lesions treated and the numbers and characteristics of the complications attributed to the procedure were evaluated.

Inclusion criteria for RF ablation in the survey were as follows: single tumor smaller than 5 cm in maximum diameter; multiple tumors (up to four) with each 3 cm in maximum diameter or smaller; absence of portal venous thrombosis or extrahepatic metastases; Child-Pugh class A or B liver cirrhosis; prothrombin time ratio greater than 50%; and platelet count greater than 70,000/µL (70 x 10⁹/L). A total of 1,520 RF ablation procedures in 1,139 patients with 1,663 hepatic tumors (1,303 hepatocellular carcinomas and 360 metastases) were included in the survey. The equipment used for RF ablation was as follows: Five institutions used equipment from RITA Medical Systems (Mountain View, Calif), four used equipment from Radiotherapeutics (Mountain View, Calif), and two used equipment from Radionics (Burlington, Mass). All procedures were performed percutaneously under ultrasonographic (US) or computed tomographic (CT) guidance on an inpatient basis. The spectrum of major complications including prevalence and prognosis is reported with representative cases. Statistical analysis was performed with the Student t test (P = .05).

	Results

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 
Thirty-seven major complications (2.43%) were encountered (Fig 1): 10 hepatic abscesses (0.66%), seven peritoneal hemorrhages (0.46%), three bilomas (0.20%), three ground pad burns (0.20%), three pneumothoraces (0.20%), two vasovagal reflexes (0.13%), one biliary stricture (0.07%), one diaphragmatic injury, one gastric ulcer, one hemothorax, one case of hepatic failure, one hepatic infarction, one renal infarction, one case of sepsis, and one transient ischemic attack. One procedure-related death (0.09%) occurred (due to a peritoneal hemorrhage). The prevalence of complications was 1.8% in the hepatocellular carcinoma group and 5.2% in the metastasis group (P > .05).

View larger version (37K): [in this window] [in a new window] [Download PPT slide]   Figure 1.  Broad spectrum of major complications after RF ablation for hepatic tumors according to the survey data of the Korean Study Group of Radiofrequency Ablation. One procedure-related death occurred (due to peritoneal hemorrhage).

The reported prevalence of hepatic abscesses in our survey (0.66%) was similar to that after transarterial oily chemoembolization (0%–1.4%) (26). Although the mechanism of abscess development after RF ablation is still not established, subsequent bacterial contamination of the ablated hepatic parenchyma may lead to abscess formation. Therefore, a colonized biliary tract (eg, bilioenteric anastomosis, endoscopic papillotomy, bilioenteric fistula, external biliary drainage, and pneumobilia of unknown origin) or an immunocompromising condition such as diabetes can be important risk factors for abscess or sepsis after RF ablation as well as after transarterial oily chemoembolization (26,27). Thus, an operator should keep in mind the risk factors for abscess formation as well as the importance of an aseptic technique during the whole procedure. Prophylactic use of antibiotics may be beneficial for patients with a high risk of infection.

Early detection will be possible only if the operator is alert to the presence of prolonged fever after the ablation and close clinical follow-up of the patient with risk factors is performed. The imaging appearance of abscesses that develop after RF ablation is very similar to that of usual hepatic abscesses (Fig 2). New gas bubbles not previously seen could signal an infection, although minimal air bubbles within the ablated area can often be seen at CT performed immediately after ablation. These minimal amounts of air within the ablated area at immediately performed CT are aggregated microbubbles produced during the ablation and usually resolve within 1 month (28). Thus, such microbubbles seen at immediate follow-up CT should not be misdiagnosed as an abscess, especially if the patient demonstrates postablation syndrome.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Hepatic abscess in a 55-year-old man with hepatocellular carcinoma. (a) Contrast material-enhanced CT scan obtained before RF ablation shows a 1.5-cm-diameter hyperattenuating nodule of hepatocellular carcinoma (arrow) in segment VI. The patient was readmitted due to abrupt development of a fever 1 week after ablation. (b) One-week follow-up CT scan shows a gas-forming abscess (arrow) in the ablated area with a perihepatic fluid collection. The abscess was successfully managed with US-guided percutaneous catheter drainage. (c) One-week follow-up CT scan shows moderate improvement of the abscess (arrow).

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Hepatic abscess in a 55-year-old man with hepatocellular carcinoma. (a) Contrast material-enhanced CT scan obtained before RF ablation shows a 1.5-cm-diameter hyperattenuating nodule of hepatocellular carcinoma (arrow) in segment VI. The patient was readmitted due to abrupt development of a fever 1 week after ablation. (b) One-week follow-up CT scan shows a gas-forming abscess (arrow) in the ablated area with a perihepatic fluid collection. The abscess was successfully managed with US-guided percutaneous catheter drainage. (c) One-week follow-up CT scan shows moderate improvement of the abscess (arrow).

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.  Hepatic abscess in a 55-year-old man with hepatocellular carcinoma. (a) Contrast material-enhanced CT scan obtained before RF ablation shows a 1.5-cm-diameter hyperattenuating nodule of hepatocellular carcinoma (arrow) in segment VI. The patient was readmitted due to abrupt development of a fever 1 week after ablation. (b) One-week follow-up CT scan shows a gas-forming abscess (arrow) in the ablated area with a perihepatic fluid collection. The abscess was successfully managed with US-guided percutaneous catheter drainage. (c) One-week follow-up CT scan shows moderate improvement of the abscess (arrow).

Bleeding
Bleeding is another important complication that occurred during and immediately after ablation. Several factors are related to bleeding after RF ablation. Coagulopathy in cirrhotic patients is the most commonly encountered problem. Screening for coagulopathy should be performed before the procedure because needle electrodes of large diameter (17–14 gauge) are used. In addition, any ablative procedure should be postponed until the coagulopathy is corrected to avoid bleeding. The bleeding may develop from direct mechanical injury to the vascular structure by the RF needle electrode rather than from RF thermal injury to the vessel. Thus, real-time monitoring of the whole procedure including positioning of the needle electrode is mandatory. The potential for bleeding depends on the operator’s skill in placing the RF needle electrode safely without traversing major vessels and in minimizing the amount of needle repositioning. In addition, traversing sufficient normal hepatic parenchyma as well as cauterization of the needle tract after ablation are practical tips for minimizing bleeding (9).

On the basis of personal experience (9), color Doppler study of the needle tract can also be helpful in early detection of arterial bleeding along the needle tract immediately after removal of the RF electrode. Furthermore, close clinical evaluation of vital signs as well as analysis of laboratory values including complete blood cell count, prothrombin time, and partial thromboplastin time immediately after the ablation is essential for early detection and proper management of this complication, which is life threatening if overlooked or improperly managed (1–4). Although most venous bleeding tends to be self-limited with conservative treatment or transfusion, transarterial embolization or surgery may be necessary in cases of arterial bleeding (Figs 3, 4).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Peritoneal bleeding in a 75-year-old man with hepatocellular carcinoma. Contrast-enhanced CT scan obtained immediately after RF ablation of a hepatocellular carcinoma nodule in the caudate lobe shows peritoneal hemorrhage in the perihepatic space (arrows). The bleeding was managed with transfusion.

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Intrahepatic bleeding in an 87-year-old man with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3.0-cm hyperattenuating tumor (arrow) in segment VIII of the liver. (b) CT scan shows an expandable RF electrode (arrow), which was used to perform RF ablation. (c) Doppler US scan shows massive intrahepatic bleeding (arrow) from the margin of the ablated area. (d) Angiogram shows that the bleeding was controlled with placement of coils (arrow). (e) Three-month follow-up CT scan shows complete ablation of the tumor. Note the metallic areas of increased attenuation (arrow) adjacent to the tumor margin.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Intrahepatic bleeding in an 87-year-old man with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3.0-cm hyperattenuating tumor (arrow) in segment VIII of the liver. (b) CT scan shows an expandable RF electrode (arrow), which was used to perform RF ablation. (c) Doppler US scan shows massive intrahepatic bleeding (arrow) from the margin of the ablated area. (d) Angiogram shows that the bleeding was controlled with placement of coils (arrow). (e) Three-month follow-up CT scan shows complete ablation of the tumor. Note the metallic areas of increased attenuation (arrow) adjacent to the tumor margin.

View larger version (178K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.  Intrahepatic bleeding in an 87-year-old man with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3.0-cm hyperattenuating tumor (arrow) in segment VIII of the liver. (b) CT scan shows an expandable RF electrode (arrow), which was used to perform RF ablation. (c) Doppler US scan shows massive intrahepatic bleeding (arrow) from the margin of the ablated area. (d) Angiogram shows that the bleeding was controlled with placement of coils (arrow). (e) Three-month follow-up CT scan shows complete ablation of the tumor. Note the metallic areas of increased attenuation (arrow) adjacent to the tumor margin.

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 4d.  Intrahepatic bleeding in an 87-year-old man with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3.0-cm hyperattenuating tumor (arrow) in segment VIII of the liver. (b) CT scan shows an expandable RF electrode (arrow), which was used to perform RF ablation. (c) Doppler US scan shows massive intrahepatic bleeding (arrow) from the margin of the ablated area. (d) Angiogram shows that the bleeding was controlled with placement of coils (arrow). (e) Three-month follow-up CT scan shows complete ablation of the tumor. Note the metallic areas of increased attenuation (arrow) adjacent to the tumor margin.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 4e.  Intrahepatic bleeding in an 87-year-old man with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3.0-cm hyperattenuating tumor (arrow) in segment VIII of the liver. (b) CT scan shows an expandable RF electrode (arrow), which was used to perform RF ablation. (c) Doppler US scan shows massive intrahepatic bleeding (arrow) from the margin of the ablated area. (d) Angiogram shows that the bleeding was controlled with placement of coils (arrow). (e) Three-month follow-up CT scan shows complete ablation of the tumor. Note the metallic areas of increased attenuation (arrow) adjacent to the tumor margin.

Bile Duct Injury
Heat from RF energy produces nonspecific thermal injury to tumor tissue as well as the adjacent normal structures (17,18,23). Bile ducts are no exception (Figs 5, 6). This is one of the dilemmas in achieving successful ablation with a 1-cm safety margin of normal liver. If a mass abuts a major bile duct, the situation becomes difficult. As the operator tries to overcome the "heat sink" effect of the major vessel around the central mass, the risk of injury to the major bile ducts may be increased (30–32). Thus, the risk of thermal damage to the bile ducts should be weighed in terms of potential risks versus benefits. RF ablation therapy combined with transarterial chemoembolization or percutaneous ethanol injection can be considered as an alternative treatment in patients with a hilar mass adjacent to major hepatic ducts.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.  Bile duct injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3-cm-diameter hypervascular mass (arrow) in segment VIII of the liver. (b) Follow-up CT scan obtained immediately after RF ablation shows complete ablation with a 1-cm safety margin (arrow). (c) Six-month follow-up CT scan shows contraction of the ablated area without marginal recurrence. However, mild dilatation of an intrahepatic bile duct (arrow) is noted in the left lobe. There was mild jaundice at admission. (d) Endoscopic retrograde cholangiopancreatogram shows moderate dilatation of the intrahepatic bile duct (arrow) with normal size of the extrahepatic bile duct. (e) Follow-up CT scan obtained 2 weeks after biliary drainage with a percutaneous catheter (arrow) shows improvement of the biliary dilatation.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.  Bile duct injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3-cm-diameter hypervascular mass (arrow) in segment VIII of the liver. (b) Follow-up CT scan obtained immediately after RF ablation shows complete ablation with a 1-cm safety margin (arrow). (c) Six-month follow-up CT scan shows contraction of the ablated area without marginal recurrence. However, mild dilatation of an intrahepatic bile duct (arrow) is noted in the left lobe. There was mild jaundice at admission. (d) Endoscopic retrograde cholangiopancreatogram shows moderate dilatation of the intrahepatic bile duct (arrow) with normal size of the extrahepatic bile duct. (e) Follow-up CT scan obtained 2 weeks after biliary drainage with a percutaneous catheter (arrow) shows improvement of the biliary dilatation.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.  Bile duct injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3-cm-diameter hypervascular mass (arrow) in segment VIII of the liver. (b) Follow-up CT scan obtained immediately after RF ablation shows complete ablation with a 1-cm safety margin (arrow). (c) Six-month follow-up CT scan shows contraction of the ablated area without marginal recurrence. However, mild dilatation of an intrahepatic bile duct (arrow) is noted in the left lobe. There was mild jaundice at admission. (d) Endoscopic retrograde cholangiopancreatogram shows moderate dilatation of the intrahepatic bile duct (arrow) with normal size of the extrahepatic bile duct. (e) Follow-up CT scan obtained 2 weeks after biliary drainage with a percutaneous catheter (arrow) shows improvement of the biliary dilatation.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.  Bile duct injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3-cm-diameter hypervascular mass (arrow) in segment VIII of the liver. (b) Follow-up CT scan obtained immediately after RF ablation shows complete ablation with a 1-cm safety margin (arrow). (c) Six-month follow-up CT scan shows contraction of the ablated area without marginal recurrence. However, mild dilatation of an intrahepatic bile duct (arrow) is noted in the left lobe. There was mild jaundice at admission. (d) Endoscopic retrograde cholangiopancreatogram shows moderate dilatation of the intrahepatic bile duct (arrow) with normal size of the extrahepatic bile duct. (e) Follow-up CT scan obtained 2 weeks after biliary drainage with a percutaneous catheter (arrow) shows improvement of the biliary dilatation.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 5e.  Bile duct injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan shows a 3-cm-diameter hypervascular mass (arrow) in segment VIII of the liver. (b) Follow-up CT scan obtained immediately after RF ablation shows complete ablation with a 1-cm safety margin (arrow). (c) Six-month follow-up CT scan shows contraction of the ablated area without marginal recurrence. However, mild dilatation of an intrahepatic bile duct (arrow) is noted in the left lobe. There was mild jaundice at admission. (d) Endoscopic retrograde cholangiopancreatogram shows moderate dilatation of the intrahepatic bile duct (arrow) with normal size of the extrahepatic bile duct. (e) Follow-up CT scan obtained 2 weeks after biliary drainage with a percutaneous catheter (arrow) shows improvement of the biliary dilatation.

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Biloma in a 46-year-old woman with hepatocellular carcinoma. (a) Doppler US scan obtained 45 days after RF ablation shows a 4-cm-diameter biloma (arrow) in the left lobe of the liver. Note the faint Doppler signal from the biloma. (b) Close-up US scan of the abdominal wall obtained with a high-frequency linear transducer shows a biconvex fluid collection (arrow) adjacent to the biloma. (c) Doppler US scan shows a fistulous communication (arrow) between the biloma and the subcutaneous collection.

View larger version (110K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Biloma in a 46-year-old woman with hepatocellular carcinoma. (a) Doppler US scan obtained 45 days after RF ablation shows a 4-cm-diameter biloma (arrow) in the left lobe of the liver. Note the faint Doppler signal from the biloma. (b) Close-up US scan of the abdominal wall obtained with a high-frequency linear transducer shows a biconvex fluid collection (arrow) adjacent to the biloma. (c) Doppler US scan shows a fistulous communication (arrow) between the biloma and the subcutaneous collection.

View larger version (191K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.  Biloma in a 46-year-old woman with hepatocellular carcinoma. (a) Doppler US scan obtained 45 days after RF ablation shows a 4-cm-diameter biloma (arrow) in the left lobe of the liver. Note the faint Doppler signal from the biloma. (b) Close-up US scan of the abdominal wall obtained with a high-frequency linear transducer shows a biconvex fluid collection (arrow) adjacent to the biloma. (c) Doppler US scan shows a fistulous communication (arrow) between the biloma and the subcutaneous collection.

Burns
The ground pad acts as a dispersive electrode in an RF circuit. A larger surface area of the return ground pad is required for more energy (heat) to be dispersed. The risk of burns at the ground pad site has increased with use of a high-current RF technique if the surface area of the ground pad is not increased. Serious skin burns have become relatively rare, although they were reported during the early experience when insufficiently sized ground pads were used. In addition, any interface between the skin and ground pad should be eliminated to prevent skin burns (Fig 7) (33).

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 7.  Skin burns in a 62-year-old man with hepatocellular carcinoma. Photograph shows third-degree skin burns (arrows) that developed at the ground pad site after RF ablation of multiple hepatocellular carcinoma nodules in segment VI, which had been treated with iodized oil (Lipiodol; Guerbet, Roissy, France). The patient received skin grafts after conservative treatment for 1 month.

View larger version (88K): [in this window] [in a new window] [Download PPT slide]   Figure 8.  Pneumothorax in a 47-year-old woman with hepatocellular carcinoma. Chest CT scan obtained after RF ablation of a tumor in segment VIII of the liver shows pneumothorax (arrow) in the right hemithorax. The pneumothorax was self-limited.

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 9.  Hemothorax in a 47-year-old woman with hepatocellular carcinoma. Chest CT scan obtained after massive RF ablation of a tumor in segment VII of the liver shows a fluid collection of relatively high attenuation (arrow) in the right hemithorax, a finding indicative of hemothorax. The hemothorax was self-limited.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Bowel injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan obtained before RF ablation shows a hyperattenuating 1.5-cm-diameter hepatocellular carcinoma nodule (arrow) in segment V. The patient experienced abdominal pain and fever after the procedure. (b) Follow-up CT scan obtained immediately after ablation shows intraperitoneal free air (arrow) around the hepatic flexure of the colon adjacent to the ablated tumor. Emergent exploratory laparotomy revealed a 0.5-cm-diameter colonic perforation at the hepatic flexure. Segmental resection of the colon was required. The pathologic diagnosis was focal transmural ischemic necrosis with perforation.

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Bowel injury in a 55-year-old woman with hepatocellular carcinoma. (a) Contrast-enhanced CT scan obtained before RF ablation shows a hyperattenuating 1.5-cm-diameter hepatocellular carcinoma nodule (arrow) in segment V. The patient experienced abdominal pain and fever after the procedure. (b) Follow-up CT scan obtained immediately after ablation shows intraperitoneal free air (arrow) around the hepatic flexure of the colon adjacent to the ablated tumor. Emergent exploratory laparotomy revealed a 0.5-cm-diameter colonic perforation at the hepatic flexure. Segmental resection of the colon was required. The pathologic diagnosis was focal transmural ischemic necrosis with perforation.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  Tumor seeding in a 55-year-old woman with hepatocellular carcinoma. (a) Follow-up CT scan obtained immediately after a second session of RF ablation for a marginal recurrent mass in the left lateral segment of the liver shows a nonenhancing ablated area (arrow), which indicates complete ablation. (b) Follow-up CT scan obtained 1 month after the second session of RF ablation shows a small enhancing nodule in the extrahepatic space (arrow), a finding suggestive of tumor seeding along the needle tract. (c) Arteriogram shows that the internal mammary artery supplies the tumor nodule (arrows).

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  Tumor seeding in a 55-year-old woman with hepatocellular carcinoma. (a) Follow-up CT scan obtained immediately after a second session of RF ablation for a marginal recurrent mass in the left lateral segment of the liver shows a nonenhancing ablated area (arrow), which indicates complete ablation. (b) Follow-up CT scan obtained 1 month after the second session of RF ablation shows a small enhancing nodule in the extrahepatic space (arrow), a finding suggestive of tumor seeding along the needle tract. (c) Arteriogram shows that the internal mammary artery supplies the tumor nodule (arrows).

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 11c.  Tumor seeding in a 55-year-old woman with hepatocellular carcinoma. (a) Follow-up CT scan obtained immediately after a second session of RF ablation for a marginal recurrent mass in the left lateral segment of the liver shows a nonenhancing ablated area (arrow), which indicates complete ablation. (b) Follow-up CT scan obtained 1 month after the second session of RF ablation shows a small enhancing nodule in the extrahepatic space (arrow), a finding suggestive of tumor seeding along the needle tract. (c) Arteriogram shows that the internal mammary artery supplies the tumor nodule (arrows).

	Discussion

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

The prevalence of major complications in sporadically reported studies of smaller series ranged from 0% to 12.7% (17,18,36–38). Our multicenter study of a larger series of patients (1,139) showed a complication rate of 2.4% and mortality of 0.09%. An Italian multicenter study of 1,766 patients recently reported a mortality rate of 0.11% and a major complication rate of 1.52% (17). The causes of the two deaths in the Italian survey were septic shock due to Staphylococcus aureus peritonitis and liver failure (17). The results of both surveys supported those of previous studies, which found that the morbidity of RF ablation is a little higher than that of percutaneous ethanol injection (39) but that the morbidity and mortality of RF ablation seem to be acceptable for a safe procedure.

The common complications in our survey were infection and bleeding, as in the Italian survey. Other complications included biliary complications, ground pad burns, and thoracic or bowel complications. However, the rate of complications after RF ablation may have decreased as the operator’s experience accumulated because our survey data include all cases in the period of initial experience of each operator. The recent investigations including our survey indicate that the rates of complications following RF ablation are not negligible but can be minimized. Therefore, a physician performing RF ablation should understand the spectrum of complications encountered after ablation for careful selection of candidates as well as early detection and proper management of complications.

There are several strategies for decreasing complications after RF ablation of hepatic tumors (1–5,17). The first key strategy is prevention. A simple shortcut to minimizing complications is not to perform ablation in patients at high risk. Therefore, meticulous preevaluation of candidates should be performed, especially in regard to coagulopathy, underlying hepatic reserve, and tumor proximity to major structures such as the bile duct or intestine. In a patient with correctable coagulopathy, ablation should be postponed until all parameters are corrected. RF ablation combined with transarterial oily chemoembolization or percutaneous ethanol injection can be considered in patients with a mass close to a major organ because this combined approach can reduce the need for the operator to completely ablate the entire tumor as well as a 1-cm safety margin (34,35,40). We believe that the complication rate may decrease as we have more experience with this procedure (9). An issue that will still need to be addressed is that many vendors of RF equipment are developing a more powerful device to produce a larger ablated lesion in a shorter time. Thus, the complication rate could contrarily increase if a physician takes a more aggressive posture for successful ablation with a wider safety margin including the perivascular area. Another tip for preventing complications is selection of the proper guiding modality. The prevalence of complications may be related to how difficult it is to place the needle electrode in the desired portion of the liver. Poor visualization of the target lesion or difficulty in the approach to the lesion can increase the risk of damage to adjacent structures. Therefore, the operator should select the best guiding modality on a case-by-case basis. A final issue in prevention of complications is the method of approach to the lesion: open versus percutaneous. The open or laparoscopic approach may be beneficial for isolating the lesion from adjacent critical structures and potentially better control of bleeding from the surface of the liver.

The second strategy in minimizing major complications is early detection. Although early detection cannot reduce the frequency of complications such as infection or bleeding, it can potentially minimize their clinical magnitude. Thus, the operator and other medical personnel should be knowledgeable about the spectrum of various complications after RF ablation because complications can be detected even during the procedure in some cases. Sound knowledge about complications may be helpful for an operator in stopping the ablation, which will prevent more serious complications. Close immediate follow-up with clinical and laboratory data is also essential for early detection of complications. Monitoring of vital signs with a complete blood cell count and measurement of prothrombin time is mandatory. Immediate (<24 hours) follow-up CT is a reliable modality for detecting any complications after RF ablation.

The last key strategy is proper management. Adequate management at the appropriate time is another important issue because a complication is not a static situation. Even if the complication is detected early, inappropriate management can result in mortality. Thus, the operator should treat patients with complications properly on the basis of the unique clinical characteristics of each complication.

In conclusion, a physician performing RF ablation of hepatic malignancies should be aware of the broad spectrum of major complications encountered after ablation for careful patient selection as well as early detection and proper management of the complications.

	Footnotes

 
Abbreviation: RF = radio-frequency

See the commentary by Razavi following this article.

	References

Top Abstract LEARNING OBJECTIVES Introduction Materials and Methods Results Discussion References

 

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