DOI: 10.1148/rg.25si055505
RadioGraphics 2005;25:S57-S68
© RSNA, 2005
Complications of Percutaneous Radiofrequency Ablation for Hepato-cellular Carcinoma: Imaging Spectrum and Management1
Masaaki Akahane, MD,
Hisao Koga, MD,
Nobuyuki Kato, MD,
Haruyasu Yamada, MD,
Kazuhito Uozumi, MD,
Ryosuke Tateishi, MD,
Takuma Teratani, MD,
Shuichiro Shiina, MD and
Kuni Ohtomo, MD
1 From the Departments of Radiology (M.A., H.K., N.K., H.Y., K.U., K.O.) and Gastroenterology (R.T., T.T., S.S.), Graduate School of Medicine, University of Tokyo, 7–3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received February 7, 2005; revision requested April 18 and received May 27; accepted June 3. All authors have no financial relationships to disclose.
Address correspondence to M.A. (e-mail: akahane-tky{at}umin.ac.jp).
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Abstract
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Percutaneous radiofrequency (RF) ablation is feasible for the treatment of unresectable hepatocellular carcinoma, and experience at the authors’ institution during 5 years indicates that percutaneous RF ablation can be performed safely in most cases. However, early or late complications related to mechanical or thermal damage may be observed at follow-up examination. Complications may be classified in three groups: vascular (eg, portal vein thrombosis, hepatic vein thrombosis with partial hepatic congestion, hepatic infarction, and subcapsular hematoma), biliary (eg, bile duct stenosis and biloma, abscess, and hemobilia), and extrahepatic (eg, injury to the gastrointestinal tract, injury to the gallbladder, pneumothorax and hemothorax, and tumor seeding). Most complications can be managed with conservative treatment, percutaneous or endoscopic drainage, or surgical repair. Because an early and accurate diagnosis is necessary for proper management, radiologists should be familiar with the imaging features of each type of complication.
© RSNA, 2005
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- List the possible complications of percutaneous radiofrequency ablation for hepatocellular carcinoma.
- Identify the key imaging features for early and accurate diagnosis of each complication.
- Discuss the risk factors for each complication.
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Introduction
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Percutaneous radiofrequency (RF) ablation has become feasible as a treatment for unresectable malignant liver tumors (1–14). Although RF ablation can be performed safely in most patients, early and late complications related to mechanical or thermal damage may be observed at follow-up examination (15–21).
Early detection and accurate evaluation are essential for the proper management of complications after the interventional procedure. Therefore, radiologists need to be familiar with the various imaging features of each type of complication. This article provides a review of the imaging features, risk factors, and management of major and minor complications of percutaneous RF ablation for hepatocellular carcinoma. Our review is based on our retrospective analysis of the records of the patients who underwent RF ablation at our institution over a 5-year period. We classified complications as vascular, biliary, and extrahepatic.
The Table lists the complications that resulted from 1000 RF ablation treatments for 2140 lesions in 664 patients at our institution in the 4 years between February 1999 and February 2003 (22). The mean age of the patients treated in this period was 67 years (44–90 years), with male patients accounting for 69% of the total. A total of 40 major complications (prevalence of 4.0% per completed treatment with RF ablation and 1.9% per individual treatment session) and 17 minor complications (prevalence of 1.7% per completed treatment and 0.82% per individual treatment session) were observed. Major complications were defined as those that, if left untreated, might threaten the patient’s life, lead to substantial morbidity and disability, result in hospital admission, or substantially lengthen hospital stay according to the previously described guidelines (23). All other complications were considered minor. Patients who underwent RF ablation at our institution had all of the following indications: total bilirubin concentration of less than 3 mg/dL, platelet count greater than 50 x 103/µL (50 x 109/L), and prothrombin activity at more than 50% of the standard level. Patients with portal vein tumor thrombosis or extrahepatic metastasis could not undergo RF ablation. We also excluded patients who had a history of bilioenteric anastomosis or sphincterotomy, procedures that are considered to involve a high risk for hepatic abscess formation. The RF devices used were 17-gauge cooled-tip electrodes.
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Vascular Complications
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Portal Vein Thrombosis
When portal vein thrombosis occurs as a complication of RF ablation of hepatocellular carcinoma, it usually manifests soon after the procedure. Because the vascular-perfusion-mediated heat-sink effect depends on the size of the vessel, small-caliber vessels are prone to thrombosis caused by thermal damage (24). The heat-sink effect also depends on the amount of blood flowing through the vessel. Thermal damage may cause thrombosis even in relatively large vessels if the blood flow is decreased, as happens during the Pringle maneuver (clamping of the porta hepatis, which interrupts hepatic arterial and portal venous flow to the liver) (25–27), especially in cirrhotic livers (18). Other conditions that can decrease the blood flow (eg, preexisting thrombus, previous intervention, and mechanical damage of vessels by electrodes) also may be considered risk factors for portal vein thrombosis.
Contrast material–enhanced computed tomography (CT) may depict the thrombus as a filling defect in the portal vein (Fig 1). Segmental enhancement of the liver parenchyma peripheral to the affected portal vein is an indirect sign of thrombosis that may be observed during the hepatic arterial phase (28). Ultrasonographic (US) images show echogenicity in the portal vein, and loss or decrease of flow may be observed on Doppler US images. Most thrombi in the portal vein are self-limited, but systemic or local thrombolysis may be required if liver function is affected.
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Figure 1. Portal vein thrombosis in a 58-year-old woman with hepatocellular carcinoma in segment II. Follow-up CT scan, obtained immediately after RF ablation, shows loss of enhancement in the umbilical portion of the left portal vein (arrow) and strong segmental enhancement of the left lobe (arrowheads).
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Hepatic Vein Thrombosis
The mechanism involved in hepatic vein thrombosis is thought to be similar to that in portal vein thrombosis. CT scans obtained during the portal venous phase or equilibrium phase may reveal a loss of enhancement in the hepatic vein; evaluation tends to be difficult, however, because of a delay and a decrease in enhancement that are caused by congestion. A comparison of images acquired before RF ablation with images acquired after the procedure may be helpful. A wedge-shaped area of decreased enhancement that represents congestion may be observed on the hepatic arterial phase images (Fig 2), as is true of hepatic venous congestion after living-donor liver transplantation (29). This feature may be useful for detecting hepatic vein thrombosis. Treatment of hepatic vein thrombosis is not required in most cases, but systemic or local thrombolysis may be necessary if liver function is affected.
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Figure 2a. Hepatic vein thrombosis in a 68-year-old man with hepatocellular carcinoma in segment VIII. Follow-up CT scans obtained immediately after RF ablation (a and b at approximately the same level but with different rotation due to different degrees of inspiration) show a wedge-shaped area with decreased enhancement (arrowheads) in the hepatic arterial phase (a) and loss of enhancement in a tributary of the right hepatic vein (arrow) adjacent to the ablated lesion in the equilibrium phase (b).
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Figure 2b. Hepatic vein thrombosis in a 68-year-old man with hepatocellular carcinoma in segment VIII. Follow-up CT scans obtained immediately after RF ablation (a and b at approximately the same level but with different rotation due to different degrees of inspiration) show a wedge-shaped area with decreased enhancement (arrowheads) in the hepatic arterial phase (a) and loss of enhancement in a tributary of the right hepatic vein (arrow) adjacent to the ablated lesion in the equilibrium phase (b).
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Hepatic Infarction
A well-defined wedge-shaped area of low attenuation that extends to the liver surface on contrast-enhanced CT images is considered to indicate hepatic infarction (30). Branching areas with attenuation similar to that of air, probably segments of the portal veins, are frequently observed in the infarcted area (Fig 3). Management is conservative and may include the prophylactic use of antibiotics.
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Figure 3a. Hepatic infarction in a 55-year-old woman with hepatocellular carcinoma in segment III. (a) Follow-up CT scan, obtained immediately after RF ablation, shows a well-defined wedge-shaped infarcted area with low attenuation (arrowheads), as well as branching areas with attenuation similar to that of air (arrow), considered to be tributaries of the portal vein. (b) Follow-up CT scan (obtained 3 cm caudad to a) shows that the area of low attenuation (arrows) extends to the liver surface.
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Figure 3b. Hepatic infarction in a 55-year-old woman with hepatocellular carcinoma in segment III. (a) Follow-up CT scan, obtained immediately after RF ablation, shows a well-defined wedge-shaped infarcted area with low attenuation (arrowheads), as well as branching areas with attenuation similar to that of air (arrow), considered to be tributaries of the portal vein. (b) Follow-up CT scan (obtained 3 cm caudad to a) shows that the area of low attenuation (arrows) extends to the liver surface.
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Subcapsular Hematoma
Mechanical damage caused by the placement of electrodes is likely to be responsible for bleeding. Coagulopathy is the most important risk factor for bleeding after RF ablation. Thus, patients with cirrhosis are considered to be at higher risk than those without cirrhosis (19). Other risk factors include the use of multiple punctures or multiple electrodes and the location of the targeted lesion behind a major blood vessel. To minimize the risk of bleeding, the electrode should be placed so that it traverses sufficient normal liver parenchyma without crossing major vessels. Cauterization of the electrode tract during withdrawal may be an effective method for avoiding or reducing hemorrhage (31,32).
Careful monitoring of vital signs and laboratory indicators including blood cell count is essential for the postprocedural care of patients with coagulopathy. If bleeding is suspected, CT is the modality of choice for the detection and evaluation of hematoma. A crescentic or biconvex lesion with attenuation higher than that of water will be observed along the hepatic surface (Fig 4) and may extend into the adjacent extraperitoneal space. Transfusion is required in patients who develop severe anemia. Transcatheter arterial embolization may be an effective treatment if bleeding is arterial.
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Figure 4a. Subcapsular hematoma in a 64-year-old man with hepatocellular carcinoma in segment IV. (a) Follow-up CT scan, obtained immediately after RF ablation, shows a biconvex lesion (arrows) with attenuation higher than that of water, located along the hepatic surface. (b) CT scan at a level lower than a shows that the hematoma extends to the subserosal space of the stomach (arrow).
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Figure 4b. Subcapsular hematoma in a 64-year-old man with hepatocellular carcinoma in segment IV. (a) Follow-up CT scan, obtained immediately after RF ablation, shows a biconvex lesion (arrows) with attenuation higher than that of water, located along the hepatic surface. (b) CT scan at a level lower than a shows that the hematoma extends to the subserosal space of the stomach (arrow).
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Biliary Complications
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Bile Duct Stenosis and Biloma
Upstream bile duct dilatation develops as a result of bile duct stenosis after RF ablation (33). It may progress for several months, and occasionally it is associated with the formation of a biloma (Fig 5).
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Figure 5a. Bile duct stenosis and biloma in a 67-year-old woman with hepatocellular carcinoma in segment III. (a) Follow-up CT scan, obtained 6 months after RF ablation, shows mild dilatation of the intrahepatic bile duct (arrows) in the lateral segment of the liver. (b) Follow-up CT scan, obtained 11 months after RF ablation and at approximately the same level as a, shows biloma formation (arrow) as well as exacerbation of dilatation of the bile duct (arrowheads). (c) US image shows an anechoic lesion that corresponds to the biloma (arrowhead) and dilated duct (arrow).
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Figure 5b. Bile duct stenosis and biloma in a 67-year-old woman with hepatocellular carcinoma in segment III. (a) Follow-up CT scan, obtained 6 months after RF ablation, shows mild dilatation of the intrahepatic bile duct (arrows) in the lateral segment of the liver. (b) Follow-up CT scan, obtained 11 months after RF ablation and at approximately the same level as a, shows biloma formation (arrow) as well as exacerbation of dilatation of the bile duct (arrowheads). (c) US image shows an anechoic lesion that corresponds to the biloma (arrowhead) and dilated duct (arrow).
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Figure 5c. Bile duct stenosis and biloma in a 67-year-old woman with hepatocellular carcinoma in segment III. (a) Follow-up CT scan, obtained 6 months after RF ablation, shows mild dilatation of the intrahepatic bile duct (arrows) in the lateral segment of the liver. (b) Follow-up CT scan, obtained 11 months after RF ablation and at approximately the same level as a, shows biloma formation (arrow) as well as exacerbation of dilatation of the bile duct (arrowheads). (c) US image shows an anechoic lesion that corresponds to the biloma (arrowhead) and dilated duct (arrow).
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Major bile ducts near the hepatic hilum are considered to be protected from thermal damage by the heat-sink effect of the portal vein (34,35). However, if the blood flow in the portal vein is decreased because of the Pringle maneuver, portal vein thrombosis, or vascular injury, the risk of bile duct stenosis may increase. RF ablation of lesions near the hepatic hilum is challenging because the complete ablation of the tumor and the protection of major bile ducts or portal venous branches are frequently incompatible goals; bile ducts at the periphery of the liver may be vulnerable to thermal ablation (35). Moreover, stenosis of the peripheral duct tends to be subclinical (33).
No treatment for these complications is necessary in asymptomatic patients, but antibiotic therapy is required for patients with infection. Percutaneous or endoscopic drainage may be necessary if jaundice, severe cholangitis, or abscess occurs.
Hepatic Abscess
Abscess is one of the most common major complications after percutaneous RF ablation in the liver (17–20,22). Two important risk factors for abscess formation are recognized: bacterial colonization of the biliary tract, and diabetes mellitus (17). The mechanism of abscess development after RF ablation has not been established, but bacterial contamination of the ablated area is thought to lead to abscess formation. Colonization of the biliary tract may take place through bilioenteric anastomosis, endoscopic sphincterotomy, or bilioenteric fistula, and pneumobilia of unknown origin may be related to retrograde enteric bacterial contamination. Although the prophylactic use of antibiotics is controversial (33,36), antibiotics are administered for prophylaxis at our institution from the day of treatment to the next morning, and antibiotic therapy is continued if the patient has a fever.
US images show coarse clumps of debris and echogenicity of gas in the abscess. CT scans depict a hypoattenuating lesion that contains gas, and a double-target sign (37) may be observed on contrast-enhanced CT scans (Fig 6). According to the published report of a previous study (38), gas was seen inside the lesion on CT scans obtained immediately after RF ablation in more than one-half of patients but disappeared by the 1-month follow-up CT examination, if the lesion was not infected. The diagnosis of hepatic abscess therefore should be based both on imaging findings and on clinical symptoms such as fever and pain. Pseudoaneurysm formation, a rare complication of hepatic abscess (39), may complicate the clinical course (Fig 7). Management of hepatic abscess is based on appropriate antibiotics and percutaneous drainage.
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Figure 6a. Hepatic abscess in a 72-year-old man with hepatocellular carcinoma in segment VIII. (a) CT scan, obtained 4 months after RF ablation, shows an abscess with the typical target sign (arrow). (b) Follow-up CT scan, obtained after percutaneous drainage, shows improvement of the abscess (arrow).
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Figure 6b. Hepatic abscess in a 72-year-old man with hepatocellular carcinoma in segment VIII. (a) CT scan, obtained 4 months after RF ablation, shows an abscess with the typical target sign (arrow). (b) Follow-up CT scan, obtained after percutaneous drainage, shows improvement of the abscess (arrow).
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Figure 7a. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Figure 7b. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Figure 7c. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Figure 7d. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Figure 7e. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Figure 7f. Bleeding from a pseudoaneurysm into a hepatic abscess in a 70-year-old man. The patient had a history of Billroth II–type gastrectomy, right hepatic lobectomy, and radiation therapy for a portal vein tumor thrombus. RF ablation was performed for recurrent hepatocellular carcinoma in segment III. (a) US image, obtained soon after RF ablation, shows an inhomogeneous and relatively hyperechoic area that corresponds to the ablated area (arrowheads). (b, c) Follow-up US image (b) and CT scan (c), obtained 5 months after RF ablation, show a biloma (arrow) in the ablated area just anterior to the proper hepatic artery (arrowhead in c), with no evidence of pseudoaneurysm. (d) Unenhanced CT scan, obtained when the patient was admitted to the hospital for fever and melena 13 months after RF ablation, shows an area of high attenuation (arrow) suggestive of hemorrhage in an abscess derived from the biloma. (e) Subsequent angiogram helps to confirm a pseudoaneurysm of the proper hepatic artery (arrow). (f ) Follow-up angiogram obtained immediately after isolation of the pseudoaneurysm with fibered platinum embolization coils (arrowheads) shows that bleeding has stopped. No complication associated with embolization was documented. The abscess was controlled with antibiotics, without drainage.
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Hemobilia
Melena and upper abdominal pain are the most common symptoms of hemobilia. Laboratory tests show elevated levels of bilirubin and biliary enzymes. Clots in the gallbladder are observed on US images, and high attenuation in the biliary tract may be seen on CT scans (Fig 8) (40). No treatment is necessary in asymptomatic patients, but endoscopic drainage may be required in patients with significant jaundice. Transcatheter arterial embolization may be performed to stop bleeding from a pseudoaneurysm or fistula.
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Figure 8a. Hemobilia in a 68-year-old man with hepatocellular carcinoma in segment VII who was readmitted for abdominal pain 3 days after RF ablation. (a) CT scan shows an area of high attenuation (arrow) that represents hemobilia in the common bile duct. (b) Endoscopic retrograde cholangiopancreatographic image helps to confirm hemobilia (arrows). The clot was removed and drainage was performed endoscopically. Bleeding was controlled without arterial embolization.
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Figure 8b. Hemobilia in a 68-year-old man with hepatocellular carcinoma in segment VII who was readmitted for abdominal pain 3 days after RF ablation. (a) CT scan shows an area of high attenuation (arrow) that represents hemobilia in the common bile duct. (b) Endoscopic retrograde cholangiopancreatographic image helps to confirm hemobilia (arrows). The clot was removed and drainage was performed endoscopically. Bleeding was controlled without arterial embolization.
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Extrahepatic Complications
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Injury to the Gastrointestinal Tract
Early detection is essential for the management of injury to the gastrointestinal tract. RF ablation of a lesion adjacent to the bowel loop, and adhesions caused by prior surgery or RF ablation, can be potential risk factors for bowel injury. The colon is considered to be at higher risk for thermal dam-age than are the stomach and small bowel, because of its lesser mobility and thinner wall thickness (19). Straight needlelike electrodes may be superior to expandable electrodes for real-time monitoring of the distance between the electrode and bowel wall (17).
Care should be taken in regard to thickening of the injured wall, fat stranding around the injured site, free air, and ascites, in order to detect unexpected injury to the gastrointestinal tract. Bowel injury occasionally causes an abscess in the liver or outside it (Fig 9). Therefore, if abscess formation is observed after RF ablation, close attention should be paid to the gastrointestinal tract. Methods for management of gastrointestinal tract injury include fasting, antibiotic therapy, drainage of the abscess, and closure of the fistula. Laparotomy may be required if the injury does not heal.
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Figure 9a. Perforation of the colon in a 70-year-old man with hepatocellular carcinoma in segment VI. (a) CT scan, obtained 2 days after RF ablation, shows scattered air bubbles (arrow) and fat stranding (arrowheads). (b) Follow-up CT scan, obtained 2 weeks after RF ablation, shows an abscess (arrowheads) in the ablated area, and, between the colon and the abscess, a fistula (arrow) that developed despite management with fasting and antibiotic therapy. (c) CT scan, obtained 5 months after endoscopic aspiration and closure of the fistula, shows the absence of the abscess (arrow).
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Figure 9b. Perforation of the colon in a 70-year-old man with hepatocellular carcinoma in segment VI. (a) CT scan, obtained 2 days after RF ablation, shows scattered air bubbles (arrow) and fat stranding (arrowheads). (b) Follow-up CT scan, obtained 2 weeks after RF ablation, shows an abscess (arrowheads) in the ablated area, and, between the colon and the abscess, a fistula (arrow) that developed despite management with fasting and antibiotic therapy. (c) CT scan, obtained 5 months after endoscopic aspiration and closure of the fistula, shows the absence of the abscess (arrow).
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Figure 9c. Perforation of the colon in a 70-year-old man with hepatocellular carcinoma in segment VI. (a) CT scan, obtained 2 days after RF ablation, shows scattered air bubbles (arrow) and fat stranding (arrowheads). (b) Follow-up CT scan, obtained 2 weeks after RF ablation, shows an abscess (arrowheads) in the ablated area, and, between the colon and the abscess, a fistula (arrow) that developed despite management with fasting and antibiotic therapy. (c) CT scan, obtained 5 months after endoscopic aspiration and closure of the fistula, shows the absence of the abscess (arrow).
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Injury to the Gallbladder
Cholecystitis may occur after RF ablation, but perforation of the gallbladder is rare even if the lesion treated with ablation is adjacent to the gall-bladder (41). Adhesion due to prior surgery or percutaneous therapy may be a potential risk factor for injury to the gallbladder. Thickening of the gallbladder wall, and surrounding fat stranding, are signs of cholecystitis. Perforation of the gall-bladder may be associated with other complications, such as injury to the colon (Fig 10), and gas in the biliary system may be an indication of this type of gallbladder injury. Management of perforation of the gallbladder requires percutaneous or endoscopic drainage.
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Figure 10a. Injury to the gallbladder and colon in a 70-year-old man with a history of anterior segmentectomy and percutaneous microwave coagulation therapy for hepatocellular carcinoma in segment VI 2 years earlier. (a) CT scan, obtained 2 days after RF ablation of hepatocellular carcinoma in segment IV, shows gas in the biliary tract (arrowheads) and fat stranding that surrounds a fistula (arrow) between the colon and the ablated area. (b) Cholangiogram obtained with contrast material injection via the drainage tube helps to confirm injury of the gallbladder (arrow) and colon (arrowhead).
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Figure 10b. Injury to the gallbladder and colon in a 70-year-old man with a history of anterior segmentectomy and percutaneous microwave coagulation therapy for hepatocellular carcinoma in segment VI 2 years earlier. (a) CT scan, obtained 2 days after RF ablation of hepatocellular carcinoma in segment IV, shows gas in the biliary tract (arrowheads) and fat stranding that surrounds a fistula (arrow) between the colon and the ablated area. (b) Cholangiogram obtained with contrast material injection via the drainage tube helps to confirm injury of the gallbladder (arrow) and colon (arrowhead).
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Pneumothorax and Hemothorax
Pneumothorax and hemothorax, which are related to the imaging-guided placement of electrodes, are rare but may be encountered if the treated lesion is near the diaphragm. Chest radiography is required if chest pain or dyspnea occurs after RF ablation. Lung window display is necessary for proper viewing of follow-up CT scans (Fig 11). Pneumothorax and hemothorax are usually self-limited.
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Figure 11. Pneumothorax in a 61-year-old man with hepatocellular carcinoma in segment VIII. CT scan obtained immediately after RF ablation shows pneumothorax (arrow), which resolved without drainage.
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Tumor Seeding
Tumor seeding is related to several factors: caliber and type of electrode used, number of punctures, subcapsular location of the tumor, and poor differentiation of the tumor (20,42). Minimizing the number of punctures and the frequency of electrode repositioning would reduce the risk of seeding. The electrode should be placed so that it traverses sufficient normal liver parenchyma, and cauterization of the electrode tract may be effective for the reduction of seeding (17,42).
A nodular or flat lesion with early-phase enhancement can be observed along the electrode tract or at the gravity-dependent position on contrast-enhanced multiphase CT scans. Because seeded tumors occasionally grow very slowly (Fig 12), a long follow-up period is necessary to exclude tumor seeding. Heterotopic splenic tissue, such as accessory spleen and peritoneal splenosis, appears as a nodular lesion that may mimic tumor seeding. It can be distinguished from tumor seeding by a characteristic pattern of heterogeneous enhancement, which is identical to that of the orthotopic spleen on arterial phase contrast-enhanced CT scans. Technetium 99m heat-damaged red blood cell scintigraphy may be helpful for achieving a definitive diagnosis.
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Figure 12. Tumor seeding in a 59-year-old woman with hepatocellular carcinoma in segment VI. Contrast-enhanced CT scan, obtained 2 years after RF ablation, shows a flat enhanced lesion (arrowhead) along the hypochondriac wall, near the ablated area (arrow).
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Conclusions
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To minimize complications of percutaneous RF ablation for hepatocellular carcinoma, knowledge of risk factors and of methods of prevention is required. In addition, because early and accurate diagnosis is necessary for the proper management of complications, radiologists should be familiar with the imaging features of each type of complication. Proper management of complications is essential for successful treatment with RF ablation.
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Footnotes
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Abbreviations: RF = radiofrequency
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