A 73-year-old woman with chronic hepatitis C and hepatocellular carcinoma (HCC) was hospitalized for radiofrequency ablation (RFA). Laboratory test results showed the following: platelet count, 62,000/mm3; prothrombin time, 12 seconds; albumin, 4.4 g/dL; bilirubin, 0.8 mg/dL; alpha-fetoprotein, 8.5 ng/mL; and des-gamma-carboxy prothrombin, 11 mAU/mL. Gadoxetic acid–enhanced magnetic resonance imaging demonstrated a low-intensity area in the hepatobiliary phase in segment VIII. Contrast-enhanced ultrasonography (CEUS) showed hyperenhancement in the vascular phase with hypoenhancement in the postvascular phase. Aspiration biopsy revealed well-differentiated HCC. We performed CEUS-guided RFA with a 2-cm Cool-tip RFA system (Radionics, Burlington, MA) through an intercostal space. No abnormalities in the chest wall were found before RFA and the patient had no complaints, except for mild pain during ablation. Increased thickness of the chest wall was found during RFA. Immediately after ablation, we performed CEUS with perflubutane and identified linear extravasation of microbubbles along the needle tract in the vascular phase (Fig. 1A). After 5 and 10 minutes, we reinjected perflubutane and could find no extravasations of microbubbles (Fig. 1B). Enhanced computed tomography (CT) demonstrated a hemorrhage in the chest wall (Fig. 1C) and a small amount of intraperitoneal hemorrhage on the hepatic surface (Fig. 1D), but no active bleeding. We speculated that an intercostal vessel had been injured by the electrode, with spontaneous resolution of the hemorrhage.
Hemorrhages resulting from RFA occur in 0.5% of cases.1 In our case, bleeding from an intercostal vessel into the chest wall was clearly detected on CEUS. CEUS is reported to show 100% sensitivity and 100% specificity for the detection of active bleeding.2 We could repeatedly and in real time confirm continued hemorrhaging, even in the pooling of contrast agent, using high-power flashes. Briefly, a high-power flash ultrasonic (US) beam (mechanical index: 1.27) destroys the majority of microbubbles in the US plane and, consequently, allows a resetting of transient perfusion. A high-power flash repeatedly enables the demonstration of contrast extravasations. Furthermore, the disappearance of extravasations indicates the resolution of hemorrhaging because of the high sensitivity of CEUS for detecting hemorrhaging. Taken together, CEUS enables real-time and repeated assessment of hemorrhaging and its resolution without radiation exposure, unlike CT. CEUS has some limitations. First, CEUS has some blind areas, such as the subphrenic area or areas surrounding intestinal gas. However, most hemorrhages after US-guided RFA occur in the visual area. Second, adequate images of deep regions cannot be obtained.3 Third, CEUS depends on the skill of the operator.
In conclusion, when hemorrhaging is suspected, CEUS is a useful tool for detecting extravasation and confirming its resolution.