Therapeutic Evaluation On Blunt Hepatic Trauma After Radiofrequency Ablation With Contrast-enhanced Ultrasonography And Contrast-enhanced Computed Tomography-An Experimental Study

ObjectivesDespite its relatively protected position, the liver is the most frequently injured solid intra-abdominal organ. Several invasive and noninvasive methods for the treatment of liver trauma have been suggested. Contrast-CT scan is the techique of choice for initial examination after blunt hepatic trauma.It is highly sensitve and accurate to find and evaluate the damage in the liver. Contrast-enhanced ultrasonography (CEUS), a new technique appeared recently, has offered great helps for the medical research, clinical diagnosis and treatment. It is a quantum jump in the field of imaging medicine, utilizing advanced acoustic contrast agent and visualization technology. It can real-time display and analyze the blood perfusion in the targeted organ by using microbubble in the acoustic contrast agent as a tracer for the red blood cell and harmonic enhancing imaging technology. The application of laproscope (LG) in the live trauma is more and more prospective because of its minimal invasiveness, safty and effect. The combination of CEUS and LG in the clinic will not only help to detect the sites of active bleeding and assess its bleeding range in the blunt liver trauma, but also be applized in the therapy of microwave or percutaneous radiofrequency ablation (PRFA). In PRFA, the emitted radiaofrequency wave can produce large amount of heat, which lead to the coagulative necrosis of exposed tissue, and prevent the progression of injury. PRFA, one of the most widely used minimally invasive techniques, has now widely been used in the treatment for liver tumors. It is also used to reduce blood loss during segmental liver resection and control hepatic bleeding in animal model. However, PRFA is rarely applized in the blunt hepatic trauma (BHT), for it is difficult to insert radiofrequency electrodes accurately into its bleeding sites. As for the dignose and treatment of liver trauma, the blunt is more difficult and complicated than the open. By using the animal model for BHT, having great diversity of damage which is similar in human, the present study aims to elucidate the consistancy of evaluation for the effect of PRFA in BHT through using CEUS and contrast CT methods. It includes:(1) To compare the value of CEUS and LG in the PRFA treatment for BHT;. (2) To investigate the value of CEUS in the PRFA treatment for BHT; (3) To compare the value of CEUS and contrast-CT in the PRFA treatment for BHT.Materials and Methods48 healthy Guangzhou domestic pigs weighing 39-49 kg were performed in the present study. The animals were anesthetized intramuscularly with ketamine hydrochloride (40～50 mg/kg). Femoral vein and artery catheters were introduced for blood sampling and arterial pressure monitoring. Electrocardiogram leads were attached for monitoring. Intravenous fluid was administered at a maintenance rate of approximately 3 mL/kg/h throughout the whole experiment. The use of the heparin can inhibit blood coagulation, which therefore helps to assess effectively the hemostatic technique under adverse conditions. Blood samples were collected to measure partial thromboplastin time (PTT) at the time before and after the use of heparin in the injured animals.CEUS was performed using chromatic ultrasonagraph (Acuson sequoia 512). Contrast-specific software (Contrast Pulse Sequencing, CPS, Siemens Acuson, USA) in a continuous mode with low mechanical indexes (0.18-0.21) was employed for all the examinations. CT was performed using Elscint Dual Spiral CT scanner, with 8mm in sice thickness and 1 in pitch. A laparoscope (Olympus VISERA OTV-S7) was used for the treatment. Acoustic contrast agent adopted sulfur hexaflouride microbubbles (SonoVue, Bracco, Italy). Generally, a 1.2 ml intravenous bolus injection of SonoVue was administrated, always followed by a flush of 5ml of saline. CT medium is nonionic contrast medium-lohexol and a volume of 1.5ml/kg iohexol was injected. The arteria phase, protal vein phase and delayed phase scans were respectively initiated at 25～30s,60～70s and 120-140s after the injection.The animal models of BHT accompanying with active bleeding were made by using a nail-driving gun (SDQ307) to impact the specific hepatic region 5～10cm to the right of the xiphoid process in pigs, under the guidance of ultrasound locatization. The gun was loaded with the S5 charge and designed with different impacting indexes. 10-20min later, CEUS and contrast-CT were used to decide the extent of injury, and also to guide the electrodes into the bleeding area for the therapy of RFA. The efficiacy of PRFA was evaluated through CEUS and contrast-CT at one hour of post-treatment. Then the animals were sacrificed and their livers were harvested. The RF-ablated region in the fresh liver was measured with calipers ex vivo before preservation. Next after fixation, paraffin imbedding, sectioning and HE staining, the central and periphery tissues in the RF-ablated region were selected for microscopic analysis, comparing with those in control group. The whole study includes three parts.1.16 pig-models having BHT with active bleeding were randomly divided into therapeutic group and control group. In the therapeutic group, PRFA was performed under the guidence of CEUS. CEUS was also used to evaluate the therapeutic effect of PRFA imediately or after 1h of therapy. In the control group, none treatment was carried out. The therapeutic effects and pathologic findings were compared between two groups.2. Blows were applied on the liver region in 24 healthy domestic pigs, resulting in the models of closed liver trauma. The models were randomly divided into two groups: CEUS and LG group. CEUS and LG were respectively used to diagnose, guide the insertion of RF needles and evaluate the effect of PRFA in each group.3. The modeles of BHT with active bleeding were made in 8 pigs and were randomly divided into therapeutic group (6 cases) and control group (2 cases). In treatment group, PRFA was used to control the hemorrhages in the livers under the guidance of CEUS and contrast-CT.. The animal models in control group didn't received any treatment. CEUS and Contrast-CT were performed to detect the livers before and 1 h after the PRFA therapy. The results were confirmed by pathologic examinations. Data were expressed as mean±standard deviation. Statistical analysis is aided by SPSS13.0. P<0.05 indicated a significant difference.ResultsAfter abdominal blowing, the models of BHT with active bleeding were sucessfully made in all the animals, which were decided by the examinations of CEUS and LG. It is shown a stellate laceration in liver and active bleeding from the liver fractures. Two or three bipolar applicators were accurately inserted into the damaged area in the livers under the guidance of CEUS and LG. With the increasing power output of radiofrequency, the bleeding from the liver began to boil, resulting in an accumulation of bubbles. Then the speed of bleeding decreased slowly. And the effluent blood from the ruptured liver gradually formed a thin layer of coagulated blood membrane covering the surface of the injured area in the liver. The liver tissues around and between the electrodes were coagulated gradually, and the hemorrhage stopped. Two hours after the PRFA treatment, all cases in the treatment group stayed alive, no rebleeding happened in the livers. In the light microscope, the boundary of hepatic lobule can be still identified in the zone of radiofrequency acting or between that and adjacent normal tissues. But ruptured and distort hepatic cord were found. The hepatocytes showed an appearance of coagulative necrosis. Thrombs or large number of red blood cell aggregated in the hepatic sinusoids, causing a narrow sinusoid cavity. Bile thrombs can be also found in the bile duct.1. In the therapeutic group, there was no active bleeding signals from the injured liver in 7 cases after the first PRFA treatment, detected by CEUS. Only one case has accepted the second PRFA treatment because active bleeding was still detected after the first. Hemorrhages were not found by CEUS in all 8 cases lh after the treatment. After the examination of cutting the belly open, a layer of coagulated blood was found to cover the surface of ablation area and some normal areas in liver. However, in the control group, blood accumulated around the livers and coagulated blood was not formed on the liver surface. The grade of BHT was from I to IV. Hemorrhages were still detected by CEU 1h after the liver injury. The results of CEU was highly consistent with those of pathology.2. All 24 pig-models of BHT were sucessfully made, following with active bleeding. And the accordance rate of diagnosis arrived at 100% in CEUS and LG groups. There was a significant difference for the final diagnosis time in the two group (P<0.05). The guiding electrodes was 100% exactly inserted into the injured area in liver of all two groups. There were no obvious difference in the treating periods and ablation scales between the two groups (P>0.05). No rebleeding was found in the livers in all treated pigs one hours of after the PRFA treatment.3. Before PRFA, both CEUS and contrast-CT indicated the injury in the liver parenchyma of 8 animals. Active bleeding from the liver was detected in all pigs by CEUS and six by Contrast-CT. After PRFA, no hemorrhage was found in pigs of treatment group by CEUS and Contrast-CT. In control group, one case died in the 30 minutes after the liver blowing. Hemorrhage was still detected in one case by CEUS and Contrast-CT 1 h after the impact. The results of CEUS and contrast-CT were highly related with the gross pathologic findings.Conclusions1. PRFA is a feasible therapy for some BHT. CEUS is a credible method in guiding the insertion of radiofrequency electrode and in evaluating the effects of PRFA in real time. CEUS has a great value in the therapy of radiofrequency ablation for BHT.2. Both CEUS and LG can fast and exactly diagnose BHT, guide the PRFA electrodes accurately inserting into the injured area of liver and evaluate the therapeutic effect of PRFA on controlling the hemorrhage of the blunt hepatic traumas. But there were some differences in the ablation areas between the two groups. CEUS for guiding PRFA is advanced in controlling hemorrhage within liver parenchyma, but LG is on the surface. CEUS has also the advantages of minimal invasiveness, easy operation and consistant repeatability. In the clinic, different examination should be selected to guide PRFA therapy, according to the different hepatic injury.3. As for the diagnosis of different grading liver trauma, CEUS is highly consistant with contrast-CT. CEUS can accurately show the degree of injury and the curative effect. Therefore it has important significance in the clinic application.