Contrast-enhanced ultrasound improves hepatic vessel visualization after orthotopic liver transplantation

Initial experience with contrast-enhanced ultrasound in the first week after liver transplantation in children: a useful adjunct to Doppler ultrasound

BACKGROUND

Doppler US is the primary screening for post-liver transplant vascular complications, but indeterminate findings require further imaging.

OBJECTIVE

To evaluate whether contrast-enhanced US improves diagnostic assessment of vascular complications suspected by Doppler US.

MATERIALS AND METHODS

We retrospectively reviewed Doppler US and contrast-enhanced US studies obtained in the first week following liver transplant. Doppler US was performed twice daily for the first 5 postoperative days, and CEUS in the first postoperative day and when vascular complications were suspected. We correlated Doppler US and CEUS with surgical findings, and clinical and imaging follow-up. We evaluated Doppler US and CEUS quality in demonstrating the main hepatic artery (HA) at the porta hepatis as follows: Grade 0 = not seen, Grade 1 = only segments, Grade 2 = entire main HA, and Grade 3 = entire main HA to the intrahepatic branching. We used a Wilcoxon signed rank test to test the difference between Doppler US and CEUS methods.

RESULTS

Twenty-nine children (15 girls, 14 boys) were identified, with median age 2.2 years (range 0.5-17.6 years). The most common transplant indication was biliary atresia (n=13). There was significantly (P<0.0001) improved main HA visualization with CEUS. In five children, CEUS was performed to evaluate suspected vascular complications; CEUS confirmed normal vascularity in two. CEUS demonstrated portal vein thrombosis (n=2) and main HA thrombosis (n=1), confirmed at surgery. In one child the main HA thrombosis was missed; marked HA narrowing was seen retrospectively on CEUS.

CONCLUSION

Immediately following liver transplantation, CEUS improves main HA visualization and diagnostic assessment of vascular complications.

Contrast-enhanced ultrasound applications in liver transplant imaging

Contrast-enhanced ultrasound (CEUS) is gaining ever-increasing acceptance in the preoperative and postoperative evaluation of liver-transplanted patients. While indications are still a matter of research, CEUS is used in tertiary centers to supplement ultrasound (US) and Color Doppler US examination, with the potential of providing a comprehensive first-line ultrasound-based diagnosis. Alternatively, CEUS is used as a problem-solving tool when previous cross-sectional or US imaging was inconclusive, especially in assessing hepatocellular carcinoma, parenchymal perfusion abnormalities, the vascular status, and even the biliary tree. This review describes the potential use for CEUS in the setting of orthotopic liver transplantation (OLT).

Influence of ultrasound contrast agents on spectral Doppler analysis in recipients of liver transplantation

Background/Aims

Clinical validation is required to determine whether Doppler measurements are comparable before and after administering ultrasound contrast agent (USCA). The purpose of this study is to explore whether the use of USCA affects spectral Doppler analysis in recipients of liver transplantation (LT).

Methods

For this study, 36 patients were examined using Doppler ultrasonography (US) along with a contrast-enhanced US for surveillance of vascular complications after LT. The following spectral Doppler US parameters were measured before and after administration of USCA: peak systolic velocity, end-diastolic velocity, resistive index, and systolic acceleration time of the graft hepatic artery; peak flow velocity of the graft portal vein; and peak flow velocity and venous pulsatility index of the graft hepatic vein.

Results

The mean peak systolic and end-diastolic velocities of the hepatic artery and the peak flow velocity of the portal and hepatic veins were increased after intravenously administration of the USCA, ranging from 10% to 13%. However, the changes were not statistically significant (P=0.097, 0.103, 0.128, and 0.190, respectively). There were no significant differences in other measured parameters, including the resistive index (P=0.205) and systolic acceleration time (P=0.489) of the hepatic artery and venous pulsatility index (P=0.494) of the hepatic vein.

Conclusions

The measured velocities of graft hepatic vessels tended to increase after administration of USCA, but without statistical significance. The comparison of serial Doppler parameters with or without injection of USCA is valid during Doppler surveillance in recipients of LT.

New diagnosis and therapy model for ischemic-type biliary lesions following liver transplantation--a retrospective cohort study

Ischemic-type biliary lesions (ITBLs) are a major cause of graft loss and mortality after orthotopic liver transplantation (OLT). Impaired blood supply to the bile ducts may cause focal or extensive damage, resulting in intra- or extrahepatic bile duct strictures or dilatations that can be detected by ultrasonography, computed tomography, magnetic resonance cholangiopancreatography, and cholangiography. However, the radiographic changes occur at an advanced stage, after the optimal period for therapeutic intervention. Endoscopic retrograde cholangio-pancreatography (ERCP) and percutaneous transhepatic cholangiodrainage (PTCD) are the gold standard methods of detecting ITBLs, but these procedures cannot be used for continuous monitoring. Traditional methods of follow-up and diagnosis result in delayed diagnosis and treatment of ITBLs. Our center has used the early diagnosis and intervention model (EDIM) for the diagnosis and treatment of ITBLs since February 2008. This model mainly involves preventive medication to protect the epithelial cellular membrane of the bile ducts, regular testing of liver function, and weekly monitor of contrast-enhanced ultrasonography (CEUS) to detect ischemic changes to the bile ducts. If the liver enzyme levels become abnormal or CEUS shows low or no enhancement of the wall of the hilar bile duct during the arterial phase, early ERCP and PTCD are performed to confirm the diagnosis and to maintain biliary drainage. Compared with patients treated by the traditional model used prior to February 2008, patients in the EDIM group had a lower incidence of biliary tract infection (28.6% vs. 48.6%, P = 0.04), longer survival time of liver grafts (24±9.6 months vs. 17±12.3 months, P = 0.02), and better outcomes after treatment of ITBLs.

Imaging of vascular complications and their consequences following transplantation in the abdomen

Transplantation is the surgical treatment of choice for end-stage organ failure. Transplantation procedures performed in the abdomen include liver, renal, pancreas, islet, intestinal, and multivisceral transplantations. Imaging plays a pivotal role in the posttransplantation setting for monitoring the transplant allograft and screening for complications. Knowledge of the surgical techniques employed in abdominal transplantation is essential because it facilitates radiologic understanding and interpretation of the posttransplantation anatomy. This article includes a basic description of the standard surgical techniques performed in the abdomen, with emphasis on the relevant vascular anastomotic reconstructions used. Posttransplantation complications can be broadly classified as vascular or nonvascular in origin. Many of these complications can be accurately depicted and characterized at imaging and dealt with definitively by using interventional radiology techniques, which can be graft- and life-saving and can obviate further complex surgical intervention. The article discusses imaging appearances of vascular complications and their consequences after transplantation in the abdomen. These vascular complications include arterial thrombosis, arterial stenosis, venous thrombosis and stenosis, arteriovenous fistula formation, and pseudoaneurysm formation. The relevant predisposing factors, clinical features, imaging appearances, and potential treatment options for vascular complications of various types of transplantation are presented in a logical and integrated fashion. Knowledge and imaging recognition of the posttransplantation vascular complications discussed in this article will aid radiologists in accurate imaging characterization and thereby facilitate appropriate clinical management and therapy.

Obstruction at middle hepatic venous tributaries in modified right lobe grafts after living-donor liver Transplantation: diagnosis with contrast-enhanced US

PURPOSE

To investigate the ability of contrast material-enhanced ultrasonography (US) to help diagnose obstruction of middle hepatic venous (MHV) tributaries soon after living-donor liver transplantation with modified right lobe grafts.

MATERIALS AND METHODS

The institutional review board approved the study and waived requirement for informed consent. Sixty-five consecutive patients (48 men, 17 women; mean age, 52.8 years; range, 33-69 years) who underwent living-donor liver transplantation with modified right lobe grafts between February and May 2009 were included. All patients underwent contrast-enhanced US and Doppler US on postoperative day 1 and underwent computed tomography (CT) within 7 days after US. At contrast-enhanced US, parenchymal enhancement patterns in the territory of each MHV tributary during arterial and portal venous phases were evaluated. With use of most frequent enhancement patterns in patients with obstruction at MHV tributaries as a criterion, diagnostic performance of contrast-enhanced US was compared with that of Doppler US for diagnosis of obstruction at MHV tributaries; CT was the reference standard. Generalized estimating equations were used to adjust for data clustering.

RESULTS

Of 148 MHV tributaries in 65 patients, 36 (24.3%) in 31 patients were diagnosed as obstructed at CT. With arterial high echogenicity or portal low echogenicity used as a criterion for hepatic venous obstruction, contrast-enhanced US had sensitivity, specificity, and accuracy of 91% (33 of 36), 97% (109 of 112), and 95% (142 of 148), respectively, whereas Doppler US had values of 83% (30 of 36), 86% (97 of 112), and 85% (127 of 148), respectively. Contrast-enhanced US was significantly more specific and accurate than Doppler US for diagnosis of obstruction at MHV tributaries (P=.024 and .01, respectively). Arterial high echogenicity was noted only in the hepatic venous obstruction group.

CONCLUSION

Contrast-enhanced US can help accurately assess hepatic venous obstruction at MHV tributaries after living-donor liver transplantation with a modified right lobe graft. Contrast-enhanced US was significantly more specific than Doppler US, with arterial hyperenhancement in the affected area being specific to hepatic venous obstruction.

Role of contrast-enhanced ultrasound in decision support for diagnosis and treatment of hepatic artery thrombosis after liver transplantation

OBJECTIVE

To assess role of contrast-enhanced ultrasound (CEUS) in decision support for diagnosis and treatment of hepatic artery thrombosis (HAT) after liver transplantation.

MATERIALS AND METHODS

Between January 2005 and January 2011, 605 patients underwent liver transplantation in our medical center. All the liver transplant recipients received Doppler ultrasound scanning and CEUS examination was performed in 45 patients with suspected HAT on Doppler ultrasound. Sensitivity, specificity, accuracy, positive predict value and negative predictive value of CEUS in diagnosing HAT were determined based on the results from angiography, surgery and clinical follow-up.

RESULTS

Fourteen HATs, including one late HAT, were diagnosed by CEUS. Twelve HAT cases were confirmed by angiographic and/or surgical findings, while the late HAT and other 31 patients with negative CEUS finding were confirmed by the clinical follow-up. There was a false positive HAT diagnosed by CEUS in which angiography revealed a patent hepatic artery. The sensitivity, specificity, accuracy, positive predict value and negative predictive value of CEUS in diagnosing HAT were 100%, 96.9%, 97.8%, 92.9% and 100%, respectively. In our series of 605 liver transplants, the incidence and mortality of HAT was 2.2% (13/605) and 53.8% (7/13), respectively.

CONCLUSIONS

Our study demonstrates the important role of CEUS in decision support for diagnosis and treatment of HAT after liver transplantation. When HAT is suspected by Doppler ultrasound, CEUS shall immediately be performed to elucidate its nature. A negative CEUS finding shall avoid invasive angiography. Such as, CEUS may alter the clinical workflow on HAT detection after liver transplantation.

CEUS: A new imaging approach for postoperative vascular complications after right-lobe LDLT

AIM: To investigate contrast-enhanced ultrasound (CEUS) for early diagnosis of postoperative vascular complications after right-lobe living donor liver transplantation (RLDLT).

METHODS: The ultrasonography results of 172 patients who underwent RLDLT in West China Hospital, Sichuan University from January 2005 to June 2008 were analyzed retrospectively. Among these 172 patients, 16 patients’ hepatic artery flow and two patients’ portal vein flow was not observed by Doppler ultrasound, and 10 patients’ bridging vein flow was not shown by Doppler ultrasound and there was a regional inhomogeneous echo in the liver parenchyma upon 2D ultrasound. Thus, CEUS examination was performed in these 28 patients.

RESULTS: Among the 16 patients without hepatic artery flow at Doppler ultrasound, CEUS showed nine cases of slender hepatic artery, six of hepatic arterial thrombosis that was confirmed by digital subtraction angiography and/or surgery, and one of hepatic arterial occlusion with formation of lateral branches. Among the two patients without portal vein flow at Doppler ultrasound, CEUS showed one case of hematoma compression and one of portal vein thrombosis, and both were confirmed by surgery. Among the 10 patients without bridging vein flow and with liver parenchyma inhomogeneous echo, CEUS showed regionally poor perfusion in the inhomogeneous area, two of which were confirmed by enhanced computed tomography (CT), but no more additional information about bridging vein flow was provided by enhanced CT.

CONCLUSION: CEUS may be a new approach for early diagnosis of postoperative vascular complications after RLDLT, and it can be performed at the bedside.

Hemodynamic changes on color Doppler flow imaging and intravenous contrast-enhanced ultrasound for assessing transplanted liver and early diagnosis of complications. ACTA ACUST UNITED AC. 2008;28:284-286. [PMID: 18563324 DOI: 10.1007/s11596-008-0312-5]

The value of color Doppler flow imaging (CDFI) and intravenous contrast-enhanced ultrasound (CEUS) for assessing the transplanted liver and early diagnosing complications by examining hemodynamic changes was discussed. Seventy-five patients with orthotopic liver transplantation (OLT) underwent CDFI. The following parameters were measured: peak systolic velocity (PS), resistance index (RI) and Doppler perfusion index (DPI) of the hepatic artery (HA), time average velocity (TAV) of portal vein (PV) and velocity of hepatic vein (HV) in different stages postoperation. And 11 patients of them received CEUS. Thirty healthy subjects were enrolled as controls. The results showed that: (1) In 23 patients without obvious complications, TAV of PV within 15 days post-operation was significantly higher than in controls (P<0.05), PS and DPI of HA within 7 days postoperation were lower, but RI was higher than in controls (P<0.05); (2) When the hepatic artery thrombosis (HAT) occurred, PS and DPI of HA were obviously decreased, but TAV of PV significantly increased like a high saw-tooth wave; (3) While rejection occurred, both TAV of PV and PS of HA were decreased with the increase in RI of HA, and the triphasic wave of HV disappeared and displayed as saw-tooth wave; (4) The incidence of biliary complications in liver transplantation was increased when DPI was reduced; (5) Seven cases of hepatic carcinoma relapse after OLT demonstrated hyperecho in the arterial phase and hypoecho in the portal and later phase on CEUS; (6) In 2 cases of HA thrombus, there was no visualized enhancement in arterial phase of CEUS, but enhancement during the portal vein and parenchymal phase. It was concluded that the hemodynamic changes of PV, HA and HV in the transplanted liver are valuable for assessing the transplanted liver and early diagnosing complications on CDFI and CEUS.

Contrast-enhanced ultrasound with SonoVue in the evaluation of postoperative complications in pediatric liver transplant recipients. J Ultrasound. 2007;10:99-106. [PMID: 23396596 DOI: 10.1016/j.jus.2007.02.008]

PURPOSE

To evaluate the utility of contrast-enhanced sonography in the study of pediatric liver transplant recipients and its potential impact in reducing the need for invasive diagnostic procedures.

MATERIALS AND METHODS

From October 2002 to December 2003 we performed routine color Doppler ultrasound and contrast-enhanced ultrasound studies on 30 pediatric patients who had undergone liver transplantation. Findings indicative of complications were confirmed with invasive studies (angiography, computed tomography, and PTC).

RESULTS

Contrast-enhanced sonography correctly identified four of the five cases of hepatic artery thrombosis and all those involving the portal (n = 6) and hepatic vein (n = 3) thrombosis. It failed to identify one case of hepatic artery thrombosis characterized by collateral circulation arising from the phrenic artery and the single case of hepatic artery stenosis. The latter was more evident on color Doppler, which revealed a typical tardus parvus waveform. The use of contrast offered no significant advantages in the study of biliary complications although it did provide better visualization of bile leaks.

CONCLUSIONS

Contrast-enhanced sonography improves diagnostic confidence and reduces the need for more invasive imaging studies in the postoperative follow-up of pediatric liver transplant recipients.

Prospective evaluation of vascular complications after liver transplantation: comparison of conventional and microbubble contrast-enhanced US

PURPOSE

To prospectively compare diagnostic performance of conventional Doppler ultrasonography (US) and microbubble contrast material-enhanced US for assessment of vascular complications after liver transplantation, with clinical follow-up or angiography as reference standard.

MATERIALS AND METHODS

This study was approved by institutional review board and was HIPAA compliant. Written informed consent was obtained. Seventy-two patients (49 men, 23 women; average age, 52.3 years) were included in this study. Patients who had undergone liver transplantation underwent conventional color Doppler and contrast-enhanced US of the liver. Quality of hepatic artery (HA) and portal vein (PV) visualization, contrast material arrival time, and time for complete evaluation of vasculature were compared for both techniques. McNemar test was used to compare vascular flow visualization scores; Student t test was used to compare mean study times with both techniques. Patients without HA flow at Doppler US underwent angiography; those with flow were followed up clinically. McNemar test was used to compare sensitivity of both techniques.

RESULTS

Contrast-enhanced US helped significantly improve flow visualization in hepatic vessels (P < .001). Mean contrast material arrival time was 13.7 seconds +/- 3.8 (standard deviation) in proper HA and 20.7 seconds +/- 6.3 in PV. Mean study time decreased from 27.4 minutes +/- 13.9 to 9.3 minutes +/- 4.5 (P < .01). Doppler US failed to depict HA flow in eight patients; contrast-enhanced US showed flow in six and no flow in two of these patients. Follow-up results confirmed contrast-enhanced US findings. Sensitivity, specificity, and accuracy for Doppler US were 91.3%, 100%, and 91.5%, respectively. Sensitivity, specificity, and accuracy of contrast-enhanced US were all 100%. Sensitivity and accuracy values of the two techniques were significantly different (P < .014); there was no significant difference in specificity (P > .99)

CONCLUSION

Contrast-enhanced US helped improve flow visualization in the HA and PV, decrease scanning time, and correctly differentiate between thrombosis and a patent artery in patients without HA flow at conventional Doppler US.

[Ultrasound contrast agents for liver diagnostics]

Ultrasound contrast agents have achieved a high level of acceptance in diagnostics of liver tumors. Contrast-enhanced ultrasound can, on the one hand, be used for detection of liver tumors, e.g., during the search for metastases in tumor staging, and, on the other hand, for tumor characterization. The dispersion behavior of the ultrasound contrast agent plays a decisive role in the characterization and the enhancement patterns correspond to a large extent to those already known from contrast-enhanced computed tomography. Contrast-enhanced ultrasound can also be employed for monitoring ablative tumor therapies, visualization of vessels difficult to depict, and measurement of the so-called liver transit time.

Contrast-enhanced duplex scanning of crural arteries by means of continuous infusion of Levovist

OBJECTIVES

To estimate the dosage needed for continuous infusion and to investigate whether continuous infusion of the ultrasound contrast-enhancing agent Levovist (SH U 508A) can improve duplex scanning of crural arteries in patients with peripheral arterial obstructive disease (PAOD) eligible for distal bypass graft surgery.

DESIGN, PATIENTS, AND METHODS

The study design consisted of two parts. Part 1 investigated the color and spectral Doppler scan enhancement of three different Levovist dosages (200, 300, and 400 mg/mL) in one arterial segment of a patent lumen of a crural artery in seven patients with PAOD. Part 2 investigated the value of the optimum Levovist dosage in the assessment of 10 crural arteries in 10 consecutive patients with PAOD. Angiography was the reference standard.

RESULTS

Part 1: Levovist significantly enhanced color and spectral Doppler scan as compared with baseline ultrasound scan, but no differences were found between the Levovist dosages. Thus, the lowest Levovist dosage sufficed for application in part 2, because of its infusion volume and prolonged enhancement time. Part 2: The agreement between contrast-enhanced duplex scanning and angiography was moderate (kappa = 0.50; 95% confidence interval [CI], 0.03-0.97). Five (50%) of 10 crural arteries that could not adequately be visualized with routine duplex scanning could be visualized with contrast-enhanced duplex scanning.

CONCLUSION

Contrast-enhanced duplex scanning by means of continuous infusion of Levovist in patients with PAOD improves the ultrasound scan investigation of crural arteries in case routine duplex scanning is inconclusive and might reduce the need for angiography.