Doppler evaluation of arterial complications of adult orthotopic liver transplantation

Intraoperative indocyanine green fluorescence imaging to predict early hepatic arterial complications after liver transplantation

The purpose of this study was to propose an innovative intraoperative criterion in a liver transplantation setting that would judge arterial flow abnormality that may lead to early hepatic arterial occlusion, that is, thrombosis or stenosis, when left untreated and to carry out reanastomosis. After liver graft implantation, and after ensuring that there is no abnormality on the Doppler ultrasound (qualitative and quantitative assessment), we intraoperatively injected indocyanine green dye (0.01 mg/Kg), and we quantified the fluorescence signal at the graft pedicle using ImageJ software. From the obtained images of 89 adult patients transplanted in our center between September 2017 and April 2019, we constructed fluorescence intensity curves of the hepatic arterial signal and examined their relationship with the occurrence of early hepatic arterial occlusion (thrombosis or stenosis). Early hepatic arterial occlusion occurred in 7 patients (7.8%), including 3 thrombosis and 4 stenosis. Among various parameters of the flow intensity curve analyzed, the ratio of peak to plateau fluorescence intensity and the jagged wave pattern at the plateau phase were closely associated with this dreaded event. By combining the ratio of peak to plateau at 0.275 and a jagged wave, we best predicted the occurrence of early hepatic arterial occlusion and thrombosis, with sensitivity/specificity of 0.86/0.98 and 1.00/0.94, respectively. Through a simple composite parameter, the indocyanine green fluorescence imaging system is an additional and promising intraoperative modality for identifying recipients of transplant at high risk of developing early hepatic arterial occlusion. This tool could assist the surgeon in the decision to redo the anastomosis despite normal Doppler ultrasonography.

Abdominal ultrasound and VExUS score in critical care

The use of ultrasound while caring for critically ill patients has been increasing exponentially in the last two decades and now is an essential component of intensive care practice. Abdominal ultrasound is an established technique in other specialties, but its use in intensive care has lagged behind other ultrasound modalities. However, its potential role in the diagnosis and management of patients will make it an invaluable tool for intensivists. The main use of abdominal ultrasound at the bedside is for free fluid detection in trauma patients. But abdominal ultrasound can also help us diagnose patients with abdominal pain, hypovolemia or anuria, and it can guide us during procedures such as paracentesis or bladder catheter and gastric tube placement.

Machine Learning Algorithm Improves the Prediction of Transplant Hepatic Artery Stenosis or Occlusion: A Single-Center Study

ABSTRACT

The aim of this study was to determine if machine learning can improve the specificity of detecting transplant hepatic artery pathology over conventional quantitative measures while maintaining a high sensitivity.This study presents a retrospective review of 129 patients with transplanted hepatic arteries. We illustrate how beyond common clinical metrics such as stenosis and resistive index, a more comprehensive set of waveform data (including flow half-lives and Fourier transformed waveforms) can be integrated into machine learning models to obtain more accurate screening of stenosis and occlusion. We present a novel framework of Extremely Randomized Trees and Shapley values, we allow for explainability at the individual level.The proposed framework identified cases of clinically significant stenosis and occlusion in hepatic arteries with a state-of-the-art specificity of 65%, while maintaining sensitivity at the current standard of 94%. Moreover, through 3 case studies of correct and mispredictions, we demonstrate examples of how specific features can be elucidated to aid in interpreting driving factors in a prediction.This work demonstrated that by utilizing a more complete set of waveform data and machine learning methodologies, it is possible to reduce the rate of false-positive results in using ultrasounds to screen for transplant hepatic artery pathology compared with conventional quantitative measures. An advantage of such techniques is explainability measures at the patient level, which allow for increased radiologists' confidence in the predictions.

Intraoperative Doppler Ultrasound for Detection of Early Postoperative Vascular Complications in Orthotopic Liver Transplants

Liver transplantation is currently the only curative treatment for patients with end-stage liver disease. However, liver transplantation can be associated with catastrophic complications in the early postoperative setting, including hepatic artery thrombosis (HAT) and portal vein thrombosis (PVT). Postoperative complications are associated with hepatic artery resistive index (RI) < 6, systolic acceleration time (SAT) > 0.08 seconds and peak systolic velocity (PSV) > 200 cm/s on doppler ultrasound (DUS). DUS is also used in an intraoperative setting to assess patency and early complications prior to the end of the operative period, allowing for early correction. This literature review evaluates the prevalence of DUS use in intraoperative settings to identify transplant complications. A lack of consistency and minimal knowledge of intraoperative DUS warrants additional research into its usage and standardization.

Diagnostic accuracy of Doppler ultrasound for detecting hepatic artery stenosis after liver transplantation

AIM

To evaluate the diagnostic accuracy of Doppler ultrasound (DUS) in detecting hepatic artery stenosis (HAS) after liver transplantation using computed tomography angiography (CTA) as the reference standard.

MATERIALS AND METHODS

This study included data from January 2005 to November 2017, where DUS of the hepatic artery of living and deceased donor liver grafts were compared with the reference standard, CTA. DUS parameters, such as intrahepatic artery (IHA) peak systolic velocity (PSV), resistive index (RI), systolic acceleration time (SAT); and extrahepatic artery (EHA) PSV were taken. The optimum cut-off was estimated using area under the receiver operating characteristic curve (AUC). Multivariable logistic regression analysis was developed to predict HAS.

RESULTS

Ninety-nine liver transplant cases were retrieved, 50 met the inclusion criteria where nine patients had significant HAS. HAS patients had a significantly low IHAPSV with a cut-off of 35.1 cm/s (sensitivity 53.8%, specificity 78.4%, AUC 0.701). IHARI had a significantly low RI with a cut-off 0.585 (sensitivity 86.7%, specificity 85.4%, AUC 0.913). The IHASAT cut-off was 0.045 seconds (sensitivity 80%, specificity 91.4%, AUC 0.857). The EHAPSV cut-off was 197.4 cm/s (sensitivity 50%, specificity 99.1%, AUC 0.648). The prediction model using DUS parameters IHARI and IHASAT demonstrated good discrimination with an AUC of 0.930 (95% CI: 0.843, 1.000; sensitivity 93.3%, specificity 88%).

CONCLUSION

A prediction model using the DUS parameters IHARI and IHASAT showed good diagnostic accuracy of 88.6% for monitoring liver transplant patients. If validated externally, this DUS model could be utilised to diagnose HAS in liver transplant recipients.

Sonography of liver transplantation

Orthotopic liver transplant (OLT) is established as the definitive treatment of choice for end stage liver disease. Over the years, refined surgical techniques as well as advancements in organ preservation and immunosuppressive regimens have improved graft and patient survival rates. Imaging has also contributed to improved graft and patient survival. Ultrasound is the initial investigation of choice for evaluation of post-transplant anatomy and for identifying early complications. A thorough knowledge of surgical techniques and normal post-operative appearance of the OLT is needed to accurately identify and characterize graft complications. The objective of this article is to review the sonographic findings of normal liver transplant as well as post-operative complications. Indications and contraindications for OLT as well as different surgical techniques will also be briefly reviewed.

Complications of liver transplant

Liver transplantation has become a definitive treatment for patients with end-stage liver disease and those meeting Milan criteria for hepatocellular carcinoma. The morbidity and mortality associated with liver transplantation continues to decrease thanks to refinements in surgical technique, immunosuppression, and imaging. In particular, imaging plays a vital role by facilitating early detection of post-operative complications and enabling prompt treatment. Post-operative complications that lead to graft failure and patient morbidity/mortality can be generally categorized as vascular, biliary, parenchymal, and malignant. Vascular complications include stenosis and thrombosis of the hepatic artery, portal vein, and inferior vena cava; hepatic artery pseudoaneurysm; arteriovenous fistula; and celiac stenosis. Biliary abnormalities include strictures, bile leak, obstruction, recurrent disease, and infection. While imaging is not primarily utilized to diagnose allograft rejection, it plays an important role in excluding mechanical causes of graft dysfunction that can mimic rejection. Ultrasound is routinely performed as the first-line imaging evaluation for the detection and follow-up of early and delayed complications. Cholangiography and magnetic resonance cholangiopancreatography are useful in detecting and characterizing biliary complications. Computed tomography is often used to further evaluate abnormal findings on ultrasound or for the characterization of post-operative fluid collections. The aim of this review is to discuss and illustrate the imaging findings of complications associated with liver transplantation and their role in facilitating treatment.

Tardus parvus waveforms in Doppler ultrasonography for hepatic artery stenosis after liver transplantation: can a new cut-off value guide the next step?

PURPOSE

Considering the high false-positive diagnosis of the tardus parvus waveform (TPW) in Doppler ultrasonography (DUS) for hepatic artery stenosis (HAS) after liver transplantation (LT), this study aimed to determine clinical features and new cut-off values to help guide treatment.

MATERIALS AND METHODS

This retrospective study was approved by an Institutional Review Board. A total of 171 LT recipients were included and underwent DUS and either computed tomography angiography or digital subtraction angiography with an interval < 4 weeks at least 1 month post-LT. The DUS of 69 patients exhibited TPW [defined as resistive index (RI) < 0.5 and systolic acceleration time (SAT) > 0.08 s]. A multilevel likelihood ratio (LR) analysis was used to explore new cut-off values for DUS. In addition, abnormal liver function was considered additional evidence (defined as any liver enzyme > 3-fold of the upper limit of normal level or 2-fold increased). The results were stratified into three categories, category 1 (subjects with traditional TPW), category 2 (subjects with traditional TPW and abnormal liver function), and category 3 (subjects with traditional TPW and abnormal liver function, or with new cut-off values), and the diagnostic performance of each category was analyzed.

RESULTS

The LR analysis revealed new cut-off values of RI < 0.4 (LR = 10.58) or SAT > 0.12 s (LR = 16.46). The false-positive rates for categories 2 and 3 were significantly lower (7.6% vs. 18.1%, P = 0.038; 1.9% vs. 18.1%, P < 0.001, respectively) than those for category 1, while the sensitivity for category 2 was significantly lower (41.8% vs. 74.6%, P < 0.001; 41.8% vs. 61.2%, P = 0.038, respectively) than that for categories 1 and 3.

CONCLUSION

Using either (1) RI < 0.4 or SAT > 0.12 s, or (2) traditional TPW (RI < 0.5 and SAT > 0.08 s) in the presence of abnormal liver functions as the DUS criteria for HAS will significantly decrease the false-positive rate compared to traditional TPW without a significant increase in the false-negative rate.

Refractory anastomotic bile leaks after orthotopic liver transplantation are associated with hepatic artery disease

BACKGROUND AND AIMS

Anastomotic bile leaks are common after orthotopic liver transplant (OLT), and standard treatment consists of placement of a biliary endoprosthesis. The objectives of this study were to identify risk factors for refractory anastomotic bile leaks and to determine the morbidity associated with refractory bile leaks after OLT.

METHODS

Consecutive adult patients who underwent ERCP for treatment of post-OLT biliary adverse events between 2009 and 2014 at a high-volume transplant center were retrospectively identified. A refractory leak was defined as a bile leak that persisted after placement of a plastic biliary endoprosthesis and required repeat endoscopic or surgical intervention.

RESULTS

Forty-three subjects met study inclusion criteria. Median age was 57 years, and 36 (84%) subjects were men. Refractory bile leaks were diagnosed in 40% of subjects (17/43). Time-to-event analysis revealed an association between refractory bile leaks and the combined outcome of death, repeat transplant, or surgical biliary revision (hazard ratio, 3.78; 95% confidence interval, 1.25-11.45; P = .01). Hepatic artery disease was more common with refractory compared with treatment-responsive bile leaks (53% vs 8%, P = .001).

CONCLUSIONS

Refractory anastomotic bile leaks after liver transplantation are associated with decreased event-free survival. Hepatic artery disease is associated with refractory leaks. Large-scale prospective studies should be performed to define the optimal management of patients at risk for refractory bile leaks.

The Sonographic Stenosis Index: A New Specific Quantitative Measure of Transplant Hepatic Arterial Stenosis

OBJECTIVES

This study evaluates the sensitivity and specificity of stenosis index (SI), which accounts for the entire spectral Doppler waveform, to detect significant transplant hepatic arterial stenosis.

MATERIALS AND METHODS

In this institutional review board-approved, HIPAA compliant study, we retrospectively analyzed 69 patients who had catheter angiography for suspected transplant hepatic arterial stenosis (THAS) between January 2006 and December 2010; all patients had Doppler ultrasound within 30 days before angiography. Patients with angiographic stenosis requiring intervention were considered positive for THAS. Stenosis index was calculated from each patient's spectral Doppler ultrasound images by obtaining the ratio of the area under the high-frequency signal to low-frequency signal in the spectral Doppler. Resistive index (RI) and pulsatility index (PI) were also calculated. Receiver operator curve analysis was performed and the area under the curve (AUC) was compared among the three metrics.

RESULTS

Forty-eight of 69 patients had THAS by angiography requiring intervention; 21patients had no angiographic evidence of THAS. SI was significantly different (P < .001) between patients with THAS (SI = 1.04 ± 0.20) and those without THAS (SI = 1.39 ± 0.30). Stenosis index had an AUC of 0.86 for detecting THAS, which was significantly higher than that from RI (AUC = 0.68, P = .038 for the comparison) and PI (AUC = 0.70, P = .029). For SI < 1.35, the sensitivity for THAS was 94% and specificity was 52%. For RI < 0.5, the sensitivity was 96% and the specificity was 29%.

CONCLUSIONS

Stenosis index is more accurate than the resistive index and the pulsatility index for detecting transplant hepatic artery stenosis.

Doppler Characteristics of Recurrent Hepatic Artery Stenosis

OBJECTIVES

We sought to assess midterm sonographic findings in patients after stenting for hepatic artery stenosis.

METHODS

Thirty-nine hepatic artery stent procedures were performed for hepatic artery stenosis after liver transplantation between September 2009 and December 2013. Thirty cases were technically successful and met the minimum follow-up time (76 days, defined by earliest diagnosed stenosis). Routine ultrasound surveillance was obtained on all patients, and statistical analysis of the findings in the patency and restenosis groups was performed.

RESULTS

Of the 30 cases, restenosis occurred 9 times in 6 patients. Mean follow-up was 677 days. Mean time to restenosis was 267 days. Five cases (56%) were identified within the first 6 months after stent placement. Four cases (44%) were recognized in the second year after stent placement. Prior to the sonographic diagnosis of restenosis, the mean resistive indices of the main (.64 versus .57, P < .0001), left (.63 versus .54, P < .0001), right anterior (.60 versus .52, P < .0001), and right posterior (.60 versus .53, P = .001) hepatic artery branches differed among patency and restenosis groups, respectively. The mean peak systolic velocity also differed significantly between the 2 groups: 254 cm/sec in patients with eventual restenosis versus 220 cm/sec in patients without restenosis (P = .02).

CONCLUSIONS

The sonographic evaluation of hepatic artery stenosis remains critical during the first 2 years after stent placement. While the vast majority of patients do not restenose, resistive index and peak systolic velocity differed significantly between the 2 groups and may be prognostic surveillance markers for the development of restenosis.

Evaluation of Pediatric Liver Transplantation-Related Artery Complications Using Intra-Operative Multi-Parameter Ultrasonography

Background

This article discusses the value of using multi-parameter evaluation of intra-operative ultrasonography in evaluating pediatric liver transplantation-related arterial complications.

Material/Methods

Sixty-eight children receiving a liver transplant underwent intraoperative ultrasonography for monitoring of artery hemodynamics. The ultrasonic measurement parameters included the diameters of the hepatic artery (HA) of the donor and anastomotic stoma, peak systolic velocity (PSV), resistance index (RI), acceleration time (SAT), and blood flow volume.

Results

After being treated immediately using surgery or other means, blood flow returned to normal in 8 cases, and did not in 3 cases, of whom 2 experienced postoperative HAT. There was a significant difference in HA diameter of the donor, anastomotic stoma diameter, PSV, RI, SAT, and blood flow volume before and after treatment of the donor in the complications group. Postoperative complications occurred in 7 of 68 recipients, including the 2 cases exhibiting complications during the surgery (complication group) and 5 without complications during the surgery (no complication group). There was a statistically significant difference (P<0.05) between the 2 groups in intraoperative ultrasonography parameters of HA diameter, anastomotic stoma diameter, RI, and blood flow volume.

Conclusions

Through intraoperative multi-parameter ultrasonic measurement, a definite diagnosis of hepatic artery complications can be made in liver transplantation patients. HA diameter of the donor, anastomotic stoma diameter, PSV, RI, SAT, and blood flow volume are important in assessing intraoperative artery complications.

Delayed diagnosis of celiac stenosis causing hepatic transplant ischaemic necrosis: diagnosis by spectral Doppler findings

Following presentation with abnormal liver function enzymes, confusion and fatigue, a 65-year-old male with alcoholic cirrhosis underwent spectral Doppler sonography that showed tardus parvus-like morphology in the main and left hepatic arteries, although peak systolic velocities and resistive indices remained normal. The patient's continuing clinical symptoms prompted CT angiography, which demonstrated an unexpected, haemodynamically significant stenosis of the celiac artery. Although the stenosis was successfully stented and the hepatic arterial waveforms normalized, the transplanted liver had already undergone ischaemic necrosis, with resulting failure and the need for retransplantation. Recognition of abnormal waveforms, despite normal peak systolic velocities and resistive indices, with prompt definitive imaging evaluation of the arterial tree beyond just the main hepatic artery, may lead to the diagnosis of unexpected flow-limiting lesions in time to allow revascularization and thus prevent ischaemic transplant failure.

Case report of hepatic artery dissection secondary to hepatic artery pseudoaneurysm after living donor liver transplantation

Background

Hepatic artery pseudoaneurysm (HAP) and Hepatic artery dissection are rare vascular complications after living donor liver transplantation (LDLT), which may lead to graft loss and death of the recipients. Conventional gray-scale and Doppler ultrasound, as well as contrast-enhanced ultrasound (CEUS), play important roles in identifying vascular complications in the early postoperative period and during follow-up. We report a case of hepatic artery dissection secondary to HAP after LDLT, which was diagnosed and followed for one year by ultrasound. To the best of our knowledge, few studies have reported similar cases after liver transplantation in the English literature.

Case presentation

A 43-year-old man underwent right-lobe LDLT for treatment of a severe acute hepatitis B infection and was followed up with ultrasound examinations for one year. Conventional gray-scale and Doppler ultrasound combined with contrast-enhanced ultrasound (CEUS) accurately revealed the occurrence of HA dissection secondary to HAP and accompanied by thrombosis and collateral circulation, as well as secondary biliary complications, which provided a prompt diagnosis and guidance for the treatment.

Conclusion

Our case suggests that ultrasound can help detect hepatic artery pseudoaneurysm and dissection, as well as secondary biliary lesions after LDLT in an accurate and timely manner and provide useful information for the treatment chosen. CEUS shows potential as an important complementary technique to gray-scale and Doppler ultrasound.

Vascular complications after adult living donor liver transplantation: Evaluation with ultrasonography

Living donor liver transplantation (LDLT) has been widely used to treat end-stage liver disease with improvement in surgical technology and the application of new immunosuppressants. Vascular complications after liver transplantation remain a major threat to the survival of recipients. LDLT recipients are more likely to develop vascular complications because of their complex vascular reconstruction and the slender vessels. Early diagnosis and treatment are critical for the survival of graft and recipients. As a non-invasive, cost-effective and non-radioactive method with bedside availability, conventional gray-scale and Doppler ultrasonography play important roles in identifying vascular complications in the early postoperative period and during the follow-up. Recently, with the detailed vascular tracing and perfusion visualization, contrast-enhanced ultrasound (CEUS) has significantly improved the diagnosis of postoperative vascular complications. This review focuses on the role of conventional gray-scale ultrasound, Doppler ultrasound and CEUS for early diagnosis of vascular complications after adult LDLT.

Late liver function test abnormalities post-adult liver transplantation: a review of the etiology, investigation, and management

Approximately 24,000 liver transplants are performed annually worldwide, almost 7000 of which are performed in the USA. Survival is excellent and continues to improve, with 1-year survival currently exceeding 85 %, but effective management of patients after liver transplantation is critical to achieve optimal results. A plethora of diseases can affect the transplanted allograft, ranging from recurrence of the original disease to de novo liver pathology, and diagnosis can be complicated by nonclassical presentation, de novo disease, or inconclusive histology. Patients can remain asymptomatic despite significant damage to the transplanted liver, so prompt identification and treatment of liver disease after transplantation is crucial to preserve allograft function. Liver function tests are routinely taken throughout the postoperative period to monitor the graft. Although nonspecific, they are inexpensive, noninvasive, and sensitive for allograft disease and can quickly alert physicians to the presence of asymptomatic pathology. This review will outline possible causes of liver function test abnormalities in the late posttransplant period and provide guidance for investigation, diagnosis, and management.

Clinical utility of hepatic-perfusion computerized tomography in living-donor liver transplantation: a preliminary study

BACKGROUND

Vascular complications are a primary diagnostic consideration in liver transplant recipients, with an overall incidence of 9%. Cross-sectional imaging techniques provide information regarding vascular structure and luminal patency but can not quantitatively assess hepatocyte damage in the liver graft parenchyma. Perfusion computerized tomography (CT) is a recently developed method that allows for quantitative evaluation of hemodynamic changes in tissue. Our objective was to evaluate the clinical utility of perfusion CT in assessing vascular complications during living-donor liver transplantation (LDLT).

METHODS

The 33 recipients were divided into 3 groups according to Doppler ultrasonographic findings: hepatic arterial complication group, portal venous complication group, and hepatic venous complication group. Blood volume (BV), blood flow (BF), arterial liver perfusion (ALP), portal venous perfusion (PVP), and hepatic perfusion index (HPI) were calculated for the affected vascular territory regions.

RESULTS

Compared with normal liver parenchyma, BV, BF, ALP, and HPI were significantly lower in the hepatic arterial complication group. Although PVP and BV were significantly lower, ALP, HPI, and BF were higher in the affected vascular territory region than in normal liver parenchyma for the portal venous complication group. In the hepatic venous complication group, PVP was significantly higher and BF, ALP, and HPI significantly lower in the affected vascular territory regions than in normal liver parenchyma.

CONCLUSIONS

Perfusion CT imaging is a noninvasive technique that enables the quantitative evaluation of vascular complications in the graft parenchyma after LDLT and permits a quantitative evaluation of the treatment response.

Endoscopic management of post-liver transplant biliary complications

Biliary complications are being increasingly encountered in post liver transplant patients because of increased volume of transplants and longer survival of these recipients. Overall management of these complications may be challenging, but with advances in endoscopic techniques, majority of such patients are being dealt with by endoscopists rather than the surgeons. Our review article discusses the recent advances in endoscopic tools and techniques that have proved endoscopic retrograde cholangiography with various interventions, like sphincterotomy, bile duct dilatation, and stent placement, to be the mainstay for management of most of these complications. We also discuss the management dilemmas in patients with surgically altered anatomy, where accessing the bile duct is challenging, and the recent strides towards making this prospect a reality.

Imaging of the porta hepatis: spectrum of disease

A wide array of pathologic conditions can arise within the porta hepatis, which encompasses the portal triad (the main portal vein, common hepatic artery, and common bile ducts), lymphatics, nerves, and connective tissue. Major vascular diseases of the portal triad include thrombosis, stenosis, and aneurysm. Portal vein thrombosis can complicate liver cirrhosis and hepatocellular carcinoma and has important therapeutic implications. Hepatic artery thrombosis and stenosis require immediate attention to reduce graft loss in liver transplant recipients. Congenital (eg, choledochal cyst) and acquired (benign and malignant) diseases of the biliary system can manifest as mass lesions in the porta hepatis. Lymphadenopathy can arise from neoplastic and nonneoplastic entities. Uncommon causes of mass lesions arise from nerves (eg, neurofibroma, neurofibrosarcoma) and connective tissue (sarcomas) and are rare. The hepatoduodenal ligament is a peritoneal reflection at the porta hepatis and is an important route for the spread of pancreatic and gastrointestinal cancers. Imaging plays a major role in diagnosis and enables appropriate management. Ultrasonography accurately demonstrates anatomic variations and pathologic conditions and is the initial modality of choice for detection of vascular and biliary lesions. Multidetector computed tomography and magnetic resonance imaging allow characterization and differentiation of various masses in the porta hepatis. Imaging-guided interventions, including embolization and stent placement, also play a key role in disease management.

Splenic Artery Syndrome after orthotopic liver transplantation: a review

Splenic Artery Syndrome (SAS) has emerged as a controversial cause for graft ischemia in orthotopic liver transplant (OLTx) recipients. A complex combination of factors including hepatic artery hypoperfusion and portal hyperperfusion can result in SAS. Clinical and laboratory findings suggest graft ischemia but are generally non-specific. Conventional angiography findings of hepatic artery hypoperfusion with early and rapid filling of the splenic artery are suggestive of the diagnosis in the appropriate clinical setting. Treatment involves proximal splenic artery embolization, surgical splenic artery ligation, or in extreme cases, splenectomy. Most patients with SAS improve clinically following treatment. However, no randomized control trials are available to compare treatment options. Identification of at risk patients with pre-operative CT scans and intra-operative ultrasound has been proposed by some and may allow for prophylactic treatment of SAS.

Hepatic transplantation: postoperative complications

Advances in surgical techniques and immunosuppression have made orthotopic liver transplantation a first-line treatment for many patients with end-stage liver disease. The early detection and treatment of postoperative complications has contributed significantly to improved graft and patient survival with imaging playing a critical role in detection. Complications that can lead to graft failure or patient mortality include vascular abnormalities, biliary abnormalities, allograft rejection, and recurrent or post-transplant malignancy. Vascular abnormalities include stenosis and thrombosis of the hepatic artery, portal vein, and inferior vena cava, as well as hepatic artery pseudoaneurysm, arteriovenous fistula, and celiac stenosis. Biliary abnormalities include strictures, bile leak, obstruction, recurrent disease, and infection. While imaging is not used to diagnose allograft rejection, it plays an important role in identifying complications that can mimic rejection. Ultrasound is routinely performed as the initial imaging modality for the detection and follow-up of both early and delayed complications. Cholangiography and magnetic resonance cholangiopancreatography are used to characterize biliary complications and computed tomography is used to confirm abnormal findings on ultrasound or for the evaluation of postoperative collections. The purpose of this article is to describe and illustrate the imaging appearances and management of complications associated with liver transplantation.

Hepatic artery reconstruction in living donor liver transplantation: risk factor analysis of complication and a role of MDCT scan for detecting anastomotic stricture

BACKGROUND

In partial liver transplantation, reconstruction of the hepatic artery is technically highly demanding and the incidence of arterial complications is high. We attempted to identify the risk factors for anastomotic complications after hepatic artery reconstruction and examined the role of multidetector-row computed tomography (MDCT) in the evaluation of the reconstructed hepatic artery in liver transplant recipients.

METHODS

A total of 109 adult-to-adult living donor liver transplantations (LDLT) were performed at our institute between 1999 and July 2011. Hepatic artery reconstruction was performed under a surgical microscope (MS group, n = 84), until we began to adopt surgical loupes (4.5×) for arterial reconstructions in all cases after January 2009 (SL group, n = 25). A dynamic MDCT study was prospectively carried out on postoperative days 7, 14, and 28, and at postoperative month 3, 6, and 12 after April 2005 (n = 60).

RESULTS

There were no cases of hepatic artery thrombosis and six cases (5.5 %) of interventional radiology-confirmed hepatic artery stenosis (HAS). Risk factor analysis for HAS showed that ABO-incompatible LDLT was associated with HAS. Use of surgical loupes provided superior results as compared to anastomosis under a surgical microscope, and it also provided the advantage of reduced operative time. The MDCT procedure was useful for detecting HAS; however, the false positive rate was relatively high until 3 months after the LDLT (100 % sensitivity and 72.8 % specificity at 3 months).

CONCLUSIONS

Hepatic arterial anastomosis using surgical loupes tended to be time-saving and to yield similar or better results than traditional microscope-anastomosis. The use of MDCT aided the diagnosis of HAS, although the substantial false positive rate should be borne in mind in clinical practice.

Post-operative imaging in liver transplantation: State-of-the-art and future perspectives

Orthotopic liver transplantation (OLT) represents a major treatment for end-stage chronic liver disease, as well as selected cases of hepatocellular carcinoma and acute liver failure. The ever-increasing development of imaging modalities significantly contributed, over the last decades, to the management of recipients both in the pre-operative and post-operative period, thus impacting on graft and patients survival. When properly used, imaging modalities such as ultrasound, multidetector computed tomography, magnetic resonance imaging (MRI) and procedures of direct cholangiography are capable to provide rapid and reliable recognition and treatment of vascular and biliary complications occurring after OLT. Less defined is the role for imaging in assessing primary graft dysfunction (including rejection) or chronic allograft disease after OLT, e.g., hepatitis C virus (HCV) recurrence. This paper: (1) describes specific characteristic of the above imaging modalities and the rationale for their use in clinical practice; (2) illustrates main imaging findings related to post-OLT complications in adult patients; and (3) reviews future perspectives emerging in the surveillance of recipients with HCV recurrence, with special emphasis on MRI.

Ultrasound findings after endovascular stent deployment in transplant liver hepatic artery stenosis

OBJECTIVE

Endovascular stenting is a safe, effective treatment of hepatic artery stenosis after liver transplant, but no detailed evaluation has been completed of changes in ultrasound monitoring parameters after stenting. This study aims to improve poststenting surveillance by delineating the expected postoperative findings.

MATERIALS AND METHODS

Thirty-one stent procedures were performed at our institution for hepatic artery stenosis after liver transplant between October 2010 and October 2012. Of these, 28 (90%) were technically successful, of which 23 met the minimum follow-up time (76 days, defined by the earliest diagnosed restenosis). These patients were followed with serial ultrasound, per the following schedule: within 1 week of stenting, 3 months after stenting, 6 months after stenting, and every 6 months thereafter; additional, unscheduled examinations were frequently performed when indicated on the basis of deterioration of clinical and laboratory status. Follow-up examinations (mean, 268 days total follow-up) were compared with prestenting examinations to evaluate changes in peak systolic velocity (PSV), resistive index (RI), and tardus-parvus waveforms. Data were analyzed to determine a normal range for postprocedure values and time course of change in values.

RESULTS

Of the 23 patients, six experienced restenosis. In all patients, mean PSV decreased by 124 cm/s, and mean RI increased by 0.13 within 48 hours after stenting. PSV differed between patency and restenosis groups only at more than 90 days after stenting (mean PSV, 234 and 400 cm/s, respectively), with PSV above 300 cm/s serving as a high-sensitivity threshold for the determination of restenosis. Prestenting RI of below 0.40 had a strong correlation with restenosis. Poststenting RI differed between patency and restenosis groups only at more than 48 hours after stenting, with RI of below 0.55 having a strong correlation with restenosis. Tardus-parvus waveform resolution was often delayed well beyond 48 hours after stenting, and time to tardus-parvus waveform resolution had no correlation with patency or restenosis.

CONCLUSION

Ultrasound is convenient and useful to follow stents in hepatic artery stenosis after liver transplant. Prestenting hemodynamics can have value in predicting restenosis. Diagnosis of restenosis can be made with RI and PSV, whereas resolution time of tardus-parvus waveform is of less concern. These parameters can guide which patients require closer monitoring and aggressive treatment.

Endovascular treatment of hepatic artery stenosis after liver transplantation

BACKGROUND

Hepatic artery stenosis (HAS) after orthotopic liver transplantation is a significant risk factor for subsequent hepatic artery thrombosis (HAT). HAT is associated with a 30%-50% risk of liver failure culminating in retransplantation or death. Traditional treatment of hepatic artery complications has been surgical, with hepatic artery revision or retransplantation. Endovascular therapy of HAS, described primarily in the interventional radiology literature, may provide a less-invasive treatment option.

METHODS

This was a retrospective review of all endovascular interventions performed for HAS after orthotopic liver transplantation over a 31-month period (August 2009 to January 2012). Patients with duplex ultrasound imaging evidence of severe main HAS (peak systolic velocity of >400 cm/s, resistive index of <.5) underwent endovascular treatment with either primary stent placement or percutaneous transluminal angioplasty (PTA) alone. Patients were followed with serial ultrasound imaging to assess for treatment success and late restenosis. Reintervention was performed if significant restenosis occurred.

RESULTS

Thirty-five hepatic artery interventions were performed in 23 patients. Over the 31-month study period, 318 orthotopic liver transplantations were performed, yielding a 7.4% (23/318) rate of hepatic artery intervention. Primary technical success was achieved in 97% (34/35) of cases. Initial treatment was with PTA alone (n = 10) or primary stent placement (n = 13). The initial postintervention ultrasound images revealed improvements in hepatic artery peak systolic velocity (267 ± 118 [posttreatment] vs 489.9 ± 155 cm/s [pretreatment]; P < .0001) and main hepatic artery resistive index (0.61 ± 0.08 [posttreatment] vs 0.41 ± 0.07 [pretreatment]; P < .0001). At a mean follow-up of 8.2 ± 1.8 months (range, 0-29), there were 12 reinterventions in 10 patients for recurrent HAS. Thirty-one percent (n = 4/13) of patients undergoing initial stent placement required reintervention (at 236 ± 124 days of follow-up) compared with 60% (n = 6/10) of patients undergoing initial PTA (at 62.5 ± 44 days of follow-up). Primary patency rates (Kaplan-Meier) after primary stent placement were 92%, 85%, and 69% at 1, 3, and 6 months, respectively, compared with 70%, 60%, and 50% after PTA (P = .17). Primary-assisted patency for the entire cohort was 97% at 6 and 12 months. Major complications were one arterial rupture managed endovascularly and one artery dissection that precipitated HAT and required retransplantation. The overall rate of HAT in the entire cohort was 4.3% (1/23).

CONCLUSIONS

Endovascular treatment of HAS can be performed with high technical success, excellent primary-assisted patency, and acceptable morbidity. Initial use of a stent may improve primary patency when compared with PTA. The need for reintervention is common, placing particular importance on aggressive surveillance. Longer follow-up and a larger cohort are needed to confirm these encouraging early results.

Contrast-enhanced ultrasound diagnosis of splenic artery steal syndrome after orthotopic liver transplantation

The aim of this study was to investigate the use of contrast-enhanced ultrasound (CEUS) for the detection of splenic artery steal syndrome (SASS) after orthotopic liver transplantation (OLT). Two hundred forty-seven patients underwent OLT. Blood tests and color Doppler flow imaging (CDFI) were performed at various time points after the operation. CEUS and celiac angiography were used for patients suspected of having SASS. If the diagnosis of SASS was confirmed, splenic artery embolization was performed to enhance hepatic artery flow. CEUS and angiography were performed for the assessment of postinterventional clinical outcomes. Three of the 247 patients died postoperatively, and 8 patients were suspected of having SASS because of elevated liver enzyme levels and slim or undetectable hepatic artery blood signals by CDFI at various points after the operation. In these 8 patients, CEUS showed a delayed and weak contrast-enhanced blood signal in the hepatic artery associated with a rapid and intense enhancement of the portal vein blood. No narrowing of the hyperintense signal was observed in the hepatic artery by CEUS. The 8 diagnoses of SASS were proven by celiac angiography, which showed delayed perfusion of the hepatic artery and rapid filling of the splenic artery. Immediately after the interventional procedure, CEUS demonstrated a significantly enlarged hyperintense blood signal in the hepatic artery. In conclusion, approximately 3.27% of SASS cases occur after OLT. SASS can be identified as a sluggish and weak hyperintense blood signal in the hepatic artery without the narrowing and interruption of the hypointense signal in CEUS imaging. CEUS is an effective imaging modality for the detection of SASS after OLT.

Hepatic arterial stenosis assessed with doppler US after liver transplantation: frequent false-positive diagnoses with tardus parvus waveform and value of adding optimal peak systolic velocity cutoff

PURPOSE

To evaluate the utility of the tardus parvus waveform of the hepatic artery at Doppler ultrasonography (US) in the diagnosis of hepatic arterial stenosis in liver transplant (LT) recipients and determine whether the accuracy of such a diagnosis is enhanced by including an optimal peak systolic velocity (PSV) cutoff.

MATERIALS AND METHODS

This retrospective study was institutional review board approved; the requirement for informed consent was waived. The authors identified 361 LT recipients (267 male, 94 female) who underwent Doppler US and either computed tomography (CT) or angiography, with an interval between these examinations of less than 1 week. At Doppler US, tardus parvus pattern was defined as a waveform with a resistive index (RI) of less than 0.5 and a systolic acceleration time longer than 0.08 second. At CT or angiography, patients were assigned to the hepatic arterial stenosis (≥50% vessel narrowing) or nonstenosis group. The capability of the tardus parvus pattern to facilitate the diagnosis of hepatic arterial stenosis was calculated. The difference in PSV between the true- and false-positive tardus parvus patterns was evaluated. Receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff PSV for diagnosing hepatic arterial stenosis. The capability of the tardus parvus pattern and an optimal PSV cutoff in the diagnosis of hepatic arterial stenosis was determined.

RESULTS

Sixty transplant recipients had the tardus parvus pattern at Doppler US. The sensitivity, specificity, and positive predictive value (PPV) of the tardus parvus pattern were 72% (23 of 32 LT recipients), 88.8% (292 of 329 LT recipients), and 38% (23 of 60 LT recipients), respectively. The false-positive rate was 11.2% (37 of 329 LT recipients). ROC analysis revealed an optimal PSV cutoff of less than or equal to 48 cm/sec for diagnosing hepatic arterial stenosis. The combination of the tardus parvus pattern and a PSV cutoff of less than or equal to 48 cm/sec improved specificity to 99.1% (326 of 329 LT recipients) and the PPV to 88% (22 of 25 LT recipients), thereby reducing the false-positive rate to 1% (three of 329 LT recipients) while slightly decreasing the sensitivity to 69% (22 of 32 LT recipients).

CONCLUSION

Use of the tardus parvus waveform of the hepatic artery resulted in a low PPV and a high false-positive rate. However, the combination of the tardus parvus pattern and an optimal PSV cutoff greatly improved the PPV and reduced the false-positive rate in the diagnosis of hepatic arterial stenosis.

Diagnostic role of colour Doppler US at 1-year follow-up after orthotopic liver transplantation

PURPOSE

This paper discusses the role of colour Doppler ultrasound (CDUS) in the midterm follow-up of patients after orthotopic liver transplantation (OLT).

MATERIALS AND METHODS

We retrospectively studied 134 patients--102 men and 32 women, age range 21-68 years--who underwent liver transplantation between May 2006 and April 2007. In the first week after OLT, CDUS examination was performed daily in patients with anastomoses at a high risk of thrombosis, and on the basis of clinical and laboratory findings in other patients. After discharge, follow-up was performed 1, 3, 6 and 12 months after transplantation. Any new parenchymal focal lesion was studied by computed tomography (CT) and, where needed, biopsy.

RESULTS

CDUS identified the following complications: 22 biliary (B), nine vascular (V) and seven focal lesions (FL). Sensitivity, specificity, positive and negative predictive values and diagnostic accuracy were, respectively: 79.2%, 97.3%, 86.3%, 95.5%, 94% (B), 100%, 99.2%, 88.9%, 100%, 99.3% (V) and 100%, 96.9%, 42.8%, 100%, 97% (FL). CDUS also showed 16 blood collections and eight suspected biliary collections (four of which were confirmed by percutaneous puncture).

CONCLUSIONS

CDUS is an essential diagnostic tool in the follow-up of OLT. An early diagnosis of complications can improve graft integrity and patient survival.

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.

Comprehensive ultrasound assessment of complications post-liver transplantation

Human liver transplantation for end-stage liver disease was first performed in 1963. Refinements in surgical technique and new immunosuppressive regimens have improved outcomes. Today, transplant patients have a 5-year survival rate of approximately 75%. Nevertheless, significant complications still occur. Ultrasonography (US), is the initial imaging modality of choice allowing bedside assessment for detection and follow-up of early and delayed graft complications, and facilitating interventional procedures. This review outlines the role of ultrasound in post-transplantation assessment.

Role of imaging in the management of splenic artery steal syndrome

OBJECTIVE

The purpose of this study is to discuss the etiology and role of imaging in the management of splenic artery steal syndrome (SASS) following orthotropic liver transplantation (OLT).

METHODS

Hepatic arterial thrombosis and stenosis have been the most commonly recognized arterial complications following OLT. Splenic artery steal syndrome is a recently described entity in the transplant literature and thought to be an under-recognized cause of graft ischemia. It is characterized by hepatic arterial hypoperfusion accompanied by splenic arterial and portal venous hyperperfusion and leads to various vascular and biliary graft complications. Because the clinical manifestations of SASS are so non-specific, imaging plays a key role in the diagnosis of this condition.

RESULTS

This article discusses the role of imaging in the management of this potentially reversible cause of graft ischemia.

CONCLUSIONS

Awareness of the imaging features and having a high index of suspicion are essential for the early diagnosis and prompt management of this condition.

False positive tardus-parvus waveforms after liver transplantation: a case of wide discrepancy between donor and recipient hepatic arteries mimicking anastomotic stenosis

BACKGROUND

Parvus-tardus waveforms of the hepatic artery after liver transplantation usually indicate an arterial complication and severe impairment of hepatic arterial perfusion with a sensitivity of 91% and a specificity of 99.1%. Thus, it has been emphasized that detection of such waveforms should prompt emergency angiography.

MATERIALS AND METHODS

Arterial reconstruction during a liver transplantation was successfully accomplished by an end-to-end anastomosis, performing a "flute-spout" widening of the anastomosis with a 7/0 prolene running suture between a small recipient proper hepatic artery and the donor common hepatic artery.

RESULTS

On day 7 posttransplantation color Doppler ultrasonography revealed a parvus-tardus waveform pattern in the hepatic arterial flow. Computed tomographic (CT) angiography showed only a caliber discrepancy between the donor and recipient stumps, excluding an arterial stenosis or thrombosis. Since normal liver function persisted, the patient underwent routine follow-up. After 15 months the patient was alive and well; hepatic artery spectral waveforms were unchanged and liver functions were consistent with a mild hepatitis C virus (HCV) recurrence.

CONCLUSIONS

This is a report of false positive tardus-parvus waveforms, due to a discrepancy between the donor and recipient arteries despite a wide anastomosis. Knowledge of technical reconstruction details may be helpful for correct interpretation of color Doppler findings. CT angiography should be considered before more invasive examinations.

Imaging in liver transplantation

The aim of this study was to illustrate the role of non-invasive imaging tools such as ultrasonography, multi-detector row computed tomography, and magnetic resonance imaging in the evaluation of pediatric and adult liver recipients and potential liver donors, and in the detection of potential complications arising from liver transplantation.

Routine intraoperative Doppler sonography in the evaluation of complications after living-related donor liver transplantation

PURPOSE

To determine whether quantitative and qualitative analysis of intraoperative Doppler sonography data are predictive of vascular complications after living-related donor liver transplantation.

METHODS

Intraoperative sonograms of 81 transplanted livers (right lobe in 61 patients, left lobe in 20 patients) were analyzed for the presence of blood flow, resistance index, systolic acceleration time (SAT), peak systolic velocity, and morphologic characteristics of spectral waveform of the hepatic artery. Peak velocity and spectral waveforms of portal and hepatic veins were also analyzed. Intraoperative sonography results were compared with information obtained with multidetector-row CT (MDCT) angiography or conventional angiography. The time interval between operation and angiography ranged from 1 to 23 days (mean, 8.5 days).

RESULTS

Hepatic artery stenosis (HAS) was identified in 20 patients via MDCT angiography, conventional angiography, or both. The Doppler parameters found helpful for predicting HAS were tardus-parvus pattern and delayed SAT. The sensitivity, specificity, and negative predictive value (NPV) were 60.0%, 73.7%, and 84.9%, respectively, for tardus-parvus pattern and 40.0%, 83.6%, and 80.9%, respectively, for delayed SAT. Peak velocities of the portal and hepatic veins were not reliable indicators of vascular complication. Loss of triphasity of the hepatic vein had a 98.4% NPV for venous obstruction.

CONCLUSIONS

Delayed SAT of the hepatic artery and loss of triphasity of the hepatic vein had a >80% for specificity for predicting vascular complications. Tardus-parvus pattern, delayed SAT of the hepatic artery, and loss of triphasity of the hepatic vein showed an acceptable NPV for identifying vascular complications.