Noninvasive Imaging of Liver Transplant Complications

Transplant Hepatic Artery Stenosis: Endovascular Treatment and Complications

Hepatic artery stenosis (HAS) is an infrequent complication of liver transplant; if left untreated, it can lead to hepatic artery thrombosis with high risk of biliary necrosis and graft loss. HAS is diagnosed with screening Doppler ultrasound, together with computed tomography angiography and magnetic resonance angiography. Endovascular treatment with angioplasty ± stent placement is safe and effective with infrequent major complications; however, when complications occur, they can devastate long-term graft survival. Herein, we present two cases of HAS treated with balloon angioplasty with resultant major complications requiring operative intervention.

Role of Doppler Sonography in Early Detection of Splenic Steal Syndrome

OBJECTIVES

To retrospectively investigate the role of Doppler sonography in the early detection of splenic steal syndrome.

METHODS

Fifty cases of splenic steal syndrome after orthotopic liver transplantation were identified. A control group was matched to the splenic steal syndrome group. Information was collected about the clinical presentation, liver enzyme levels, Doppler sonographic results, and follow-up after patients underwent splenic artery embolization.

RESULTS

A persistent hepatic arterial diastolic reversal waveform was observed in 25 patients with splenic steal syndrome versus 0 control patients. The mean hepatic arterial resistive index (RI) values ± SD were 0.95 ± 0.09 in patients with splenic steal syndrome and 0.80 ± 0.10 in control patients (P < .0001). One week after orthotopic liver transplantation, the area under the receiver operating characteristic curve for the RI was 0.884 (95% confidence interval, 0.793-0.975; P = .001) for splenic steal syndrome diagnosis. After splenic artery embolization, there was normalization of the reversal waveform, with an average RI of 0.77 ± 0.11 (P < .0001).

CONCLUSIONS

Dynamic changes in the hepatic arterial waveform and RI are keys to detecting splenic steal syndrome with Doppler sonography.

Resolution of Hepatic Artery Thrombosis in 2 Pediatric Liver Transplant Patients

Hepatic artery thrombosis (HAT) is a serious complication after liver transplantation. This is the first report of spontaneous resolution of HAT in pediatric liver transplant patients on low molecular weight heparin therapy. A total of 2 patients, a 26-month-old boy who presented with acute liver failure and required emergent liver transplantation and a 15-year-old boy with ulcerative colitis and autoimmune hepatitis-primary sclerosing cholangitis overlap underwent liver transplantation for progressive cirrhosis; both developed HAT during the postoperative period. They were both treated with low molecular weight heparin. Follow-up imaging for both patients showed resolution of HAT without evidence of collateral flow.

Nontumoral portal vein thrombosis in patients awaiting liver transplantation

Portal vein thrombosis (PVT) occurs in approximately 2%-26% of the patients awaiting liver transplantation (LT) and is no longer an absolute contraindication for LT. Nearly half of PVT cases are accidentally found during the LT procedure. The most important risk factor for PVT development in cirrhosis may be the severity of liver disease and reduced portal blood flow. Whether other inherited or acquired coagulation disorders also play a role is not yet clear. The development of PVT may have no effect on the liver disease progression, especially when it is nonocclusive. PVT may not increase the risk of wait-list mortality, but it is a risk factor for poor early post-LT mortality. Anticoagulation and transjugular intrahepatic portosystemic shunt (TIPS) are 2 major treatment strategies for patients with PVT on the waiting list. The complete recanalization rate after anticoagulation is approximately 40%. The role of TIPS to maintain PV patency for LT as the primary indication has been reported, but the safety and efficacy should be further evaluated. PVT extension and degree may determine the surgical technique to be used during LT. If a "conventional" end-to-end portal anastomotic technique is used, there is not a major impact on post-LT survival. Post-LT PVT can significantly reduce both graft and patient survival after LT and can preclude future options for re-LT.

Postoperative haemodynamic changes in transplanted liver: Long-term follow-up with ultrasonography

OBJECTIVE

To investigate haemodynamic changes in the transplanted liver without postoperative complications.

METHODS

Colour Doppler ultrasound was used to monitor recipients of liver transplants who had no postoperative complications. The haemodynamic data for the hepatic vasculature were compared at different time-points during the first 4 years after liver transplantation.

RESULTS

A total of 144 liver transplant patients were enrolled in the study. Portal vein flow velocity decreased significantly from 72.1 ± 30.3 cm/s at 1 day to 44.2 ± 20.1 cm/s at 1 month after liver transplantation. Hepatic artery flow velocity was 61.4 ± 33.2 cm/s at day 1; it then decreased slowly but significantly to 48.3 ± 20.4 cm/s at 3 years after transplantation. There were 81 (56.3%) patients with high hepatic artery resistance index (HARI) (>0.80) and 19 (13.2%) with low HARI (<0.50) measured at least once during the 4-year follow-up examination.

CONCLUSIONS

Decreased portal vein flow velocity was the typical change observed during the first month after liver transplantation. Abnormal haemodynamic Doppler results should be interpreted with caution because they may not be clinically significant and may improve spontaneously.

Radiologic assessment of hepatobiliary surgical complications

The complexity of hepatobiliary procedures continues to evolve at a rapid rate, with an increasing number of living donor liver transplants and extensive cancer resections being performed. The associated complications are a significant cause of morbidity and mortality, and are often complex injuries, involving both vascular and biliary structures. In this paper we describe the complications associated with laparoscopic cholecystectomy, liver transplant surgery, and hepatic resection. Focus is on the classical imaging appearances, imaging modality options, and varying management strategies for these injuries, to show how the radiologist's role is vital in ensuring the correct diagnosis is made and the appropriate treatment is instigated.

Arterioportal fistulas in liver transplant recipients

Arterioportal fistulas (APFs) are classified into intrahepatic (>75% of all reported) and extrahepatic (<25% of all reported ). Anecdotally, investigators are more likely to report more sensational cases (typically extrahepatic APFs), so the actual prevalence of intrahepatic APFs is probably much higher (likely >90% of APFs). All reported APFs in liver transplant recipients have been intrahepatic. Hemodynamically significant APFs in liver transplant recipients are rare, occurring in 0.2%; however, APFs (hemodynamically significant or not) are not uncommonly seen in hepatic angiograms of liver transplant recipients (up to 5.4% of hepatic arteriograms in transplants). Interestingly, hemodynamically significant APFs warranting endovascular treatment are reported more commonly in the literature in native compared with transplanted livers (n >280-300 versus n = 13, respectively). This article discusses APFs that are specific to liver transplant recipients; their incidence, etiology, pathogenesis, natural history, clinical presentation, and endovascular management are discussed in detail.

Portal interventions in liver transplant recipients

Portal vein interventions in liver transplant recipients represent a group of interventions in the management of several disease entities including portal vein stenosis, portal vein thrombosis, and recurrent liver cirrhosis with portal hypertension with and without gastric varices. The procedures performed in these patient populations include portal vein angioplasty with or without stent placement for portal vein stenosis, portal vein thrombolysis with or without stent placement for portal vein thrombosis, transjugular intrahepatic portosystemic shunts or splenic embolization for cirrhosis, and balloon-occluded retrograde transvenous obliteration for gastric varices. This article discusses these disease entities and the minimal invasive procedures used in their management.

Multimodality imaging of normal hepatic transplant vasculature and graft vascular complications

Orthotopic liver transplantation is an important treatment option for patients with end-stage liver disease. Advances in surgical technique, along with improvements in organ preservation and immunosuppression have improved patient outcomes. Post-operative complications, however, can limit this success. Ultrasound is the primary imaging modality for evaluation of hepatic transplants, providing real-time information about vascular flow in the graft. Graft vascular complications are not uncommon, and their prompt recognition is crucial to allow for timely graft salvage. A multimodality approach including CT angiography, MRI, or conventional angiography may be necessary in cases of complex transplant vascular anatomy or when sonography and Doppler are inconclusive to diagnose the etiologies of these complications. The purpose of this article is to familiarize radiologists with the normal post-transplant vascular anatomy and the imaging appearances of the major vascular complications that may occur within the hepatic artery, portal vein, and venous outflow tract, with an emphasis on ultrasound.

Role of magnetic resonance imaging in the detection of anastomotic biliary strictures after liver transplantation

INTRODUCTION

Biliary complications after orthotopic liver transplantation (OLT) are the principal cause of morbidity and graft dysfunction, ranging in incidence from 5.8% to 30% of cases. Biliary strictures are the most frequent type of late complication. The aim of this study was to evaluate the role of magnetic resonance cholangiography (MRC) to detect biliary anastomotic strictures among patients undergone OLT with abnormal liver function tests.

MATERIALS AND METHODS

One hundred twenty-one of 300 patients who underwent OLT were evaluated by MRC for clinically suspected anastomotic biliary strictures. In all patients, we performed various precholangiographic sequences including T1- and T2-weighted and MRC (radial SE 2D and SS-TSE 3D). Magnetic resonance imaging findings were subdivided as absence or presence of an anastomotic stricture. Diagnostic confirmation was obtained by endoscopic retrograde cholangiography (n=32), percutaneous transhepatic cholangiography (n=21) or surgical treatment (n=18).

RESULTS

MRC detected 56 anastomotic biliary strictures, 53 of which were confirmed by other imaging modalities. MRC showed two false-negative cases and three false-positive cases. The sensitivity, specificity, positive and negative predictive values, and accuracy of MRC to detect biliary strictures were 96%, 96%, 95%, 97%, and 96%, respectively.

CONCLUSION

MRC proved to be a reliable noninvasive technique to visualize the biliary anastomosis and depict biliary strictures after OLT. MRC should be used when a biliary anastomotic stricture is suspected in an OLT patient.

Understanding the spectral Doppler waveform of the hepatic veins in health and disease

Duplex Doppler sonography is a fundamental component of the complete ultrasonographic examination of the liver. Accurate interpretation of the spectral Doppler tracing from the hepatic veins is valuable, as it reflects important cardiac and hepatic physiology. Normally, there are four phases: A, S, V, and D; the S and D waves indicate flow in the antegrade direction toward the heart. In hepatic and cardiac disease, these normal waves may be absent, a finding indicative of flow in a nonphysiologic manner. In addition, transient patient factors such as phase of the respiratory cycle may influence the appearance of the spectral tracing. Familiarity with the normal and abnormal spectral Doppler waveforms from the hepatic veins and knowledge of their respective physiology and pathophysiology provide valuable insights. Systematic analysis of the direction, regularity, and phasicity of the spectral tracing and the ratio of the amplitudes of the S and D waves allows one to arrive at the correct differential diagnosis in most situations.

Percutaneous portal venoplasty and stenting for anastomotic stenosis after liver transplantation

AIM: To review percutaneous transhepatic portal venoplasty and stenting (PTPVS) for portal vein anastomotic stenosis (PVAS) after liver transplantation (LT).

METHODS: From April 2004 to June 2008, 16 of 18 consecutive patients (11 male and 5 female; aged 17-66 years, mean age 40.4 years) underwent PTPVS for PVAS. PVAS occurred 2-10 mo after LT (mean 5.0 mo). Three asymptomatic patients were detected on routine screening color Doppler ultrasonography (CDUS). Fifteen patients who also had typical clinical signs of portal hypertension (PHT) were identified by contrast-enhanced computerized tomography (CT) or magnetic resonance imaging. All procedures were performed under local anesthesia. If there was a PVAS < 75%, the portal pressure was measured. Portal venoplasty was performed with an undersized balloon and slowly inflated. All stents were deployed immediately following the predilation. Follow-ups, including clinical course, stenosis recurrence and stent patency which were evaluated by CDUS and CT, were performed.

RESULTS: Technical success was achieved in all patients. No procedure-related complications occurred. Liver function was normalized gradually and the symptoms of PHT also improved following PTPVS. In 2 of 3 asymptomatic patients, portal venoplasty and stenting were not performed because of pressure gradients < 5 mmHg. They were observed with periodic CDUS or CT. PTPVS was performed in 16 patients. In 2 patients, the mean pressure gradients decreased from 15.5 mmHg to 3.0 mmHg. In the remaining 14 patients, a pressure gradient was not obtained because of > 75% stenosis and typical clinical signs of PHT. In a 51-year-old woman, who suffered from massive ascites and severe bilateral lower limb edema after secondary LT, PVAS complicated hepatic vein stenosis and inferior vena cava (IVC) stenosis. Before PTPVS, a self-expandable and a balloon-expandable metallic stent were deployed in the IVC and right hepatic vein respectively. The ascites and edema resolved gradually after treatment. The portosystemic collateral vessels resulting from PHT were visualized in 14 patients. Gastroesophageal varices became invisible on poststenting portography in 9 patients. In a 28-year-old man with hepatic encephalopathy, a pre-existing meso-caval shunt was detected due to visualization of IVC on portography. After stenting, contrast agents flowed mainly into IVC via the shunt and little flowed into the portal vein. A covered stent was deployed into the superior mesenteric vein to occlude the shunt. Portal hepatopetal flow was restored and the IVC became invisible. The patient recovered from hepatic encephalopathy. A balloon-expandable Palmaz stent was deployed into hepatic artery for anastomotic stenosis before PTPVS. Percutaneous transhepatic internal-external biliary drainage was performed in 2 patients with obstructive jaundice. Portal venous patency was maintained for 3.3-56.6 mo (mean 33.0 mo) and all patients remained asymptomatic.

CONCLUSION: With technical refinements, early detection and prompt treatment of complications, and advances in immunotherapy, excellent results can be achieved in LT.