Imaging follow-up after liver transplantation

Algorithmic Approach to Deranged Liver Functions After Transplantation

Liver transplant (LT) recipients require close follow-up with regular monitoring of the liver function tests (LFTs). Evaluation of deranged LFT should be individualized depending upon the time since LT, peri-operative events, clinical course, and any complications. These derangements can range from mild and asymptomatic to severe and symptomatic elevations requiring expedited personalized assessment and management. Pattern of LFT derangement (hepatocellular, cholestatic, or mixed), donor-recipient risk factors, timing after LT (post-operative, 1-12 months, and >12 months since LT) along with clinical context and symptomatology are important considerations before proceeding with the initial evaluation. Compliance to immunosuppression and drug interactions should be ascertained along with local epidemiology of infections. Essential initial evaluation must include an ultrasound abdomen with Doppler to rule out any structural causes such as biliary or vascular complications apart from focussed laboratory evaluation. Early allograft dysfunction, ischemia reperfusion injury, small-for-size syndrome, biliary leaks, hepatic artery, and portal vein thrombosis are usual culprits in the early post-operative period whereas viral hepatitis (acute or reactivation), opportunistic infections, and recurrence of the primary disease are more frequent in the later period. Graft rejection, biliary strictures, sepsis, and drug induced liver injury remain possible etiologies at all times points after LT. Initial evaluation algorithm must be customized based on history, clinical examination, risk factors, and pattern and severity of deranged LFT. Allograft rejection is a diagnosis of exclusion and requires liver biopsy to confirm and assess severity. Empirical treatment of rejection sans liver biopsy is discouraged.

Improving the radiological diagnosis of hepatic artery thrombosis after liver transplantation: Current approaches and future challenges

Hepatic artery thrombosis (HAT) is a devastating vascular complication following liver transplantation, requiring prompt diagnosis and rapid revascularization treatment to prevent graft loss. At present, imaging modalities such as ultrasound, computed tomography, and magnetic resonance play crucial roles in diagnosing HAT. Although imaging techniques have improved sensitivity and specificity for HAT diagnosis, they have limitations that hinder the timely diagnosis of this complication. In this sense, the emergence of artificial intelligence (AI) presents a transformative opportunity to address these diagnostic limitations. The develo pment of machine learning algorithms and deep neural networks has demon strated the potential to enhance the precision diagnosis of liver transplant com plications, enabling quicker and more accurate detection of HAT. This article examines the current landscape of imaging diagnostic techniques for HAT and explores the emerging role of AI in addressing future challenges in the diagnosis of HAT after liver transplant.

European Society of Pediatric Radiology survey of perioperative imaging in pediatric liver transplantation: (1) pre-transplant evaluation

BACKGROUND

Liver transplantation is the state-of-the-art curative treatment in end-stage liver disease. Imaging is a key element for successful organ-transplantation to assist surgical planning. So far, only limited data regarding the best radiological approach to prepare children for liver transplantation is available.

OBJECTIVES

In an attempt to harmonize imaging surrounding pediatric liver transplantation, the European Society of Pediatric Radiology (ESPR) Abdominal Taskforce initiated a survey addressing the current status of imaging including the pre-, intra-, and postoperative phase. This paper reports the responses on preoperative imaging.

MATERIAL AND METHODS

An online survey, initiated in 2021, asked European centers performing pediatric liver transplantation 48 questions about their imaging approach. In total, 26 centers were contacted and 22 institutions from 11 countries returned the survey. From 2018 to 2020, the participating centers collectively conducted 1,524 transplantations, with a median of 20 transplantations per center per annum (range, 8-60).

RESULTS

Most sites (64%) consider ultrasound their preferred modality to define anatomy and to plan surgery in children before liver transplantation, and additional cross-sectional imaging is only used to answer specific questions (computed tomography [CT], 90.9%; magnetic resonance imaging [MRI], 54.5%). One-third of centers (31.8%) rely primarily on CT for pre-transplant evaluation. Imaging protocols differed substantially regarding applied CT scan ranges, number of contrast phases (range 1-4 phases), and applied MRI techniques.

CONCLUSION

Diagnostic imaging is generally used in the work-up of children before liver transplantation. Substantial differences were noted regarding choice of modalities and protocols. We have identified starting points for future optimization and harmonization of the imaging approach to multicenter studies.

European Society of Pediatric Radiology survey of perioperative imaging in pediatric liver transplantation: (3) postoperative imaging

BACKGROUND

Liver transplantation is the state-of-the-art curative treatment for end-stage liver disease. Imaging is a key element in the detection of postoperative complications. So far, limited data is available regarding the best radiologic approach to monitor children after liver transplantation.

OBJECTIVE

To harmonize the imaging of pediatric liver transplantation, the European Society of Pediatric Radiology Abdominal Taskforce initiated a survey addressing the current status of imaging including the pre-, intra-, and postoperative phases. This paper reports the responses related to postoperative imaging.

MATERIALS AND METHODS

An online survey, initiated in 2021, asked European centers performing pediatric liver transplantation 48 questions about their imaging approach. In total, 26 centers were contacted, and 22 institutions from 11 countries returned the survey.

RESULTS

All sites commence ultrasound (US) monitoring within 24 h after liver transplantation. Monitoring frequency varies across sites, ranging from every 8 h to 72 h in early, and from daily to sporadic use in late postoperative phases. Predefined US protocols are used by 73% of sites. This commonly includes gray scale, color Doppler, and quantitative flow assessment. Alternative flow imaging techniques, contrast-enhanced US, and elastography are applied at 31.8%, 18.2%, and 63.6% of sites, respectively. Computed tomography is performed at 86.4% of sites when clarification is needed. Magnetic resonance imaging is used for selected cases at 36.4% of sites, mainly for assessment of biliary abnormalities or when blood tests are abnormal.

CONCLUSION

Diagnostic imaging is extensively used for postoperative surveillance of children after liver transplantation. While US is generally prioritized, substantial differences were noted in US protocol, timing, and monitoring frequency. The study highlights potential areas for future optimization and standardization of imaging, essential for conducting multicenter studies.

Computed Tomography and Magnetic Resonance Imaging Signs of Chronic Liver Rejection: A Case-Control Study

OBJECTIVE

In liver transplantation, chronic rejection is still poorly studied. This study aimed to investigate the role of imaging in its recognition.

METHODS

This study is a retrospective observational case-control series. Patients with histologic diagnosis of chronic liver transplant rejection were selected; the last imaging examination (computed tomography or magnetic resonance imaging) before the diagnosis was evaluated. At least 3 controls were selected for each case; radiological signs indicative of altered liver function were analyzed. χ 2 Test with Yates correction was used to compare the rates of radiologic signs in the case and control groups, also considering whether patients suffered chronic rejection within or after 12 months. Statistical significance was set at P < 0.050.

RESULTS

A total of 118 patients were included in the study (27 in the case group and 91 in the control group). Periportal edema was appreciable in 19 of 27 cases (70%) and in 6 of 91 controls (4%) ( P < 0.001); ascites and hepatomegaly were present in 14 of 27 cases (52%) and 12 of 27 cases (44%), respectively, and in 1 of 91 controls (1%) ( P < 0.001); splenomegaly was present in 13 of 27 cases (48%) and in 8 of 91 controls (10%) ( P < 0.001); and biliary tract dilatation was present in 13 of 27 cases (48%) and in 11 of 91 patients controls (5%) ( P < 0.001). In the controls, periportal edema was significantly less frequent beyond 12 months after transplant (1% vs 11%; P = 0.020); the other signs after 12 months were not significant.

CONCLUSIONS

The identification of periportal edema, biliary dilatation, ascites, and hepatosplenomegaly can serve as potential warning signs of ongoing chronic liver rejection. It is especially important to investigate periportal edema if it is present 1 year or more after orthotopic liver transplantation.

Biliary complications after liver transplantation: A computed tomography and magnetic resonance imaging pictorial review

Biliary complications are the most common complications after liver transplantation. Computed tomography (CT) and magnetic resonance imaging (MRI) are cornerstones for timely diagnosis of biliary complications after liver transplantation. The diagnosis of these complications by CT and MRI requires expertise, mainly with respect to identifying subtle early signs to avoid missed or incorrect diagnoses. For example, biliary strictures may be misdiagnosed on MRI due to size mismatch of the common ducts of the donor and recipient, postoperative edema, pneumobilia, or susceptibility artifacts caused by surgical clips. Proper and prompt diagnosis of biliary complications after transplantation allows the timely initiation of appropriate management. The aim of this pictorial review is to illustrate various CT and MRI findings related to biliary complications after liver transplantation, based on time of presentation after surgery and frequency of occurrence.

Ultrasonographic evaluation of patients with abnormal liver function tests in the emergency department

Ultrasonography is often the initial modality used to evaluate patients found to have abnormal liver function tests (LFTs) in the emergency department. While an assessment for biliary ductal dilatation and obstruction remains one of the main questions to answer, radiologists should also be aware of the ultrasonographic appearance of other conditions that can cause abnormal LFTs. This may be crucial for the management and disposition of patients in the emergency department. This article reviews the ultrasonographic features of diseases that may cause abnormal LFTs.

Magnetic Resonance Imaging of Liver Transplant

MR imaging increasingly has been adopted for follow-up imaging post-liver transplantation and for diagnosis of its complications. These include vascular and biliary complications as well as post-transplant malignancies. Interpretation of postoperative MR imaging should take into account the surgical technique and expected post-transplant changes. Contrast-enhanced MR imaging has high sensitivity for identification of vascular complications. MR cholangiopancreatography on the other hand is the most accurate noninvasive method for evaluation of biliary complications.

Imaging findings of en bloc simultaneous liver-kidney transplantation

Simultaneous liver-kidney transplantations (SLKTs) are increasing in incidence, and the en bloc surgical approach is associated with a unique spectrum of vascular complications. En bloc SLKTs have a common arterial supply from the celiac axis and post-operative assessment with Doppler ultrasound can help to localize vascular lesions as either proximal in the shared arterial supply or distal in the organ-specific arteries. Venous complications predominantly include thrombosis or stenosis of the portal vein, hepatic veins, renal vein, or IVC, but have a much lower incidence. Radiologists familiar with the post-operative anatomy and complications can provide meaningful and accurate assessment to help direct clinical care. The purpose of this article is to provide a targeted review of SLKT, review the post-surgical anatomy associated with en bloc SLKT, and review the imaging evaluation of vascular complications associated with SLKT.

Intra-procedural dual phase cone beam computed tomography has a better diagnostic accuracy over pre-procedural MRI and MDCT in detection and characterization of HCC in cirrhotic patients undergoing TACE procedure

PURPOSE

This study was directed to compare diagnostic accuracy of dual-phase cone beam computed tomography (DP-CBCT) vs pre-procedural second line imaging modality (SLIM [multidetector computed tomography and magnetic resonance imaging]) to detect and characterize hepatocellular carcinoma (HCC) in cirrhotic patients with indication for trans-arterial chemoembolization (TACE).

METHODS

This is a single centre, retrospective, and observational study. Exclusion criteria were not-assisted DP-CBCT TACE, and unavailable follow-up SLIM. We evaluated 280 consecutive patients (January/2015-Febraury/2019). Seventy-two patients were eligible. Three radiologists in consensus reviewed: pre-procedural SLIM, DP-CBCT, and SLIM at follow-up, with 4 months of interval between each reading. Hyper-vascular foci (HVF) were detected and characterized. Diameter was recorded. Radiological behaviour, according to LI-RADS criteria, of HFV throughout follow-up time was the reference standard. Diagnostic accuracy was calculated for pre-procedural SLIM and DP-CBCT and evaluated through receiver operating characteristic curve. HVF only visible on DP-CBCT (defined as occult) were analysed. Tumour diameters were compared.

RESULTS

Median time between pre-procedural SLIM and DP-CBCT and between DP-CBCT and definitive radiological diagnosis of HVF were 46.0 days (95%CI 36.5-55.0) and 30.5 days (95%CI 29.0-33.0), respectively. DP-CBCT had a better diagnostic performance than pre-examination SLIM (sensitivity 99%vs78%; specificity 89%vs85%; PPV 99%vs99%; NPV 92%vs30%; and accuracy 94%vs79%). DP-CBCT diagnosed 63 occult HVF. Occult HCC were 54/243 (22.2%). Six were occult angiomas. Three were false positive. Mean diameter was significantly higher in DP-CBCT vs pre-procedural SLIM (+7.5% [95%CI 3.7-11.3], p < 0.05).

CONCLUSIONS

DP-CBCT has a better diagnostic accuracy and NPV than pre-procedural SLIM in cirrhotic patients with indication for TACE.

Normal and transitory ultrasonography findings in the immediate postoperative period after liver transplantation

OBJECTIVE

Liver transplantation is one of the treatments for patients with advanced stage chronic liver disease and for selected patients with hepatic tumors. Ultrasonography is the first-choice imaging technique to evaluate liver transplants. This article reviews the surgical technique, anatomy, and normal findings on ultrasonography in the immediate postoperative period in patients who have undergone liver transplantation, which will be used as a reference in follow-up studies.

CONCLUSION

Early vascular (arterial and portal) complications can represent a threat for the graft or the patient. During the period after liver transplantation, the patient is recovering from surgery and the transplanted organ is adapting to its new environment. In this period, ultrasonography can show alterations in the parenchyma or Doppler findings that would be considered abnormal in other situations; these findings are usually transitory. Knowing how to interpret them is key to detecting or ruling out complications.

The short-term effect of liver transplantation on the low-frequency fluctuation of brain activity in cirrhotic patients with and without overt hepatic encephalopathy

Previous neuropsychological studies have demonstrated that liver transplantation (LT) is an effective method for improving the cognitive function of cirrhotic patients. However, the neural basis underlying the effects of LT is still unclear. Neuroimaging studies investigating changes in brain structures or functional networks mainly focus on patients without overt hepatic encephalopathy (HE). In this study, we recruited patients with and without overt HE and studied alterations in resting-state brain activity by quantizing the amplitude of low-frequency fluctuation (ALFF) before and 1 month after LT to study the short-term effect of LT in each group. Neuropsychological analyses indicated significant improvement of cognitive function in both groups. ALFF analysis showed that the brain activity in regions regulating motor function, vision, attention, and working memory were restored in both groups, reflecting the neuroplasticity of the brain. However, some persistent impairments and new-onset impairments in other regions related to these cognitive functions were observed in each group. Between-group comparison showed that although cognitive performance improved in both groups, the specific neural basis of LT in each group was different. The significant correlations of altered brain activity in regions showing LT and group effect with altered performance in neuropsychological and biochemical tests suggest a possible neuroimaging marker for the monitoring of short-term recovery of HE and the difference in individual recovery of cognitive performance. The findings in the present study help us further understand the neural effect of LT in patients with and without overt HE.

Imaging of liver transplantation

Liver transplantation (LT) is the treatment of choice for end-stage chronic liver disease, fulminant liver failure and early stage hepatocellular carcinoma. As discussed in this review, state-of-the-art imaging modalities including ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) play a pivotal role in the selection of patients and donors, as well as in early detection of those complications at risk of impairing graft function and/or survival. We also illustrate main imaging findings related to the wide spectrum of clinical problems raised by LT.