Multimodality postoperative imaging of liver transplantation

Amino acid metabolomics and machine learning for assessment of post-hepatectomy liver regeneration

Objective

Amino acid (AA) metabolism plays a vital role in liver regeneration. However, its measuring utility for post-hepatectomy liver regeneration under different conditions remains unclear. We aimed to combine machine learning (ML) models with AA metabolomics to assess liver regeneration in health and non-alcoholic steatohepatitis (NASH).

Methods

The liver index (liver weight/body weight) was calculated following 70% hepatectomy in healthy and NASH mice. The serum levels of 39 amino acids were measured using ultra-high performance liquid chromatography-tandem mass spectrometry analysis. We used orthogonal partial least squares discriminant analysis to determine differential AAs and disturbed metabolic pathways during liver regeneration. The SHapley Additive exPlanations algorithm was performed to identify potential AA signatures, and five ML models including least absolute shrinkage and selection operator, random forest, K-nearest neighbor (KNN), support vector regression, and extreme gradient boosting were utilized to assess the liver index.

Results

Eleven and twenty-two differential AAs were identified in the healthy and NASH groups, respectively. Among these metabolites, arginine and proline metabolism were commonly disturbed metabolic pathways related to liver regeneration in both groups. Five AA signatures were identified, including hydroxylysine, L-serine, 3-methylhistidine, L-tyrosine, and homocitrulline in healthy group, and L-arginine, 2-aminobutyric acid, sarcosine, beta-alanine, and L-cysteine in NASH group. The KNN model demonstrated the best evaluation performance with mean absolute error, root mean square error, and coefficient of determination values of 0.0037, 0.0047, 0.79 and 0.0028, 0.0034, 0.71 for the healthy and NASH groups, respectively.

Conclusion

The KNN model based on five AA signatures performed best, which suggests that it may be a valuable tool for assessing post-hepatectomy liver regeneration in health and NASH.

Pancreatic Transplantation: Surgical Anatomy and Complications

Pancreatic transplantation is a complex surgical procedure performed for patients with chronic severe diabetes, often performed in combination with renal transplantation. Vascular and exocrine drainage anatomy varies depending on the surgical technique. Radiology plays a critical role in the diagnosis of postoperative complications, requiring an understanding of grayscale/Doppler ultrasound as well as computed tomography and MR imaging. In this review, we detail usual surgical methods and normal postoperative imaging appearances. We then review the most common complications following pancreatic transplants, emphasizing diagnostic features of vascular (arterial/venous), surgical, and diffuse parenchymal pathologic conditions on multiple imaging modalities.

Prediction of Liver Weight Recovery by an Integrated Metabolomics and Machine Learning Approach After 2/3 Partial Hepatectomy

Liver has an ability to regenerate itself in mammals, whereas the mechanism has not been fully explained. Here we used a GC/MS-based metabolomic method to profile the dynamic endogenous metabolic change in the serum of C57BL/6J mice at different times after 2/3 partial hepatectomy (PHx), and nine machine learning methods including Least Absolute Shrinkage and Selection Operator Regression (LASSO), Partial Least Squares Regression (PLS), Principal Components Regression (PCR), k-Nearest Neighbors (KNN), Support Vector Machines (SVM), Random Forest (RF), eXtreme Gradient Boosting (xgbDART), Neural Network (NNET) and Bayesian Regularized Neural Network (BRNN) were used for regression between the liver index and metabolomic data at different stages of liver regeneration. We found a tree-based random forest method that had the minimum average Mean Absolute Error (MAE), Root Mean Squared Error (RMSE) and the maximum R square (R²) and is time-saving. Furthermore, variable of importance in the project (VIP) analysis of RF method was performed and metabolites with VIP ranked top 20 were selected as the most critical metabolites contributing to the model. Ornithine, phenylalanine, 2-hydroxybutyric acid, lysine, etc. were chosen as the most important metabolites which had strong correlations with the liver index. Further pathway analysis found Arginine biosynthesis, Pantothenate and CoA biosynthesis, Galactose metabolism, Valine, leucine and isoleucine degradation were the most influenced pathways. In summary, several amino acid metabolic pathways and glucose metabolism pathway were dynamically changed during liver regeneration. The RF method showed advantages for predicting the liver index after PHx over other machine learning methods used and a metabolic clock containing four metabolites is established to predict the liver index during liver regeneration.

Imaging complications of liver transplantation: a multimodality pictorial review

Liver transplantation is one of the most commonly performed surgical procedures for the treatment of end-stage liver disease and hepatocellular carcinoma. Post-transplantation complications include vascular, nonvascular, and biliary. Common imaging techniques used to evaluate the hepatic graft are ultrasonography (US), CT, MR imaging, cholangiography, angiography, and scintigraphy. The purposes of this pictorial review are to review imaging findings of complications of liver transplantation and provide a framework for early detection of post-surgical complications.

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.

Complications and mortality after adult to adult living donor liver transplantation: A retrospective cohort study

BACKGROUND AND AIMS

Living donor liver transplantation (LDLT) is widely performed for patients to resolve the critical shortage of organs from cadavers. Despite rapid implementation of the procedure, both complications and mortality of LDLT are annoying problems. The aim of this study was to analyze complications and mortality of patients after adult to adult LDLT (A-ALDLT) in a single center.

METHODS

Between April 2003 and November 2013, 167 (A-ALDLT) recipients in National Liver Institute, Egypt were included. We retrospectively analyzed complications and mortality in them.

RESULTS

The overall incidence of complications was 86.2% (n = 144) and classified as biliary 43.7% (n = 73), vascular 21.6% (n = 36), Small for size syndrome (SFSS) 12.6% (n = 21), Gastrointestinal tract (GIT) 19.8% (n = 33), wound 12.6% (n = 21), chest 19.8% (n = 33), neurological 26.3% (n = 44), renal 21% (n = 35), intra abdominal collection 21.6% (n = 36), recurrent hepatitis C virus (HCV) 16.8% (n = 28), recurrent hepatocellular carcinoma (HCC) 2.4% (n = 4), acute rejection 19.2% (n = 32). 65 (45.1%) of 144 complicated patients died, while 10 (43.5%) of 23 non complicated died. The incidence of whole, in hospital and late mortalities were 44.9%, 28.7% and 16.2% respectively.

CONCLUSIONS

Mortality was higher among complicated cases where vascular complications and SFSS had significant effect on it so prevention and treatment of them is required for improving outcome.

Complications and mortality after adult to adult living donor liver transplantation: A retrospective cohort study

Background and aims

Living donor liver transplantation (LDLT) is widely performed for patients to resolve the critical shortage of organs from cadavers. Despite rapid implementation of the procedure, both complications and mortality of LDLT are annoying problems. The aim of this study was to analyze complications and mortality of patients after adult to adult LDLT (A-ALDLT) in a single center. Methods: Between April 2003 and November 2013, 167 (A-ALDLT) recipients in National Liver Institute, Egypt were included. We retrospectively analyzed complications and mortality in them.

Results

The overall incidence of complications was 86.2% (n = 144) and classified as biliary 43.7% (n = 73), vascular 21.6% (n = 36), Small for size syndrome (SFSS) 12.6% (n = 21), Gastrointestinal tract (GIT) 19.8% (n = 33), wound 12.6% (n = 21), chest 19.8% (n = 33), neurological 26.3% (n = 44), renal 21% (n = 35), intra abdominal collection 21.6% (n = 36), recurrent hepatitis C virus (HCV) 16.8% (n = 28), recurrent hepatocellular carcinoma (HCC) 2.4% (n = 4), acute rejection 19.2% (n = 32). 65 (45.1%) of 144 complicated patients died, while 10 (43.5%) of 23 non complicated died. The incidence of whole, in hospital and late mortalities were 44.9%, 28.7% and 16.2% respectively. Conclusions: Mortality was higher among complicated cases where vascular complications and SFSS had significant effect on it so prevention and treatment of them is required for improving outcome.

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Mortality was higher among complicated cases.

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Vascular complication was independent predictors of poor outcome.

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Small for size syndrome was independent predictors of poor outcome.

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Proper management of the previous complications improve outcome of LDLT.

Role of multi-detector computed tomography for biliary complications after liver transplantation

AIM: To investigate the diagnostic performance of multi-detector computed tomography (MDCT) in detecting biliary complications after orthotopic liver transplantation (OLT).

METHODS: Eighty-three consecutive OLT recipients, who presented with clinical or biochemical signs of biliary complications, underwent MDCT examination. Two experienced radiologists assessed MDCT images in consensus to determine biliary complications. Final confirmation was based on percutaneous transhepatic cholangiography or endoscopic retrograde cholangiography in 58 patients, surgery in four patients, liver biopsy in 10, and clinical and sonography follow-up in 11 patients.

RESULTS: Biliary complications were eventually confirmed in 62 of 83 patients (74.7%), including anastomotic biliary strictures in 32, nonanastomotic biliary strictures in 21, biliary stones in nine (5 with biliary strictures), anastomotic bile leak in five, and biloma in six (all with nonanastomotic strictures, and 2 with biligenic hepatic abscess). Twenty-one patients had no detection of biliary complications. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of MDCT for detecting biliary strictures were 90.6%, 86.7%, 89.2%, 92.3% and 83.9%, respectively. For detecting biliary stones, anastomotic bile leak and biloma, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value of MDCT were all 100%.

CONCLUSION: MDCT is a useful screening tool for detecting biliary complications after OLT.

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.

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.

The role of noninvasive vascular imaging in splanchnic and mesenteric pathology

Traditionally, catheter angiography (CA) has been the mainstay of diagnosis for mesenteric arterial diseases. However, CA is invasive and is associated with complications that result from the procedure itself, depending on the experience of the operators, site of vascular access, ionized radiation that could be significant when combined with interventional procedures, and administered contrast material. During the past 2 decades, technical improvements in computed tomography (CT) and magnetic resonance hardware and methods have contributed new, noninvasive tools, specifically CT angiography (CTA) and 3-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA). This article outlines the current applications, strengths, and weaknesses of CTA and 3D Gd-MRA in imaging of the mesenteric vessels.