Expectations from imaging for pre-transplant evaluation of living donor liver transplantation

A World Update of Progress in Lower Extremity Transplantation: What's Hot and What's Not

ABSTRACT

The field of vascularized composite allotransplantation (VCA) is the new frontier of solid organ transplantation (SOT). VCA spans life-enhancing/life-changing procedures such as upper extremity, craniofacial (including eye), laryngeal, tracheal, abdominal wall, penis, and lower extremity transplants. VCAs such as uterus transplants are life giving unlike any other SOT. Of all VCAs that have shown successful intermediate- to long-term graft survival with functional and immunologic outcomes, lower extremity VCAs have remained largely underexplored. Lower extremity transplantation (LET) can offer patients with improved function compared to the use of conventional prostheses, reducing concerns of phantom limb pain and stump complications, and offer an option for eligible amputees that either fail prosthetic rehabilitation or do not adapt to prosthetics. Nevertheless, these benefits must be carefully weighed against the risks of VCA, which are not trivial, including the adverse effects of lifelong immunosuppression, extremely challenging perioperative care, and delayed nerve regeneration. There have been 5 lower extremity transplants to date, ranging from unilateral or bilateral to quadrimembral, progressively increasing in risk that resulted in fatalities in 3 of the 5 cases, emphasizing the inherent risks. The advantages of LET over prosthetics must be carefully weighed, demanding rigorous candidate selection for optimal outcomes.

Effect of Portal Vein Types on Estimated Remnant Volume in Living Donor: Preoperative CT Assessment

PURPOSE

The aim of this study is to examine the effect of portal vein types on the ratio of the right-left lobe liver volumes, as well as the insufficient estimated remnant liver volume (ERLV) during the preoperative assessment of donor candidates for right-lobe liver transplantation.

MATERIALS AND METHODS

The preoperative abdominal CT examinations of the donor candidates in a single institution between December 2018 and May 2022 were retrospectively evaluated. Portal vein types are divided into 3; classical anatomy was considered type 1, PV trifuction was considered type 2, and if the first branch arising from the main portal vein is the right posterior branch, it was accepted as type 3. Other configurations were defined as type 4. The total, right-left lobe liver volumes, the ERLV, and the portal vein variations were noted. The chi-square test was performed to assess the correlation between portal vein types, the ratio of the right-left lobe volumes, and the ERLV ratio below 30%. Tamhane's T2 post hoc tests were performed for pairwise comparison to assess the right-left lobe volume ratio among groups.

RESULTS

287 donor candidates (mean age, 35 years ± 8.2; 174 men) were evaluated. The volume ratio of median volume of the right and left lobe was significantly higher in candidates with type 3 portal veins compared to those with type 1 portal veins (2 (1.3-3.5) and 2.1 (1.6-3.2), respectively, p = 0.017). The ERLV ratio below 30% was significantly higher in donor candidates with type 3 portal veins (42.9%) compared to those with type 1 and 2 portal veins (24.6%, 20%)) respectively, p = 0.030).

CONCLUSION

Due to its propensity to result in insufficient ERLV in the donor, the presence of a type 3 portal vein should be evaluated during the preoperative evaluation. Secondary abstract: This study suggests that donor candidates with type 3 portal vein exhibit a notable rise in the frequency of insufficient remnant liver volume during the preoperative assessment.

Angiography with cone-beam CT versus contrast-enhanced MRI for living donor transplant imaging: Is MRI enough?

The purpose of this study is to compare the subjective and objective quality and confidence between conventional angiography with cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI) for the preoperative evaluation of potential donors for living donor liver transplant. Seventeen patients undergoing preoperative donor evaluation for living donor liver transplantation that underwent angiography with CBCT and contrast-enhanced MRI for evaluation of hepatic vascular anatomy were included in the study. Four attending radiologists interpreted anonymized, randomized angiography with CBCT images and MRIs, rating the diagnostic quality and confidence of their interpretation (on a 3-point scale) for each element, as well as clinically relevant measurements. Overall, the readers rated the quality of angiography with CBCT to be higher than that of MRI (median [interquartile range] = 3 (2, 3) vs. 2 (1-3), p < 0.001) across all patients. Readers of angiography with CBCT had more confidence in their interpretations as an average of all elements evaluated than the MRI readers (3 (3) vs. 3 (2, 3), p < 0.001). When the same reader interpreted both MRI and CBCT, the right hepatic artery diameter (3.8 mm ± 0.72 mm vs. 4.5 mm ± 1.2 mm, p < 0.005) and proper hepatic artery diameter (4.43 mm ± 0.98 mm vs. 5.4 mm ± 1.05 mm, p < 0.003) were significantly different between MRI and CBCT. There was poor interrater reliability for determining segment IV arterial supply for both modalities (κ < 0.2). Angiography with CBCT provides higher subjective diagnostic quality and greater radiologist confidence than MRI. The difference in measurements between CBCT and MRI when the same reader reads both studies suggests CBCT adds additional information over MRI evaluation alone.

Arterial Anastomosis Using Microsurgical Techniques in Adult Live Donor Liver Transplant: A Focus on Technique and Outcomes at a Single Institution

BACKGROUND

 Microvascular hepatic artery reconstruction (MHAR) is associated with decreased rates of hepatic artery thrombosis (HAT) in living donor liver transplantation (LDLT). There is a paucity of literature describing the learning points and initiation of this technique at the institutional level. The objective of this study is to report our institutional experience using MHAR in adult LDLT with a focus on technique and outcomes.

METHODS

 A retrospective review of adult patients who underwent LDLT from January 2012 to December 2020 was conducted. Patients were divided into two groups, those who underwent LDLT without MHAR and with MHAR. We analyzed cases for technical data including donor and recipient artery characteristics, anastomotic techniques, intraop events, and postop complications. A Mann-Whitney test was performed to compare outcomes between non-MHAR and MHAR patients.

RESULTS

 Fifty non-MHAR and 50 MHAR patients met inclusion criteria. Median age at transplantation was 58 (interquartile range [IQR] 11.8) and 57.5 years (IQR 14.5), respectively. Median follow-up for MHAR patients was 12.8 months (IQR 11.6). The most common recipient arteries were the right hepatic artery (HA) (58%) and left HA (20%). Median size of recipient and donor arteries were 3.3 mm (IQR 0.7) and 3.1 mm (IQR 0.7), resulting in a median mismatch size of 0.3 mm (IQR 0.4). Median microanastomosis time was 44 minutes (IQR 0). HAT, graft failure, and mortality rates were higher in the non-MHAR cohort (6% vs. 0%, 8% vs. 0%, and 16% vs. 6%, respectively); however, these did not reach statistical significance.

CONCLUSION

 This study found lower rates of HAT and graft failure after implementing MHAR, though statistical significance was not achieved. Larger cohort studies are needed to further assess the potential benefit of MHAR in adult LDLT. From our experience, MHAR requires cooperation between the transplant and microsurgical teams, with technical challenges overcome with appropriate instrumentation and planning.

Accuracy of Inflow Inversion Recovery (IFIR) for Upper Abdominal Arteries Evaluation: Comparison with Contrast-Enhanced MR and CTA

Background: Inflow-sensitive inversion recovery (IFIR) is a recently introduced technique to perform unenhanced magnetic resonance angiography (MRA). The purpose of our study is to determine the accuracy of IFIR-MRA in the evaluation of upper abdominal arteries, compared to standard MRA and computed tomography angiography (CTA). Materials and Methods: Seventy patients undergoing upper abdomen Magnetic Resonance Imaging (MRI) in different clinical settings were enrolled. The MRI protocol included an IFIR-MRA sequence that was intra-individually compared by using a qualitative 4-point scale in the same patients who underwent concomitant or close MRA (n = 65) and/or CTA (n = 44). Celiac trunk (CA), common-proper-left-right hepatic artery (C-P-L-R-HA), left gastric artery (LGA), gastroduodenal artery (GDA), splenic artery (SA), renal arteries (RA) and superior mesenteric artery (SMA) were assessed. Results: IFIR-MRA images were better rated in comparison with MRA. Particularly, all arteries obtained a statistically significant higher qualitative rating value (all p < 0.05). IFIR-MRA and MRA exhibited acceptable intraclass correlation coefficients (ICC) values for CA, C-L-R-HA, and SMA (ICC 0.507, 0.591, 0.615, 0.570, 0.525). IFIR-MRA and CTA showed significant correlations in C-P-L-R-HA (τ = 0.362, 0.261, 0.308, 0.307, respectively; p < 0.05), and in RA (τ = 0.279, p < 0.05). Conclusions: Compared to MRA, IFIR-MRA demonstrated a higher image quality in the majority of upper abdomen arterial vessels assessment. LHA and RHA branches could be better visualized with IFIR sequences, when visualizable. Based on these findings, we suggest to routinely integrate IFIR sequences in upper abdomen MRI studies.

Circuitous Path to Live Donor Liver Transplantation from the Coordinator's Perspective

Background: The live donor liver transplantation (LDLT) process is circuitous and requires a considerable amount of coordination and matching in multiple aspects that the literature does not completely address. From the coordinators’ perspective, we systematically analyzed the time and risk factors associated with interruptions in the LDLT process. Methods: In this retrospective single center study, we reviewed the medical records of wait-listed hospitalized patients and potential live donors who arrived for evaluation. We analyzed several characteristics of transplant candidates, including landmark time points of accompanied live donation evaluation processes, time of eventual LDLT, and root causes of not implementing LDLT. Results: From January 2014 to January 2021, 417 patients (342 adults and 75 pediatric patients) were enrolled, of which 331 (79.4%) patients completed the live donor evaluation process, and 205 (49.2%) received LDLT. The median time from being wait-listed to the appearance of a potential live donor was 19.0 (interquartile range 4.0–58.0) days, and the median time from the appearance of the donor to an LDLT or a deceased donor liver transplantation was 68.0 (28.0–188.0) days. The 1-year mortality rate for patients on the waiting list was 34.3%. Presence of hepatitis B virus, encephalopathy, and hypertension as well as increased total bilirubin were risk factors associated with not implementing LDLT, and biliary atresia was a positive predictor. The primary barriers to LDLT were a patient’s critical illness, donor’s physical conditions, motivation for live donation, and stable condition while on the waiting list. Conclusions: Transplant candidates with potential live liver donors do not necessarily receive LDLT. The process requires time, and the most common reason for LDLT failure was critical diseases. Aggressive medical support and tailored management policies for these transplantable patients might help reduce their loss during the process.

Post-operative imaging anatomy in liver transplantation

The article describes and illustrates the surgical techniques and the post-operative imaging anatomy in liver transplantation. Special attention is paid to the variant vascular and biliary anatomy that are important for surgical planning. Considering the ever-growing number of liver transplants performed and the key role that imaging plays in the pre-operative planning and post-operative assessment, it is important for the radiologist to be familiar with the surgical techniques and the normal post-operative appearance in these patients.

Prevalence of Different Hepatobiliary Tree Variants on Magnetic Resonance Cholangiopancreatography in Patients Visiting a Tertiary Care Teaching Hospital in Karachi

Introduction

Hepatobiliary tree variant anatomy is crucial to understand the preoperative planning of hepatobiliary surgeries. Although the presence of variant anatomy is not an absolute contraindication for liver transplantation, inadvertent mapping can lead to postoperative biliary complications. These variants are also important to be recognized in various hepatobiliary surgeries and interventional procedures. Magnetic resonance cholangiopancreatography (MRCP) is an excellent non-invasive imaging tool that can identify biliary anatomy. The purpose of the current study is focused on determining anatomical variants of the biliary tree on MRCP in our population visiting a teaching hospital in Karachi.

Methods

This cross-sectional study was conducted on patients referred to Dr. Ziauddin Hospital for MRCP. MRCP was performed on MAGNETOM Avanto, SIEMENS, Belgium, Germany. Images were analyzed on a workstation by two radiologists and a postgraduate trainee. A senior radiologist reviewed equivocal cases. SPSS 22.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. Chi-square test was used to see the link between anatomical variants of biliary tree and gender. P-value of ≤0.05 was considered as statistically significant.

Results

We recruited 369 patients undergoing MRCP consecutively for our study. Out of 369, 342 patients were eligible for analysis (139 males and 203 females). Standard anatomy was found to be prevalent in 65.8%. Type 3 was the leading variant. A statistically significant difference was recorded for the type 2 anatomic variant which was more frequent in males than females (p-value <0.001), while types 1, 3, and 4 anatomic variants were found to be more in females than males but this difference was not statistically significant. Few other variants were also recorded.

Conclusion

This study is robust evidence regarding biliary variants in Pakistan. It is important to consider these variants in our region, owing to an increased trend of liver transplants and other hepatobiliary procedures.

A Novel Surgical Technique to Assure Donor and Recipient Safety: Pyloric to Segment 4 Arterial Reconstruction

Background.

Strategies to extend the pool of organs include and promote the use of segmental liver grafts. While performing a living donor left lateral segment (LLS) liver transplant and in split procedures, the hepatic artery´s division becomes critical when a dominant segment 4 artery (S4A) emerges from the left hepatic artery (LHA). We aim to describe a novel technique that consists of performing microsurgical reconstruction from the pyloric artery (PA) to S4A.

Case Reports.

A 45-y-old living donor was evaluated to use his LLS as a graft for a pediatric recipient. During the procedure, a dominant S4A born from the LHA was dissected. To obtain an appropriate LHA length and diameter for the recipient, it was necessary to transect it. An extended right lobe split graft was used in a 61-y-old patient. The S4A born from LHA had to be sectioned during the split procedure. In both cases, segment 4 remained incompletely perfused. The PA was dissected with enough length to be rotated, to perform a microsurgical anastomosis to the S4A, recovering parenchyma’s color and Doppler signal while vascular permeability was demonstrated using CT scan. There was no biliary or cut surface complication.

Conclusions.

PA to S4A reconstruction is a simple and novel technique that can be used for LLS and extended right lobe split graft and might contribute to increase donor selection and reduce living donor and recipient S4A-related complications.

Role of CT Imaging With Three-Dimensional Maximum Intensity Projection Reconstruction in the Evaluation of Portal Vein Variants at a Tertiary Care Hospital

INTRODUCTION

Portal vein (PV) is the principal blood vessel transporting blood from the alimentary tract and spleen to the liver. The aim of this study is to determine the prevalence of PV anatomical variations in our population using multidetector CT with maximum intensity projection (MIP) technique at a tertiary care hospital.

METHODS

This cross-sectional study was prospectively conducted from November 2018 to June 2019 in the Department of Radiology at a tertiary care hospital in Karachi. After informed consent, all the patients with no known hepatic pathology undergoing routine abdomen CT were included in this study. Patients with previous hepatic resection surgeries, undiagnosed large hepatic tumors/metastasis, and those with PV thrombosis were excluded.

RESULTS

A total of 500 patients (256 males and 244 females) were included in the study; the mean age of female patients was relatively higher as compared to the male patients (53.80 ± 18.44 vs. 44.15 ± 19.94 years; p = 0.000). Standard PV anatomy (type 1) was found in 438 patients (87.6%). Trifurcation (type 2) occurred in 18 patients (3.6%). Right posterior portal vein as the first branch of main PV (type 3) was found in 22 patients (4.4%). A separate branch of the right portal vein (RPV) to segment VII (type 4) and separate branch of the RPV to segment VI (type 5) were found in 6 (1.2%) and 16 (3.2%) patients, respectively.

CONCLUSION

Our study displayed a relatively higher frequency of standard PV anatomy (type 1) compared to previous studies. We highlight the role of MIP in the analysis of hepatic venous anatomy with its utility demonstrating improved detection of variations.

Noncontrast Magnetic Resonance Angiography Clinical Application in Pre-Liver Transplant Recipients With Impaired Renal Function

Image evaluation of the vascular architecture is essential before living donor liver transplantation (LDLT). However, the use of contrast-enhanced study in recipients with impaired renal function is limited due to the risk of acute kidney injury and nephrogenic systemic fibrosis. Therefore, a contrast medium-free method is both valuable and necessary for preoperative vascular evaluation. Recent literature reported inflow-sensitive inversion recovery (IFIR) magnetic resonance angiography (MRA) without the use of a contrast medium to be a reproducible and noninvasive tool to assess hepatic vasculature with adequate-to-good image quality. The purpose of this study is to clinically apply IFIR MRA preoperatively in LDLT recipients. We retrospectively reviewed 31 LDLT recipients with renal function impairment from March 2013 to August 2018 who received IFIR MRA as a pretransplant vascular architecture evaluation and who underwent a subsequent LDLT. The image findings were assessed for subjective image quality and were compared with intraoperative findings. Our results showed that the pretransplant vascular anatomy was well correlated with intraoperative findings in all recipients. Successful ratings with image quality scores ≥2 for proper hepatic arteries (PHAs), portal veins, and inferior vena cavas (IVCs) were 100.0%, 96.8%, and 93.5%, respectively. Readable ratings with imaging quality score ≥1 for left and right hepatic arteries and gastroepiploic arteries were 83.9%, 96.7%, and 22.6%, respectively. We also found that recipients with higher Model for End-Stage Liver Disease scores (>23) had lower image quality scores for PHAs (P = 0.003) and IVCs (P = 0.046). However, images were still satisfactory for pre-liver transplantation (LT) vascular evaluation. In conclusion, in pre-LT recipients with impaired renal function, IFIR MRA is a feasible and reproducible image modality.

Predictors of early recipient mortality after living donor liver transplantation in a tertiary care center in Egypt

BACKGROUND

Living donor liver transplantation (LDLT) has evolved into a widely accepted therapeutic option. Many different risk factors may affect early mortality after LDLT.

OBJECTIVES

Analyze risk factors that can affect early (<6 months) mortality of patients after LDLT in a single center.

DESIGN

Retrospective chart review of patients who underwent LDLT.

SETTING

University hospital.

PATIENTS AND METHODS

Adult cirrhotic patients who underwent LDLT were classified by early (first 6 months) or late mortality. A full pre, intra- and post-operative evaluation had been done on all patients including a full history, examination and investigations to identify risk factors that might affect mortality post-LDLT.

MAIN OUTCOME MEASURES

Determination of pre-, intra- or postoperative factors that might affect recipient mortality post-LDLT.

SAMPLE SIZE

123.

RESULTS

Pre-operative factors that increased early mortality in a univariate analysis were higher model for end-stage liver disease (MELD) scores, lower graft-recipient weigh ratio (GRWR), older donor age, and recurrent spontaneous bacterial peritonitis. Intraoperative factors included more transfusion units of blood, plasma, platelets and cryoprecipitate, a longer time for cold and warm ischemia, and a longer anhepatic phase among others. Postoperative factors included a longer ICU or hospital stay and abnormal postoperative laboratory data. In the final logistic regression model, the most significant factors were pre-operative GRWR, length of hospital stay, units of intraoperative blood transfusion, postoperative alanine aminotransferase, postoperative total leukocyte count, and MELD score.

CONCLUSION

LDLT outcomes might be improved by attempting to resolve clinical factors that have been identified as contributors to early post-LDLT mortality.

LIMITATIONS

More risk factors, such as those relevant to patient portal vein hemodynamics, should be included in an analysis of predictors of early mortality.

CONFLICT OF INTEREST

None.

Pre-hepatic and pre-pancreatic transplant donor evaluation

Innovations in surgical techniques coupled with advances in medical and pharmacological management in the past few decades have enabled organ transplantation to become integral to the management of end stage organ failure. In this review article, we will review the role of the radiologist in the work up of liver and pancreas donors during evaluation of their donor candidacy. The critical role of imaging in assessing the parenchymal, biliary and vascular anatomy in liver donor candidates will be reviewed, as well as highlighting the anatomical findings that may pose a contraindication to transplantation. The limited role of imaging in pancreas donor evaluation is also covered, as well as a brief overview of the surgical techniques available and how the radiologist's findings influence operative technique selection.

Role of natural killer cells in liver transplantation treatment of liver cancer

Liver cancer caused by diet or life style is a significant public health problem. Liver transplantation (LT) is a commonly used method of treatment for the liver cancer. The present study aimed to determine whether assessing the net state of natural killer (NK) cell function following LT distinguishes patients at risk for transplantation rejection. A total of 53 patients were involved; all underwent LT for hepatocellular carcinoma with (n=13) or without (n=40) transplantation rejection. The density of interferon-γ (IFN-γ) in blood serum was examined and patients were divided into two groups: Higher (H) and lower (L), on the basis of IFN-γ density. The percentage of NK cells and their producing cytokines was detected using fluorescence-activated cell sorting in peripheral blood and liver samples. As evaluation indexes of liver function, aspartate transaminase (AST) and alanine transaminase (ALT) were detected in blood serum. NK cell activation of the H-group was observed to be higher than the L-group, specifically the expression of NK group 2D, cluster of differentiation 69 and IFN-γ were higher than the L-group. The H-group exhibited a higher level of AST and ALT, which indicates the potential for acute transplantation rejection. The results of the present study indicate that NK cells and NK-derived IFN-γ serve an important function in regulating the rejection of LT and tumor metastasis in response to LT.

Macrovesicular steatosis in living related liver donors: correlation of biopsy findings with CT liver attenuation index and body mass index

BACKGROUND

Hepatic steatosis threatens post-transplant graft survival; therefore, pre-operative quantification of steatosis is crucial. Gold standard for evaluation is donor liver biopsy but it is invasive. An alternative non-invasive method is a calculation of CT liver attenuation index. BMI can be an independent factor predicting grade of steatosis but it is necessary to re-define appropriate BMI cut-off points that are specific for Asians.

OBJECTIVE

To retrospectively analyze CT LAI and BMI for quantitative assessment of macrovesicular steatosis in living related liver donors, using histological analysis as gold standard.

MATERIALS AND METHODS

A radiologist blinded to histological grading calculated mean CT hepatic attenuation in 48 potential living related liver donors.

RESULTS

CT-derived LAI correctly predicted steatosis in all except 1 patient. Parametric analysis for CT LAI and BMI showed overall weak positive correlation. No significant association was found between BMI and biopsy findings.

CONCLUSION

Liver biopsy remains a gold standard for evaluation of steatosis. CT LAI of ≤0 correlates well with significant hepatic steatosis and biopsy may be avoided in such cases. Biopsy may be reserved for patients with CT LAI between 1 and 5. BMI alone is not a good predictor of hepatic steatosis in our study population.

Intra-Operative Contrast Cholangiography in Living Donor Liver Transplantation: The ISMETT Experience

BACKGROUND

We evaluated the clinical impact of donor biliary anatomy discrepancies (DBAD) achieved by comparing pre-operative evaluation obtained with magnetic resonance (MR)/magnetic resonance cholangiopancreatography (MRCP) imaging, with intra-operative cholangiography (IOC) on the living related liver donor (LDLT) and recipient.

METHODS

This single-center, retrospective study included 97 consecutive adult-to-adult (A2A) LDLT performed in our hospital in the last 12 years. Donor sex and age, living donors with biliary and/or vascular anomalies, recipient age, sex, primary etiology, re-transplantation, Model of End-Stage Liver Disease score, co-morbidities, arterial and biliary recipient complications assessed on the basis of clinical follow-up were collected and analyzed for significance through the use of a multivariate linear regression model.

RESULTS

Biliary complications in the donor (DBC) were detected in 8 (8.2%) cases. Biliary complications in the recipients (RBC) were detected in 38 (39%) cases. DBADs were found in 32 (33%) cases and resulted strictly related to RBC (P = .05).

CONCLUSIONS

After adjusting for co-variables, results of the linear regression analysis confirmed that DBAD is an independent predictor of RBC, but it is not significantly associated with vascular complications or patient survival. We showed that RBCs after LDLT were influenced by DBAD.