Doppler ultrasonography in living donor liver transplantation recipients: Intra- and post-operative vascular complications

Diagnostic accuracy of CT and Doppler US for hepatic outflow obstruction after pediatric liver transplantation using left lobe or left lateral section grafts

PURPOSE

The aim of this study was to evaluate diagnostic accuracy and to establish computed tomography (CT) and Doppler ultrasonography (US) criteria for hepatic outflow obstruction after pediatric liver transplantation (LT) using left lobe (LL) or left lateral section (LLS) grafts.

METHODS

Pediatric patients who underwent LT using LL or LLS grafts between January 1999 and December 2021 were retrospectively included. The diagnostic performance of Doppler US and CT parameters for hepatic outflow obstruction was calculated using receiver operating characteristic (ROC) curve analysis. A diagnostic decision tree model combining the imaging parameters was developed.

RESULTS

In total, 288 patients (150 girls; median age at LT, 1.8 years [interquartile range, 0.9 to 3.6 years]) were included. Among the Doppler US parameters, venous pulsatility index (VPI) showed excellent diagnostic performance (area under the ROC curve [AUROC], 0.90; 95% confidence interval [CI], 0.86 to 0.93; Youden cut-off value, 0.40). Among the CT parameters, anastomotic site diameter (AUROC, 0.92; 95% CI, 0.88 to 0.95; Youden cut-off, 4.2 mm) and percentage of anastomotic site stenosis (AUROC, 0.88; 95% CI, 0.84 to 0.92; Youden cut-off, 35%) showed excellent and good diagnostic performance, respectively. A decision tree model combining the VPI, peak systolic velocity, and percentage of anastomotic site stenosis stratified patients according to the risk of hepatic outflow obstruction.

CONCLUSION

VPI, anastomotic site diameter, and percentage of anastomotic site stenosis were reliable imaging parameters for diagnosing hepatic outflow obstruction after pediatric LT using LL or LLS grafts.

European Society of Pediatric Radiology survey of perioperative imaging in pediatric liver transplantation: (2) intraoperative 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 intraoperative and postoperative complications. So far, only limited data regarding the best radiological approach to monitor children during liver transplantation is available.

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 phase. This paper reports the responses related to intraoperative 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

Intraoperative ultrasound (US) is used by all sites to assess the quality of the vascular anastomosis in order to ensure optimal perfusion of the liver transplant. Vessel depiction is commonly achieved using color Doppler (95.3%). Additional US-based techniques are employed by fewer centers (power angio mode, 28.6%; B-flow, 19%; contrast-enhanced US, 14.3%). Most centers prefer a collaborative approach, with surgeons responsible for probe handling, while radiologists operate the US machine (47.6%). Less commonly, the intraoperative US is performed by the surgeon alone (28.6%) or by the radiologist alone (23.8%). Timing of US, imaging frequency, and documentation practices vary among centers.

CONCLUSION

Intraoperative US is consistently utilized across all sites during pediatric liver transplantation. However, considerable variations were observed in terms of the US setup, technique preferences, timing of controls, and documentation practices. These differences provide valuable insights for future optimization and harmonization 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.

Early postoperative duplex ultrasound findings of the hepatic artery in postoperative vascular complications from paediatric liver transplantation

PURPOSE

To evaluate duplex US findings of the HA in all three postoperative vascular (HA, PV, HV and IVC) complications of paediatric LT for early detection and some helpful secondary signs to determine these vascular complications.

MATERIALS AND METHODS

We collected data from 44 post-LT paediatric patients who underwent daily duplex US for seven consecutive days and three months after LT during January 2017-June 2020. Four duplex US parameters of the HA (extrahepatic PSV, intrahepatic PSV, RI and AT) were compared in patients with and without complications.

RESULTS

The PSV of the extrahepatic HA in patients with HA complications was higher than that in patients without complications (P value = 0.019). The PSV at 107.7 cm/s is the optimal cut-off parameter associated with HA complications [a sensitivity of 88.9% and a specificity of 80.0% (ROC area is 0.84)]. The intrahepatic RI was higher on the first day than on the last day and gradually decreased in patients without vascular complications (P value = 0.000). The intrahepatic PSV significantly decreased with time when comparing the first and last days in patients without PV and HV-IVC complications (P value = 0.014 and 0.038). In contrast, patients with vascular complications showed no significant decrease.

CONCLUSION

The extrahepatic PSV relates to HA complications after paediatric LT but not PV and HV-IVC complications. Non-significantly decreased intrahepatic RI and PSV from the first day to the day of complication diagnosis may correlate with the occurrence of vascular complications.

The impact of portal vein reconstruction on portal vein complications after pediatric living-donor liver transplantation with left lobe graft

BACKGROUND

This study aimed to determine whether the different methods of portal vein reconstruction have an impact on the occurrence of portal vein complications after pediatric living-donor liver transplantation with left lobe graft.

METHODS

A total of 567 recipients were eligible for enrollment in this study and were divided into the following 2 groups according to the type of portal vein reconstruction: group 1 underwent anastomosis of the left and right bifurcations of the recipient portal vein to the donor portal vein (type 1), whereas group 2 underwent anastomosis of the bevel formed by the main trunk and right branch of the recipient portal vein to the donor portal vein (type 2). Postoperative portal vein complications and recipient and graft survival rates were compared between the 2 groups before and after propensity score matching.

RESULTS

Portal vein complications occurred in 53 (9.3%) patients, including 46 recipients with portal vein stenosis and 7 with portal vein thrombosis. After propensity score matching, the incidence of portal vein stenosis in group 2 was lower than that in group 1 (P = .035). The first diagnosis time of portal vein stenosis in group 2 was later than that in group 1 (P = .033), and the incidence of early portal vein stenosis was lower than that in group 1 (P = .009). There were no statistically significant differences in the incidence of portal vein thrombosis and recipient and graft survival rates between the 2 groups.

CONCLUSIONS

Type 2 portal vein reconstruction appears to be a viable technique in pediatric living-donor liver transplantation with left lobe graft that can effectively reduce the incidence of portal vein stenosis.

Doppler Ultrasound of Vascular Complications After Pediatric Liver Transplantation: Incidence, Time of Detection, and Positive Predictive Value

Purpose Doppler ultrasound (DUS) is widely used to detect vascular complications after pediatric liver transplantation (LT). This study aimed to assess the moment of first detection of vascular complications with DUS, and to determine the positive predictive value (PPV) of DUS.

Materials and Methods Patients aged 0–18 years who underwent LT between 2015 and 2019 were retrospectively included. 92 LTs in 83 patients were included (median age: 3.9 years, interquartile range: 0.7–10.5). Patients underwent perioperative (intra-operative and immediately postoperative) and daily DUS surveillance during the first postoperative week, and at 1, 3, and 12 months. Vascular complications were categorized for the hepatic artery, portal vein, and hepatic veins. DUS findings were compared to surgical or radiological findings during the 1-year follow-up.

Results 52 vascular complications were diagnosed by DUS in 35/92 LTs (38%). 15 out of 52 (28.8%) were diagnosed perioperatively, 29/52 (55.8%) were diagnosed on postoperative days 1–7, and 8/52 (15.4%) after day 7. The PPV for all vascular complications diagnosed with DUS was 92.3%. During the 1-year follow-up, 18/19 (94.7%) hepatic artery complications, 19/26 (73.1%) portal vein complications, and 7/7 (100%) hepatic vein complications were diagnosed perioperatively or during the first week.

Conclusion The majority of vascular complications during the first year after pediatric LT were diagnosed by DUS perioperatively or during the first week, with a high PPV. Our findings provide important information regarding when to expect different types of vascular complications on DUS, which might improve DUS post-LT surveillance protocols.

4D Flow MRI in the portal venous system: imaging and analysis methods, and clinical applications

Thus far, ultrasound, CT, and 2D cine phase-contrast MRI has been adopted to evaluate blood flow and vascular morphology in the portal venous system; however, all these techniques have some shortcomings, such as limited field of view and difficulty in accurately evaluating blood flow. A new imaging technique, namely 3D cine phase-contrast (4D Flow) MRI, can acquire blood flow data of the entire abdomen at once and in a time-resolved manner, allowing visual, quantitative, and comprehensive assessment of blood flow in the portal venous system. In addition, a retrospective blood flow analysis, i.e., "retrospective flowmetry," is possible. Although the development of 4D Flow MRI for the portal system has been delayed compared to that for the arterial system owing to the lower flow velocity of the portal venous system and the presence of respiratory artifacts, several useful reports have recently been published as the technology has advanced. In the first part of this narrative review article, technical considerations of image acquisition and analysis methods of 4D Flow MRI for the portal venous system and the validations of their results are described. In the second part, the current clinical application of 4D Flow MRI for the portal venous system is reviewed.

Understanding Local Hemodynamic Changes After Liver Transplant: Different Entities or Simply Different Sides to the Same Coin?

Liver transplantation is an extremely complex procedure performed in an extremely complex patient. With a successful technique and acceptable long-term survival, a new challenge arose: overcoming donor shortage. Thus, living donor liver transplant and other techniques were developed. Aiming for donor safety, many liver transplant units attempted to push the viable limits in terms of size, retrieving smaller and smaller grafts for adult recipients. With these smaller grafts came numerous problems, concepts, and definitions. The spotlight is now aimed at the mirage of hemodynamic changes derived from the recipients prior alterations. This article focuses on the numerous hemodynamic syndromes, their definitions, causes, and management and interconnection with each other. The aim is to aid the physician in their recognition and treatment to improve liver transplantation success.

Doppler evaluation of hepatic hemodynamics after living donor liver transplantation in infants

Objective: The aim of this study was to explore the hemodynamic changes of hepatic artery and portal vein detected by Doppler ultrasound (DU) in infants who underwent living donor liver transplantation (LDLT).

Methods: The data of 41 infant patients (22 Males, 19 Females, median age of 5 months) were collected in the Children’s Hospital affiliated to the Chongqing Medical University from May 2018 to December 2019. The patients underwent left lateral segment LDLT (LLS -LDLT) because of biliary atresia (BA). Hemodynamic parameters, including the peak systolic velocity (PSV), resistivity index (RI) of the hepatic artery (HA), portal vein velocity (PVV), and portal vein flow (PVF) were recorded from Doppler ultrasound on the day before the operation, and on the 1st, the 7th, the 14th and the 30th day after LDLT procedures. The changes of PSV_HA, RI_HA, PVV and PVF before and on the 1st day after transplantation were analyzed by paired t-test. The comparison of the data between different postoperative time points were assessed by ANOVA.

Results: Compared with the parameters measured before LDLT, PSV_HA, and RI_HA decreased, and PVV and PVF increased significantly (p < 0.001) on the 1st day after LLS-LDLT. As for PSV, there was no significant difference between the 7th day and the 1st day after transplantation (POD7 VS POD1, p = 0.167) while there was a substantial difference between the 14th, 30th and 1st day after LT (POD14 vs. POD1, p = 0.003) (POD30 vs. POD1, p ＜0.001). And there was a significant difference between the 14th, 30th, and 7th days after LT (POD14 vs. POD7, p = 0.014) (POD30 vs. POD7, p ＜0.001). There was no significant difference between 30th and 14th after transplantation (POD30 vs. POD14, p = 0.092). As for RI_HA and PVV, the decrease was slow within the first month after the operation, and there was no significant difference at different times.

Conclusion: We have identified major hepatic flow changes that occurred in 41 infants who underwent LLS -LDLT due to BA. The data could be used for future studies of LDLT in infants including hemodynamic modeling, liver regeneration and clinical management.

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.

Multimodality Imaging after Liver Transplant: Top 10 Important Complications

Patients who have undergone liver transplant are now regularly seen in day-to-day radiology practice. All surgical techniques for liver transplant require arterial, portal venous, hepatic venous and caval, and biliary anastomoses. This review is focused on the 10 "not to be missed" complications of liver transplant that affect the health and life of the graft and graft recipient. Arterial complications are the most common and devastating. Early hepatic artery thrombosis may be catastrophic because the biliary tree is solely dependent on the hepatic artery after transplant and collateral vessels have not yet formed. In contrast, delayed hepatic artery thrombosis may be more insidious as collateral arteries develop. US findings of delayed hepatic artery thrombosis may be similar to those of hepatic artery stenosis and celiac artery stenosis. Splenic artery steal syndrome is an increasingly recognized cause of graft ischemia. Venous complications are much less common. Hepatic venous and caval complications are notable for their increased incidence in living-donor and pediatric transplants. Biliary complications often result from arterial ischemia. Biliary cast syndrome is a notable example in which ischemic biliary mucosa sloughs into and obstructs the duct lumens. Neoplasms also may occur within the hepatic graft and may be due to recurrent malignancy, posttransplant lymphoproliferative disorder, or metastases. US is the initial imaging modality of choice, particularly in the acute postoperative setting. Further evaluation with contrast-enhanced US, CT, or MRI; catheter angiography; endoscopic retrograde cholangiopancreatography; and/or nuclear medicine studies is performed as needed. An invited commentary by Bhargava is available online. Online supplemental material is available for this article. ^©RSNA, 2022.

Usability of intraoperative cine-portogram during liver transplantation in young pediatric patients with biliary atresia

BACKGROUND

Pediatric patients with biliary atresia (BA) often present liver cirrhosis-associated portal hypertension and portal vein (PV) hypoplasia. For successful liver transplantation (LT), it is essential to maintain sufficient PV inflow through stenosis-free PV reconstruction with effective ligation of collateral veins. The aim of this study was to assess the clinical usability of intraoperative cine-portogram (IOCP) in young pediatric patients who underwent LT for BA.

METHODS

Medical records of pediatric patients younger than 10 years who underwent primary LT for BA from 2018 to 2020 were reviewed.

RESULTS

A total of 31 patients had undergone Kasai portoenterostomy soon after birth. Their median ages at Kasai portoenterostomy and LT were 1 and 11 months, respectively. Types of LT were living-donor LT in 13, deceased-donor split LT in 15, and deceased-donor whole LT in three patients. PV interposition using an iliac vein homograft was performed in 28 patients receiving partial liver grafts. Side-to-side PV unification venoplasty was performed in three patients undergoing whole LT. All patients underwent ligation of collateral veins. IOCP was performed in 6 (19.4%) patients. Four showed no or faint residual venous collaterals. Collateral vein embolization and endovascular stenting were performed in one patient each. PV insufficiency-free survival rate was 100% at 1 year and 93.8% at 3 years. All patients are currently alive with a median follow-up period of 23 months.

CONCLUSIONS

Intraoperative cine-portogram can be a useful method for identification and embolization of residual portosystemic collateral veins in young pediatric patients who undergo LT for biliary atresia.

Contrast-enhanced ultrasound of transplant organs - liver and kidney - in children

Ultrasound (US) is the first-line imaging tool for evaluating liver and kidney transplants during and after the surgical procedures. In most patients after organ transplantation, gray-scale US coupled with color/power and spectral Doppler techniques is used to evaluate the transplant organs, assess the patency of vascular structures, and identify potential complications. In technically difficult or inconclusive cases, however, contrast-enhanced ultrasound (CEUS) can provide prompt and accurate diagnostic information that is essential for management decisions. CEUS is indicated to evaluate for vascular complications including vascular stenosis or thrombosis, active bleeding, pseudoaneurysms and arteriovenous fistulas. Parenchymal indications for CEUS include evaluation for perfusion defects and focal inflammatory and non-inflammatory lesions. When transplant rejection is suspected, CEUS can assist with prompt intervention by excluding potential underlying causes for organ dysfunction. Intracavitary CEUS applications can evaluate the biliary tract of a liver transplant (e.g., for biliary strictures, bile leak or intraductal stones) or the urinary tract of a renal transplant (e.g., for urinary obstruction, urine leak or vesicoureteral reflux) as well as the position and patency of hepatic, biliary and renal drains and catheters. The aim of this review is to present current experience regarding the use of CEUS to evaluate liver and renal transplants, focusing on the examination technique and interpretation of the main imaging findings, predominantly those related to vascular complications.

Ultrasound-Based Multimodal Imaging Predicting Ischemic-Type Biliary Lesions After Living-Donor Liver Transplantation

BACKGROUND

Ischemic-type biliary lesions (ITBL) are accepted as the most incomprehensible biliary complications after living-donor liver transplantation (LDLT). Early predicting the development of ITBL in pediatric patients permits more preventive strategies. However, few studies have focused on the early prediction of ITBL.

OBJECTIVE

This study aimed to establish a nomogram including ultrasound-based multimodal imaging to predict ITBL in children with biliary atresia (BA) within 2 years after receiving LDLT.

METHODS

The records of 94 BA children with at least one year of follow-up after LDLT were reviewed retrospectively. They were randomly divided into a training cohort for constructing a nomogram (n=64) and a validation cohort (n=30). In the training cohort, patients diagnosed as ITBL were included in the ITBL group and those without any vascular and biliary complication were included in the non-ITBL group. Multivariate Cox regression was used for the establishment of the nomogram in predicting the risk of ITBL within 2 years post-LDLT. The discrimination and calibration of the nomogram were internally and externally validated. The performances of the nomogram and the individual components were compared by the area under the curve (AUC) of receiver operating characteristic (ROC) curve.

RESULTS

In the training cohort, 18 BA children were included in the ITBL group and 46 were in the non-ITBL group. Last pediatric end-stage liver disease (PELD) score, gamma-glutamyl transpeptidase (GGT), resistive index (RI), and liver stiffness measurement (LSM) were the independent predictors for the development of ITBL within 2 years post-LDLT. The nomogram incorporating these independent predictors showed good discrimination and calibration by the internal and external validation. Its performance was better than any individual component in predicting the prognosis (P < 0.05).

CONCLUSION

The established nomogram may be used to predict the risk of ITBL within 2 years post-LDLT in BA children.

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.

Endovascular management of portal steal syndrome due to portosystemic shunts after living donor liver transplantation

Background and Aim

After liver transplant, pre‐existent porto‐systemic shunts (PSS) may persist, causing “portal steal,” leading to graft dysfunction, hepatic encephalopathy (HE), and eventual rejection. In recipients of small‐for‐size transplant liver grafts, shunts may be created intraoperatively, facilitating diversion of portal flow to systemic circulation to avoid ill‐effects of portal overperfusion. These iatrogenic shunts may also subsequently lead to portal steal. We aim to evaluate safety and efficacy of endovascular techniques in management of portal steal due to PSSs in living donor liver transplantation (LDLT) recipients.

Methods

Between 2013 and 2020, we encountered five LDLT recipients with large PSS, who presented with graft dysfunction and/or HE. One patient had a surgically created shunt and four had spontaneous shunts, not surgically ligated during transplant. Endovascular techniques including plug‐assisted or balloon‐occluded retrograde transvenous obliteration (PARTO/BRTO) or covered inferior vena cava (IVC) stent grafts were to occlude these PSS and counter the portal steal in all patients. Technical success and clinical outcomes at 1‐year‐follow‐up were assessed.

Results

Imaging showed large PSS causing portal steal syndrome in all five patients. IVC stent graft was used to isolate the shunt in two patients and PARTO/BARTO was performed in three patients. One patient had guarded prognosis due to multiple organ dysfunction and died 5 days after endovascular procedure. At 1‐year follow up, graft functions normalized in four patients with no recurrence of HE. No procedure‐related complications were seen.

Conclusion

Endovascular techniques can be safely and effectively used to counter portal steal syndrome in LDLT recipients, thus avoiding surgical re‐exploration in these patients.

Time-resolved 3D cine phase-contrast magnetic resonance imaging (4D-flow MRI) can quantitatively assess portosystemic shunt severity and confirm normalization of portal flow after embolization of large portosystemic shunts

Diagnosis and severity assessments of portosystemic shunts (PSSs) are important because the pathology sometimes results in severe hepatic encephalopathy, which can be treated almost completely by shunt embolization. At present, morphological assessment of PSS is performed mainly by computed tomography, and ultrasound is used for blood flow assessment. In two cases of PSS-related hepatic encephalopathy, we used time-resolved 3D cine phase-contrast (4D-flow) magnetic resonance imaging (MRI) to assess blood flow before and after shunt embolization. Before the intervention, blood flow in the main trunk of the superior mesenteric vein was mostly hepatofugal. However, post-interventional 4D-flow MRI revealed hepatopetal superior mesenteric vein flow with significantly increased portal vein blood flow. 4D-flow MRI is an ideal adjunct to Doppler ultrasonography, allowing for objective and visual assessment of morphology and blood flow of the portal venous system, including PSSs, and is useful in determining the indications for, and outcome of, PSS embolization.

Study of Early Postoperative Doppler Changes Post Living Donor Liver Transplantation and Their Impact on Early Mortality and Small-for-Size Syndrome: A Retrospective Study

Background

Adult-to-adult living donor liver transplantation (LDLT) has been a common practice because of the deficiency of deceased donor liver transplants. Liver hemodynamics differ substantially between cases with end-stage liver disease undergoing LT because of various degrees of hepatic affection, nature of implicated causative factors, and pathogenesis of the hepatic disorder. The present retrospective study primarily aimed to study the early postoperative doppler changes after adult to adult LDLT. The secondary aim was to assess these hemodynamics’ impact on early in-hospital deaths and small for size syndrome (SFSS) development.

Methods

This retrospective work was done on 123 adult cases with end-stage liver disease for whom adult LDLT was performed after exclusion of pediatric patients and those with vascular complications.

Results

Postoperative (PO) mean portal vein velocity (PVV), hepatic artery (HA) peak systolic velocity (PSV), and HA resistivity index (RI) declined gradually but significantly post adult LDLT. Phasicity of hepatic veins changes towards the triphasic waveform gradually in the early PO period. There is a notable negative relationship between PO mean PVV with PO mean HA PSV. Higher PO HA RI affected PO mortality, while higher PO PVV and lower HA PSV increased the incidence of SFSS.

Conclusion

Early postoperative Doppler changes post-LDLT (PO PVV, HA RI, and HA PSV) can affect both mortality and SFSS development.

Fluoroless intravascular ultrasound image-guided liver navigation in porcine models

Background

An intravascular ultrasound catheter (IVUSc) was developed for intracardiac ultrasound to assess interventions with compelling results. However, intrahepatic vascular exploration was rarely tested and was always associated with X-ray techniques. The aim of this study was to demonstrate the feasibility to navigate through the whole liver using an IVUSc, providing high-quality images and making it unnecessary to use ionizing radiation.

Methods

An ex vivo pig visceral block and an in vivo pig model were used in this study. The IVUS equipment was composed of an US system, and of an 8 French lateral firing IVUSc capable of producing 90-degree sector images in the longitudinal plane. After accessing the intravascular space with the IVUSc into the models, predetermined anatomical landmarks were visualized from the inferior vena cava and hepatic veins and corroborated.

Results

IVUS navigation was achieved in both models successfully. The entire navigation protocol took 87 and 48 min respectively, and 100% (21/21) and 96.15% (25/26) of the landmarks were correctly identified with the IVUSc alone in the ex vivo and in vivo models respectively. IVUS allowed to clearly visualize the vasculature beyond third-order branches of the hepatic and portal veins.

Conclusions

A complete IVUS liver navigation is feasible using the IVUSc alone, making it unnecessary to use ionizing radiation. This approach provides high-definition and real-time images of the complex liver structure and offers a great potential for future clinical applications during diagnostic and therapeutic interventions.

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.

Pediatric living donor left lateral segment liver transplantation for biliary atresia: Doppler ultrasound findings in early postoperative period

PURPOSE

To analyze hepatic hemodynamic parameters detected by Doppler ultrasound (DU) of uncomplicated children with biliary atresia who underwent left lateral segment living donor liver transplantation (LLS-LDLT), explore its normal change trend over time and determine the normal reference interval.

METHODS

We retrospectively involved the data from 227 biliary atresia patients (100 Males,127 Females). Hemodynamic parameters include peak systolic velocity (PSV), end-diastolic velocity (EDV), resistivity index (RI), and pulsation index (PI) of the hepatic artery (HA), portal vein velocity (PVV), portal vein flow (PVF) and hepatic vein velocity (HVV) during intra-operative and on the 1st, 3rd, 5th and 7th day after operation were collected. Repeated measures analysis of the variance and Friedman test were used to analyze the changing trend of hemodynamic parameters over time in the first week after the operation.

RESULTS

PSV_HA and EDV_HA showed a similar changing tendency at one week after surgery, with an overall decrease-rise trend; RI_HA and PI_HA also changed similarly with an overall rise-decrease trend. The HVV and PVV at surgery were lower than at all time points after surgery. As for PVF, the value of POD5 was the highest and then decreased. Additionally, this study provided the normal reference interval of hemodynamic parameters for LLS-LDLT patients, which were PSV_HA: 18.4-98.3 cm/s, EDV_HA: 0-43.3 cm/s, RI_HA: 0.41-1.0, PI_HA: 0.51-2.0, PVV: 19.0-83.7 cm/s, HVV: 19.4-68.0 cm/s, and PVF:99.5-500.0 ml/min/100 g at intraoperation. Within the first postoperative week: PSV_HA: 21.0-97.7 cm/s, EDV_HA: 0-32.7 cm/s, RI_HA: 0.47-1.0, PI_HA: 0.62-2.0, PVV: 23.0-92.0 cm/s, HVV: 19.7-86.0 cm/s, and PVF: 100.0-513.0 ml/min/100 g.

CONCLUSION

The hepatic hemodynamic of post-transplanted children detected by DU had specific changing trends and normal ranges, which provides valuable reference values for ultrasonologists and pediatric transplant clinicians.

Relationship Between Change Rate of Tacrolimus Clearance During Continuous Intravenous Infusion and Recipient Recovery at an Early Stage After Living Donor Liver Transplantation

BACKGROUND AND OBJECTIVE

Tacrolimus clearance (CL) is significantly altered according to recovery of liver function at an early stage after living donor liver transplantation (LDLT). In this study, we aimed to examine the impact of the change rate from postoperative day (POD) 1 in CL (ΔCL) of tacrolimus during continuous intravenous infusion (CIVI) on recipient recovery.

METHODS

A tacrolimus population pharmacokinetic model on POD1 after LDLT was developed using Phoenix NLME 1.3. The CL_POD1 was calculated using the final model. The CL_POD4-7 was calculated by dividing total daily tacrolimus dose by the area under the concentration-time curve from 0 to 24 h.

RESULTS

Data were obtained from 57 LDLT recipients, along with 540 points (177 points on POD1, 363 points on POD4-7) of tacrolimus whole blood concentrations at CIVI. The median tacrolimus CL decreased from POD1 to POD4 (from 2.73 to 1.40 L/h) and was then stable until POD7. Stepwise Cox proportional hazards regression analyses showed that the graft volume (GV)/standard liver volume (SLV) ratio (GV/SLV) and the tacrolimus ΔCL_POD6 were independent factors predicting early discharge (within 64 days median value) of recipients after LDLT [hazard ratio (HR) = 1.041, P = 0.001 and HR = 1.023, P = 0.004].

CONCLUSIONS

The tacrolimus ΔCL during CIVI immediately after LDLT in each recipient was a useful indicator for evaluation of recovery at an early stage after LDLT.

Duplex Doppler evidence of high hepatic artery resistive index after liver transplantation: Role of portal hypertension and clinical impact

BACKGROUND

Early increase of hepatic artery resistive index (HARI) is frequently observed after liver transplant (LTx).

AIM

We aimed to investigate contributing factors and prognostic relevance of high HARI after LTx from deceased donor.

METHODS

We conducted a retrospective analysis of prospectively collected data from January 2017 and February 2019. According to the Duplex Doppler HARI values (3^d post-operative day), patients were grouped in normal (0.55-0.80) and high (>0.80-1) HARI groups.

RESULTS

Among 81 LTx, 36 had a high HARI and 45 a normal HARI. Patients developing high HARI were older, exhibited lower platelet, hemoglobin, platelet count/spleen diameter ratio, higher serum creatinine, and a more pronounced spleen enlargement (median values 170 versus 120 mm). At multivariate analysis, PLT/spleen diameter ratio (OR 0.994, p < 0.001) creatinine levels (OR 2.418, p = 0.029), and recipient age (OR 1.157, p = 0.004) significantly predicted the occurrence of high HARI. Patients with high or normal HARI had similar vascular complications, rejection rate and 90-day mortality. In most cases, HARI recovered to normal without any clinical effect.

CONCLUSIONS

HARI rises in presence of several surrogate markers of portal hypertension. The increase is mostly transitory, and it may result from the hepatic artery spasm due to the high portal blood flow.

Ultrasound imaging of the arterial system

Ultrasound (US) and Doppler are often the first imaging to be carried out for arterial disease, and with good reason. US is noninvasive, free of radiation exposure and crucial for follow up imaging. The review that follows aims to highlight the various applications of US in imaging of the arterial system.

Practical Management of Indeterminate Biliary Strictures

Indeterminate biliary strictures pose a diagnostic and therapeutic challenge. Although underlying malignancy is a primary concern, biliary strictures may result from benign processes. An accurate diagnosis is paramount to define the treatment strategy and minimize morbidity. The limitations of traditional endoscopic retrograde cholangiopancreatography-based tissue acquisition with cytology brushings are well-documented. Endoscopic retrograde cholangiopancreatography is generally unable to determine a stricture's etiology. Complementary advanced endoscopic imaging and multimodal tissue acquisition have evolved. Careful consideration of the clinical presentation, location of the stricture, and interpretation of imaging constitute the most optimal approach for diagnosis and management.

Aggressive prevention and preemptive management of vascular complications after pediatric liver transplantation: A major impact on graft survival and long-term outcome

Vascular complications are a major cause of patient and graft loss after LTs. The aim of this study was to evaluate the effect of a multimodal perioperative strategy aimed at reducing the incidence of vascular complications. A total of 126 first isolated LTs-performed between November 2008 and December 2015-were retrospectively analyzed. A minimum follow-up period of 24 months was analyzable for 124/126 patients (98.4%). The aggressive preemptive strategy consisted of identifying and immediately managing any problem and any abnormality in the vascular flow, in any of the hepatic vessels, and at any time after the liver graft revascularization. As a result, with a median follow-up of 57 months (3-112 months), not a single graft has been lost from vascular or biliary problems. The actuarial 8-year graft survival is 96.5%. These results have shown that a combination of technical attention, medical prevention, an early diagnosis, and rapid interventions reduced the negative impact of vascular problems on the outcome of both grafts and patients.

Critical Care Management of Living Donor Liver Transplants

This article represents a review of the postoperative management of donors and recipients after living donor liver transplant, including monitoring, liberation from mechanical ventilation, nutritional support, and pain control. Vascular complications, such as biliary and sepsis, and bleeding are also discussed. Finally, commonly used immunosuppression and antimicrobial prophylaxes are reviewed.

Fence Angioplasty Prevents Narrowing of Venous Anastomosis in Solitary Pancreas Transplant

Background

Graft thrombosis is the leading cause of early graft failure in pancreas transplants. Direct anastomosis grafting of the portal vein to the iliac vein or vena cava generally appears narrowed on postoperative computed tomography (CT) scans. However, modification of surgical techniques may prevent venous narrowing, which also prevents thrombosis-related graft failure.

Material/Methods

We performed 31 solitary pancreas transplants since 2015. Retrospective analysis of these patients was performed.

Results

Fence angioplasty was applied in the final 12 cases, and no technical failures or early graft losses occurred in these cases. Three graft losses, including 2 immunologic losses and 1 patient death with functioning graft, occurred after at least postoperative 4 months. The venous anastomoses were evaluated via intraoperative Doppler ultrasound and postoperative CT scans. Intraoperative Doppler ultrasound revealed improved spectral waves of venous anastomoses in the fence group (monophasic spectral wave, 42.9% vs. 0%, p=0.017). The fence-graft applied group had no cases of narrowing, whereas the non-fence group had high narrowing rates on CT scans (84.2% vs. 0%, p<0.001). Furthermore, with less use of postoperative heparin, postoperative bleeding rates were lower in the fence group (36% vs. 0%, p=0.026).

Conclusions

Fence angioplasty is a definitive method for avoiding venous anastomotic stenosis and preventing graft failure due to thrombosis.

Postoperative Doppler Ultrasonography in Liver Transplantation

BACKGROUND

Doppler ultrasonography plays an important role in the postoperative management of liver transplantation. We present our initial experiences evaluating liver transplants with the use of postoperative Doppler sonography.

METHODS

In our hospital, we performed 20 liver transplantations from July 2014 to October 2016. Among 20 patients, we performed 15 deceased-donor liver transplantations (DDLTs) and 5 living-donor liver transplantations (LDLTs). For deceased donors, inferior vena cava anastomoses were performed with the use of the piggyback technique, and for living donors, modified right grafts were used with middle hepatic vein reconstruction by Dacron graft. In the intensive care unit, we performed Doppler ultrasound at least once a day and at every clinical need. We checked hepatic blood flow by means of Doppler ultrasound.

RESULTS

Eighteen patients underwent Doppler ultrasonography once a day up to postoperative day 6. Of the patients who received LDLT, 2 patients underwent Doppler ultrasonography twice a day because the operator was concerned about the hepatic artery anastomosis. Findings on Doppler ultrasound showed no abnormal wave form in hepatic artery, portal vein and hepatic veins. No patient had abnormal findings on angiographic computerized tomography. There was 1 graft failure in 20 recipients. The graft failure was primary nonfunction, and retransplantation was done. During the hospitalizations, there were no vascular complications.

CONCLUSIONS

Doppler ultrasonography can be used to evaluate postoperative vascular complications in liver transplant patients. When the operator checks postoperative Doppler ultrasonography, it is possible to differentiate between patients, and it may help to detect the vascular complications earlier.

Modified triangular hepatic vein reconstruction for preventing hepatic venous outflow obstruction in pediatric living donor liver transplantation using left lateral segment grafts

HVOO can be a critical complication in pediatric LDLT. The aim of this study was to evaluate a modified triangular technique of hepatic vein reconstruction for preventing HVOO in pediatric LDLT. A total of 298 pediatric LDLTs were performed using a left lateral segment graft by 2 methods for reconstruction of the hepatic vein. In 177 recipients, slit-shaped anastomosis was indicated with partial clamp of the IVC. A total of 121 recipients subjected to the modified triangular anastomosis with total clamp of the IVC. We compared the incidence of hepatic vein anastomotic complications between these 2 methods. Nine of the 177 cases (5.3%) treated with the conventional technique were diagnosed with outflow obstruction. All 9 cases underwent hepatic vein reconstruction with the slit-shaped hepatic vein anastomosis. In contrast, there were no cases of outflow obstruction in the 121 cases treated with the modified triangular anastomosis. The modified triangular technique of hepatic vein reconstruction with total clamping of the IVC was useful for preventing HVOO in pediatric LDLT.

Intraoperative Doppler sonogram in pediatric liver transplants: a pictorial review of intraoperative and early postoperative complications

A spectrum of vascular complications can be seen in pediatric liver transplant patients, including occlusion and hemodynamically significant narrowing of the vessels that provide inflow to or outflow from the graft. Intraoperative Doppler ultrasound (US) has the potential benefit of identifying vascular complications in pediatric liver transplant patients prior to abdominal closure. Importantly, intraoperative Doppler US can be used as a problem-solving tool in situations such as position-dependent kinking of the portal or hepatic veins, or in suspected vasospasm of the hepatic artery. Furthermore, this technique can be used for real-time reassessment after surgical correction of vascular complications. This pictorial review of intraoperative Doppler US in pediatric liver transplant patients illustrates normal findings and common vascular complications, including examples after surgical correction, in the perioperative period.

A novel technique for the assessment of total liver blood flow in pregnancy: interrater and intrarater agreements

OBJECTIVE

To improve the technique for hepatic blood flow examination, with the objective of investigating the role for Doppler flowmetry of the liver in monitoring pregnant females with pre-eclampsia.

METHODS

Two physicians independently examined a group of 50 healthy pregnant females. The main difference in the proposed technique is the measurement of the vessel cross-sectional area and the adjustment of the Doppler samples according to the diameter of each vessel. The portal vein was studied by using two approaches: in the epigastrium, to measure the diameter, and in the intercostal, for Doppler sample collection. The common hepatic artery was studied by using the epigastric approach. The average of three measurements of each vessel, in each subject, with intrarater and interrater agreements, was compared.

RESULTS

The intraclass correlation coefficient for the intrarater flow measurements of the hepatic artery and portal vein ranged from 0.98 to 0.99 (p < 0.0001). The intraclass correlation coefficients for the interrater flow measurements was 0.93 for the flow of the portal vein (p < 0.0001), 0.94 for the flow of the hepatic artery (p < 0.0001) and 0.96 for the measurement of the portal vein diameter (p < 0.0001).

CONCLUSION

The new technique for evaluation of blood flow to the liver displayed excellent reproducibility, possibly because of the adjustment of the Doppler samples according to the diameter of each vessel. Advances in knowledge: This approach will add reliability to the method. It opens a vast field of investigation given the importance of liver vascular lesions in pre-eclampsia.