Clinical application of modern ultrasound techniques after liver transplantation

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.

Superb Microvascular Imaging (SMI) Compared with Color Doppler Ultrasound for the Assessment of Hepatic Artery in Pediatric Liver Transplants: A Feasibility Study

(1) Background: Despite progression in surgical techniques and immunological treatments, hepatic artery (HA) thrombosis and stenosis still develop as an early or late liver transplant (LT) complication. We aimed to compare superb microvascular imaging (SMI) with conventional Doppler imaging (CDI) in the assessment of HA in a cohort of pediatric patients undergoing follow-up ultrasound (US) for LT. (2) Methods: This prospective, observational study included 73 pediatric LT recipients (median age, 7 years; IQR, 5.8 years; 35 females) who underwent US during LT follow-up from March to December 2019. For each examination, CDI and SMI were separately assessed in terms of HA visibility and spectral waveform morphology (SWM). The former was scored based on HA discrimination from the blooming signal of the surrounding vessels, as follows: 0, not visible; 1, majority course hardly distinguishable; and 2, majority course clearly distinguishable. The latter was scored on a two-point scale: 0, combined venous and arterial SWM, and 1, pure arterial SWM. The patient’s overall score was finally calculated by adding the two individual scores. (3) Results: Both the absolute scores and frequency of overall scores equal to 3 (maximum global score) were higher using SMI compared with CDI. The median overall score was 3 for SMI and 2 for CDI (p = 0.011; IQR = 1). An overall score equal to 3 was obtained in 74% and 49.3% of the study population using SMI and CDI, respectively (p = 0.002). This was attributable to a better score in HA visibility (p = 0.007). (4) Conclusions: SMI has shown promise for assessing HA in pediatric LT recipients, possibly serving as a complementary non-invasive tool of CDI in everyday practice.

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.

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.

Vascular Anomalies of the Extrahepatic Artery as a Predictable Risk Factor for Complications After Liver Transplant

OBJECTIVES

Vascular variations of the extrahepatic artery occur in up to 50% of the population. Exact knowledge of any anomalies is of great significance in hepatobiliary surgery to avoid perioperative complications. In fact, in liver transplant, vascular complications are rare but have a major impact on graft function and survival. This study evaluated variations of the extrahepatic artery in donors and recipients as risk factors for vascular complications after liver transplant.

MATERIALS AND METHODS

From January 2010 until June 2015, 469 liver transplant procedures were performed at our institution. We included 323 patients in our retrospective analysis after exclusion of retransplants, split-livertransplants, and pediatric patients. We analyzed the impact of anatomic variations of recipients and donors on postoperative vascular complications and organ and patient survival.

RESULTS

Of total study recipients, 71.2% had a normal vascular supply according to Michel classification I. However, these patients developed significantly more vascular complications (25.65%) than those with vascular anomalies (15.05%), especially showing higher incidence of arterial stenosis (8.26% vs 2.15%). In contrast, vascular variations in donors and the need for a vascular reconstruction of the graft led to significantly higher mortality (26.76% vs 15.48%). An abnormality of the graft did not influence incidence of postoperative complications or graft survival.

CONCLUSIONS

Unexpectedly, recipients with variations of the hepatic artery and grafts with an abnormal arterial supply did not show higher rates of com-plications or mortality. Only vascular reconstruction of the graft before transplant raised the mortality of recipients.

Contrast-Enhanced Ultrasound for identifying circulatory complications after liver transplants in children

Our main goal with this study was to share our off-label experience with CEUS for identifying circulatory complications after liver transplantation in children. A total of 74 CEUS examinations performed on 34 pediatric patients who underwent a liver transplant were retrospectively included. About 53% of the examinations were performed on children 2 years old or younger. About 82% of the examinations were performed within 30 days from the transplant. About 62% of patients were transplanted due to a cholestatic disease, 11% due to a metabolic disease, 8% were re-transplanted due to graft failure, and 19% was due to other conditions. BA was the most common reason for transplantation and represented 38% of patients. About 38% of the transplantations were performed with whole grafts from DD, 40% with split liver grafts, and 22% with left lateral segments from LD. For diagnosing arterial circulatory complications, the PPV was 80%. For diagnosing portal vein circulatory complications, the PPV was 66.7%. NPV was 100%. In 28% of the examinations, the examiner could not visualize the normal arterial blood flow without CEUS. CEUS is a non-invasive and safe imaging technique that seems valuable in these patients and further efforts are needed to license its use in the post-transplant setting.

Meta-analysis of the diagnostic value of contrast-enhanced ultrasound for the detection of vascular complications after liver transplantation

BACKGROUND

contrast-enhanced ultrasound (CEUS) is increasingly used to identify vascular complications in patients after liver transplantation. The present study aimed to evaluate the diagnostic accuracy of CEUS using all available data.

MATERIALS AND METHODS

relevant studies published before February 2018 were retrieved from PubMed, EMBASE, ScienceDirect and Web of Science. Pooled sensitivity and specificity, diagnostic odds ratio (DOR) and summary receiver operating characteristic curve (SROC) were calculated to estimate the diagnostic performance of CEUS for vascular complications. Sensitivity analysis was performed that stratified studies according to age, study design and sample size in order to determine the influence of these factors on the overall effect. Meta-regression analyses were performed to examine the possible sources of heterogeneity. Quality assessment and publication bias of the included studies were also evaluated.

RESULTS

thirteen studies which consisted of 2,781 CEUS cases were included in the analysis. The pooled weighted estimates of sensitivity and specificity were 0.90 (95% CI, 0.84 to 0.95) and 1.00 (95% CI, 1.00 to 1.00), the diagnostic odds ratio (DOR) was 431.96 (95% CI, 164.60 to 1,133.59) and the area under the curve (AUC) of SROC was 0.9741. According to the sensitivity analysis, age, study design and sample size had an insignificant influence on the diagnostic performance of CEUS. The meta-regression analyses did not reveal a strong correlation between CEUS accuracy and study design, treatment time of patients and experience of the radiologists.

CONCLUSION

the results of our meta-analysis showed a high sensitivity, specificity and accuracy of the CEUS modality for the identification of vascular complications in patients after liver transplantation. Since this is the first meta-analysis investigating in this aspect, more evidence is required to validate the clinical utility of CEUS for the identification of vascular complications in patients with a transplanted liver.

Diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in monitoring vascular complications in patients after liver transplantation - diagnostic performance compared with histopathological results

PURPOSE

To analyse the diagnostic performance of contrast-enhanced ultrasound (CEUS) in patients with vascular complications and transplant rejection compared to histopathological results.

MATERIALS AND METHODS

Our study consisted of 45 retrospectively analysed patients that underwent liver transplantations between January 1993 and December 2015 and developed post-transplant vascular complications with transplant rejection. CEUS examinations took place between September 2006 and December 2015. CEUS findings were correlated with histopathological results.

RESULTS

CEUS showed a sensitivity of 61.5%, a specificity of 100.0%, a positive predictive value (PPV) of 100.0% and a negative predictive value (NPV) of 86,5% in the detection of vascular complications with post-transplant rejection. 5 examinations were reported as normal whereas the histopathological result showed a transplant rejection (false-negative).

CONCLUSION

CEUS might be a useful additional non-invasive technique for the assessment of vascular complications with post-transplant rejection in patients after liver transplantation.

An inflammatory myofibroblastic tumor in the transplanted liver displaying quick wash-in and wash-out on contrast-enhanced ultrasound: A case report

RATIONALE

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm, and its presence in a grafted liver is exceedingly rare.

PATIENT CONCERNS

A 54-year-old woman was admitted to our hospital with a half-month history of intermittent melena. She had undergone deceased-donor liver transplantation (LT) for hepatitis B virus related liver cirrhosis without hepatocellular carcinoma 5 months previously.

DIAGNOSIS

Laboratory examination showed impaired liver and renal functions and Epstein-Barr virus (EBV) infection, but tumor markers within normal ranges. Gastroscopy showed esophageal varices. Ultrasound and computed tomography angiography revealed an ill-defined and irregular solitary lesion in the porta hepatis, encasing both the portal vein and the hepatic artery. The lesion was characterized by arterial hyper-enhancement and hypo-enhancement in the remaining phases with contrast-enhanced ultrasound (CEUS). The lesion was finally confirmed as an IMT by ultrasound-guided biopsy.

INTERVENTION

The patient received conservative treatment, including immunosuppression, endoscopic variceal ligation, antibiotics, steroids, and antiviral agents.

OUTCOME

The patient's gastrointestinal bleeding was controlled, but the symptoms associated with portal hypertension worsened. Attempts to perform a transjugular intrahepatic portosystemic shunt were unsuccessful, and she unfortunately died soon after.

LESSONS

A differential diagnosis of IMT should be considered in LT recipients presenting with EBV infection, normal tumor markers, and a de novo hepatic lesion with quick wash-in and wash-out on CEUS. Ultrasound is associated with the advantages of convenience and nonionizing radiation, and should thus be the priority approach for monitoring transplanted liver.

Impact of Doppler Ultrasound on Diagnosis and Therapy Control of Lienalis Steal Syndrome After Liver Transplantation

Background

Lienalis steal syndrome is a rare complication after orthotopic liver transplantation leading to severe complications. Routine duplex sonography allows early and safe detection of lienalis steal syndrome and secondarily helps to monitor the outcome by evaluating the hemodynamics.

Material/Methods

This analysis included eight patients who after orthotopic liver transplantation needed splenic artery embolization due to lienalis steal syndrome. Lienalis steal syndrome was assumed in case of elevated transaminases, bilirubinemia or persistent ascites, and the absence of further pathologies. Diagnosis was supported by ultrasound, confirmed by digital subtraction angiography, and followed by splenic artery embolization for treatment. We analyzed blood levels and ultrasound findings before and after splenic artery embolization as well as during follow-up and evaluated for incidence of severe biliary complications and survival.

Results

Arterial resistive index (RI) significantly regularized after splenic artery embolization while the maximum arterial velocity increased. The portal venous flow volume and maximum velocity decrease. Laboratory parameters normalized. Two of eight patients developed ischemic-type biliary disease. Survival rate was 88% over a median follow-up of 33 months.

Conclusions

Beside unspecific clinical findings, bedside ultrasound examination enabled a quick verification of the diagnosis and allowed direct treatment to minimize further complications. Furthermore, ultrasound can immediately monitor the therapeutic effect of splenic artery embolization.

Imaging of liver transplantation

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