Arterial waveforms on Doppler ultrasonography predicting or supporting hepatic arterial thrombosis in liver transplantation

Prognostic value of ultrasound in early arterial complications post liver transplant

Liver transplantation is the primary therapeutic intervention for end-stage liver disease. However, vascular complications, particularly those involving the hepatic artery, pose significant risks to patients. The clinical manifestations associated with early arterial complications following liver transplantation are often nonspecific. Without timely intervention, these complications can result in graft failure or patient mortality. Therefore, early diagnosis and the formulation of an optimal treatment plan are imperative. Ultrasound examination remains the predominant imaging modality for detecting complications post liver transplantation. This article comprehensively reviews common causes and clinical presentations of early hepatic artery complications in the post-transplantation period and delineates abnormal sonographic findings for accurate diagnosis of these conditions. Overall, ultrasound offers the advantages of convenience, safety, effectiveness, and non-invasiveness. It enables real-time, dynamic, and precise evaluation, making it the preferred diagnostic method for post-liver transplantation assessments.

Application of contrast-enhanced ultrasound after liver transplantation: Current status and perspectives

Liver transplantation is an effective treatment for patients with end-stage liver disease. Accurate imaging evaluation of the transplanted patient is critical for ensuring that the limited donor liver is functioning appropriately. Ultrasound contrast agents (UCAs), in combination with contrast-specific imaging techniques, are increasingly accepted in clinical use for the assessment of the hepatic vasculature, bile ducts and liver parenchyma in pre-, intra- and post-transplant patients. We describe UCAs, their technical requirements, the recommended clinical indications, image interpretation and the limitations for contrast-enhanced ultrasound applications in liver transplantation.

Implantable sensor for blood flow monitoring after transplant surgery

A limited number of techniques are employed in clinical medicine for regional tissue perfusion assessment. These methods are marginally effective and are not well suited for implantation due to the inability to miniaturize the associated technologies. Consequently, no standardized techniques exist for real-time, continuous monitoring of organ perfusion following transplantation. In this paper, a brief overview of the relevant clinical techniques employed for regional tissue perfusion assessment is given with particular emphasis on post-surgical monitoring of transplanted organs. The ideal characteristics for a perfusion monitoring system are discussed and the development of a new, completely implanted local tissue monitoring system is summarized. <I>In vivo</I> and <I>in vitro</I> data are presented that establish the efficacy of this new technology, which is a photonics-based sensor system uniquely suited for continuous tissue monitoring and real-time data reporting. The suitablity of this sensor technology for miniaturization, which enables implantation for monitoring localized tissue perfusion, is discussed.

Vascular complications in living-related and deceased donation pediatric liver transplantation: single center's experience from Turkey

The aim of the study was to assess early and long-term incidence of venous complications, in both deceased donation (DD) and living-related (LR) liver transplantation (LT) in a pediatric population. Seventy-five liver transplants performed in 69 (39 boys, 30 girls) children at Ege University Hospital between 1997 and 2004 were prospectively monitored and reviewed. Age, sex, primary diagnosis, graft type, vascular complications and their management were evaluated. All patients received Doppler ultrasonographic examination both during operation and daily for the first three postoperative days and when necessary thereafter. The complications were classified as early and late presented. Thirty-three grafts (47.8%) were from DD and 36 (52.2%) were from LR donors. Recipients of DD were older than LR donors (mean age 10.5 +/- 5.1 and 5.0 +/- 0.7, respectively) (p < 0.05). Vascular complication occurrence was not statistically different between DDLT and LRLT recipients (p = 0.2), and between infants and children (p = 0.9). Overall, stenosis was more common than thrombosis. We observed hepatic artery (HA) thrombosis, in five of 75 (6.7%) transplants within 30 days post-transplant. Portal vein (PV) thrombosis and hepatic vein (HV) thrombosis were detected in six and one patients (8.7% and 1.3%), respectively. Six PV stenosis were identified (8.7%), while HA and HV-VC (vena cava) stenosis occurred in one and six patients (1.4% and 8.7%), respectively. All PV stenosis (6/33, 18.2%) and one PV aneurysm occurred in DDLT recipients while HV-VC stenosis were detected almost equally in LRLT and DDLT recipients (4/36 vs. 2/33). Except one, all PV stenosis were detected as a late complication and no intervention were needed. Stenosis of HV-VC was more common in girls (5/30 vs. 1/39) (p < 0.05) and the incidence was not different in DDLT and LRLT recipients (p = 0.8). In conclusion, overall incidences of thrombosis and stenosis formation after orthotopic liver transplantation (OLT) were 17.4% and 18.8%, respectively in our center. We suggest that in the cases with HA thrombosis manifested intra-operatively or within the early postoperative period, graft salvage was successful. Thrombosis of HA causes significant mortality. Thrombosis of PV was among the causes of mortality and morbidity. Stenosis of HV-VC could be managed by angioplasty and endovascular stenting with no significant effect to mortality.

Doppler ultrasonographic findings on hepatic arterial vasospasm early after liver transplantation

OBJECTIVE

Hepatic arterial vasospasm has not been well recognized clinically as a post-liver transplant vascular complication because of the lack of sufficient data and diagnostic standards. The goal of this study was to provide new evidence and a diagnostic model for the clinical appreciation of hepatic arterial vasospasm and evaluate the role of ultrasonography in the diagnostic process.

METHODS

Nine post-orthotopic liver transplant cases were retrospectively reviewed. Multiple clinical measurements were analyzed. Routine Doppler ultrasonography was performed within 24 hours, and additional ultrasonographic examinations were conducted as indicated. Each of the 9 patients was given a single 10 mg dose of nifedipine sublingually and monitored by ultrasonography when vasospasm was suspected on the basis of the Doppler ultrasonographic results.

RESULTS

Doppler ultrasonography showed high-resistance hepatic arterial flow with absence of antegrade flow and even reversal of flow during diastole both extrahepatically and intrahepatically in all cases. Ten to 45 minutes after administration of the vasodilator, antegrade diastolic flow was observed along the course of the main hepatic artery and its intrahepatic branches with the resistive indices decreasing on average from 1.0 to 0.76. In addition, the peak systolic velocities increased from 57 cm/s before nifedipine administration to 77 cm/s after administration.

CONCLUSIONS

High-resistance hepatic arterial flow (resistive index = 1) early after liver transplantation is indicative of hepatic arterial vasospasm if it responds to vasodilators. Doppler ultrasonography is a useful tool for the diagnosis of this vascular complication.

Significance of and contributing factors for a high resistive index on Doppler sonography of the hepatic artery immediately after surgery: prognostic implications for liver transplant recipients

OBJECTIVE

The goal of our study was to investigate the contributing factors, clinical repercussions, and implications for prognosis of high-resistance flow at the hepatic artery detected on Doppler sonography during the period immediately after orthotopic liver transplantation.

MATERIALS AND METHODS

We retrospectively studied the transplanted livers of 90 patients who had been examined on Doppler sonography within the first 3 days after grafting. Seventeen variables from organ donors, transplant recipients, graft characteristics, and surgical procedures were investigated. Early clinical evolution was also analyzed. Follow-up was performed for 5 years.

RESULTS

Forty-one (45.6%) of the 90 patients showed a high resistive index at the hepatic artery during the first 72 hr after transplantation. Two factors showed a statistically significant effect on the occurrence of a high resistive index at the hepatic artery immediately after transplantation: an older liver donor (p = 0.008) and extended preservation time (p = 0.005). No relation with early graft function was detected. The incidence of bile duct complications, retransplantation, or death was not higher at follow-up in patients with high-resistance flow than in those with normal flow.

CONCLUSION

High-resistance flow at the hepatic artery detected on Doppler sonography during the period immediately after transplantation is a frequent finding and is related to older donor age and prolonged period of ischemia. This finding has neither significant clinical repercussions nor prognosis implications for early and long-term follow-up.

Hepatic artery thrombosis in pediatric liver transplantation

PURPOSE

Children have been reported to be at greater risk for hepatic artery thrombosis when compared to adults due to small arterial size, nonuse of intraoperative microscope, and postoperative hypercoagulable state.

METHODS

We evaluated arterial anastomosis type, intraoperative field magnification, and hepatic artery complications and how they were managed. All patients underwent ultrasound, anticoagulation consisted of 41 mg aspirin once a day, and 35 patients received alprostadil (PGE) for the first 7 days after transplantation. No patients were administered intravenous heparin following liver transplantation.

RESULTS

Of the 74 livers transplanted, 36 grafts (48.6%) were whole organ transplants and 38 grafts (51.4%) were partial livers. We observed HAT in 1 of 74 (1.35%) transplants in our pediatric liver transplant population. The only patient with HAT was a young girl with a history of biliary atresia. The occurrence of a hepatic artery thrombosis on day 7 was caused by the migration of an intimal plaque dissection within the artery graft. She was emergently taken back into the operating room for graft revision. This individual currently has a survival time of 426 days following her last transplant.

CONCLUSIONS

Hepatic artery thrombosis may be minimized in pediatric liver transplantation without the use of microsurgery. Anticoagulation utilizing ASA and alprostadil is sufficient to avoid HAT. Accurate use of ultrasound is crucial to avoid this complication. Graft and patient salvage is possible with expedient surgical treatment; microsurgery, anticoagulant therapy, site of arterial inflow, and recipient size and weight.

Analysis of portal venous waveform after living-related liver transplantation with pulsed Doppler ultrasound

We evaluate the portal venous waveform (PVW) with pulsed Doppler ultrasound (US) after living-related liver transplantation (LRLT) and correlate it with subsequent abnormalities. In the first 2 wk after LRLT, pulsed Doppler US demonstrated three types of PV waveform (PVW) in 33 recipients: non-phasic PVW in 19 patients, pulsatile in 10, and turbulent in 4. In the pulsatile PVW group, arterio-portal (A-P) shunt was confirmed in three grafts by either arteriograhy or computed tomography during hepatic arteriography. A severe stenosis in the grafted vein was confirmed in one case by both US and venography. The pulsatile PVW in the remaining six cases spontaneously disappeared and turned to the non-phasic PVW without treatment. The graft volume/liver standard volume (GV/SV) ratio was significantly smaller in the pulsatile PV waveform group than in the non-phasic PVW group (p<0.01). In the turbulent PVW group, aneurysmal-like dilatation of the portal vein at the umbilical portion was formed in 3 of the 4 patients. The pulsatile waveform in the PV is frequently observed with pulsed Doppler after LRLT, especially in patients that received small grafts. We should keep in mind that they often disappear without any treatment, although some examples of pulsatile waveforms represent vascular complications.

Color Doppler sonography in the diagnosis and monitoring of arterial complications after liver transplantation

PURPOSE

We assessed the usefulness of color Doppler imaging in the diagnosis and monitoring of arterial complications after liver transplantation.

METHODS

Subjects were 142 liver transplant recipients who underwent serial color Doppler sonographic evaluations of the hepatic arteries after surgery. Patients with abnormal sonographic findings underwent subsequent angiography.

RESULTS

Eighteen subjects experienced 20 hepatic arterial complications (13 thromboses and 7 stenoses). In 7 of the 13 thrombosis incidents, hepatic arterial obstruction occurred within a month of surgery and was evident from the absence of Doppler signals; angiography confirmed the absence of hepatic arterial perfusion in these cases. In the other 6 thrombosis cases, the thrombosis developed 3 or more months after surgery and became apparent from the absence of color Doppler signals at the level of the main arterial trunk and the presence of intraparenchymal "tardus parvus" waveforms. In these cases, angiography showed obstruction of the main arterial trunk and the development of compensatory collateral vessels. In 3 of the 7 cases of stenosis, high flow velocities were recorded at the site of the narrowing, and intrahepatic tardus parvus waveforms were present. In the other 4 stenosis cases, the site of stenosis could not be identified, but intraparenchymal tardus parvus waveforms were recorded.

CONCLUSION

The use of color Doppler sonography allows the early diagnosis of hepatic arterial complications after liver transplantation. Tardus parvus waveforms indicated severe impairment of hepatic arterial perfusion, from either thrombosis or severe stenosis. The presence of these waveforms enhanced the accuracy of color Doppler diagnosis (100% positive predictive value), and their detection should prompt angiography.