Imaging of Vascular Complication After Liver Transplantation

Introduction

A liver transplant is a standard treatment option for end-stage liver disease, both acute and chronic. Liver transplantation can be from a living donor or a cadaver. There is a risk of mortality within six months of the transplant. Vascular complications are a diagnostic sign in liver transplantation patients. Hepatic artery thrombosis is a common complication that leads to liver transplantation failure and an increasing need for retransplantation. Angiography is a choice of imaging study in liver transplant patients.

What Is the Complication for Liver Transplantation?

Orthotopic liver transplantation is a preferred technique. The graft is placed in the right upper quadrant in the anatomical liver location after surgical resection of the diseased liver. Anastomosis is an area where complications develop. The four anastomoses must be carefully examined:

1. Portal vein.

2. Bile duct.

3. Anastomosis of recipient inferior vena cava to donor hepatic veins.

4. Anastomosis of the hepatic artery.

Complications associated with liver transplantation are as follows:

• Increased risk potential for acquiring infections.

• Graft rejection or failure.

• Biliary conditions like hepatitis or cirrhosis.

• Chance of developing some cancer types or malignancies.

What Are the Clinical Manifestations of Post-liver Transplantation?

• Right-sided pleural effusion (fluid build-up between tissue in lung and chest).

• Ascites (excess abdominal fluid).

• Perihepatic hematoma.

• Periportal edema.

The findings were resolved within a week of transplantation.

What Are the Imaging Options for Vascular Complications After Liver Transplantation?

The clinical symptoms of liver transplantation complications are subtle and non-specific. Therefore, radiographic imaging plays a role in early diagnosis and treatment establishment.

• Color Doppler Ultrasound: They enable early detection of complications and evaluate graft vessel patency. It has high sensitivity and specificity to detect thrombus and grade stenosis in the hepatic artery and intrahepatic branches. If vascular abnormalities appear in Doppler imaging, further imaging is necessary to identify surgical anatomy in patients with diminishing clinical status.

• Computed Tomography- CT angiography can evaluate difficult cases with high accuracy in a short time with minimal patient compliance.

• Magnetic Resonance Imaging (MRI) - This imaging method helps detect vascular abnormalities seen in liver tissue.

• Diagnostic Arteriography- It can confirm thrombosis diagnosis and facilitate treatment planning.

• Hepatic Intra-Operative Ultrasonography- It can evaluate anastomosis in real-time, enabling immediate treatment.

What Are the Guidelines for Radiographic Imaging?

• Doppler study is done 24 to 48 hours, 7 hours, 1st month and 3rd-month post-surgery. The vascular and biliary anastomosis must be examined.

• Contrast-enhanced CT is done when vascular complications are seen in a Doppler study along with impaired liver function.

• MRI is done if the use of contrast CT is contraindicated.

• T-tube cholangiography with opacification on the 4th day and 3rd-month post-surgery help evaluate the biliary tree.

What Are the Vascular Complications After Liver Transplantation?

Vascular complications after liver transplantation are less common and seen in 7 percent of cadaveric transplantations and 13 percent of living donor transplantation. The complications appear early after surgery and can cause transplant rejection or mortality.

• The hepatic artery can exhibit complete or branch artery occlusion, stenosis, pseudoaneurysm, or anastomosis.

• The portal vein undergoes occlusion or stenosis.

• Pseudoaneurysm.

• Dissecting aneurysm.

• Mycotic aneurysms.

• Inferior vena cava occlusion.

Hepatic Artery Complications.

Hepatic artery thrombosis presents in three forms- Massive hepatic necrosis, delayed biliary leak, and intermittent episodes of sepsis. The evaluation of the patient with CT or sonography reveals bilomas (excess bile in the abdominal cavity), abscesses, or infarcts (tissue death due to ischemia) that suggest arterial occlusion.

• Hepatic artery thrombosis is the most serious complication resulting in a nonfunctional liver transplant.

• It is diagnosed five days to three months after transplantation.

• Patients with complete occlusion require immediate retransplantation.

• Some patients develop hepatopetal arterial collaterals (blood flow toward the liver).

• Intraarterial thrombolytic therapy is beneficial in mild hepatic artery occlusion.

• Intrahepatic biloma, if developed, is treated with percutaneous drainage.

• The biliary-portal vein fistula is resolved with conservative treatment.

Stenosis

• It may progress to thrombosis.

• They may cause splenic steal artery syndrome.

• The stenosis presentation varies on the patient's condition but is often seen within three months post-transplantation.

• Doppler study is useful for evaluation.

• Power Doppler study shows.

  • Prestenotic segment with increased resistance and low flow.

  • The stenotic segment has high flow and distorted (aliasing) artifacts due to turbulent flow.

  • The post-stenotic segment has low resistance, weak pulse in a spectral curve, and long systolic acceleration time. Turbulent flow is present.

• CT examination is done in patients with poor sonographic visibility.

• MRI angiography may be used but yield false positivity.

Pseudo Aneurysms

• Patients complaining of back pain when examined with CT revealed an aneurysm that was later confirmed by angiography as a pseudoaneurysm. It is a rare complication.

• Pseudoaneurysm appears as a hypoechoic (area that is more solid than usual in ultrasound) structure with turbulent flow in ultrasound. Yin- Yan sign appears due to a swirl of blood formed by the inlet and blood outlet.

• The aneurysms can be extrahepatic or intrahepatic.

• Extrahepatic aneurysm appears at the site of arterial anastomosis. The appearance is spontaneous or as a complication of pre-existing stenosis. The aneurysm shows the presence of bacterial or fungal infection in most cases.

• Intrahepatic pseudoaneurysms are a complication of liver biopsy or secondary to bile duct infections. If aneurysms rupture, fistula formation is seen.

Ischemia or Liver Infarction.

• It is an uncommon complication due to the high vascularization of the liver.

• Post transplantation, blood flow stops due to artery or portal vein occlusion by thrombosis, stenosis, or pseudoaneurysm.

• CT examination in some patients revealed right lobe infarction and may require lobectomy.

Portal Vein Complications.

• It is an uncommon condition occurring in less than 2 percent of liver transplants.

• The donor's portal vein is anastomosed with the recipient in most of the surgery.

• If portal vein thrombosis is present, the anastomosis is difficult and requires bypass with a donor iliac vein.

• The thrombosis is demonstrated with the absence of color Doppler imaging.

• Portal vein thrombosis can cause portal hypertension and massive gastroesophageal varices. The condition is treated with retransplantation.

• Hepatopetal venous collaterals in patients are treated by endoscopic esophageal sclerotherapy.

• Portal hypertension require splenorenal shunt.

• Portal vein stenosis with anastomosis present with upper gastrointestinal bleeding from varices.

Other Complications.

• Intrahepatic hematoma.

• In rare instances, aneurysms in pancreaticoduodenal arterial collaterals.

• Hepatic artery-portal vein fistula secondary to needle biopsy may occur.

• Bilateral external iliac thrombosis demonstrated by angiography was caused by femoral catheter indwelling.

• Inferior vena cava thrombosis and portal vein occlusion.

• Central venous endo phlebitis (vein inflammation) with necrosis and occlusion may occur.

What Is the Procedure for Angiographic Study in Liver Transplantation Patients?

• Patients are mildly sedated, and patients below 12 years require general anesthesia.

• The femoral artery is used for angiographic studies. In rare instances, the left axillary artery may be used.

What Are the Treatment Options for Vascular Complication After Liver Transplantations?

In patients with hepatic thrombosis, the following procedures are done:

1. Intra-arterial thrombolysis.

2. Percutaneous transluminal angioplasty.

3. Stent placement.

4. Retransplantation is a last resort when other treatment options fail.

In patients with hepatic stenosis, angioplasty may be done. Retransplantation is indicated if angioplasty fails.

Pseudoaneurysms are treated with coil embolization and stent placement to prevent blood inflow. Surgical resection is a last resort.

Conclusion

Angiography has revealed hepatic artery thrombosis most frequently. The arterial lesions formed after liver transplant rejection are more evident in medium-sized hepatic vessels. Chronic rejection presents the deposition of foam cells (a type of cell that contains cholesterol), myo-intimal hyperplasia (smooth muscle disorder), and intimal sclerosis (hardening of body tissue due to excessive growth of connective tissue) that results in progressive arterial narrowing and thrombosis. The occlusion can cause ischemia and necrosis of the graft. Patients require immediate retransplantation to increase survivability.