Evaluation of the Efficacy of Contrast Enhanced Ultrasound Compared to MRI for Differentiation of Hepatic Lesions

Hepatic imaging plays an important role in identifying and differentiating both benign and malignant neoplasms of the liver. One of the clinical and radiologic dilemmas facing hepatic medicine is the accurate differentiation of focal nodular hyperplasia (FNH) and hepatic adenoma (HA). This is a question of some import, as there are significant prognosis and treatment differences between these entities, as well as overlap in the patient populations in whom they occur.

FNH is the second most common benign neoplasm of the liver, with a strong female predilection. These lesions are usually asymptomatic and incidentally discovered, and carry only a small risk of complication such as bleeding. There is no malignant potential. Hepatic adenomas (HAs) are more rare benign neoplasms that also have a female predilection. However, these lesions are more likely to be symptomatic, and carry a higher bleeding risk especially as they grow over 4 cm. In addition, they harbor a small risk of malignant transformation to hepatocellular carcinoma (HCC). Of note, patients may present with both types of lesion concurrently.

Currently, MRI with hepatobiliary contrast agents is the standard for differentiation of these lesions. These agents (such as gadoxetate disodium, or Eovist) are actively transported into hepatocytes, which are present in FNH and only in very rare cases with HA. Previous research (such as from Grazioli et al.) has shown that hepatobiliary agents can differentiate these lesions with excellent accuracy. However, there is still overlap between these lesions on imaging, and for certain patients MRI may be difficult or impossible.

FDA approval of contrast enhanced ultrasound (CEUS) agents in 2016 has opened a new avenue for abdominal imaging. CEUS utilizes gas containing lipid microbubbles to provide pure intravascular contrast, allowing for evaluation of vascular and solid organ perfusion. It has an excellent safety profile and is not excreted by the kidneys, allowing for use in patients with acute and chronic renal disease. It has been used for some time outside of the US for liver lesion evaluation, and the enhancement patterns of both FNH and HA have been described in the literature by Kim et al. as having different appearances. CEUS can be especially useful for focal liver lesion imaging for patients who cannot or will not undergo MRI, and it has the advantages of flexibility, increased temporal resolution, and decreased cost. This study aims to compare the utility of CEUS for differentiating FNH and HA with the current standard of hepatobiliary contrast MRI.