A 29yr old girl has an ultrasound scan which reveals a focal liver lesion. The lesion is ill defined and hypoechoic, measuring 2.2cm x 1.5cm. The radiologist then performed a contrast enhanced ultrasound to further characterise the lesion. Which of the following findings would best support a diagnosis of Focal Nodular Hyperplasia (FNH)?
Prominent arterial centrifugal filling | |
Washout of contrast in the portal venous phase | |
Early contrast enhancement around the periphery of the lesion | |
Prominent arterial centripetal filling | |
Heterogeneous enhancement in the delayed phase |
Although contrast enhanced ultrasound may not currently be widely used, the principles of the enhancement patterns still apply. FNH is usually discovered incidentally, and is thought to represent benign proliferation of normal hepatocytes around a pre-existing AVM. This means that the lesion gets its blood supply from the hepatic artery, and therefore demonstrates arterial enhancement. This enhancement is classically centrifugal (from centre to periphery), starting within a central scar and radiating outwards through stellate arteries. There is often homogenous sustained enhancement of the mass in the portal venous phase (which on CT makes the lesion look isodense in the portal venous phase.) In young patients the differential is often that of an adenoma. Centripetal or mixed arterial enhancement is more common in adenoma. Adenomas also have a more mixed appearance in the portal venous phase, and can washout or show sustained enhancement.