American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What characterizes the portal vein contrast enhancement in FNH?

1. Normal washout

2. Delayed enhancement

3. Hypodense appearance

4. Rapid washout

The correct answer is: Normal washout

The portal vein contrast enhancement in focal nodular hyperplasia (FNH) is characterized by normal washout, which means that the contrast material remains visible in the lesion for a duration that is consistent with normal hepatic tissue. This occurs because FNH is a vascular lesion that contains a mixture of normal hepatocytes, bile duct elements, and a central scar, which all contribute to a typical perfusion pattern. During imaging, particularly with CT or MRI after the administration of contrast, the enhancement seen within FNH tends to mirror that of surrounding liver tissue. This is indicative of its unique vascular structure, allowing for normal blood flow and perfusion characteristics. It is essential to distinguish these features in FNH from other hepatic lesions, where abnormal washout patterns may suggest malignancy or other pathologies. In contrast, other options, such as delayed enhancement or rapid washout, point towards different pathological processes typically associated with other types of liver lesions, making them not applicable to FNH. A hypodense appearance can be observed in certain conditions but does not characterize the vascular enhancement pattern seen with FNH in imaging studies. Hence, recognizing normal washout as the key characteristic helps differentiate FNH from other liver abnormalities during evaluations.