Indeterminate Observations (Liver Imaging Reporting and Data System Category 3) on MRI in the Cirrhotic Liver: Fate and Clinical Implications

OBJECTIVE. The purpose of this article is to retrospectively evaluate the imaging characteristics and outcomes of indeterminate observations (Liver Imaging Reporting and Data System category 3) detected on MRI in patients with cirrhosis. MATERIALS AND METHODS. Sixty-nine indeterminate observations in 52 patients with cirrhosis were imaged with hepatobiliary contrast agent-enhanced MRI. Observations were evaluated retrospectively in terms of the location, size, enhancement pattern, and follow-up results. Each observation was categorized as stable or progressed observations according to serial follow-up MRI. RESULTS. The mean follow-up interval was 11.2 months. Forty-six (67%) of the total observations showed arterial enhancement, and 23 (33%) observations showed isointense signal or low signal intensity on arterial phase. The indeterminate observations were classified as arterial enhancement with fade-out appearance (41 observations [59%]), arterial enhancement with washout appearance (five observations [7%]), and nonhyperenhancing observations (23 observations [33%]). Two of 69 observations (3%) were hyperintense on T2-weighted images, and four of 55 observations (7%) were hyperintense on hepatocellular phase. On the final follow-up MRI examinations, four (6%) observations proved to be probable or definite hepatocellular carcinoma, 55 (80%) remained stable, and 10 (14%) decreased in size or were no longer visible. CONCLUSION. The most common cause of indeterminate observations on MRI is hypervascular pseudolesions that were clinically stable on follow-up imaging.