Management of Hypodense Liver Lesions

Initial Risk Stratification

The American College of Radiology recommends categorizing patients into one of three clinical contexts to determine the diagnostic pathway, with normal liver, no known malignancy, having a high likelihood of benign lesions such as hemangioma, cysts, and focal nodular hyperplasia, occurring in up to 15% of the general population 1, 3
In patients with known chronic liver disease or cirrhosis, hepatocellular carcinoma (HCC) becomes the primary concern, particularly for lesions ≥10 mm, with a high probability of HCC if AFP is elevated and the lesion is >2 cm in a cirrhotic liver 1, 4, 8
In patients with known extrahepatic malignancy, metastatic disease must be excluded, though benign lesions still occur in nearly 30% of cancer patients 3

For indeterminate lesions >1 cm discovered on ultrasound, noncontrast CT, or single-phase CT, in patients with normal liver and no known malignancy, the American College of Radiology recommends proceeding with either multiphase contrast-enhanced CT, MRI with and without IV contrast, or contrast-enhanced ultrasound (CEUS) as equivalent first-line options 1, 5, 6
Multiphase CT should include arterial and portal venous phases at minimum, with 2.5-5 mm slice thickness for optimal lesion characterization, and MRI with gadolinium differentiates between common benign lesions in 70% of cases 1, 3
CEUS reaches a specific diagnosis in 83% of indeterminate lesions and distinguishes benign from malignant in 90% of cases, correctly characterizing 90% of hemangiomas and 90% of focal nodular hyperplasia 1, 4

MRI with and without IV contrast or multiphase contrast-enhanced CT is appropriate, with FDG-PET/CT as an additional equivalent option when the lesion was initially found on noncontrast or single-phase imaging, to distinguish metastases from benign lesions in oncology patients 1, 4, 7
For subcentimeter lesions that appear noncystic on grayscale ultrasound, CEUS correctly characterizes 95% of lesions overall and 98% of metastases 2, 4

The Liver Imaging Reporting and Data System (LI-RADS) algorithm using either MRI with and without IV contrast, multiphase contrast-enhanced CT, or CEUS is recommended, with triple-phase contrast CT (arterial, portal venous, delayed) being the preferred option 1, 4, 8
Lesions ≥10 mm are required for definitive HCC diagnosis by imaging alone, and if AFP is elevated and the lesion is >2 cm in a cirrhotic liver, there is >95% probability of HCC, and further imaging is primarily for treatment planning rather than diagnosis 1, 2, 8

For lesions <1 cm in patients with known malignancy, MRI with and without IV contrast is the preferred modality, and for lesions <1 cm in chronic liver disease, either MRI with and without IV contrast or multiphase contrast-enhanced CT is appropriate 1, 5, 9
In cirrhotic patients, lesions <10 mm cannot be definitively diagnosed as HCC by imaging criteria and require surveillance 1, 2

Tc-99m sulfur colloid scans have no role in the modern evaluation of indeterminate liver lesions, according to the American College of Radiology 1, 2, 4