MRI with Contrast is the Preferred Next Step for Nodular Liver on Ultrasound
Order multiphasic contrast-enhanced MRI as the preferred imaging modality to definitively characterize the liver parenchyma and detect any focal lesions that may be obscured by the nodular contour. 1 If MRI is contraindicated or unavailable, multiphasic CT is an acceptable alternative. 1
Immediate Workup Alongside Imaging
While arranging cross-sectional imaging, obtain:
- Liver function tests, complete blood count, and AFP level to assess for underlying liver disease and HCC risk 1
- Screening for chronic liver disease etiologies including hepatitis B and C serology, alcohol use history, and metabolic syndrome components 1
Why MRI Over CT
MRI with hepatobiliary contrast agent (gadoxetic acid) provides superior tissue characterization compared to CT, establishing a definitive diagnosis in up to 95% of liver lesions. 2 This is particularly important because:
- MRI better differentiates regenerative nodules from dysplastic or malignant nodules 3
- Hepatobiliary phase imaging helps characterize nodules that may appear similar on arterial and portal venous phases 3
- MRI avoids radiation exposure, which is relevant if serial surveillance becomes necessary 1
Risk Stratification Based on Results
If MRI/CT confirms cirrhosis or advanced fibrosis:
- Initiate HCC surveillance protocol immediately with ultrasound every 6 months 1
- Add AFP measurement to each surveillance ultrasound, as AFP ≥10 ng/dL increases HCC likelihood 26-fold in at-risk patients 1
Any nodule ≥1 cm detected requires immediate characterization with the multiphasic imaging to assess for typical HCC features (arterial hyperenhancement with portal venous washout). 1, 3
Common Pitfalls to Avoid
Do not rely on ultrasound alone for characterization. Ultrasound has lower sensitivity than CT/MRI for detecting liver nodules, particularly in patients with underlying liver disease. 4 The nodular appearance itself indicates the need for cross-sectional imaging regardless of whether discrete nodules are visible. 1
Do not assume all nodules are malignant. In cirrhotic livers, more than 20% of nodules are regenerative macronodules rather than HCC. 5 However, the approach should be to consider any nodule in a cirrhotic liver as potentially HCC until proven otherwise. 6
Be aware that standard LI-RADS criteria may not apply in certain contexts. In conditions like Fontan-associated liver disease, portal venous washout can occur in benign FNH-like nodules due to inherent congestion, potentially overestimating malignancy risk. 3 In such cases, nodules >10 mm with irregular contours or rapid growth require biopsy for definitive diagnosis. 3
Special Considerations for Nodule Size
For nodules <1 cm: Follow with ultrasound at 3-6 month intervals if detected during surveillance. 3 However, if the nodular liver contour itself is the primary finding without discrete nodules, proceed directly to MRI/CT for comprehensive evaluation. 1
For nodules 1-2 cm: Two dynamic imaging studies showing typical HCC features (arterial hypervascularity with washout) allow diagnosis without biopsy. 3
For nodules >2 cm: A single dynamic imaging study showing typical HCC features is sufficient for diagnosis without biopsy. 3