CT with Contrast for Hepatomegaly
For patients presenting with hepatomegaly, ultrasound is the recommended initial imaging modality, not CT with contrast. 1 If advanced imaging is needed after ultrasound, MRI with and without IV contrast is superior to CT for liver characterization and receives higher appropriateness ratings from the American College of Radiology. 1, 2
Initial Imaging Approach
Abdominal ultrasound should be performed first as it is noninvasive, widely available, and provides excellent diagnostic accuracy for evaluating hepatomegaly and identifying underlying causes such as fatty liver, cirrhosis, focal lesions, and biliary abnormalities. 1
Ultrasound can be enhanced with acoustic radiation force impulse (ARFI) elastography to simultaneously assess for liver fibrosis if chronic liver disease is suspected. 2
When CT with Contrast May Be Appropriate
If CT imaging is necessary (when MRI is contraindicated or unavailable), specific technical requirements must be met:
Order multiphase contrast-enhanced CT (triphasic protocol) including arterial phase, portal venous phase, and delayed venous phase—never single-phase CT. 1, 2
Triphasic CT achieves diagnostic accuracy of 95.5% compared to only 74-95% for standard single-phase contrast CT. 2
Use slice thickness of 2.5-5 mm for adequate lesion detection. 2
CT with IV contrast can identify complications of hepatomegaly including ischemic hepatitis, portal hypertension sequelae (ascites, collateral vessels), acute hepatitis findings (periportal edema, gallbladder wall thickening), and hepatic congestion. 3
Why MRI Is Preferred Over CT
MRI with and without IV contrast receives a rating of 6 out of 9 from the American College of Radiology for chronic liver disease assessment, compared to only 5 out of 9 for CT with contrast. 2
MRI establishes a definitive diagnosis in 95% of liver lesions, significantly higher than CT's 74-95% accuracy. 3, 1, 2
MRI with hepatobiliary contrast agents (gadoxetate) can be performed with MR elastography to simultaneously assess fibrosis and characterize focal lesions. 1, 2
MRI has superior soft tissue contrast resolution and can detect hepatic fat content as low as 5% with sensitivity of 76.7%-90.0% and specificity of 87.1%-91%. 3
Critical Pitfalls to Avoid
Never order CT without contrast alone—it receives only a 4 out of 9 appropriateness rating and has minimal diagnostic value for liver characterization. 2
Never order CT with and without contrast—the unenhanced phase adds no diagnostic value for hepatomegaly evaluation and doubles radiation exposure. 1, 2
CT without contrast can only detect moderate hepatic steatosis (≥30% fat content) and misses early fatty infiltration, making it inadequate for initial hepatomegaly workup. 3
Single-phase contrast CT is insufficient; if using CT, always obtain multiphase imaging with proper arterial and portal venous phase timing. 2
Clinical Context Modifications
For suspected hepatocellular carcinoma in cirrhotic patients with hepatomegaly:
Multiphase contrast-enhanced CT using Liver Imaging Reporting and Data System (LI-RADS) criteria is appropriate for lesions ≥10 mm. 4
Classic arterial enhancement with delayed washout on a single imaging modality is diagnostic for HCC in lesions >2 cm. 3
For suspected biliary complications causing hepatomegaly:
- Magnetic resonance cholangiopancreatography (MRCP) is superior to CT for detecting biliary tree abnormalities, choledocholithiasis, and biliary strictures. 1
For known extrahepatic malignancy with hepatomegaly:
- Either multiphase CT or MRI with contrast is appropriate to distinguish metastases from benign lesions, with FDG-PET/CT as an additional option. 4