Most are hypovascular and best seen in the portal venous phase; hypervascular ones (neuroendocrine, renal, melanoma, thyroid) need an arterial phase; MRI with DWI and hepatobiliary contrast finds the small ones that change resection plans.
Orient first
- Colorectal liver metastases are often resected or ablated — count and segment location matter.
- Small hypodensities under 10 mm are usually benign in patients without cancer but not in those with it.
- After chemotherapy, lesions can "disappear" on CT and persist microscopically.
Acquire the study
- Portal venous phase CT (arterial phase added for hypervascular primaries), ≤ 3 mm reconstructions.
The manoeuvre
- Portal venous phase: hypoattenuating lesions with rim enhancement; count and Couinaud segment.
- Arterial phase for hypervascular primaries.
- Largest lesion size in mm; relation to hepatic and portal veins.
- Extrahepatic disease: nodes, peritoneum, lung.
What confirms it
- Multiple lesions with typical features in a patient with a known primary; biopsy when a single lesion would change management.
What licenses you to exclude it
- A normal liver on MRI with DWI and hepatobiliary phase excludes metastases over a few millimetres.
The classic misread
- Calling small cysts metastases or the reverse — MRI with T2 and DWI settles it.
- Missing hypervascular metastases on a portal-only CT.