What it means
CT shows tissues in shades of gray according to how much they block X-rays. Dense things like bone look white. Less dense things like fluid, fat, air and swollen tissue look darker. Hypodense simply says a spot is darker than what surrounds it. It describes how the area looks, not what it is.
When it matters
Many hypodense spots are harmless, such as simple cysts or small areas of fat. The radiologist narrows it down using the exact density in Hounsfield units, the shape and edges, and how the area changes after contrast. A spot that looks solid gets a closer look. Some spots are too small to characterize, meaning too small to tell what they are. These are often compared with older scans or checked again later.
Questions to ask your doctor
- Does the density suggest fluid, fat or solid tissue?
- Is it too small to characterize, and does it need a follow-up scan?
- Do I have older scans it could be compared with?
