Indeterminate

What it means

Radiology is built on pattern recognition. Most findings line up with a typical look — a simple cyst behaves one way, a benign growth another, a suspicious area another. When a finding doesn't quite match any of the familiar patterns, the radiologist refuses to guess and uses this word instead. It is a statement of honest uncertainty: "I see something, I can't tell you exactly what it is from this scan alone."

Why it appears on a CT or MRI report

Common reasons include a finding that is too small for the scanner to characterise reliably, a feature missing that would normally settle the question (no prior scan to compare against, no contrast given, motion blur on the image), or an appearance that overlaps between benign and worrying categories. The report will usually pair the word with a recommendation: a follow-up scan at a specific interval, a different type of scan, or sometimes a biopsy. Standardised systems like LI-RADS for the liver, PI-RADS for the prostate, or Bosniak for kidney cysts include a category for these in-between findings precisely because they are so common.

What it usually means

The word causes more alarm than it should. In statistical terms, most findings labelled this way turn out to be benign once the follow-up is done — the radiologist is being cautious, not pessimistic. The point of the follow-up scan is to see whether something changes. Benign findings tend to stay the same size and appearance over time. Concerning ones tend to grow, change shape, or develop new features. A few months of waiting feels uncomfortable, but for most findings in this category that interval is safe and is the standard of care. Why not just biopsy everything to be sure? Because biopsies carry their own risks, many tiny findings aren't even reachable with a needle, and the time-based approach catches the rare changing finding while sparing thousands of people unnecessary procedures. Specialised scans with different settings, contrast given in different timing, or PET-CT can also help sort the uncertain cases without needing tissue.

When to follow up

Take the recommendation seriously and book the follow-up at the suggested interval. Don't bring it forward by months out of anxiety — the interval is set so that meaningful change has time to become visible, and a scan done too early may simply repeat the uncertainty. Don't push it later either; follow-ups exist to catch the rare changing finding while it is still small. Talk to your doctor about what the result of the follow-up will mean, so the next conversation feels less open-ended.

A plain-language way to picture it

Imagine a friend texts you a blurry photo of an animal in their garden and asks what it is. You can see something, but the photo doesn't show enough detail to say whether it's a cat, a fox, or someone's small dog. You ask them to send a clearer photo tomorrow rather than guessing. That second photo is what the follow-up scan does — same animal, better light, and usually the answer becomes obvious.