Ultrasound Misdiagnosis — Why It Happens and How to Reduce the Risk
Ultrasound is operator-dependent in a way no other common scan is. That single fact explains most of what can go wrong — and most of what you can do about it.
Every diagnostic test has limits, and a clinic that pretends otherwise is not being straight with you. Ultrasound is accurate and safe, and for many questions it is the best first test available — but it is not infallible, and its accuracy varies more with who is holding the probe than with almost any other factor.
That is worth understanding before you book anything, anywhere. It shapes what you should ask, what a good report looks like, and when it is reasonable to seek another opinion.
Why ultrasound is different from CT and MRI
A CT or MRI scanner acquires a complete dataset of a region regardless of who presses the button. A radiologist later reviews those images, and if something was missed it can be found on review, because the images exist.
Ultrasound does not work like that. The image is created in real time by a person moving a probe, choosing angles, adjusting settings, and deciding what to record. If a structure is never brought into view, it is not on the images, and no amount of later review will recover it. The examination and the interpretation happen simultaneously, in the same head, in the room.
This is why operator training and experience matter so much, and why the professional bodies — the British Medical Ultrasound Society and the Society of Radiographers — have long argued for statutory regulation of sonographers, a title that remains legally unprotected in the UK. Our guide to unregulated scan clinics covers what that means in practice.
What actually affects accuracy
| Factor | How it affects the scan |
|---|---|
| Operator skill and experience | The largest single variable — knowing where to look, recognising subtle appearances, and knowing when the view obtained is not good enough |
| The question being asked | A scan looking for gallstones is performed differently from one assessing the pancreas. A vague or missing clinical question produces a vague examination |
| Body habitus | Sound weakens as it travels through tissue, so deeper structures are harder to resolve in larger patients — a physics limitation, not a judgement |
| Bowel gas | Sound cannot pass through gas. Overlying bowel can hide the pancreas, aorta or an ovary entirely on a given day |
| Preparation | Not fasting for an abdominal scan, or an empty bladder for a pelvic one, can make a diagnostic scan non-diagnostic |
| Scarring and previous surgery | Alters anatomy and reflects sound unpredictably |
| Equipment and settings | Matters, but far less than the operator. A skilled sonographer on modest equipment outperforms the reverse |
Four different things people mean by “misdiagnosis”
1. A missed finding. Something was present and not seen — because it was obscured, outside the area examined, too small to resolve, or simply not looked for. Some conditions are inherently difficult on ultrasound: early ovarian cancer is a recognised example, which is precisely why a normal scan is not treated as an all-clear when symptoms persist.
2. A false alarm. Something normal reported as abnormal. This is not harmless — it leads to further tests, sometimes biopsies, and genuine and lasting anxiety. Being told to come back in three months for something that turns out to be nothing has a cost that rarely gets counted.
3. Misinterpretation. The finding is seen correctly but read wrongly — a normal variant called pathology, or a measurement interpreted without the context that gives it meaning, such as reading an endometrial thickness without knowing the cycle day.
4. An incomplete examination reported as complete. Arguably the most dangerous, because it reads as reassurance. If bowel gas hid the pancreas, the report must say so. A report that quietly omits what could not be seen invites everyone to assume it was seen and was normal.
Overdiagnosis — finding things that were never going to matter
Not every error is a miss. Modern ultrasound resolves small structures very well, and it therefore finds a great many things that would never have caused a symptom in a lifetime — small thyroid nodules, simple kidney cysts, benign liver lesions, incidental findings of every kind.
Detecting them is not a triumph in itself. Each one can trigger follow-up scanning, referral, sometimes biopsy, and a period of worry — for a finding that was never a threat. This is the core argument against scanning without a clinical question, and it is why we decline to sell whole-body screening to people with no symptoms and no risk factors, as our guide to preventative screening sets out.
A good report handles incidental findings proportionately: describing them, saying plainly when something needs no action, and reserving follow-up recommendations for findings that genuinely warrant them.
Five things that genuinely improve your scan
- 1
Follow the preparation exactlyFour hours fasting for abdominal scans, a full bladder for abdominal pelvic scans. It is not bureaucracy — it is the difference between a diagnostic and a non-diagnostic examination.
- 2
Say what your symptom actually isWhere the pain is, how long it has been there, what makes it worse, what your GP is worried about. A sonographer told “left-sided pain for three months, worse after eating” scans differently from one told “abdominal scan”.
- 3
Mention previous scans, surgery and conditionsComparison with a previous scan is often more informative than any single examination, and knowing about previous surgery explains appearances that would otherwise puzzle.
- 4
Ask what could not be seenA fair and useful question, and a good clinic will answer it directly. If part of the examination was limited, you want to know rather than assume everything was checked.
- 5
Do not treat a normal scan as an all-clear if symptoms persistThe single most important point on this page. A normal ultrasound reduces the likelihood of certain conditions; it does not exclude everything. Persistent or worsening symptoms warrant going back to your GP regardless.
What we do about it — and what you can verify
Rather than assert that we do not make mistakes, here is what is checkable. Scans are performed by HCPC-registered sonographers whose registration numbers we publish — Yianni Kiromitis RA38415 and Tareq Ismail RA42614 — both of whom also work within London NHS trusts. We are a CQC-registered diagnostic imaging provider, Provider ID 1-2775844974.
On reports specifically: we state what was examined, we state what could not be adequately assessed and why, and we say when a different test is the one that will actually answer the question. Where a finding needs onward care, the report says so plainly rather than leaving you to interpret a hedge.
Your questions answered
How accurate is ultrasound?
Can an ultrasound miss something serious?
Should I get a second opinion on a scan?
Does more expensive equipment mean a more accurate scan?
What should a good ultrasound report contain?
What if I think my scan was wrong?
Choosing well
The checks that separate a verifiable clinic from a plausible one.
Read the checklist →
ReportsUnderstanding Your ReportHow reports are structured, and the phrases that signal a limitation.
Read the guide →
ModalityUltrasound vs MRI vs CTWhen ultrasound is the wrong test, and which one is right.
Read the guide →
Scanned by named, registered sonographers
HCPC registration numbers published, CQC-registered clinic, findings explained on screen, and a written report usually within two hours that states its own limitations.
Kensington, London W8 4ED
3 mins from Notting Hill Gate
Professional positions on sonographer regulation and prudent use are those of the British Medical Ultrasound Society and the Society of Radiographers. Our CQC registration can be verified at provider 1-2775844974. This article is general information, not individual medical advice — concerns about a specific scan should be raised with your GP, who can arrange review or further imaging.
Written and clinically reviewed by the HCPC-registered sonographers who perform this scan at IUS London — a CQC-registered diagnostic ultrasound clinic (Provider ID 1-2775844974). Your own findings are explained to you at the scan and set out in your report.
Author: Yianni Kiromitis, Senior Sonographer, HCPC RA38415
Medically reviewed: 1 August 2026
