How an unexpected anomaly on an X-ray or scan can lead to unnecessary treatment

No medical investigation is 100 per cent accurate

You go to your GP with low back pain. She organises an MRI scan to check if you have a slipped spinal disc. Your spine is fine, but the radiologist notices an abnormality in one of your ovaries. A surgeon then decides to operate to remove your ovary. However, you develop postoperative bleeding and are admitted to ICU. Meanwhile pathological examination of your ovary finds it is completely normal.

A nightmare? Yes.

Common? No – but such scenarios are on the increase.

This is an example of how an incidental finding on an X-ray or scan can lead to unnecessary treatment and further harm. Commonly known as an incidentaloma, these are unanticipated findings which are not related to the original reason for the test.


A major review of the increasing number of incidentalomas occurring in medical practice, published in the British Medical Journal, defines an incidentaloma as something a radiologist spots on an imaging test while looking for something else, either because the patient’s symptoms were unrelated, or because the patient had no symptoms at all.

The researchers from University of Oxford and Stanford University have reviewed hundreds of studies to learn how often incidental abnormal findings from imaging tests are found, how often those turn out to be malignant tumours, and how often they turn out to be harmless.

The demand for imaging tests – including PET scans, CT scans, and MRIs – has increased at the same time the tests have become more advanced, and better able to detect any abnormalities. This has led to an increase in finding incidentalomas.

Categorised by imaging test, researchers found the highest rate of incidentalomas was in chest CAT scans (45 per cent) followed by colonoscopy CAT scan at 38 per cent and cardiac MRI (34 per cent). MRI scans of the brain and spine both had incidentaloma rates of 22 per cent.

Patient anxiety

The frequency of cancerous tumours found in incidentalomas varied by body part. The highest percentage occurred in the breast (42 per cent), followed by ovaries, thyroid, and kidney, where cancer was found about 25 per cent of the time. Colon and prostate incidentalomas were malignant 10-20 per cent of the time. Meanwhile, cancer was rarely found in incidentalomas of the brain, salivary gland, and adrenal gland.

Risks associated with incidentalomas include patient anxiety as well as the potential for more testing and treatment. Additional procedures are costly and put more strain on the medical system. And the risk of unnecessary harm constantly hovers in the background.

Doctors speaking to Pulse magazine in Britain say there is no sense of there being a handle on the incidenataloma problem. And it has led to some interesting acronyms: SPEW refers to “scans propagating exponential workload”; while if you are a patient you do not want to become a “victim of modern imaging technology” (VOMIT).


It’s a difficult problem to resolve. Even though most unexpected anomalies are unlikely to be clinically relevant, it is natural for the doctor and patient to want to evaluate them further if both are unwilling to accept the uncertainty that often surrounds the diagnosis.

It has to be said that, occasionally, such a discovery can be beneficial and even life saving. But if doctors are to honour the ethical maxim of primum non nocere (first do no harm), they need to start thinking of unexpected anomalies as side effects of medical imaging, and seek fully informed consent before going ahead.

To do this effectively and rigorously will require the collection of more data of the standard produced by the authors of the BMJ paper. And an updated definition of incidentaloma such as “those findings that are discovered by chance which can potentially affect the health of an individual”, may be needed.

Of course the topic is yet another reminder that, as we are discovering via the ongoing CervicalCheck controversy, no medical investigation is 100 per cent accurate.