Incidentaloma, cascade and overdiagnosis
Expansion
Incidental findings are common and rise with imaging resolution: adrenal nodules in around 4 per cent of abdominal CTs, thyroid nodules in up to half of neck ultrasounds, pulmonary nodules in a substantial proportion of chest CTs, and renal, hepatic and pituitary lesions frequently. The great majority are benign and inconsequential.
The cascade effect: an incidental finding leads to a follow-up scan, then to a biopsy, then to a complication or a diagnosis of disease that would never have caused harm. Each step feels individually reasonable, and the cumulative harm is invisible at any single point.
Overdiagnosis is the detection of disease that would never have become symptomatic in the patient’s lifetime. It is not a diagnostic error; the pathology is genuinely present. The harm is that every overdiagnosed patient is treated, and so receives all of the harm of treatment and none of the benefit. It is well documented in thyroid cancer, prostate cancer, breast ductal carcinoma in situ, small renal masses and pulmonary embolism detected on high resolution imaging.
The harms of testing itself: radiation, contrast, procedural complications, anxiety, the consequences of a false positive, false reassurance from a false negative, cost, insurance and employment consequences, and the labelling of a well person as a patient.
Managing an incidental finding
- Use the published guidance for that organ, which usually stratifies by size and features
- Consider the patient’s age, comorbidity and wishes; surveillance is rarely justified where treatment would never be offered
- Communicate clearly, giving the likelihood of significance rather than only the plan
- Document the finding and who is responsible for follow-up, since incidental findings are a recognised source of harm when they are simply lost
Before ordering: what is the pre-test probability, what will I do with a positive result, what will I do with a negative one, and does the answer change management.