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Thyroid Incidentalomas


Bandolier has previously carried information about incidentalomas, disorders found by sophisticated and highly sensitive imaging techniques which were hitherto undiscovered and whose significance is unknown ( Bandolier 10 ).

Thyroid imaging


A new paper from the Mayo Clinic [1] has shown another fascinating example of the problems caused by highly sensitive imaging. This was a review of all relevant articles on the identification of thyroid nodules. The authors called non-palpable nodules "incidentalomas" and found that most nodules that are bigger than 1 cm diameter can be palpated, particularly if they are on the surface of the thyroid gland.

Two autopsy studies with a combined total of 1033 individuals with clinically normal thyroids found a prevalence of 46% of them with at least one nodule.

Modern ultrasonography has the sensitivity to detect lesions as small as 1 to 3 mm. So it is possible to identify non-palpable nodules in anything between 13% and 50% of people in whom nodules cannot be identified by palpation.

Prospective studies of randomly selected patients have shown that up to 67% of people can be shown to have nodules when the thyroid gland is incidentally scanned, for example during carotid ultrasonography. It nicely brackets the 46% autopsy figure.

When is a nodule solitary?


In patients in whom solitary nodules were detected clinically, between 20 and 48% of patients were shown to have additional nodules on ultrasonography (34% overall in 456 patients).

So what does it all mean?


High resolution ultrasonography is pretty good at picking up thyroid nodules. Unfortunately no-one knows the significance of the nodules when found. What is certain is that only a small proportion of the glands will become malignant. Thus the imaging advance has created a new clinical problem, yet another example of what we have pointed out so often in Bandolier - that developments in diagnostic testing lead to and create increased demand for treatment services which have never been evaluated.

Tan & Gharib do more than leave us hanging there, though. They provide an algorithm outlining an approach to thyroid incidentalomas, which is a useful guide to what to do depending on history of radiation exposure, family history and ultrasound appearance.

Bandolier confidently predicts that the incidence of incidentalomas will increase.

Reference:

  1. GH Tan, H Gharib. Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging. Annals of Internal Medicine 1997 126: 226-31.



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