When a
patient shows some sign or symptom that just might point to a
serious condition, a clinician must decide whether to perform more tests, or let it go.
If tests are not performed, a problem can be missed. Maybe that
shadow is really cancer; maybe that blood pressure reading reflects hyperaldosteronism, and maybe that fall caused a
subdural hematoma.
But if they are performed, a problem can be created. Every time a test is run, we may activate the Iatrogenic Cascade. Every test and every treatment has risks, and those can snowball. In an extreme form: a patient has a cough, so we get a chest x-ray. A vague shadow is seen, so we get a Chest CT for a better picture. That CT shows that the shadow was nothing, but that the liver contains a cyst. So we aspirate the cyst, and it turns out to be nothing, but in aspirating it we caused an infection.
And that is the iatrogenic cascade in action.
Or perhaps a patient is admitted to the ED with some chest pain that is most likely heartburn. If we ignore a heart attack or angina, we do the patient serious harm. But I happen to know a fellow who once had heartburn and was sent for cardiac catheterization "just in case", who then developed a hematoma at the site of the entry (his thigh. This would not be a large deal, except that the resident caring for him placed a weight on the hematoma to help it resolve, and then accidentally dropped it on the patient's testicles. Accidents do sometimes happen.
The iatrogenic cascade strikes again.
Sometimes it's better to leave remote possibilities lie, than to follow every abnormal value or rule out every remote possibility.