Around the 70's there was a bestselling book about an English country doctor. The title eludes me at the moment, but I seem to remember that at one point the doctor smelled a patient's breath, noticed a hint of rotten apples, and from this correctly concluded that the patient had appendicitis.
A father noticed that his little girl always had really salty skin, to the point of calling her "my little potato chip". Then as she got older and "failed to thrive", he found out why she was so salty. Her body did not handle chlorine properly - she had cystic fibrosis. I'll link the article later when I'll have a lot more to say about it.
Lately a medblogger wrote of a patient that had been eating a lot of ice. Of all things, this often indicates an iron deficiency.
Incidentally, how do you think doctors discovered that the urine of diabetes mellitus patients was sweet?
Instrumentation and diagnostic equipment are terrific. But I have to wonder what is lost by using these artificial senses if they are used to the exclusion of the original 5.