What if you dont know what's the diagnosis?

There have been many times in which I had no idea what the diagnosis was. In Emergency, this a bit difficult to deal with, as usually its nice to give people a reason as to whats causing their pain. I was given some good advice today.

Basically a high percentage of cases never get a diagnosis. For example abdominal pain, or chest pain. It is sometimes tempting to label these people with gastritis, or gastroenteritis. However I was told if you really dont know, you should probably just discharge with a diagnosis of No specific illness found.

The reason for this, is that when people look back on their case notes later on, they will realise that actually we didnt know, instead of seeing, oh this patient has come in 3 times with gastro, when actually they may have had a AAA.