Please help docs! is 'rule out pneumonia' really a proper medical diagnosis?

Rule out pneumonia: is not a diagnosis. "Pneumonia" is a diagnosis. "Rule out pneumonia" on an xray or other request means that the doctor thinks pneumonia is on the list(differential diagnosis) of possibilities, and wants to either confirm it or take it off the list(rule out) of possibilities.

Xray, clinical signs: Not really. On radiograph sometimes pneumonia is consolidation or density on radiograph. Atelectasis or volume loss can some times have similar appearance. Clinical symptoms and physical exam should be considered in determination of proper clinical diagnosis

Get clarification: It isn't very specific, but very often is the only information provided to the radiologist. Limited history provides limited guidance to the interpretation of findings, but gross abnormalities are generally screened for. Increasing availability of electronic medical records have helped to clarify clinical indications. However, the more directed info shared up front, the better the imaging read.