What finding on an X-ray indicates normal lungs?

A finding of rounded hemidiaphragms on an X-ray typically indicates normal lungs because the appearance suggests healthy lung volume and function. The diaphragm should be dome-shaped and well-defined, indicating that there is no significant underlying pathology affecting the lungs. In a healthy individual, the lungs appear black on the X-ray due to the air they contain, which allows for optimal visualization against the denser tissues of the heart and chest wall.

In contrast, the appearance of fluid would indicate an abnormal condition, such as pleural effusion, which is not a normal finding. Similarly, an enlarged heart shadow could suggest cardiomegaly or other cardiac issues, indicating potential heart disease or conditions affecting heart size. These findings would be indicative of various pathologies rather than normal lung conditions. Thus, rounded hemidiaphragms, reflecting normal lung inflation and diaphragm function, is the correct interpretation when evaluating for normal lung findings on an X-ray.