Please see an earlier proz.com answer:
http://webcache.googleusercontent.com/search?q=cache:2eDwDOM...

and also:
Diaphragmatic hump
This is due to incomplete muscularization of the diaphragm. instead of the normal diaphragmatic muscle, the diaphragm is now consists of a thin membranous sheet. This is a very common abnormality.
Most of the time, the abnormality is partial, involving one half to one third of the hemidiaphragm. Usually the anteromedial portion is affected.
http://webcache.googleusercontent.com/search?q=cache:ByEJoxc...

No pleural effusion is however demonstrated.
Trachea appears central and there is no midline shift. The diaphragms appear normal. Note
that there is right-sided diaphragmatic hump. The soft tissues and the bony structures of the
thorax appeared normal.No pleural effusion is however demonstrated. Trachea appears central and there is no midline shift. The diaphragms appear normal. Note that there is right-sided diaphragmatic hump. The soft tissues and the bony structures of the thorax appeared normal.
http://docs.google.com/viewer?a=v&q=cache:tooaGvEcaEAJ:fcds....

DIAPHRAGMS. These have a smooth outline and are convex upwards. The right dome lies 1-2cm higher than the left. Usually at or below the level of the 10th posterior rib or 6th anterior rib (The posterior ribs are differentiated from the anterior ribs by being more horizontal.). There may be a fat pad (low density shadow) adjacent to the heart border in obese patients. A diaphragmatic hump (localised bulge) is a normal variant.
http://webcache.googleusercontent.com/search?q=cache:2dpaa-I...