At times the question arises as to whether a given shadow is that of a calculus in the gallbladder or kidney. Such a problem presented itself in a recent case in which a shadow in the right renal area appeared on the plain roentgenographic film. We deemed it advisable to study the relation of this shadow (A) to a cholecystogram.
In the ordinary anteroposterior exposure (B) the suspected renal calculus shadow is entirely included in that of the gallbladder. In another exposure (C) taken at a slightly different angle the shadow projects a little mesially to that of the cholecystogram, thus revealing the fact that the calculus is not in the gallbladder. In a third (D) lateral view the separation of the shadow of the calculus from that of the gallbladder is most marked. We believe that this method will be of great value in cases in which pyelography