Since the introduction of excretory urography, a simple method of demonstrating the ability of the bladder to empty its contents has become available. An adequate kidney function is necessary, so that the concentration of the excreted opaque material will give a fairly clear cystogram. Owing to the fact that an excretory urogram is indicated in all obstructive conditions at the neck of the bladder to determine the physiologic and anatomic state of the upper urinary tract, no additional measures are necessary to visualize the ability of the bladder to empty itself.
Before taking the last roentgenogram, the patient is allowed to void as completely as possible, and then the picture is taken and a graphic expression of the residue left in the bladder after voiding is obtained. This simple procedure avoids all instrumental interference with the bladder, avoids the dangers of infection, trauma of too sudden emptying of the organ and the occasional complete obstruction that follows the passing of a catheter. Even though one does not obtain an