Double contrast cystography (pneumocystography) is an older technique to evaluate the bladder lumen. It has rarely been used (if ever) after the advent of cross-sectional imaging.
The exam is performed similarly to a conventional cystogram, but gas is also introduced through the Foley catheter. The concept is similar to a double contrast upper GI study; the combination of water-soluble iodine-based contrast (e.g. Cystografin) and gas allows better evaluation of the bladder lumen than a single-contrast cystogram.