This is a preliminary report on ammonium alum as a substitute for the tannic acid formerly used in barium sulfate enemas to promote colon contraction and barium coating of the colon mucosa. The "mucosal pattern" thus produced on postevacuation films is useful in tumor diagnosis because a tumor larger than the contracted lumen produces a bulge or distortion of this pattern.
Experimental and clinical studies indicate that alum is equal to tannic acid in every respect except that it does not maintain colon contraction quite as long. Either additive is far better than none. Alum was not toxic in the amounts found effective.