The tubeless detection of gastric acidity, as developed by Segal and associates,1 makes it possible to ascertain the state of gastric acidity in specific cases or in mass screening examinations without the use of complicated or cumbersome chemical procedures. The rationale of tubeless analysis depends on the use of a dye, azure A, which is released from a cation exchange resin by free hydrochloric acid in the stomach. In the presence of free acid, the free dye is absorbed and consequently excreted in the urine and the blue color of the urine may then be visually compared with a solution of azure A of known concentration.
It has been reported by other workers2 that in about 50% of the tests the azure A is excreted in a reduced, colorless form that requires oxidation with acid and heat to bring out the color. In our experience, about 75% of
Rosenthal HL, Buscaglia S. TUBELESS GASTRIC ANALYSIS. JAMA. 1958;168(4):409. doi:10.1001/jama.1958.63000040001010