NCIt definition : A radiolabelled urea molecule used to diagnose stomach ulcers caused by Heliobacter
pylori. In the presence of H. pylori, urea C-13 is metabolized by urease to produce
ammonia and radioactive carbon dioxide at the interface between the gastric epithelium
and lumen. The radioactive carbon dioxide is absorbed in the blood and is detected
when exhaled in the breath.;