Urea is synthesized in the body of many organisms as part of the urea cycle, either from the oxidation of amino acids or from ammonia. Uric acid is a substance resulting from the breakdown of purines, which are part of all human tissue and are found in many foods. Uric acid dissolves in the blood, passes through the kidneys, and is then eliminated in the urine. The buildup of this substance in the body may lead to problems, including kidney stones and gout. . If Uric crystals found between the joints, the surrounding tissue becomes inflamed.