Loading tests for diagnosis of metabolic anomalies in urinary stone formers

Four per cent of the population in the industrialized countries of Europe suffer once or several times from urinary calculus in the course of their lives. The high number of recurrences (50 to 60%) necessitates specific prophylaxis. Depending on the precise stone composition, a specific metabolic investigation should be undertaken in cases with recurrent urinary calculus. Within a special laboratory diagnostic program, all major anomalies can be diagnosed by means of loading tests. With the ammonium chloride loading test, renal tubular acidosis is diagnosed; the calcium loading test differentiates the types of hypercalciuria and the purine loading test verifies "latent hyperuricaemia".