title: An estimate of the ion-activity product of magnesium ammonium phosphate in urine.
abstract: Based on the analysis of magnesium (Mg), ammonium (NH4), phosphate (P), urine pH, and urine volume (V), a simplified estimate (AP[MAP] index) of the ion-activity product of magnesium ammonium phosphate (AP MAP) was derived: (Formula: see text). The factor A varies according to the collection period. In 4-hour urine samples more than half of the patients with staghorn calculi had values above 5 in contrast to normal subjects and calcium oxalate stone formers in whom lower values apparently were the rule. The AP(MAP) index might be of value in the evaluation and follow-up of patients with staghorn calculous disease.
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007669:Kidney Calculi / Q000652:urine*; D008274:Magnesium / Q000652:urine*; D017616:Magnesium Compounds; D010710:Phosphates / Q000652:urine*; D000069877:Struvite; D014545:Urinary Calculi / Q000032:analysis
chemical_list: D017616:Magnesium Compounds; D010710:Phosphates; D002129:Calcium Oxalate; D000069877:Struvite; D008274:Magnesium