DIAGNOSTIC MARKERS IN CALCIUM NEPHROLITHI ASIS - NEW IDEAS OR OLD ONES WITH A NEW LOOK

About 80% of all renal stones contain calcium oxalate and/or calcium p hosphate as their main crystalline components. The most important risk factors for increases in calcium oxalate crystallization are low urin e volume, hyperoxaluria and hypocitraturia. Hypercalciuria, however, i s of secondary importance as a cause of increased crystallization: whe reas calcium and oxalate crystallize in a 1:1 ratio, the molar concent ration ratio in urine amounts to about 10:1 in favor of calcium. There fore, increases in urinary calcium will not be followed by a rise in c rystallization as long as oxalate remains constant, whereas even the s lightest increases in urinary oxalate immediately cause more crystals to precipitate. Thus, low calcium diet is not only unnecessary but is contraindicated since it may cause secondary hyperoxaluria (increased intestinal oxalate absorption) and osteopenia (negative calcium balanc e). On the other hand, overconsumption of animal protein (meat, poultr y, fish) induces more pronounced hyperoxaluria and hypocitraturia and contributes to an overall negative calcium balance. It is, however, on ly by the interplay of ''bad'' dietary habits with underlying abnormal ities such as up-regulation of calcitriol production, incomplete renal tubular acidosis or defective macromolecular crystallization inhibito rs, that people become recurrent calcium renal stone formers.