Renal handling of silicon in normals and patients with renal insufficiency.

We have compared the renal handling of silicon in 16 patients with renal insufficiency to 14 normal individuals. Silicon, phosphate and creatinine were measured in plasma and urine samples. The renal insufficiency group showed significant increases in plasma silicon (1.28 +/- 0.19 vs. 0.17 +/- 0.03 mg/liter), creatinine (5.19 +/- 0.85 vs. 0.89 +/- 0.03 mg/dl) and phosphate (1.33 +2- 0.11 vs. 1.07 +/- 0.4 mmol/liter). Fractional phosphate excretion was increased in the renal insufficiency group (0.55 +/- 0.07 vs. 0.14 +/- 0.01). In contrast, the fractional excretion of ultrafiltrable silicon was not significantly different between groups (0.78 +/- 0.07 vs. 0.87 +/- 0.06). It is concluded that renal insufficiency does not alter the tubular handling of silicon and that regulatory control of silicon excretion is unlikely.