Gastrointestinal absorption and urinary excretion of aluminium in patients with predialysis chronic renal failure.

In a randomized cross-over study, serum and urinary aluminum (A1) was measured in 8 patients with predialysis chronic renal failure. Samples were taken after ingestion of an A1-containing phosphate binder (ACPB) with either water or 7% citric acid, and A1 was analyzed by electrothermal atomic absorption spectrometry. Both serum levels and urinary excretion of A1 increased markedly after ingestion of ACPB with citric acid. Only urinary A1 excretion increased significantly after ACPB with water. Citric acid alone caused no change in serum concentration or urinary excretion of A1. The serum A1 increase after ACPB with citric acid indicates that absorption of A1 is taking place in both upper and lower intestines. Marked individual variations in gastrointestinal A1 absorption, independent of kidney function, were seen after intake of ACPB with citric acid. These variations could not be predicted from changes in serum concentrations or from urinary excretion of A1 after intake of ACPB with water. Intake of ACPB caused a significant decrease in serum phosphate.