Renal osteodystrophy (2): its treatment before dialysis.

1. In the patient with renal insufficiency before dialysis, the phosphocalc ic disorders appear insidiously. They are dominated by hyperparathyroidism which will be diagnosed on the initially yearly determination of plasma int act PTH as soon as creatinine clearance decreases below 60 ml/min, eventhou gh there is still no modification in plasma concentrations of calcium and p hosphate. Its diagnosis should lead to initiate the therapeutic measures in order to prevent the irreversible thining of the corticals by endosteal re sorption and later the occurrence of histological and radiological osteitis fibrosa favoring fractures. 2. Hyperparathyroidism prevention relies on two main measures: - prevention of phosphate retention and hypocalcemia is implemented by prog ressive phosphate and protein restriction (from 1g/kg/day when Ccr < 60 ml/ min to 0.6 g/kg/day when Ccr < 20 ml/min) and administration of CaCO3 (1.5 g at lunch and dinner to better complex the phosphate) as soon as PTH is ab ove normal; - optimal vitamin D repeletion will be implemented sysystematic supplementa tion of native vitamin D or 25OH vitamin D3 in order to bring P25OHD betwee n 30-60 ng/ml (75-150 nmol/l) or more generally around the upper limit of t he epidemiologic range of the laboratory; - these measures should aim at maintaining plasma intact PTH in its optimal range variable with the degree of renal insufficiency: 0.5-1; 1-2.5; and 2 -3 folds the upper limit of normal for creatinine clearance respectively at 60-30; 30-10 and < 10 ml/min. 3. Because of their hyperphosphatemic and hypercalcemic effect, 1<alpha>- h ydroxylated vitamin D derivatives will be regularly efficient and safe only when non-calcemic non-aluminic phosphate binder will be available and prov en to be without side-effects. 4. Instrumental (surgical or by alcohol injection) parathyroidectomy should be considered when plasma intact PTH is > 5 to 7 times the upper limit of normal in the presence of hypercalcemia (> 2.60 mmol/l) and/or hyperphospha temia (> 1.70 nmol/l) in spite of the above measures, the decision being re inforced by coexistence of bone radiologic abnormalities and metastatic cal cifications. 5. Adynamic bone diseases are rare before hemodialysis in the absence of al uminum exposition by the drinking water or the aluminum-phosphate binders. In absence of aluminum it will be prevented by maintaining PTH in its optim al range. 6. Osteomalacia before hemodialysis is mainly due, in the absence of alumin um exposition; to vitamine D deficiency, hypocalcemia and acidosis. It is r eadily cured by physiological doses of native vitamin D or 25OH vitamin D3 bringing plasma 25 OHD above 16 ng/ml, in association with alkaline salts o f calcium and if necessary of sodium bicarbonate.