The source and clinical significance of serum alkaline phosphatases in patients treated by chronic dialysis.

A group of 25 patients with chronic terminal renal failure, treated regularly by haemodialysis, was examined. Activity of the bone serum alkaline phosphatase isoenzyme was significantly elevated in 12 patients with signs of bone disease, either isolated or combined with liver damage, even when total alkaline phosphatase activity was within normal limits. The intensity and incidence of raised bone isoenzyme activity increased with the duration of dialysis therapy. Elevated activity of liver alkaline phosphatase isoenzyme correlated with the other laboratory and clinical signs of liver involvement in 16 patients. Activity of the intestinal isoenzyme was elevated in over half the patients, unrelated to liver or bone damage, and was in an inverse correlation to the total serum calcium level. The evaluation of total serum alkaline phosphatase activity had no diagnostic value.