Azotaemic renal osteodystrophy: a quantitative study on iliac bone

The histopathology of bone is described in 60 patients with chronic renal failure due to a variety of renal diseases. Changes of azotaemic renal osteodystrophy included osteitis fibrosa, osteomalacia, and osteosclerosis. Quantitative histology using a point-counting technique revealed a significant increase in total bone, mineralized bone, and osteoid in comparison with a control group of 68 individuals. Osteitis fibrosa due to secondary hyperparathyroidism occurred in 93%, osteomalacia in 40%, and osteosclerosis in 30% of patients. Woven bone formation was a characteristic feature and was related to the severity of osteitis fibrosa. There were significant correlations between the weights of parathyroid glands and the number of osteoclasts, amounts of woven bone, and marrow fibrosis in the ilium. Hyperparathyroidism caused degradation of mineralized bone but the loss was balanced or exceeded by the aggradation of woven mineralized bone. Woven bone formation together with excess osteoid gave rise to osteosclerosis. The histological findings indicate that hyperparathyroidism and osteitis fibrosa usually occur early in chronic renal failure and that osteomalacia develops subsequently.