Histopathology of renal osteodystrophy with particular reference to the effects of 1alpha-hydroxyvitamin D3 in patients treated by long-term haemodialysis.

(1) The bone histology of 233 non-dialysed and 276 haemodialysed patients with chronic renal failure is reviewed. In non-dialysed patients osteitis fibrosa occurred in 83.7% and osteomalacia in 23.6% of patients. Osteomalacia was not found in the absence of osteitis fibrosa. In haemodialysed patients there was a more variable bone histology, sometimes resembling non-dialysed bone disease, but in general with a greater incidence of osteomalacia, especially with increasing time on dialysis. In some patients there was a predominance of osteomalacia accompanied by no or only mild osteitis fibrosa and the serum alkaline phosphatase was normal. (2) The results of treating twenty-six haemodialysed patients with 1alpha-hydroxyvitamin D3 (1alpha-OHD3) are described. Patients with osteomalacia and minimal or no osteitis fibrosa and a normal serum alkaline phosphatase (Group I) in general failed to respond and it is suggested that 1,25-dihydroxyvitamin D3 deficiency is not the sole factor responsible for the osteomalacia in these patients. In contrast, 1alpha-OHD3 therapy was effective in improving osteitis fibrosa and osteomalacia in some patients with moderate to severe degrees of osteitis fibrosa and osteomalacia (Group IIa) and in improving osteitis fibrosa where this occurred alone (Group IIb).