The case records of 327 patients who underwent bone biopsy in late or terminal
renal failure, before any form of dialysis or
transplantation, were examined for clues to the aetiology of renal
osteomalacia and its manifestations. Fifty four per cent of the biopsies showed pure
osteitis fibrosa, 34 per cent
osteomalacia with
osteitis fibrosa and 12 per cent showed neither abnormality.
Osteomalacia was strongly associated with chronic
pyelonephritis and obstructive uropathy as primary renal disease. In two matched groups of 100 each, and within the major primary diseases, it was associated with
acidosis, hypocalcaemia and normophosphataemia (as opposed to hyperphosphataemia). There was no association with known length or uraemia and only a weak and inconsistent relationship with severity of uraemia. In the few patients studied, there was no relationship between
osteomalacia and serum
25-hydroxycholecalciferol level. In contrast to the state of patients treated by haemodialysis,
osteomalacia in this undialysed group was manifested by a higher level of serum
alkaline phosphatase than pure
osteitis fibrosa, serum iPTH did not differ between the groups, there was no predominance of symptoms in one group, other than proximal
myopathy which had a weak association with
osteomalacia, and Looser zones were more common than complete fractures. Our study shows that
osteomalacia has different manifestations, and probably different causes, before and after the start of haemodialysis. These two stages of
renal failure should be clearly distinguished in reports of renal
bone disease.