[Renal osteodystrophy (1): invasive and non-invasive diagnosis of its pathologic varieties]

1. Renal osteodystrophy is a general term encompassing all the disturbances of the phosphocalcic metabolism and their associated bone and soft tissue abnormalities, which progressively occur in chronic renal failure. In this article we detail their main histopathological and etiopathogenic aspects as well as their invasive and non invasive diagnostic approach. 2. Osteitis fibrosa is characterized by extensive medullary fibrosis and osteoclastic hyperresorption linked to PTH hypersecretion. 3. Adynamic bone disease is mainly related to iatrogenic oversuppression of PTH secretion. It is favored by aluminum overload which directly inhibits the osteoblasts. It is characterized by a low bone formation rate without primary mineralization defect so that the osteoid seam thickness is normal or low, in contrast to osteomalacia in which by definition osteoid thickness is increased. 4. Osteomalacia is mainly due to aluminum intoxication, vitamin D insufficiency, hypocalcemia, acidosis and exceptionally to hypophosphatemia. 5. The differential diagnosis between the histopathological entities may be oriented on clinical, radiological and biochemical means. Only the bone biopsy can make the diagnosis with certainty. This latter is however necessary for appropriate treatment only in the patients who have been exposed to aluminum and who are symptomatic or hypercalcemic in order to distinguish severe osteitis fibrosa from aluminic bone disease, and more particularly from mixed osteopathy. Indeed surgical parathyroidectomy in patients with mixed osteopathy associating bone hyperremodeling and mineralization defect with inappropriately thick osteoid seam may induce fracturing low turn over aluminic bone disease.