Renal osteodystrophy is the most complex, multifactorial metabolic bone disease.
Different exposures to these factors result in a spectrum of histological changes. Types of renal osteodystrophy are based on the bone formation rate, presence of fibrosis or increased osteoid, and amount of aluminum staining. These types do not necessarily correspond to the bone density or the risk of fracture. Low bone density may be associated with either low bone formation rates or with secondary hyperparathryoidism and high bone formation rates. Furthermore, many patients have hyperparathyroidism, which increases the trabecular bone volume while it decreases the cortical bone volume, so that the effects on bone density depend on the site that is measured.