Adynamic bone disease is being increasingly recognized as the most common form of renal osteodystrophy. It is characterized by the reduced synthesis of bone matrix due to decreased osteoblastic and osteoclastic activity. Adynamic bone disease is distinct from osteomalacia, in which osteoid (the bone protein matrix, composed primarily of type I collagen) accumulates due to a lack of osteoblast activity or defective osteoid mineralization, as opposed to the simple decreased rate of turnover seen in adynamic bone disease.
Adynamic bone disease is particularly common in the peritoneal dialysis population in that the constant exposure to calcium in the dialysate fluid leads to episodic hypercalcemia and suppression of PTH levels which results in adynamic bone. A 2006 study by Haris et al in Kidney International randomized PD patients with adynamic bone disease (as assessed by bone biopsy) to normal Ca (1.62mM) versus low Ca (1.0mM) dialysate. The low-Ca dialysate group developed a higher PTH and bone turnover rates within the normal range, suggesting that the low Ca dialysate strategy is a good one for PD patients in order to avoid adynamic bone.