Renal osteodystrophy hyperphosphatemia

Renal osteodystrophy Altered bone turnover that results from sustained metabolic conditions that occur in chronic kidney disease, including secondary hyperparathyroidism, hyperphosphatemia, hypocalcemia, and vitamin D deficiency. 

Secondary hyperparathyroidism Increased secretion of parathyroid hormone from the parathyroid glands caused by hyperphosphatemia, hypocalcemia, and vitamin D deficiency that result from decreased kidney function. It can lead to bone disease (renal osteodystrophy). 

Patients with end-stage renal disease hyperphosphatemia ineffectively filter excess phosphate that enters the body in the normal diet.278 Elevated phosphate produces the bone disorder renal osteodystrophy. Skeletal deformity may occur, possibly associated with cardiovascular disease. Calcium deposits may further build up around the body and in blood vessels creating further health risks. The use of lanthanum carbonate is being promoted as an alternative to aluminum-based therapies.279,280 Systemic absorption, and cost have produced a clinical candidate, Fosrenol (AnorMED), an intriguing use of a lanthanide compound in therapy. 

Patients with chronic renal failure develop hyperphosphatemia, hypocalcemia, secondary hyperparathyroidism, and severe metabolic bone disease. The secondary hyperparathyroidism is thought to be due to hyperphosphatemia and decreased 1, 25-(OH)2 formation. Oral or intravenous l,25-(OH)2D3 (calcitriol) therapy along with oral phosphate-binding agents and calcium supplementation is effective in reducing the effects of renal osteodystrophy. 

Contraindications Hypercalcemia, hypervitaminosis D, or renal osteodystrophy with hyperphosphatemia. Use with caution in patients with arteriosclerosis, hyperphosphatemia, hypersensitivity to vitamin D, and renal or cardiac impairment. 

The major effects of hyperphosphatemia are related to the development of hypocalcemia (caused by phosphate inhibition of renal la-hydroxylase) and its related consequences, as well as vascular and organ damage resulting from the deposition of calcium-phosphate crystals. Extravascular calcification can result in band keratopathy, red eye, pruritus, and periarticular calcification, especially in renal failure patients (see Chap. 44). In addition, soft-tissue calcifications in the conjunctiva, skin, heart, cornea, lung, gastric mucosa, and kidney have been observed, primarily in chronic renal failure patients." Hyperphosphatemia associated with chronic renal disease may result in renal osteodystrophy because of overproduction of parathyroid hormone. This condition is discussed in detail in Chap. 44. 

Renal osteodystrophy (ROD)—The condition resulting from sustained metabolic changes that occur with chronic kidney disease including secondary hyperparathyroidism, hyperphosphatemia, hypocalcemia, and vitamin D deficiency. The skeletal complications associated with ROD include osteitis fibrosa cystica (high bone turnover disease), osteomalacia (low bone turnover disease), adynamic bone disease, and mixed bone disorders. 

Hyperphosphatemia occurs commonly in chronic renal failure. The increased phosphate level direcdy stimulates PTH secretion and also has secondary effects due to the reduction in serum Cd . Because renal function is impaired, the increased PTH is unable to increase phosphate excretion sufficiently to avoid ongoing phosphate retention. The chronic secondary hyperparathyroidism may result in a bone disease called renal osteodystrophy. 

Patients with advanced renal insufficiency (Ccr less than 30 mL/min) exhibit phosphate retention and some degree of hyperphosphatemia. The retention of phosphate plays a role in causing secondary hyperparathyroidism associated with osteodystrophy and soft-tissue calcification. Calcium acetate, when taken with meals, combines with dietary phosphate to form insoluble calcium phosphate, which is excreted in the feces. 

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