Mineral metabolism and bone abnormalities in children with chronic renal failure

Abnormalities in mineral metabolism and changes in skeletal histology may contribute to growth impairment in children with chronic renal failure. Hyperphosphatemia, hypocalcemia, metabolic acidosis, alterations in vitamin D and IGF synthesis and parathyroid gland dysfunction play significant roles in the development of secondary hyperparathyroidism and subsequently, bone disease in renal failure. The recent KDIGO conference has made recommendations to consider this as a systemic disorder (chronic kidney disease-mineral bone disorder) and to standardize bone histomorphometry to include bone turnover, mineralization and volume (TMV). The use of DXA to assess bone mass is controversial in children with chronic renal failure. Questions arise regarding the accuracy of bone measurements and difficulty in data interpretation especially in children with renal failure who are not only growth retarded but often have pubertal delay and osteosclerosis. The validity and feasibility of new modalities of skeletal imaging which can detect changes in both trabecular and cortical bone are currently being investigated in children. The management of mineral abnormalities and bone disease in chronic renal failure is multifactorial. To manage hyperphosphatemia, dietary phosphate restriction accompanied by intake of calcium-free and metal-free phosphate binding agents are widely utilized. Vitamin D analogs remain the primary therapy for secondary hyperparathyroidism, although the use of the less hypercalcemic agents is preferred due to concerns of calciphylaxis and vascular calcification. Future clinical studies are needed to evaluate the long-term effects of calcimimetic agents and bisphosphonate therapy in children with chronic renal failure.