Long-term parenteral nutrition and metabolic bone disease.

Home parenteral nutrition has prevented malnutrition in patients who cannot maintain adequate nutrition by enteral feedings alone. The risk of bone and mineral abnormalities in these patients is significant for several reasons. Pre-existing skeletal disease can occur from factors known to affect the population at large as well as from malnutrition, malabsorption, and corticosteroid use related to the underlying disease process. Long-term use of infused nutrients and potential toxins can further alter bone turnover. Hypercalciuria is frequently present during HPN, yet its etiology is poorly defined. Parenteral nutrition admixture concentrations of calcium, phosphorus, protein, sodium, and dextrose may all play a role. Any development of acidosis can certainly aggravate hypercalciuria, which may be an indirect marker of abnormal bone turnover. Although increased protein intake can promote the development of acidosis-induced calciuresis, infused phosphorus and acetate can help reduce calcium excretion. Parenteral nutrition contamination by aluminum can cause a spectrum of osteomalacic bone disease similar to aluminum-associated changes seen in renal failure patients. Even with recent attempts to remove aluminum from the parenteral admixture, low-turnover bone disease can still occur. At present, HPN-related bone disease is a poorly understood entity because of its multifaceted nature. Patients receiving long-term parenteral nutrition should be considered to have an increased risk for the development of metabolic bone disease. Early monitoring for and treatment of bone disease should be considered in all patients receiving HPN.