Bone Health in Kidney Disease

Q) What are the current recommendations for the use of DXA and bisphosphonates in patients with chronic kidney disease and end-stage renal disease?

For patients with kidney disease, mineral and bone disorder (MBD) is a common complication, affecting the majority of those with moderate to severe chronic kidney disease (CKD; see Table 1).^1,2 CKD-MBD is a systemic disorder that encompasses abnormalities in mineral metabolism, skeletal health, and soft-tissue calcifications.^1,2 It manifests as one or more of the following:

• Abnormalities of calcium, phosphorus, parathyroid hormone (PTH), or vitamin D metabolism
• Abnormalities in bone turnover, mineralization, volume, linear growth, or strength
• Vascular or other soft-tissue calcification.²

The Figure provides an illustration of the effect of CKD on bone health: In the general population, risk for hip fracture increases with age; risk is further exacerbated in those who have CKD.³

To assess for fracture risk in patients with advanced stages of CKD (3-5) who have evidence of CKD-MBD and/or risk factors for osteoporosis, the Kidney Disease: Improving Global Outcomes (KDIGO) group recommends bone mineral density testing with dual-energy X-ray absorptiometry (DXA).² Bone biopsy—the gold standard for diagnosis of renal osteodystrophy, a form of osteoporosis and one type of bone abnormality seen in CKD-MBD—is “reasonable” to perform in cases in which knowing the type of renal osteodystrophy would inform treatment choices.² KDIGO also recognizes limitations in the ability to perform a bone biopsy and therefore recommends monitoring serial PTH and bone-specific alkaline phosphatase to evaluate for bone disease.²

Prevention of fractures and treatment of patients with CKD-MDB has historically been challenging, since many of the available pharmacologic agents have not been developed for or studied in patients with CKD.¹ According to KDIGO, it is acceptable for patients with CKD stages 1 and 2 to receive the same osteoporosis/fracture risk management as recommended for the general population.² Patients with CKD stages 3a and 3b can also receive treatment as recommended for the general population, as long as the patient’s PTH level is in normal range.² Table 2 outlines the FDA-approved glomerular filtration rate cutoffs for some bisphosphonates commonly used to treat osteoporosis.

Before initiating treatment for CKD-associated osteoporosis, no matter what the stage, it is important to manage vitamin D deficiency, hyperphosphatemia, and hyperparathyroidism.¹ In CKD patients with abnormalities of calcium, phosphorus, PTH, and/or vitamin D, involve the nephrology team to assist in providing MBD care. Different approaches to treatment may include, but are not limited to, adjusting phosphorus binders; using vitamin D supplements or analogs; using calcimimetics; prescribing dialysis; providing dietary education; and addressing medication costs.