Division of Nephrology, Brody School of Medicine, Greenville, North Carolina
An 81-yr-old African-American woman with endstage kidney disease (ESKD) who has been on hemodialysis for 10 yr seeks a consultation with you. Her primary physician obtained a dual-energy xray absorptiometry (DEXA) scan andasked her to discuss the results with her nephrologist for further management. She is diagnosed with osteoporosis based on her T-scores of 5.1 (AP spine), 4.1 (left femoral neck), and 5.4 (left total hip). Her last dialysis laboratory results show serum calcium is 10.7 mg/dl, intact parathyroid hormone (PTH) is 207 pg/ml, phosphorus is 5.7 mg/dl, and alkaline phosphatase (ALP) is 122 IU/L. Shereceives paricalcitol 5 mg intravenously on hemodialysis three times per week. Chronic kidney disease (CKD)-related bone disease is known as renal or uremic osteodystrophy. It is associated with derangements in bone and mineral metabolism that leads to abnormal regulation of calcium, phosphorous, vitamin D, and PTH. It encompasses a spectrum of conditions that are classified based on bone biopsyfindings including osteitis fibrosa (high turnover disease), mixed uremic osteodystrophy, osteomalacia (low turnover disease), and adynamic bone disease. KDIGO (kidney disease: improving global outcomes) has proposed to define CKD-related bone and mineral metabolic abnormalities in the context of a systemic disorder called CKD–mineral and bone disorder (CKDMBD).1 Osteoporosis is a conditioncharacterized by low bone mass leading to reduced bone strength and an increased risk of fractures. Hip, spine, and wrist are most commonly affected. The WHO definition of osteoporosis is based on bone mineral density (BMD) measurements. The NIH consensus statement refers to osteoporosis as a skeletal disorder characterized by compromised bone strength predisposing to increased risk of fracture.Osteoporosis and renal osteodystrophy may coexist in elderly patients with CKD, which makes the
American Society of Nephrology
issue problematic to define. Osteoporosis in CKD is only a part of the constellation of metabolic bone problems. Therefore, its diagnosis and management may differ from general population. Bones are more severely affected in CKD than that from normal aging. In a patient withrenal osteodystrophy, there is the potential for low BMD to coexist with an enormous range of functional abnormalities. These range from high turnover bone lesions in patients with uncontrolled hyperparathyroidism to severely reduced bone remodeling activity in patients with adynamic bone disease. This is in contrast to the non-CKD patient with osteoporosis where bone remodeling is not severelyaffected.
IMPACT ON QUALITY OF LIFE
Patients with CKD-MBD and osteoporosis are associated with increased risk of fractures and are at a high risk of cardiovascular disease.2 The overall incidence of hip fractures among dialysis patients is about four-fold higher than that expected for general population. The risk is increased in both men and women.3 Fractures may limit ambulation, leading to lossof independence and chronic pain, thereby decreasing quality of life. Mortality risk in dialysis patients with hip fracture is twice that of patients without hip fracture.4 Women who are 65 yr of age and older and have moderate renal dysfunction (eGFR 60 ml/min per 1.73 m2) are also at an increased risk of hip fractures.5 In addition to the traditional risk factors, several risk factors for lowBMD have been identified in the CKD population such as renal osteodystrophy, ethnicity, transplant status, and duration of dialysis.6
Correspondence: Harmeet Singh, Division of Nephrology, Brody School of Medicine, 2355 W. Arlington Boulevard, Greenville, NC 27834. E-mail: firstname.lastname@example.org Copyright 2009 by the American Society of Nephrology Geriatric Nephrology Curriculum