AGA technical review on osteoporosis in hepatic disorders.

B one disease is a major complication of chronic liver disease (CLD) and liver transplantation and can result in spontaneous or low-trauma fracturing that significantly impacts on morbidity, quality of life, and even survival. The etiology of these disorders is complex and multifactorial. The general biology and pathogenesis of osteoporosis, including its relationship with inflamma-tory states, diagnostic tools, and clinical utility of bone densitometry, has been reviewed elsewhere in the AGA Technical Review on Osteoporosis in Gastrointestinal Diseases. 1 In this review, issues specific to osteoporosis and hepatic disease will be discussed. Methods routinely used in skeletal assessment and relevant terminology will be briefly summarized. The development of bone densitometry has made it possible to measure bone mass and assess its contribution to fracture risk. It is generally accepted that bone mass is the single best predictor of in vitro skeletal strength 2– 4 and fracture risk. 5 The most widely available bone density technology is dual-energy x-ray absorptiometry (DXA), which is currently the gold standard for measurement of bone mass. Conventional DXA (also known as central DXA) is able to measure all skeletal structures, including those in the thicker body regions such as the lumbar spine and hip. The related isotopic method, dual-photon absorptiometry (DPA), is now rarely used. Other methods are available for measuring bone in the extremities using radionuclide sources, x-ray, or ultra-sonography. Quantitative computed tomography can be used to measure bone density but is infrequently used outside of research settings. Conventional diagnostic ra-diographs are still an important component in the assessment of osteoporosis because the presence of fragility fractures (such as vertebral compression fractures) indicates osteoporosis and high fracture risk independent of bone mineral density (BMD). Bone density measurements follow a bell-shaped (Gaussian) distribution. Therefore, they are described as the number of standard deviations (SD) that the value deviates from the mean for normal controls. Age-related changes in bone density must be taken into account. The Z-score refers to the number of SD above or below the mean for an age-matched population. The T-score refers to the number of SD above or below the mean for a young adult population (corresponding to peak bone mass). A World Health Organization report formulated diagnostic ranges for osteoporosis based on T-score 6 : normal is a T-score greater than Ϫ1.0 (i.e., the patient's BMD is no more than 1 deviation below the young adult mean), osteopenia (low bone mass) …