Impacto do distúrbio mineral e ósseo da doença renal crônica na perda de acurácia da bioimpedância

Abstract

Chronic kidney disease (CKD) is defined by decreased glomerular filtration rate and changes in renal structure and function, irreversibly, over months or years. It is a decisive parameter in the diagnosis, and it is of great importance to monitor the progression of kidney disease. The main causes of mortality in patients with CKD are cardiovascular diseases. The association between CKD and bone mineral disease generates a high risk of hip fracture, associating physical incapacity, being an important mechanism for the indirect correlation of eGFR (glomerular filtration rate) and physical function. Dialysis patients have a high rate of fractures in relation to the general population, and the prevention of fractures in this population is somewhat challenging. However, phosphorus retention occurs due to the reduction in the glomerular filtration rate observed at the onset of CKD, which results in an increase in the production of fibroblast growth factor 23 (FGF-23), which is secreted by osteocytes. However, secondary hyperparathyroidism is usually associated with increased bone remodeling and consequent loss of bone mass. Due to progressive loss of renal function there is a reduction in sodium filtration and inadequate renal tubular reabsorption occurring with volume retention, even in patients receiving conservative treatment. Hypervolemia is a risk factor for mortality in cardiovascular diseases. Dual-energy X-ray absorptiometry (DXA) analyzes bone fragility and measures the volume of cortical and trabecular bone, as well as soft tissue properties based on measurements at the molecular level of fat mass, lean mass, bone mineral content (BMC). However, Bioimpedance (BIA) is highly specialized to determine the water between the intracellular and extracellular spaces. The aim of our study was to evaluate the concordance between BIA and DXA for body composition measurements, specifically BMC, in patients with CKD, and to evaluate the relationship of BCA difference between BIA and DXA with BMD-CKD markers. The study included 28 patients with stage 5 CKD with secondary hyperparathyroidism who underwent hemodialysis treatment three times a week with indication of parathyroidectomy and patients with chronic non-dialytic chronic kidney disease of both sexes, aged between 18 and 75 years old, under conditions stable clinics upon presentation of medical authorization, who signed the Informed Consent Form. All patients underwent BIA and DXA. Patients in the hemodialysis group with secondary hyperparathyroidism were younger and lean, reflecting the BMI value. PTH, alkaline phosphatase and P were higher in relation to the group under conservative treatment. The hemodialysis group with secondary hyperparathyroidism presented lower fat mass, bone mineral content and bone mineral density of the left hip and greater percentage value of lean mass in DXA. The same group had lower fat mass and higher percentage of lean mass in BIA. When comparing the evaluation methods, we observed that the BIA underestimated the fat mass and overestimated the bone mineral content, mainly in the hemodialysis group with secondary hyperparathyroidism. There is a correlation between BAC difference between DXA and BIA with phosphorus, alkaline phosphatase and PTH. Since phosphorus and alkaline phosphatase presented a significant correlation with the difference in BMC in both methods.