#1574 Effect of hydration status on fat mass assessment in patients with advanced chronic kidney disease

Abstract Background and Aims Obesity is defined as “an excessive accumulation of energy in the form of fat” (>33% in women; >25% in men), being a significant risk factor in chronic kidney disease (CKD). One of the most common methods to determine fat mass (FM) is bioimpedance analysis (BIA). In CKD, overhydration can occur, affecting the measurement; therefore the need to use more complex methods (dual-energy X-ray absorptiometry—DXA, air displacement plethysmography—ADP) for accurate assessment. To evaluate the influence of hydration status on fat mass determination by bioimpedance in advanced CKD patients. Method A prospective study was conducted on 30 patients (age: 65 ± 11 years, 19 men, BMI: 27.5 ± 3.7 kg/m², 50% diabetics) diagnosed with CKD stages 4–5 (glomerular filtration rate [GFR]: 18.9 ± 6.1 ml/min). Clinical data were collected, and body composition was evaluated using BIA and DXA. Results Patients were classified into two groups according to hydration status: normohydrated (NH, n = 16) and overhydrated (OH, n = 14), based on the ratio of extracellular water (ECW) to total body water (TBW), with a cutoff of 0.390. FM determined by BIA was significantly higher in the OH group (36.8 ± 7.5% vs. 30.2 ± 5.2%, P < 0.01) compared to the NH group. However, FM measured by DXA did not show significant differences between groups (NH: 33.5 ± 7.8%, OH: 34.1 ± 6.4%, P = NS). Conclusion Hydration status significantly affects the measurement of fat mass by bioimpedance analysis in patients with advanced CKD. Overhydration leads to an overestimation of fat mass. DXA provides a more reliable assessment of fat mass in these patients, independent of hydration status. Further studies are required to validate these findings in larger populations.