Does peritoneal dialysate affect body composition assessments using multi-frequency bioimpedance in peritoneal dialysis patients?

BACKGROUND/
OBJECTIVES: Multi-frequency bioelectrical impedance analysis (MFBIA) is increasingly being used to assess peritoneal dialysis patients. Protein energy wasting (PEW) is a recognised complication of peritoneal dialysis. Although MFBIA can be used to assess body composition, measurements can be affected by fluid overload, and we wished to determine whether the presence of peritoneal dialysate in the peritoneal cavity equally could affect MFBIA-derived body composition assessments. SUBJECTS/
METHODS: Fifty consecutive adult patients had MFBIA made with 2l 22.7 g/l dextrose dialysate instilled into the peritoneal cavity and then after draining out.
RESULTS: When full, extracellular water (ECW) and the ratio of ECW to total body water (TBW) were greater compared with when empty: 13.9 ± 3.0l versus 13.4 ± 3.0, and 0.393 ± 0.01 versus 0.391 ± 0.01, P<0.001, respectively. Segmental ECW/TBW was only different for the trunk, 0.395 ± 0.01 full versus 0.392 ± 0.01 empty, P<0.0001. Body composition changed with a fall in skeletal muscle mass from 26.1 ± 6.3 to 25.2 ± 6.1 kg, P<0.001, and a smaller reduction in body fat from 19.3 ± 8.4 to 19.1 ± 8.0 kg, P=0.0104.
CONCLUSION: MFBIA measurements made in peritoneal dialysis patients with peritoneal dialysate instilled can overestimate body composition, including muscle mass, and as such potentially delay the recognition of PEW. Thus, for more accurate MFBIA in peritoneal dialysis patients, the dialysate should be drained out.