Segmental bioelectrical impedance in patients with chronic renal failure

We studied changes in hydration by whole body and segmental (arm, leg and trunk)bioelectrical impedance analysis (BIN in patients with chronic renal failure (CRF) undergoing haemodialysis and continuous ambulatory peritoneal dialysis (CAPD). Mean (SD) fluid removal by haemodialysis of 1.38 (0.81) kg was overestimated by whole body BIA at 1.83 (1.13) I, P< 0.005. Peritoneal fluid drained from the CAPD patients of 1.88 (0.36) kg was underestimated by whole body BIA at 0.59 (0.35) I, P< 0.0001. Resistance and reactance significantly increased for the whole body and all segments (except trunk reactance) after haemodialysis. Drainage of CAPD fluid resulted in smaller increases in trunk resistance and whole body resistance. The increase in trunk resistance was less in CAPD than haemodialysis patients, even though the volume of fluid drained from the peritoneum in CAPD patients exceeded that removed from the whole body during haemodialysis. We conclude that whole body BIA does not estimate changes in body fluid with sufficient accuracy to be of use in clinical practice. Segmental impedance may be a potentially useful method for investigation of regional changes in body fluid, though is insensitive to changes within the peritoneal cavity.