Body composition and nutritional status in patients on continuous ambulatory peritoneal dialysis (CAPD)

Total body water (TBW), extracellular water (ECW), exchangeable potassium pool (EKP), and alkali-soluble nitrogen in skeletal muscle tissue (N) were determined in 9 CAPD patients on treatment from 5 to 14 months (mean 8.6 months). The parameters were reevaluated in 6 of these patients 5 to 13 months later (mean 8.6 months). The mean value of TBW was normal and directly correlated to body weight (BW), but TBW was abnormally distributed between extracellular and intracellular space. ECW volume was significantly lower than the predicted value (12.1 +/- 1.4 versus 16.8 +/- 1.9 l) and out of proportion to TBW (34.8 +/- 3.9% versus 47.8 +/- 1.5%). The calculated intracellular water, therefore, appeared clearly hyperexpanded. The mean value of EKP was slightly reduced, but in three patients there was a 25% reduction. N content was low in 5 out of 9 patients. When the parameters were re-evaluated BW and TBW were unchanged in two subjects. A third patient showed a simultaneous increase in both BW (12.7%) and TBW (19%). TBW variations (+19%, -23%, -24%) without changes in BW were seen in three patients. The mean value of EKP was unchanged, but there was a 25% reduction in one patient. N content improved in two and worsened in one of the three patients in whom it was determined. The data suggest that cell overhydration was the distinctive feature in our CAPD patients, and that the evolution of the nutritional status was variable, since the patients could remain stable, gain or loose body fat, and probably change their lean body mass.