Weight deficit in patients on continuous ambulatory peritoneal dialysis.

Small solute clearances were compared between two groups of patients on continuous ambulatory peritoneal dialysis (CAPD), an underweight group with a ratio of actual-to-ideal weight (W/IW) less than 0.9 and a normal-weight group with W/IW between 0.9 and 1.2 at the first clearance study after initiation of CAPD. Adequate clearance levels were set according to the K/DOQI guidelines. Duration of follow-up during CAPD and time on CAPD until the first clearance study was similar in the two groups. Initial weekly Kt/V urea and creatinine clearance also were similar. Kt/V urea values were adequate in 41.8% of the underweight subjects and 41.0% of the normal-weight subjects (not significant). Corresponding percentages for creatinine clearance were 36.4% and 39.7% (not significant). Serum creatinine and albumin concentration, creatinine excretion, and lean body mass estimated from creatinine kinetics were lower in the underweight group. Weight measurements from initiation of CAPD were available in 37 underweight patients. At initiation of CAPD, 31 subjects had W/IW less than 0.9, and 6 subjects had W/IW greater than 0.9. Chronic catabolic illness was present at CAPD initiation in 19 patients. Among the 37 patients, 17 lost weight and 6 gained weight during the course of CAPD. Compared with patients who lost weight, those who gained weight were younger (35.6 +/- 9.3 years old versus 58.4 +/- 15.0 years old; P = 0.0069) and had a higher percent of women (80.0% versus 11.8%; P = 0.0093), higher initial weekly Kt/V urea (2.58 +/- 0.50 versus 1.91 +/- 0.24; P = 0.0087), and a higher percent of adequate Kt/V urea (80.0% versus 11.8%; P = 0.0093). Small solute clearances do not differ between underweight CAPD patients and normal-weight CAPD patients. Underweight CAPD patients usually start CAPD with a weight deficit and have associated catabolic illnesses. Catabolic illness is the sole cause of weight deficit in 40% of the underweight CAPD patients and is present in the remaining 60%. The role of inadequate clearances in the development of weight deficit in CAPD populations is difficult to assess. It seems, however, that adequate Kt/V urea may be necessary for weight gain in underweight CAPD patients.