The other side of the coin: interdialytic weight gain as an index of good nutrition.

Excessive interdialytic weight gain (IDWG) is usually attributed to fluid and sodium overload. Abnormal thirst regulation, hormonal derangements, and social, cultural, and psychological habits may account for low compliance with fluid and salt restrictions. However, food intake is an important determinant of IDWG, and high IDWG may reflect the nutritional status of hemodialyzed patients, rather than their scanty compliance. The relationship between IDWG, efficacy of dialysis, and nutritional status was investigated in 38 patients (28 men and 10 women), in whom urea kinetics was studied by means of an on-line urea sensor (UM 1000, Baxter Healthcare, McGraw Park, IL), and Kt/V and protein catabolic rate (PCR) were calculated. Records from 161 dialysis sessions were analyzed and grouped according to their IDWG (group A, weight gain > 5% and group B, weight gain < 5% of dry body weight). In group A, Kt/V, solute removal index, urea reduction ratio, predialytic blood urea nitrogen (BUN), urea removed, and PCR were statistically higher than in group B (P < 0.05). Regression analysis showed a significant and positive correlation between IDWG and PCR. In 17 of 38 patients with steadily high IDWG, serum albumin levels, predialytic BUN, and PCR were significantly higher than in patients with low IDWG (P < 0.05). Sex and predialytic blood pressure did not correlate with IDWG; in contrast, age negatively affected both IDWG and PCR (age v IDWG and age v PCR, r = 0.22; P < 0.008 and P < 0.006, respectively). These results confirm that high IDWG is associated with better nutritional status.