Body Composition in Chronic Renal Failure1

In severe chronic renal failure loss of weight is common due to a reduction in body fat and fat-free solids. The lean body mass forms an increased proportion of body weight. Body water is relatively increased largely due to an excess extracellular fluid. Intracellular fluid is reduced relative to standard weight in the majority of patients. The exchangeable sodium is increased. The changes are not confined to patients with terminal uraemia but are most marked in those who have received prolonged treatment with low-protein diets. After the start of regular haemodialysis body weight falls because of losses of body water from both extracellular and intracellular spaces. Thereafter body weight increases, due to gains in body fat and fat-free solids. Changes in exchangeable sodium are variable. Intercurrent illness, poor dialysis, or fluid indiscretions rapidly induce a return of the original abnormalities and recovery is slow. Similar changes in body composition are observed after renal transplantation though these may be modified by large doses of prednisone. In general, transplantation is more effective in restoring body composition to normal than haemodialysis. These changes closely resemble those found in malnutrition and it is suggested that the abnormalities of body composition found in chronic renal failure are attributable to protein-calorie deficiency.