Protein intake can not be estimated from urinary urea excretion.

We assessed the relationship between protein intake (calculated from a 3-day prospective dietary diary) and 24-h urinary urea excretion in 37 children with chronic renal failure. Protein intake was not restricted during the investigation period. The 24-h urinary urea excretion correlated poorly with the protein intake estimated from the dietary diary (r = 0.58). We conclude that although it is common practice to assess compliance with a protein-restricted diet in children with chronic renal failure with a dietary diary and 24-h urinary urea excretion, the value of this assessment is questionable.