The Energy Cost of the Excretion of Urine

The energy consumption of the kidney has been estimated by a number of experimenters and by different methods; and the values obtained are all of the same order of magnitude. The concordance of these values justifies an estimate of the efficiency of the kidney, i.e., of the ratio of the work performed, calculated from the constitution of the urine, to the energy used. The efficiency of the kidney, defined in this way, appears, even in health, to be about 1-2 per cent. So far as the authors are aware, there are no data inconsistent with this low figure. Rather the reverse, this association of the thermodynamic work with the observed energy consumption of the kidney permits the correlation of a large number of facts regarding the behavior of the kidney in health and disease.