The kinetics of urinary excretion of 51Cr from labeled erythrocytes in hemolytic anemia and the anemia of blood loss.

Abstract

The urinary excretion of 51Cr was studied in conjunction with studies of erythrocyte survival, fecal blood loss, and erythrocyte volume in 54 patients with various hematologic disorders. It was confirmed that excretion of 51Cr is predominantly urinary, and the rate approximates a simple exponential function. In anemias unaccompanied by hemolysis or blood loss, the halftime for urinary excretion of erythrocyte-bound 51Cr (Tu½) ranged from 43 to 63 days. Tu½ was shortened in patients with hemolytic disease but prolonged in patients with severe blood loss; these deviations were proportional to the severity of hemolysis or blood loss, respectively. Determination of the rate of urinary 51Cr excretion may prove to be useful in differentiating various causes of anemia, especially because (1) it distinguishes severe or chronic blood loss from hemolysis, which is not possible with conventional erythrocyte survival studies; (2) the need for multiple venipunctures may be obviated; (3) fluctuations in blood volume or erythrocyte volume do not appear to affect the rate of urinary 51Cr excretion; (4) only a very small dose of radiochromium is needed.