[Quantitative determination of blood loss by means of 51 Cr-labeled erythrocytes in occult hemorrhages of the gastrointestinal tract].

By means of 51 Cr-labelled erythrocytes the stools of 17 patients were examined for occult admixtures of blood. Hereby a method well suited for routine work was developed, the manipulations with stool were reduced to a minimum measure. As measuring device an animal total body counter was used. The average excretion of blood in persons without diseases of the gastro-intestinal tract was 0.49+/- 0.38 ml/d. In three patients a haemorrhage could be proved. The quantitative determination of blood losses through the intestine is diagnostically valuable. It is useful particularly in unclear iron deficiency anaemis. A combination of the method with the determination of the survival time of erythrocytes is possible.