Principle: After intravenous injection of in vitro 99mTc-labeled autologous erythrocytes, their uptake occurs at the site of bleeding. This appears on the scintigram as a saturated accumulation of the radiopharmaceutical. The presence of blood in the stool on the day of examination is ideal. Indication: Evidence and determination of the site of bleeding, especially in the middle and lower GIT – polyps, diverticula Patient preparation: none Duration of examination: approx. 60 minutes,in rare cases also on the next day (only scanning) Radiopharmaceutical: 99mTc – labelled autologous erythrocytes Method of application: Intravenous Examination methodology: The patient is given an intravenous cannula and the HDP kit is injected. Approximately 20 min later, 20 ml of blood is drawn into a syringe and the 99mTc pharmacopeia is added to this blood. With occasional stirring, in about 10 min the blood is returned to the patient. The patient lies down on the gamma table and we slowly inject the blood. We start a dynamic study that lasts 60 minutes. At the end of the study, we take a 2-minute static picture of the patient. We then repeat this static image at approximately hourly intervals as needed, in rare cases on a second day.