[Nuclear Medicine in the diagnosis of lower gastrointestinal bleeding]

Lower gastrointestinal bleeding appears to be a frequent problem in the every day practice. The exact localisation of the bleeding site plays a major role in treatment planning. Nuclear Medicine imaging techniques allow the diagnosis of ectopic gastric mucosa-Meckel's diverticulum (MD) and the extravasation of red blood cells. Meckel's diverticulum is the most frequent congenital anomaly of the gastrointestinal system moreover bleeding seems to be the most important clinical symptom during childhood. Scintigraphy using technetium-99m pertechnetate ((99m)TcO(4)(-)) is the method of choice for the diagnosis of ectopic gastric mucosa in MD. The use of this test in children is of high diagnostic accuracy, with a sensitivity of 85%-95% and specificity of 90%-95%. In adults, lower gastrointestinal bleeding is commonly caused by tumors, colitis, dysplasias or polyps, while MD is rare. Scintigraphic demonstration of active lower gastrointestinal bleeding contributes to risk-stratification, to prognosis, appropriate timing for angiography and to planning of surgical intervention. (99m)Tc labelled erythrocytes and (99m)Tc sulphur colloid are commonly used radiopharmaceuticals each having its own indications and used for the diagnosis of active bleeding. Moreover delayed imaging is possible using (99m)Tc labelled erythrocytes, enabling the diagnosis of intermittent bleeding. Careful interpretation of the scintiscan images is essential to avoid numerous pitfalls. The indications for using the specific nuclear medicine technique as above, for the diagnosis of lower gastroinstestinal bleeding and the indications for using other methods besides those of nuclear medicine are described.