During the last two decades significant advances have been made in the in vivo-diagnosis of gastrointestinal diseases. Although Ultrasound and CT as well as Endoscopy have had a major impact on the evaluation of liver, pancreas and bile diseases, there are a lot of indications for Nuclear Medicine procedures. These include new investigational procedures like esophageal scintigraphy, proof of bleeding sites, scintigraphy of inflammatory diseases, and intestinal resorption tests. Further, immunoscintigraphy with radiol- elled antibodies has gained wide-spread application especially in colon cancer. The differential diagnosis of liver tumors like haemangioma and focal nodular hyperplasia by means of blood pool and HID A-scintigraphy is nowadays a routine procedure. Other established methods like hepatobiliary scintigraphy and liver perfusion scintigraphy have proved to be reliable tools in the pre-and postoperative evaluation of patients with bile duct obstruction and portal hypertension. The aim of this book is to present the entire spectrum of Nuclear Medicine in Gastroenterology to our colleagues from internal medicine and surgery. Ultrasound and Sonography as well as CT will rule the field of gastroenterology, but there remain a certain number of unanswered questions. Nuclear Medicine provides a lot of reliable answers. H. J. Biersack and P. H. Cox July 1990 VB List of contributors Duncan M. Ackery, Department of Nuclear Medicine, Southampton General Hospital, Tremona Road, Southampton, Hampshire S09 4XY, U. K. Roland Bares (co-author: U. Buell), Department of Nuclear Medicine, Te- nical University of Aachen, Pauwelsstr. 1, DW-5100 Aachen, Germany.