Once again the gastroenterologists of northwestern Canada have come out with a series of essays advancing important modem concepts. As indefatigable as ever, they bring together the latest in clinical-pathophysiological considera tions for the clinician. The topics run the gamut from the lovely liver to HIV infection, from the pathophysiology of bile flow to comments on antigens in colorectal cancer. It is always easy to publish a first volume, for enthusiasm is high and everyone is anxious to win a place. Bringing out a second volume, the carrying forward of a good idea, is so much harder. In many ways this second volume in the series marks the coming of age of Canadian gastroenterology, as 11 of the 21 contributors currently reside in Canada. Still, the contributions from the United Kingdom and the United States make this an Anglo-American festival. Reading the chapters will make you appreciate the care with which the contributors have garnered recent references to give up-to-date practical infor mation for us all. I enjoyed all that I read. My congratulations to Drs. Shaffer and Thomson for a job well done. Howard M. Spiro, M.D. New Haven, Connecticut ix Preface This book is based on papers presented at the third symposium on Recent Ad vances in Gastroenterology held by the Canadian Association of Gastroenter ology. The proposed audience for this volume is the internist and the general surgeon, as well as those in the specialties of gastroenterology and hepatology.