Crohn's disease is a chronic inflammatory bowel disease which may affect any part of the gastrointestinal tract with a preference for the terminal ileum and ileocaecal region. The disease was first described in 1932 and has increased during the last decades. The clinical manifestations could be referred to as inflammation, malabsorption and obstruction. The annual incidence of Crohn's disease in the county of Västerbotten, North Sweden, was found to be 4.9/105 inhabitants. In a study of 87 patients in a medical gastrointestinal unit, 23% of non-operated patients and 66% of resected patients had increased fecal fat excretion. D-xylose test and lactose tolerance test were abnormal 1n 19% and 24% respectively of the non-operated patients. No clear relation could be found between the outcome of these malabsorption tests and localization, extension or activity of the disease. This suggests the cause of malabsorption 1n Crohn's disease to be complex and multi- factorial . The morphology of jejunal biopsies from 18 patients with Crohn's disease elsewhere 1n the gastrointestinal tract demonstrated an abnormal picture 1n 13 patients when assessed by light microscopy and scanning electron microscopy. A high proportion of these patients had abnormal Intestinal absorptive tests. Skeletal muscle biopsies were performed 1n 13 patients showing a depletion of muscle potassium content and more Infrequently low skeletal muscle magnesium content. This depletion 1s not reflected by subnormal plasma concentration. In the Initial clinical assessment of a new gamma labelled synthetic bile ac1d-SeHCAT, 45 patients, 19 of whom had Crohn's disease, were studied. The outcome of the test correlated well with the excretion of fecal bile acids. It was possible to discriminate patients with terminal Ileal disease from other patient groups. In a follow-up study, the SeHCAT test was modified as to make it simpler and to shorten the test period. Nine patients with Crohn's disease were tested, showing a suffi cent accuracy of the outcome of the test within 48 hours, using simple equipment available in many hospitals. The elimination of radioactivity was calculated as WBR50*» the time for 50% of the administered dose to be excreted. This gives information as to the rate of excretion, reflecting the degree of terminal ileal malfunction. / <p>S. 1-41: sammanfattning, s. 43-115: 5 uppsatser</p> / digitalisering@umu