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Aim of the studies The subject of our investigation was to analyze bone and mineral metabolism after longsegment small bowel resection in the rat model, to detect functional and morphological alterations and to describe the development of osteopathy. 9.2 Methods 12-week-old male Lewis rats were randomized into a short (8 weeks) or long (16 weeks)follow-up group, sham operation, resection of the proximal third of the small bowel, resection of the distal third of the small bowel, resection of the distal third of the small bowel inclusive caecum and resection of the entire jejunum and ileum were carried out. 19 days prior to the end of the experiment, the animals were transferred into a metabolic cage to analyze weight gain/loss, food intake and fecal excretion/24 hours. At the end of the experiment the animals were desanguinated, blood samples, bowel and bone specimens were collected, length,weight, volume, density, mineral content and fracturing energy were determined and bone histology was examined. The calcium/phosphorus ratio, non-mineralized tissue content and the ratio fracturing energy/mean bone density were calculated. 9.3 Results Resection of the entire jejunum and ileum and of the distal third of the small bowel inclusive the ileocaecalvalve proved to be good models to induce a short bowel syndrome in the rat. After 8 weeks, significant differences in comparison with the control group were found for theparameters body weight, weight gain, food efficiency, femur length, weight, volume, mineral content and mineral density, and in the fracturing energy per bone volume and bone density but not in the bone minerals calcium and magnesium. After 16 weeks differences were found for body weight, weight gain, food efficiency, femur length, weight, volume, bone mineral content and density (DXA), bone minerals and nonmineralized tissue but not for the fracturing energy. The average values of all the named parameters were lower in the resected groups, and lowest in the group after resection of the entire jejunum and ileum. 9.4 Conclusions Long-segment small bowel resection causes significant changes in bone mineralisation and calcium metabolism. There is a loss of anorganic bone mass (ash) and bone histology shows a reduction of trabecular bone mass. Bone mineral density is lowered and the fracture risk is elevated in the short follow up group after long-segment small bowel resection.