This thesis focuses on the clinical importance of the ileocaecal junction. Shows evidence and justifies attempts for its surgical reconstruction in Short Bowel Syndrome, Crohn’s disease and in otherwise healthy children. In the first section using clinical database analyses, the surgical conditions leading to loss of the original ileocaecal junction in children were established. The main cause leading to loss of the ileocaecal junction is age related: necrotising enterocolitis in the newborn period, intussusception in infancy, complicated appendicitis and inflammatory bowel disease and large bowel volvulus in adolescence. Accurate diagnosis of these conditions and the appreciation of the value of the ICV may prevent the need for resection of the valve. In the second section the long term complications seen after the loss of the ileocaecal junction is analysed in otherwise healthy patients. Three groups of patients underwent limited hemicolectomy, hemicolectomy and resection of 10-25 cm ileum have been statistically compared. The results showed the loss of the original junction has significant long term morbidity. 27% of the patients developed long term diarrhoea and it comes only from the loss of the ileocaecal valve. The loss of 10-25 cm terminal ileum and the loss of the ascending colon have no significant role in the postoperative complications. In the third section the relation of the intact ICV and the survival in Short Bowel Syndrome has been analysed. Our results suggested that a significantly shorter (40.5 ± 7.74 cm vs. 74 ± 29.0 cm) small bowel length is required for survival if the ICV is intact. In the fourth section we looked at patients with Crohn’s disease undergoing surgical intervention and ileocaecal resection. It was shown that a very high rate (75%) of chronic diarrhoea and disease recurrence (50%) occurred after loss of the ICV. However this is not attributable only to loss of the ICV. CD patients, especially, may benefit from preservation or reconstruction of the ICV. Our results showed that ileocaecal valve reconstruction should be considered as part of Autologous Gastrointestinal Reconstructive Surgery in Short Bowel Syndrome. Patients with Crohn’s disease and even otherwise healthy patients may benefit from ileocaecal reconstruction as well.