Anastomotic leakage is a serious complication after LAR with high morbidity and mortality rates. Early diagnosis and treatment is mandatory. The primary aim of the present study is to investigate the clinical use of peritoneal microdialysis and whether is able to detect anastomotic leakage prior to clinical symptoms.

Patients undergoing LAR for rectum cancer is subjected to peritoneal microdialyses during the postoperative period until the 7. postoperative day. Samples are collected every 4-hour. Samples will be analyzed continuously but the results will not be included in the clinical evaluation of the patient. Before removing the microdialysis catheter a CT whit rectal enema is preformed. Every day the patient will be evaluated whit a standardised clinical scoring system with attention at anastomotic leakage.

A total of 150 patients will be included in this study. The results of the peritoneal microdialyses will be compared with the clinical scorings system in each patient. The results form the uncomplicated courses will be used to define the normal variations in peritoneal microdialysis. This will be compared to results from patients with various complications.

The study is approved by the local scientific ethical committee No. ------

Inclusion Criteria:

• Histological verified cancer
• The cancer must be located in rectum maximum of 15 cm.
• Diverting stoma is allowed
• Perioperative radio-chemotherapy is allowed

Exclusion Criteria:

• Disseminated cancer