Postoperative nutritional therapy administered in group I will not include immunomodulating factors. Early postoperative enteral nutrition, based on standard elementary diet (Peptisorb), starts 20 hours post-surgery. The initial flow rate will be 8 ml/h, which will be increased gradually, with the volume doubled every 24 hours, up to 100 ml/h. The enteral nutrition will be continued for six days. During the initial five days post-surgery, the patients will be additionally supplemented parenterally via peripheral veins (commercially available two-chamber bag for peripheral access with 480 kcal of energetic value and 5.7g of N contained in standard amino acids).

The nutritional therapy of group II patients will start post-surgery. It will be based on early enteral nutrition with elementary diet (Peptisorb) with simultaneous parenteral nutrition with two-chamber bag with 480 kcal energetic value and 5.7g of N contained in standard amino acids administered via peripheral veins. Additionally, glutamine (100 ml of Dipeptiven) will be added to the two-chamber bag. The parenteral nutrition will be administered for five days.

Preoperatively, group III patients will be given commercially available oral diet enriched with arginine (Cubitan, 1 package 3 times per day). Additionally, they will be administered commercially available two-chamber bag with 480 kcal energetic value and 5.7g of N in standard amino acids via peripheral access. The duration of pre-operative preparatory phase ranged between 5 and 10 days (8 days on average). Enteral nutrition with commercially available arginine-containing diet (Cubison) will start 20 hours post-surgery at an 8 ml/h flow rate; the rate will be increased gradually, with the volume doubled every 24 hours, up to 100 ml/h and continued for six days. Simultaneously, commercially available two-chamber bags for peripheral access with composition identical to that used preoperatively will be administered via peripheral veins for five days.

Early postoperative enteral nutrition with standard elementary diet (Peptisorb), will start 20 hours post-surgery. The initial flow rate will be 8 ml/h, which will increase gradually, with the volume doubled every 24 hours, up to 100 ml/h. The enteral nutrition wil be continued for six days. During the initial five days post-surgery, the patients will be additionally supplemented parenterally via peripheral veins (commercially available two-chamber bag for peripheral access with 480 kcal of energetic value and 5.7g of N contained in standard amino acids).

Platelet count and phagocytic activity of thrombocytes will be examined twice in each patient. Blood samples for laboratory tests will be drawn prior to surgery and nutritional therapy and 12 days after the surgery. Thrombocyte count will be determined using ADVIA 120 haematological analyser. Phagocytic activity of blood platelets will be determined against Staphylococcus aureus ATCC 6538P bacterial strain. It expresses as the fraction of phagocytizing platelets and the phagocytic index. The fraction of phagocytizing platelets corresponds to the percentage of phagocyting thrombocytes per 1000 consecutive cells of this type. The phagocytic index represents the ratio of phagocytized bacteria per 100 phagocytic platelets.