Production of Intraperitoneal Interleukin-6 Following Open or Laparoscopic Assisted Distal Gastrectomy

The interleukin (IL)-6 concentration in plasma or serum has been considered to represent the degree of stress resulting from surgery. However, IL-6 in peritoneal fluid has rarely been considered. The aim of this study was to assess the concentration and amount of IL-6 in peritoneal fluid as indicators of surgical stress. To obtain basic data on peritoneal release of IL-6 during gastric cancer surgery, we measured IL-6 in peritoneal drainage samples, stored for up to 72 hours postoperatively, from patients who had undergone conventional open (ODG group, n = 20) and laparoscopic-assisted (LADG group, n = 19) distal gastrectomy. Within 24 hours, 61 and 77% of the IL-6 was released into the peritoneal cavity in the LADG and ODG groups, respectively. In both groups, the concentration and amount of peritoneal fluid IL-6 were significantly correlated with each other (LADG group: Spearman''s rank correlation test rS] = 0.48, P = 0.04; ODG group: rS = 0.58, P = 0.01). The concentration and amount of IL-6 in peritoneal fluid was 2.8- and 3.6-fold higher in the ODG than in the LADG group, respectively (P < 0.01). With regard to the relationship between the serum C-reactive protein (CRP) peak and the concentration or amount of peritoneal fluid IL-6 released within 24 hours, only the concentration of peritoneal fluid IL-6 in the LADG group was significantly correlated (rS = 0.60, P = 0.01) with the serum CRP peak. Our findings suggest that the amount and concentration of IL-6 released into the peritoneal cavity for up to 24 hours after surgery can each be a reliable parameter for assessment of surgical stress.Key words: Interleukin (IL)-6, Cytokine, Peritoneal fluid, Surgical stress, Gastric cancer, Laparoscopic surgery, GastrectomyRecent advances in laparoscopy techniques have heralded a new era in the field of abdominal surgery, and laparoscopic approaches are now being employed for the treatment of malignant neoplasms of the stomach, colon and other organs.^1–5It has been reported that levels of circulating proinflammatory cytokines such as interleukin (IL)-1 beta, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha are related to the extent and severity of surgical procedures.^6–8 Interleukin 6 is a sensitive and early marker of tissue damage, and in general the greater the surgical trauma, the greater the response of IL-6.⁹ Many studies have shown that the level of IL-6, as an indicator of surgical stress, is significantly lower after laparoscopic surgery than after open surgery.^9–15 Most of the studies reported so far have measured and analyzed the concentration of IL-6 in plasma or serum,^{9,10,12–16,18} and only rarely in peritoneal fluid,^{11,12,15,17,19,20} and the results have indicated significant correlations between the level of IL-6 and several clinical parameters. However, there is some concern as to whether the concentration of IL-6 in peritoneal fluid adequately reflects the degree of surgical stress. Interleukin 6 is released into the abdominal cavity in response to surgical injury.^16,20,21 Therefore, the total amount of IL-6 contained in peritoneal fluid might be regarded as a gold standard for assessing the severity of local surgical stress. However, this possibility has never been fully addressed.In the present study, we analyzed both the concentration and total amount of IL-6 in peritoneal fluid sequentially in the early postoperative period after distal gastrectomy, and compared laparoscopic and open surgical procedures in terms of intraperitoneal IL-6 production in order to observe the basic pattern of IL-6 release.