Effect of omentectomy on peritoneal defence mechanisms in rats.

OBJECTIVE

To assess the effect of omentectomy on peritoneal defence mechanisms in rats.

DESIGN

Randomised study.

MATERIAL

Sixty Wistar Albino rats.

INTERVENTIONS

Rats were divided in three groups of 20. All rats underwent midline laparotomy and 10 rats in each group had omentectomy. Samples were taken two hours (early period) and 30 days (late period) after omentectomy.

MAIN OUTCOME MEASURES

Effect of omentectomy on bactericidal activity of peritoneal fluid (PBA), chemotactic indices (CI) of polymorphonuclear leucocytes (PMNL), phagocytic activity of PMNL in the peritoneal fluid (PHA), total cell counts, and cell types of peritoneal washing fluid.

RESULTS

In the early period omentectomy reduced total cell counts from 3440 (1400-4800) x 10(6)/10 ml to 1480 (800-2080) x 10(6)/10 ml (p = 0.0022), and the CI of PMNL from 2.86 (2.32-4.02) to 1.43 (1.29-1.77) (p = 0.0002), and increased the PHA from 11.9 (8.3-17) to 17 (16-19) (p = 0.0006). The PBA was not significantly altered. The proportion of macrophages decreased (p = 0.0001), while the proportion of lymphocytes increased in the peritoneal fluid (p = 0.0002). In the late period total cell counts in the control and omentectomy groups were 3440 (1400-4800) x 10(6) and 3160 (1040-5120) x 10(6)/10 ml fluid, respectively (p = 0.52). Omentectomy reduced the CI of PMNL from 2.86 (2.32-4.02) to 2.01 (1.82-1.49) (p = 0.0003). The difference between the proportion of PHA of either group was not significant (p = 0.06). PBA in the control and omentectomy groups was 99.03 (70-100) and 99.48 (71.5-100), respectively (p = 0.97). Although the total cell count in the peritoneal fluid did not differ, the proportion of macrophages decreased (p = 0.0003) while the proportion of lymphocytes increased (p = 0.0002). The proportion of PMNL did not change in either of the experimental settings.

CONCLUSIONS

The omentum has an important role in local peritoneal defence mechanisms in experimental conditions. Its removal may effect some of these mechanisms adversely.