Objective: Preoperative radiotherapy of patients with rectal carcinoma is frequently used to reduce the incidence of local recurrence. However, the radiation therapy is associated with several complications, including diarrhea, retarded anastomotic healing and mucosal atrophy. Exogenous administration of lactobacilli has been demonstrated to be effective in stimulating intestinal mucosal growth and reduce mucosal inflammation. The objective of this study was to examine the effects of Lactobacillus plantarum 299v administration on external radiation injury in colon anastomotic healing at different time points.

Material and methods: Sprague-Dawley rats were treated with Lb. plantarum 299v or saline as control and received external radiation of the lower abdomen (10 Gy/day) on day 3 and 7 of the experiment. After 4 days, a colonic resection with anastomosis was performed. Animals were sacrificed on 4th, 7th and 11th day postoperatively. Body weight, white blood cell (WBC) count, mucosal myeloperoxidase (MPO) activity, hydroxyproline, nucleotide, DNA and RNA content, colonic bacterial microflora, bacterial translocation and histology were evaluated.

Results: On the 4th postoperative day body weight, WBC and MPO decreased significantly after radiation. On the 7th postoperative day MPO decreased after radiation. In the two irradiated groups it decreased significantly in the Lb. plantarum group compared to the radiated group without treatment. Collagen concentration on the 7th postoperative day was significantly higher in Lb. plantarum group without radiation compared to the group with radiation without Lb. plantarum. On the 11th postoperative day MPO was significantly higher in irradiated rats without treatment compared to Lb. plantarum treatment. The collagen concentration increased significantly in the irradiated Lb. plantarum group compared to the other two groups.

Conclusion: The collagen content decreased and MPO activity increased significantly of the colonic anastomosis in irradiated rats without treatment compared to those treated with Lb. plantarum. It therefore seems that administration of Lactobacillus plantarum 299v reduces the intestinal injury and inflammation following external radiation and improves the colonic anastomotic healing.