Comparative effects of different sclerosing agents used to treat rectal prolapse: an experimental study in rats.

Background/purpose: Sclerosing agents injected into the rectal submucosal area produce an inflammatory response and scar that prevent rectal prolapse. This study aimed to investigate the histopathological changes following submucosal injection of different sclerosing agents in rats.
Methods: Rats (n=35) were divided into control, sham, and five experimental groups, each treated with a different sclerosing agent: cow's milk, 30% saline solution, 30% dextrose solution, 70% ethyl alcohol, and 5% phenol in almond oil (PAO). All agents were injected into the submucosal area. After 4 weeks, all animals were sacrificed. Histopathological evaluation was performed according to a semi-quantitative fibrosis scoring system (grades 0 to 3), by using Masson trichrome and hematoxylin and eosin staining.
Results: Histopathological changes in the 5% phenol in almond oil group were significantly different from other groups (p=0.0001). Prominent submucosal fibrosis (grade 3), lymphatic vascular dilation, foreign body reaction, and lipogranuloma were observed in the 5% PAO group (p=0.007). No significant histopathological differences were seen between the 30% saline, 30% dextrose, and 70% ethyl alcohol groups. Significantly increased mucosal fibroblast proliferation (grade 2) was seen in 60% rats of the 30% dextrose group (p=0.026). The cow's milk and ethyl alcohol groups had mucosal erosions and congestion (grade 1) which were significantly different from the control group (p=0.024). No statically significant difference was observed between the 30% saline group and the control group.
Conclusions: In this study we showed that 5% PAO can induce some histopathological changes in the submucosal area that increase the mucosal tightness of the mucosa, which are necessary for the treatment of rectal prolapse.
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