Histopathological comparison of topical therapy modalities for acute radiation proctitis in an experimental rat model

To evaluate the prevalent topical therapeutic modalities available for the treatment of acute radiation proctitis compared to formalin.

A total of 120 rats were used. Four groups (n = 30) were analyzed with one group for each of the following applied therapy modalities: control, mesalazine, formalin, betamethasone, and misoprostol. A single fraction of 17.5 Gy was delivered to each rat. The rats in control group rats were given saline, and the rats in the other three groups received appropriate enemas twice a day beginning on the first day after the irradiation until the day of euthanasia. On d 5, 10, and 15, ten rats from each group were euthanized and a pathologist who was unaware of treatment assignment examined the rectums using a scoring system.

The histopathologic scores for surface epithelium, glands (crypts) and lamina propria stroma of the rectums reached their maximum level on d 10. The control and formalin groups had the highest and mesalazine had the lowest, respectively on d 10. On the 15th d, mesalazine, betamethasone, and misoprostol had the lowest scores of betamethasone.

Mesalazine, betamethasone, and misoprostol are the best topical agents for radiation proctitis and formalin has an inflammatory effect and should not be used.