A semiquantitative histological method to estimate acute and chronic radiation injury in the small intestine of the cat.

To study the radiation injury in the small bowel of the cat after doses close to and above the threshold for chronic radiation injury (15 Gy), an attempt was made to quantify these changes. For this purpose a semiquantitative method was developed by using 13 different histological alterations that were considered to mirror the acute and chronic radiation changes in the mucosa. Fibrosis was difficult to quantify; micrometric measurements of the bowel wall and its different layers were therefore carried out. The histological alterations were tabulated in increasing degree of severity. The sum of points of registered alterations in the specimen yielded scores that together with the micrometric measurements made it possible to differentiate specimens irradiated with high doses from those irradiated with low doses. The method may be valuable in estimating radiation injury in surgical specimens and in experimental studies of radiation injury.