Abstract

Hemorrhoids are one of the commonest disorders specific to the human. However, the pathogenesis is not well understood so far. Anal submucosa is largely composed of blood vessels, loose connective tissue and smooth muscles, forming muscular network around the venous plexuses. We analyzed the distribution of smooth muscles in the hemorrhoidal tissues. Immunohistochemical stainings for desmin, vimentin, and Factor VIII related antigen were performed using six freshly frozen hemorrhoidal tissues. All of them were diagnosed as external hemorrhoids. Four anal tissues from Miles' operation specimen without hemorrhoids were used as normal controls. In all six cases, venous plexuses were variably dilated and smooth muscle cells were unevenly distributed. In minimally involved areas, there were relatively sufficient amount of perivascular smooth muscles which were arranged in their bundles. In contrast, only single scattered cells or very small amount of smooth muscle bundles were noted around the dilated vascular plexuses in severely affected areas. In two severe hemorrhoidal tissue samples, vascular plexuses were markedly dilated and only single scattered smooth muscle cells were seen. In conclusion, the total amount of smooth muscles in the submucosa of hemorrhoid tissue was reduced than those of the normal controls. The degree of hemorrhoidal dilation was inversely related to the amount of smooth muscles. However, causal relation between diminution of submucosal smooth muscles and venous dilation remains to be clarified.

• Keywords: Hemorrhoids;Submucosal venous plexuses;Smooth muscles;