Sclerotherapy is a form of treatment for protruding or dilated hemorrhoidal veins. The physician injects a needle into a vein and then infuses a sclerosing agent. This particular agent will cause scarring within the vein, and the dilated vein gradually shrinks. In some instances, there may be residual scars and sometimes these scars can cause ulceration in the region of the hemorrhoidal vein. In a small number of cases, it may have an effect on the anal sphincter, such that a patient may subsequently experience episodes of incontinence or the seepage of stool after this therapy.