Short and thin stool with incomplete bowel movement is considered to be caused by anal stenosis, rectal polyps, rectal cancer and other diseases. 1. Anal stenosis: it may be caused by congenital anus deformity, local injury or inflammation of anus and anal canal, which leads to short and thin stool, difficulty in defecation, pain in anus and so on, and may be accompanied by incomplete defecation. 2. Rectal polyps: mostly related to heredity, inflammation stimulation and other factors, most of the patients have no obvious symptoms, which can be found in the process of examination, some patients will have short and thin stools with incomplete defecation due to the pressure of polyps, if the surface of the polyp is ulcerated, the patients can also have blood in the stool, and some of the patients will have the phenomenon of prolapse of the polyp. 3. Rectal cancer: there is no obvious symptom in the early stage, but as the cancer grows, it can oppress the anus, and even lead to narrowing of intestinal tube, resulting in short and thin stool with incomplete bowel movement and mucus on the surface of stool. In addition, there are many other reasons that can cause short stool with incomplete bowel movement, so it is recommended to go to the hospital in time to find out the cause of the disease and receive treatment as soon as possible.