If it is chronic colitis, it is possible to cause anal fistulas. Most patients with chronic colitis have symptoms of unformed stools and loose feces. Some feces, which are relatively thin, tend to accumulate in the anal crypts, leading to infection of the anal glands in these areas. The inflammation then spreads to the normal soft tissues around the anus, including subcutaneous tissues, forming perianal abscesses. If a perianal abscess ruptures or is surgically incised to release pus, the external opening and the pus cavity gradually heal and narrow, thus forming an anal fistula. If chronic colitis is diagnosed, it should be promptly diagnosed and treated to prevent the formation of anal fistula.