Pus from the anus is often observed in "anal fistula" in which pus tunnels are formed. It may be caused by the intestines far inside from the anus or the skin around the anus.
"Crohn's disease" is an inflammatory bowel disease that develops inflammation in the entire gastrointestinal tract from the mouth to the anus. In particular, it often occurs in the ileum, the lowest part of the small intestine, and large intestine, but inflammation may also occur in all parts of the gastrointestinal tract from the mouth to the anus and skin around the anus. It often develops in young people aged 15–25 years. Although the cause is not well understood, there is a theory indicating that the intestines react excessively to factors such as diet and infection due to dysfunction of the immune system.
Common symptoms of Crohn's disease include chronic diarrhea, abdominal pain, fever, loss of appetite, and weight loss, but symptoms such as swelling, pain, and itching occur in the anus, which are likely to be mistaken for hemorrhoids. Crohn's disease is often accompanied by hemorrhoids, such as anal fistula and anal fissure.
A chronic disease caused by inflammation of the apocrine gland (one of sweat glands) around the anus. A layer that accumulates pus is formed under the skin from the perianal region to the buttocks and thighs. Although not all of them are connected to the anal canal, many pus exits are formed on the skin. This is repeated and the skin becomes thick and darker. Thus, surgery to cut the thick skin and pus layer will be required.
The main symptoms of pyoderma are pus discharge and swelling. It is very likely to be mistaken for anal fistula that forms pus tunnels connecting the skin between the rectum and perianal region. Pyoderma is also often complicated by anal fistula. If it is left untreated, the range will gradually become large. So visit a hospital early.
It is regular folliculitis that develops on the skin around the anus. Folliculitis is a type of bacterial infection. Inflammation occurs to the hair follicles in the anus (where the hair roots are wrapped) and the pores become red. It occurs due to infection with bacteria when the anus is damaged or not clean.
Perianal folliculitis has very similar symptoms to anal fistula, which discharges pus and causes painful small lumps (swelling). It may cure spontaneously. If pain or swelling is severe, visit a hospital.