An anal fistula generally refers to a tract left behind after an anal abscess bursts on its own or is surgically opened. It usually consists of a primary internal opening and a secondary external opening. The main clinical manifestations, or primary symptoms, are: The first is discharge of pus, which occurs due to recurrent infections in the anal fistula; The second is pain. When the external opening is closed, the pus inside cannot drain properly, or when drainage is poor, this leads to accumulation of pus in the fistula tract, causing localized pain; The third is itching. Continuous irritation of the skin around the external opening by pus draining from the fistula tract can cause itching around the anus and may lead to symptoms like anal eczema.