These are collections of pus in the surrounding area of the anorectal region, usually happening due to an extension of an anal pathology. In most cases, it starts as an infection of a gland called the anal gland which is situated inside the anal canal. Other causes are fissuring of the rectal wall by a very hard stool or a foreign body like a fish bone, any blood-borne infection or an extension of a skin boil.
These abscesses present as painful swellings in the perianal region associated with difficulty in sitting and fever. The patient may also have constipation if the abscess is closely aligned with the anal canal.
Antibiotic therapy may be attempted in the initial phases when the abscess is small but it may not suffice and the patient usually requires the surgical procedure of incision and drainage.
Here it is very important to understand that perianal abscesses may recur because of constant reinfection from the anal canal or rectum and the opening may continue to discharge blood and pus. This is now the stage of fistula formation.