Anal abscess

Essentials

In 90% of the cases the disease is cryptoglandular, i.e. inflammation of the anal glands.
10% of the cases have another aetiology: e.g. Crohn’s disease, trauma, HIV, radiation therapy, neoplasia.

Inspection of the anus usually reveals the diagnosis: a tender mass is observed near the anus.
Touch per rectum may be impossible because of the pain. Perineal palpation may reveal a painful mass in these patients.
If needed, the diagnosis can be confirmed by perineal ultrasonography.
The abscess may be located in the anal canal between the sphincter muscles (intersphincteric abscess), in which case it is palpable through digital rectal examination or visible by endoanal ultrasonograpy, CT or MRI.
If the patient has several abscesses or if there is a suspicion of Crohn’s disease (Crohn’s disease) for some other reason, an ileocolonoscopy should be carried out after having treated the abscesses.

An anal abscess always requires surgical incision and drainage.
General anaesthesia is necessary for clinical examination and sufficiently wide incision.
The incision is performed in an operating theatre setting, and if a fistula tract is found, it can be treated simultaneously [Evidence Level: B].
If a fistula was not found in the operation, the wound should still be monitored until it has healed. Up to 50% of the patients develop an anal fistula, which requires new operation.