Drainage of perianal abscesses is a well established treatment. Traditionally its been done in general anesthesia after the swelling has been localised its been drained with a knife. After surgical intervention complications can occur with recidivism, chronic fistulas that go from the anal to the skin and sometimes the anal sphincter is damaged which can cause problems with incontinence.

Through ultrasound the abscess is opened under more controlled forms with a better visual overview. This is a new technique that has not been tested in larger studies. The aim with ultrasound-drainage as with traditional incision to drain the abscess so that the infected area can heal.

The hypothesis is a reduction of recurrences and formation of fistulas with the use of 3D ultrasonography.

The individual patient is informed about the condition and if meets criteria is offered to take part in the study. Written information and informed consent always noted. Questions about the patients general medical condition is noted and if the person has had problems with perianal abscesses before.

Inclusion Criteria:

• perianal abscess that needs surgical treatment, over the age of 18

Exclusion Criteria:

• Under the age of 18 or unable to understand study information because of language difficulties or dementia.