Anal fistula and anal abscess
A worsening feeling of painful pressure around the anus typically indicates a perianal abscess. General symptoms such as a fever and feeling unwell are also typical. The abscess usually “wanders” towards the skin where it then erupts. The pus then drains off, often with minor bleeding.
The cause is revealed to be small passageways, termed “fistulas”, which extend from the anal canal in the direction of the abscess.
The fistulas themselves, which persist even after the spontaneous draining of the abscess, cause few symptoms: they are usually noticed due to continuous secretion near the anus. We distinguish between the following types of fistula: surface pathways (submucous); pathways in-between the sphincters (high and low intersphincteric fistulas), pathways through both sphincters (transsphincteric fistula) and fistulas whose pathways are above the sphincter apparatus (suprasphincteric fistula).
Other – although rarer – causes include fistulas and abscesses caused by inflammatory bowel disease (Crohn’s disease), diverticulitis or some types of cancer.
Diagnosis involves a combination of examination, palpation and rectoscopy. Confirmation is achieved by imaging the fistula with a metal probe. Endosonography is also a good method for imaging fistula pathways to the sphincters, if the patient is able to tolerate this procedure. Often, however, fistulas can be identified only during examination under anaesthetic. Complex fistula pathways (e.g. with Crohn’s disease) may also be imaged by using an MRT of the pelvic floor.
The occurrence of a perianal abscess must always result in rapid surgical treatment (fistulas occurring due to Crohn’s disease may form an exception here). Following a successful operation, a course of antibiotics is not necessary. Perianal abscesses should not be treated solely with antibiotics.
Surgical intervention must include both abscess and fistula. Treatment of the abscess involves extensive “uncapping” of the abscess without adversely affecting the sphincter. As a general rule, fistulas whose pathways run underneath the sphincter muscle or within the lower third can be split and excised. Since fistula pathways may also run through larger portions of the continence apparatus (see above), radical excision may sometimes be problematic, since it can lead to incontinence. On the other hand, leaving the fistula alone results in the continual incidence of abscesses, which can also pose a considerable risk to the sphincter.
Here, it is crucial to involve the patient in a full and precise discussion of the surgical procedure, to achieve consensus in selecting a method.
The following surgical procedures are suitable and can be performed in our clinic:
- Fistula splitting and conservative excision
- Inserting a seton drain (silicone loop)
- Fistula excision and capping of inner defect using a mucosal flap
- Sphincterotomy, fistula excision and primary sphincter closure
- Excision of external fistula track and insertion of a “plug” (anal fistula plug)