Anal Abscess and Anal Fistula: Information on the Symptoms and Treatment of Anal Abscesses

An anal abscess is a pus-filled cavity that typically forms in the immediate vicinity of the anus. It develops when the ducts of the proctodeal glands become blocked by bacteria, causing the glands to become inflamed. As soon as bacteria multiply unchecked in this area, a purulent inflammation develops, causing the surrounding tissue to swell rapidly. The mucous membrane of the anal canal is sensitive to pressure and inflammation, so the symptoms are usually very pronounced. 

The course of the condition is acutely severe and is characterized by significant pain. In patients with pre-existing bowel diseases, particularly Crohn’s disease or other chronic inflammatory conditions, the risk of developing an abscess is increased. Patients with diabetes mellitus are also more likely to develop such infections due to their weakened immune system.

A key difference between an anal abscess and an anal fistula lies in their progression over time and their anatomical structure. The abscess represents the acute phase of the condition: a closed cavity fills with pus, pain increases, and without treatment, pressure continues to build.

If this pressure becomes too great, the pus finds a way out. In the process, a passage may form from the internal anal canal to the skin’s surface: the fistula. This creates a permanent connection between the rectum and the skin, through which pus, fluid, or fecal matter can drain. Although this often visible fistula opening provides short-term relief from pain, it causes the condition to become chronic.

The formation of an anal fistula is therefore a common and undesirable consequence of an untreated abscess. The risk of developing an anal fistula is particularly high in patients with Crohn’s disease, intestinal disorders, and recurrent infections.

Both an anal abscess and an anal fistula are important indicators of suspected chronic inflammatory bowel disease, which is why careful diagnosis is essential in these cases as well. 

Symptoms usually begin suddenly and worsen significantly within a few hours. Typical symptoms include:

• severe pain, especially during bowel movements, while sitting, or when standing up
• clearly visible swelling and redness
• tenderness and warmth in the anal region
• Discharge of secretions or pus-like fluids
• fever and a general feeling of illness

The pain is so severe that many people affected can barely perform everyday activities. An anal abscess usually does not resolve on its own, so early medical evaluation is necessary to prevent complications such as sepsis or the development of an anal fistula. 

Various areas where anal abscesses can form © nmfotograf | AdobeStock

The diagnosis is primarily made through a thorough physical examination. The doctor assesses the affected area, the extent of the swelling, and tenderness. Abscesses located particularly close to the surface can be identified quickly.

In cases of deeper abscesses or suspected fistulas, additional diagnostic steps are required. These include an anoscope examination of the anal canal, during which the proctologist uses a proctoscope to assess the mucosa. This examination also makes it possible to detect hidden fistula openings and better assess the extent of the condition. 

If the abscess is located in the inner part of the anal canal or if a complex fistula is suspected, an MRI is often used. This imaging provides a precise depiction of the anatomical structures and clarifies whether the condition is an anal abscess or a perianal abscess. 

In most cases, an anal abscess is treated surgically, as only by opening the abscess cavity can the pus be completely drained. Small abscesses can occasionally be managed with conservative measures, such as ointments, but this remains the exception. Rapid drainage of the pus is crucial, as the condition requires immediate treatment.

The surgery usually begins after local anesthesia or general anesthesia, as the area is highly sensitive to pain and care must be taken not to damage the sphincter muscle. Once the skin is incised, the pus is drained, and the entire cavity is carefully cleaned and irrigated. Any fistula tracts or an existing fistula opening are also examined.

Open wound healing is necessary to prevent a recurrence of pus accumulation. Patients with diabetes mellitus, immunosuppressive conditions, or intestinal diseases are at particularly high risk for a recurrent abscess, making follow-up visits and consistent wound care essential. In complicated cases, additional surgery may be necessary. Antibiotic therapy may also be used as a supplementary treatment.

The healing process after surgery is generally favorable, provided the wound is consistently treated with open wound care. During the first few days and weeks, daily showering, careful cleaning, and regular dressing changes are required to minimize the risk of reinfection. Sitz baths improve well-being and promote blood circulation, which aids in healing.

In the weeks following surgery, soft stools are particularly important. A high-fiber diet is recommended in the long term but should be reintroduced cautiously immediately after the procedure.

Untreated or inadequately treated cases can lead to fecal incontinence, recurrent abscesses, or lifelong fistulas. With proper diagnosis and treatment, however, the prognosis is very good. 

An anal abscess develops when a gland in the anal canal becomes inflamed, pus accumulates, and purulent inflammation occurs in the surrounding tissue. This can be exacerbated by bacterial infections, intestinal diseases such as Crohn’s disease or ulcerative colitis, or immunodeficiency.

Spontaneous healing is very unlikely, as the pus cannot drain on its own. Surgery is usually unavoidable. Without treatment, there is a risk of developing an anal fistula or a systemic infection.

If the condition is left untreated, it can lead to a fistula, recurrent abscesses, severe infections, and even sepsis. Prompt medical attention is therefore necessary.

Good anal hygiene, managing bowel disorders, controlling diabetes mellitus, and maintaining a balanced diet reduce the risk. Recurrent cases should be evaluated by a proctologist.