B34. Perianal abscesses and fistulae. Surgical management of hemorrhoids.

Page created on September 21, 2021. Not updated since.

Perianal abscess and fistula

Definition and epidemiology

Perianal abscess and fistula are the two most common perianal disorders. Perianal abscess is the acute manifestation and perianal fistula is the chronic manifestation of purulent perianal infection. Fistulas may connect the abscess to the anal canal or to the perianal skin.

These disorders more commonly affect men, and they usually affect people in the age between 20 and 60.


These disorders are primary in almost all cases, due to idiopathic obstruction and infection of the glands of the anal crypt. Rare causes include Crohn disease, ulcerative colitis, and colorectal cancer.

Clinical features

Perianal abscess presents with local discomfort, pruritus, and pain. An erythematous subcutaneous mass is present. The pain and discomfort worsen with sitting and defecation. Some may present with signs of systemic inflammation like fever.

Perianal fistula may present similarly, with the addition of purulent discharge from the anal canal or from perianal skin. Multiple fistulas are suspicious for Crohn disease.

Goodsall’s rule state that fistulas which open anteriorly tend to follow a simple, direct course while fistulas that open posteriorly tend to follow a more curving path. However, this rule is not always true and is, according to some, best forgotten altogether.

Diagnosis and evaluation

Clinical examination and inspection are usually enough to give the diagnosis. Digital rectal examination is usually impossible due to pain.

Very small abscesses and fistulas may be detected by transanal ultrasound.


Perianal abscess is treated with incision and drainage, under general anaesthesia or local anaesthesia. In the acute inflamed stage, we don’t look for fistulas because 2/3 of the fistulas heal spontaneously after opening the abscess, and the risk for complications is high if fistulas are treated while there is inflammation.

If the fistula persists over weeks/months, treatment is necessary. Superficial fistulas may be excised. Deeper fistulas are treated with loose setons. A loose seton (a nonabsorbable suture) is guided through the fistula tract and tied together. The seton allows any fluid to drain alongside it, and it prevents the fistula from closing prematurely, potentially forming an abscess. Inflammation close to the anal sphincter may lead to incontinence and is important to avoid. After some weeks/months, the seton may be removed and the fistula allowed to close, if deemed peaceful. If not, fistulotomy may be necessary.

Cutting setons are still used but should be avoided due to injury to the sphincter, yielding a higher complication rate.

A technique known as “advanced mucosal flap” may also be used. A tissue flap is used to cover the internal opening of the fistula, allowing it to heal while preserving faecal continence.


Definition and epidemiology

Haemorrhoids, also called piles, are swollen or inflamed “cushions” of veins in the anal canal. Haemorrhoids are normal anatomical structures which are involved in maintaining continence, but the term is usually used to refer to cases where they cause symptoms. They may be classified as internal (above the dentate line), external (below the dentate line), or mixed.


Haemorrhoids are usually the result of increased intraabdominal pressure, due to chronic constipation, heavy lifting, extended periods of sitting, pregnancy, etc. This leads to higher hydrostatic pressure in the haemorrhoids, causing the swelling which make them clinically manifest.

Cirrhosis may cause anorectal varices which may present similarly to haemorrhoids.

Classification of internal haemorrhoids

Stage Description
I Haemorrhoid does not prolapse out of the anus
II Haemorrhoid prolapses when straining, but spontaneously reduce at rest
III Haemorrhoid prolapses when straining, but is manually reducible
IV Haemorrhoid is irreducible

Clinical features

Haemorrhoids cause painless fresh bleeding at the end of defecation and may cause mucous discharge. If they are internal and prolapse or they are external, a palpable anal mass is present. They are usually painless but may be painful.

Haemorrhoids may thrombose, causing acute pain or subacute pain (which occurs over multiple days). They may also incarcerate, causing acute intolerable pain.

Diagnosis and evaluation

The diagnosis of haemorrhoids is clinical. However, it’s important to exclude malignancy, IBD, and rectal prolapse as causes of the symptoms before proceeding to treatment.


Generally, stage I and II internal haemorrhoids and all external haemorrhoids are treated conservatively while stage III and IV are treated surgically.

Conservative therapy involves lifestyle changes to decrease the hydrostatic pressure, like increasing fluid intake and fibre intake. Time on the toilet should also be reduced. Local ointments or suppositories may also be used.

There are multiple options for outpatient surgical treatment. A Barron ligature is the most effective procedure, and involves placing a rubber ring around the haemorrhoid, causing fibrosis and reduction in size. Other options include sclerotherapy or photocoagulation.

There are also multiple options for inpatient surgical treatment, most being a form of submucosal total excision (haemorrhoidectomy). This procedure may be performed with a scalpel or with more advanced tools like staples, electrocautery, or ultrasonic excision. Haemorrhoidal artery ligation with recto-anal repair (HAL-RAR) is a new and minimally invasive technique, where the haemorrhoidal artery is ligated, and the prolapsed haemorrhoidal tissue is stapled or sutured to the mucosa.

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