Perineal abscesses and fistulae

^T^^l^Dj Perineal abscess: A pus collection in the perineal region.

Perineal fistula: An abnormal chronically infected tract communicating be-


tween the perineal skin and either the anal canal or rectum.

Bacteria, often tracking from anal glands cause infection that the body's defenses do not overcome, with fistulae developing as a complication of abscess. The latter are also a complication of Crohn's disease, where multiple perineal fistulae may develop (pepperpot perineum).

May be associated with IBD, DM or malignancy (rectal carcinoma).


Constant throbbing pain in the perineum and intermittent discharge (mucus or faecal staining) near the anal region.

Enquire about personal and family history of IBD.

Localised tender perineal mass (may be fluctuant) or a small skin lesion near the anus corresponding to the opening of a fistula.

PR examination: An area of induration corresponding to the abscess or fistula tract may be felt. Not always possible due to pain or sphincter spasm. Examination under sedation or general anaesthesia may be warranted. Goodsall's rule: Rule of thumb to correlate location of internal fistula opening based on location of external fistula opening. If external opening is anterior to the anal canal (i.e. lies anterior to a transverse anal line), the fistula runs radially and directly into the anal canal. The exception to this is a fistula 3 cm away. This and any other fistula whose external opening is posterior to the anal canal (i.e. lies posterior to a transverse anal line) will follow a curved path, opening internally in the posterior midline (see Fig. 25a).

Abscess types: Classified according to location: submucous, SC, intersphinc-teric, ischiorectal and pelvirectal abscesses.

Fistula types: Park's classification as superficial, intersphincteric, transsphincteric, suprasphincteric or extrasphincteric, or alternatively as low anal (below puborectalis) or high anal (at or above puborectalis) and pelvirectal (involving levator ani). (See Fig. 25b.)

Blood: FBC, CRP, ESR, blood culture.

Imaging: MRI is extremely useful in allowing detailed study of the often complex and deep pus-filled tracts. Allows for surgical planning ensuring complete excision.

Endoanal USG: Also used, though less useful than MRI.

Requires surgical treatment under general anaesthesia. Analgesia. Open drainage of abscess: Most common procedure is deroofing of abscess. A cross-shaped 'cruciate' incision is made over the abscess to open it. The loculi of pus are digitally broken up and all necrotic material is extracted. Packs soaked in antiseptic, e.g. Kaltostat are then inserted into the cavity. Laying open of fistula: A probe is used to gently explore the tract. Hydrogen peroxide or methylene blue can be injected into the external opening to demonstrate the internal opening.

Low fistulae: Treatment with a fistulotomy involves cutting down on and laying open the tract, curetting away granulation tissue and allowing healing by secondary intention. Extreme care must be taken to avoid damage to the sphincter muscles.

High fistulae: For fistulae involving the upper half of the sphincter complex, where muscle division would cause incontinence, a seton is used. This is a nonabsorbable suture that is threaded through the fistula tract. It first allows drainage of sepsis. It can then be tightened, whereby it slowly cuts through the sphincter in a manner that preserves continence. An alternative procedure

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