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Peri-anal abscess

Usually painful in anal region
Swinging pyrexia
Treatment is drainage with appropriate antibiotics

Classification of Perianal abscess

1. Peri-anal 60%- suppuration of anal gland (can also occur as result of thrombosed external pile)
2. Ischio-rectal 30% (IR fossa communicates with opposite side via the post-sphincteric space; involvement of contralateral fossa not uncommon)
3. Sub-mucous 5%; usually resolves (result of injection of haemarrhoids)
4. Pelvi-rectal 5% (supralevator) - usually secondary to appendicitis, salpingitis, diverticulitis, parametritis

Procedure

1. Cruciate incision over abscess + excise skin over abscess (de-roof)
2. (Take microbiological cultures - if enteroccocci, high incidence of fistula; up to 40% risk)
3. As soon as infection subsided, wound explored under anaesthesia + careful search for fistulous opening
4. If no fistula found, cavity should be lightly packed with gauze + apply T-bandage

Fistula in Ano

Track lined by granulation tissue that connects deeply in anal canal/rectum and superficially on the skin around the anus
Usually results from an anorectal abscess which bursts spontaneously
Associated with underlying diseases - eg TB, Crohns
Gives recurrent discharge
Goodsall's rule: fistulae with external opening anterior to anus have a direct (straight) opening. Fistulae with posterior opening have curved tracks.

Classification of Perianal fistula

1. Simple or complex - associated or not with abscess cavity
2. High or Low - above or below anorectal (puborectalis) ring
   • Subcutaneous
   • Submucous
   • Low anal
   • High anal
   • Pelvirectal
3. Park's Classification - by origin of fistula track
   
   
   
   
   • Intersphincteric (between internal/external sphincters) 70%
   • Transphincteric (across external sphincters) 25%
   • Suprasphincteric (over sphincters)
   • Extrasphincteric (above and through levator ani)

Procedure

1. Decide whether fistula is low or high
2. Proctoscopy - reveals internal opening
3. Endoluminal ultrasonography / MRI to map complex fistulae (may have multiple openings)
   • Low: Lay open
     1. Prep cleaning enema
     2. Lithotomy position
     3. Identify the fistula: protoscopy + retrograde probe + dilute methylene blue dye
     4. Track opened along director and bleeding controlled
     5. Trim edges of track
   • High: (risk of incontinence if laid open) - staged procedure + protective diverting colostomy to prevent septic complications and to shorten healing time between procedures
     1. Treat the cause: TB, Crohns
     2. Insertion of a seton
        
        1. (a heavy ligature of silk, nylon, silastic or linen) used when internal opening near anorectal ring
        2. acts as wick/drain to allow acute inflammatory reaction around track to subside
        3. Can be serially tightened to cut through sphincter (allows healing) to maintain sphincter integrity
        4. Acts to drain fistula
     3. + Covering colostomy

[Levator ani = Pubo-rectalis + Pubo-coccygeus + Ilio-coccygeus]

Fissure in Ano

• Longitudinal tear in anal canal (90% posterior midline)
• ?Constipation / large stools primary cause or result of them
• Combination of local trauma to epithelium + ischaemia preventing adequate healing
• Also seen in STDs and IBD
• Symptoms: pain, bleeding, itching, pruritis ani

Treatment

1. Conservative
   • High fibre diet, stool bulking
   • Topical LA
   • Topical GTN (controls anal spasm)
2. Surgical
   • Lateral sphincterotomy: divide distal internal sphincter to dentate line with incision lateral and away from fissure (complications - transient flatus incontinence)