perineal abscess and fistulae

Question 1

definition of the perineal abscess

Answer 1

pus collection in perineal region

Question 2

definition of perineal fistula

Answer 2

abnormal chronically infected tract communicating between the perineal skin and either the anal canal or rectum

Question 3

aetiology of perineal fistula/abscess

Answer 3

bacteria, often tracking from anal glands (rarely staph/TB) = infection that the body’s defences dont overcome

= fistula develop as complication of abscess

fistulae are also complications of crohn’s - multiple perineal abscesses may develop (pepperpot perineum)

Question 4

RF for perineal abscess/fistulae

Answer 4

IBD

DM

rectal carcinoma

Question 5

epidemiology of perineal abscess/fistula

Answer 5

common

abscess - men slightly more

Question 6

sx of perineal abscess/fistula

Answer 6

constant throbbing in the perineum

intermittent discharge (mucus or faecal staining) near the anal region

enquire about personal and FH of IBD

abscess above dentate line = visceral nerve innervation = no pain sensation

below = somatic innervation - very painful

Question 7

signs of perineal abscess/fistula

Answer 7

localised tender, inflammed, swollen perineal mass (may be fluctuant) at anal verge

small skin lesion near the anus - opening of the fistula

Question 8

PR exam findings for perineal abscess/fistula

Answer 8

area of induration corresponding to the abscess or fistula tract may be felt

not always possible due to pain or sphincter spasm

exam under GA or sedation may be warrented

Question 9

Goodsall’s rule - for perineal abscess/fistulae

Answer 9

rule of thumb to locate internal fistula opening based on location of external opening

if external is anterior to the anal canal (ie anterior to the transverse anal line) - fistula runs radially and directly into the canal

except if fistula is 3cm away

this and any fistula whose external opening is posterior to the anal canal (ie lies posterior to a transverse anal line) - folow curved path, opening internally in the posterior midline - always at 6oclock

Question 10

pathology of perineal abscess

Answer 10

classified according to location:

• submucous
• SC
• intersphincteric
• ischiorectal
• pelvirectal

Question 11

pathology of perineal fistula

Answer 11

Park’s classification as superficial, intersphincteric, transsphincteric, suprasphincteric, or extrasphincteric

or

low anal (below puborectalis), high anal (at or above puborectalis) and pelvirectal (involving levator ani)

Question 12

Ix for perineal fistula/abscess

Answer 12

Blood - FBC, CRP, ESR, blood culture

imaging - MRI

endoanal USG - less useful than MRI

Question 13

MRI in perineal abscess/fistula

Answer 13

detailed study of the complex and deep pus filles sacs

allows for surgical planning allowing complete excision

Question 14

Mx of perineal abscess/fistula

Answer 14

needs surgical treatment under GA and analgesia

• open drainage of abscess
• layting open of fistula

AB - samples taken from abscess and cultured - start with cefiroxime and metronidazole

Question 15

AB for perineal fistula and abscess

Answer 15

cefuroxime

metronidazole

Question 16

open drainage of abscess for perineal abscess/fistula

Answer 16

most common procedure is deroofing of abscess

cross shaped ‘cruciate’ incision is made over the abscess to open it

loculi of pus are digitally broken up and the necrotic material is extracted

packs soaked in antiseptic eg Kaltostat are then inserted into the cavity

under GA

Question 17

laying open of the fistula - perineal fistula

Answer 17

probe used to explore the tract

hydrogen peroxide or methylene blue can be injected into the external opening to demonstrate the internal opening

different technique for low and high fistulae

Question 18

laying open of low perineal fistulae

Answer 18

treatment with fistulotomy - cutting down on and layoing open the tract

curetting away granulation tissue and allowing healing by secondary intention

care to avoid damage to the sphincter muscles

division of sphincters poses no risk to continence

Question 19

laying open high perineal fistulae

Answer 19

involving the upper half of the sphincter complex - muscle division would = incontinence

use seton

• seton is a non-absorbable suture threaded through the fistula tract
• 1st allows drainage of sepsis
• can then be tightened - it slowly cuts through the sphincter in a manner that preserves continence

alternatively excise the external part of the fistula and closure of the internal opening by a mucosal advancement flap

Question 20

complications of perineal abscess/fistula

Answer 20

recurrence

damage to the internal anal sphincter and incontinence

persisting pain

Question 21

prognosis of perineal abscess/fistula

Answer 21

high recurrence rate w/o complete excision

Question 22

mechanism of perineal fistula

Answer 22

blockage of deep intramuscular gland ducts - predispose to formation of abscesses which discharge from the fistula

Question 23

aetiology of perineal FISTULAE

Answer 23

perianal sepsis

abscesses

Crohn’s

TB

diverticular disease

rectal ca

immunocompromise