perineal abscess and fistulae Flashcards
definition of the perineal abscess
pus collection in perineal region
definition of perineal fistula
abnormal chronically infected tract communicating between the perineal skin and either the anal canal or rectum
aetiology of perineal fistula/abscess
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)
RF for perineal abscess/fistulae
IBD
DM
rectal carcinoma
epidemiology of perineal abscess/fistula
common
abscess - men slightly more
sx of perineal abscess/fistula
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
signs of perineal abscess/fistula
localised tender, inflammed, swollen perineal mass (may be fluctuant) at anal verge
small skin lesion near the anus - opening of the fistula
PR exam findings for perineal abscess/fistula
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
Goodsall’s rule - for perineal abscess/fistulae
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
pathology of perineal abscess
classified according to location:
- submucous
- SC
- intersphincteric
- ischiorectal
- pelvirectal
pathology of perineal fistula
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)
Ix for perineal fistula/abscess
Blood - FBC, CRP, ESR, blood culture
imaging - MRI
endoanal USG - less useful than MRI
MRI in perineal abscess/fistula
detailed study of the complex and deep pus filles sacs
allows for surgical planning allowing complete excision
Mx of perineal abscess/fistula
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
AB for perineal fistula and abscess
cefuroxime
metronidazole
open drainage of abscess for perineal abscess/fistula
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
laying open of the fistula - perineal fistula
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
laying open of low perineal fistulae
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
laying open high perineal fistulae
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
complications of perineal abscess/fistula
recurrence
damage to the internal anal sphincter and incontinence
persisting pain
prognosis of perineal abscess/fistula
high recurrence rate w/o complete excision
mechanism of perineal fistula
blockage of deep intramuscular gland ducts - predispose to formation of abscesses which discharge from the fistula
aetiology of perineal FISTULAE
perianal sepsis
abscesses
Crohn’s
TB
diverticular disease
rectal ca
immunocompromise
