abscess

Question 1

definition of abscess

Answer 1

collection of pus walled off by an area of inflammation

Question 2

aetiology of abscess

Answer 2

pyogenic abscesses are caused by infection that the body’s defences have failed to completely overcome

common bacteria:

• staphylococcus aureus,
• streptococci (especially S pyogenes),
• enteric organisms (eg E coli)
• other coliforms and anaerobes (Bacteroides spp)
• TB causes cold abscesses

Question 3

RF for local abscesses

Answer 3

tissue necrosis

a closed underperfused space or foreign body that provides a focus for infection eg tooth or root fragment, splinters, mesh of hernia repairs, embedded hair, malignancy

Question 4

RF for systemic ulcers

Answer 4

dm

immunosuppression - although may interfere with pus formation

Question 5

epidemiology of abscesses

Answer 5

common in all ages

Question 6

sx of abscess

Answer 6

local effects of pain, swelling, heat, redness and impaired function of the area where the abscess is present

(dolor, calor, rubor, functio laesa)

fever

generally feeling unwell

Question 7

signs of abscess

Answer 7

dolor, tumor, calor, rubor, functio laesa

if abcess in an organ, localising signs may be absent

swinging pyrexia - caused by periodic release of microbes or inflammatory mediators into systemic circulation - should initiate search for an infected collection

if pus is somewhere, and pus is nowhere - then pus is under the diaphragm (subphrenic abscess)

Question 8

pathology of abscesses

Answer 8

bacteria = intense acute inflammatory respinse with formation of pus, a collection of dead and dying neutrophils, cellular debris and bacteria, if there is resistance to phagocytosis and killing

abscess forms as it becomes surrounded by fibrinous exudate and granulation tissue (macrophages and fibroblasts), with subsequent collagen deposition and walling off

Question 9

what are cold abscesses

Answer 9

collections of caseating necrosis containing mycobacterium

cold because there is no associated acute inflammatory response

Question 10

Ix for abscesses

Answer 10

blood - FBC = v high neutrophils

imaging - US, CT or MRI scanning, 67Ga white cell scanning may be used in the search for the site of a collection or abscess

aspiration - pus is low in glucose, acidic/ culture for organisms and sensitivity to AB

Question 11

prevention of abscess

Answer 11

prophylactic AB eg during operations

or AB early in infection

not effective once an abscess has formed

Question 12

Mx for abscess

Answer 12

• general
  
  • drainage of pus
  • removal of necrotic and foreign material
  • antimicrobial cover
  • correction of predisposing cause
• surgery
  
  • drainage by incision and drainage
  • debridement of the cavity
  • subsequent free drainage by packing of the cavity if superficial, or by drains if deep
• interventional radiology
  
  • US or CT guidance used to localise and aspirate contents

Question 13

complications of abscess

Answer 13

spread can = cellulitis or bacteraemia with systemic sepsis

if focus of infection not removed a chronic abscess or discharging sinus or fistula form

occaisionally AB may penetrate and = sterile collection or antibioma

of constrained by strong facial planes, slow expansion can cause pressure necrosis of surrounding tissues

Question 14

prognosis of abscess

Answer 14

good if adequately drained and predisposing factor is removed

if left untreated, abscesses tend to ‘point’ to the nearest epithelial surface and may spontaneously discharge their contents

deep abscesses can become chronic, undergoing dystrophic calcification