• Intra-abdominal infections results in two major clinical manifestations
  • Early or diffuse infection results in localised or generalised peritonitis
  • Late and localised infections produces an intra-abdominal abscess
• Pathophysiology depend on competing factors of bacterial virulence and host defences
• Bacterial peritonitis is classified as primary or secondary

Primary peritonitis

• Diffuse bacterial infection without loss of integrity of GI tract
• Often occurs in adolescent girls
• Streptococcus pneumonia commonest organism involved

Secondary peritonitis

• Acute peritoneal infection resulting
  • GI perforation
  • Anastomotic dehiscence
  • Infected pancreatic necrosis
• Often involves multiple organisms - both aerobes and anaerobes
• Commonest organisms are E. coli and Bacteroides fragilis

Surgical management

• The management of secondary peritonitis involves
  • Elimination of the source of infection
  • Reduction of bacterial contamination of the peritoneal cavity
  • Prevention of persistent or recurrent intra-abdominal infections
• Could be combined with fluid resuscitation, antibiotics and ITU / HDU management 
• Source control achieved by closure or exteriorisation of perforation
• Bacterial contamination reduced by aspiration of faecal matter and pus
• Recurrent infection prevented by the used of:
  • Drains
  • Planned re-operations
  • Leaving the wound open / laparostomy

Peritoneal lavage

• Peritoneal lavage often used but benefit is unproven
• Simple swabbing of pus from peritoneal cavity may be of same value
• Has been suggested that lavage may spread infection or damage peritoneal surface
• No benefit of adding antibiotics to lavage fluid
• No benefit of adding Chlorhexidine or Betadine to lavage fluid
• If used, lavage with large volume of crystalloid solution probably has best outcome

Intra-abdominal abscesses

• An intra-abdominal abscess may arise following:
  • Localisation of peritonitis
  • Gastrointestinal perforation
  • Anastomotic leak
  • Haematogenous spread
• They develop in sites of gravitational drainage
  • Pelvis
  • Subhepatic spaces
  • Subphrenic spaces
  • Paracolic gutters

Clinical features

• Postoperative abscesses usually present at between 5 and 10 days after surgery
• Suspect if unexplained persistent or swinging pyrexia
• May also cause abdominal pain and diarrhoea
• A mass may be present with overlying erythema and tenderness
• A pelvic abscess may be palpable only on rectal examination

Management

• Ultrasound scanning may reveal the diagnosis
• Contrast-enhanced CT is probably the investigation of choice
• May delineate a gastrointestinal or anastomotic leak
• Identifies collection and often allows percutaneous drainage
• Operative drainage may be required if:
  • Multi-locular abscess
  • No safe route for per cutaneous drainage
  • Recollection after percutaneous drainage
• Patients should receive antibiotic therapy guided by organism sensitivities

Bibliography

Bausch K, van Vroonhoven Th J M, van der Werken Ch. Surgical management of severe secondary peritonitis. Br J Surg 1999; 86: 1371-1377.

Mens M,  Akhan O, Koroglu M.  Percutaneous drainage of abdominal abscess.  Eur J Radiol 2002;  43:  204-218.

Platell C,  Papadimitiriou J M,  Hall J C.  The influence of lavage fluid on peritonitis.  J Am Coll Surg 2000; 191: 672-680.

vanSonnenberg E,  Wittich G R,  Goodacre B W et al.  Percutaneous abscess drainage:  update.  World J Surg 2001;  25:  362-369.