Peritonitis

Background

  • Can be classified as acute or chronic, septic or aseptic, and primary or secondary
    • Most common type is acute suppurative (septic) peritonitis secondary to visceral disease
      • Primary peritonitis is rare; as is chronic peritonitis (e.g. due to TB infection; although the incidence is highest in patients receiving peritoneal dialysis)
      • Aseptic peritonitis is usually due to chemical (e.g. urine, bile, gastric contents, blood, meconium) or foreign body irritants (e.g. starch, talc, cellulose) and will often develop into a secondary septic peritonitis
  • High mortality rate

Causes

  • Bacterial peritonitis can be a serious complication of a number of conditions (see below).
    • Liver cirrhosis carries significant risk of spontaneous bacterial peritonitis.
    • Aseptic and bacterial peritonitis is most commonly caused by either bleeding or perforation of an intra-abdominal organ OR is iatrogenic (i.e. from GI surgery)

sbp

 

  • The main organisms that cause bacterial peritonitis include
    • E coli/Gram negative bacteria- particularly in cases of perforation (e.g. ischaemic bowel, obstruction, trauma etc)
    • Staph aureus- particularly in post-operative cases

Presentation

  • Abdominal pain
    • may be insidious, dull and poorly localised initially, worsening in severity OR may be acute onset severe pain
    • may become more localised or may be generalised
    • tenderness, guarding (tensing during palpation) and rebound tenderness are classical of peritonism, often maximal over the affected area
  • Anorexia, nausea and vomiting may precede the pain (especially in cases with obstruction)
  • Patients usually unwell/distressed (however, some patients, particularly with end-stage liver disease and SBP of ascites, may have no pain/distress etc, although they will usually look unwell
  • Hypo- or hyperthermia
  • Bowel sounds may be absent (although note that this can be a normal feature after surgery to the abdomen)
  • May have signs of shock/sepsis e.g. tachycardia, tachypnoea

Investigations

  • Erect CXR- air under the diaphragm is the classical sign
  • FBC, U&Es, LFTs
  • Blood cultures
  • Amylase
  • Ascitic/peritoneal fluid drain sample for microscopy/culture (particularly in patients with cirrhosis and ascites)
    • Neutrophils >250 cells/mm³ OR
    • WCC >250 cells/mm³ and >90% polymorphs
  • Contrast (oral) CT

Management

  • Fluid and electrolyte replacement
  • Nasogastric suction (where appropriate) and nil by mouth
  • Antibiotics
    • SBP in liver disease (i.e. in the ascitic patient)
      • Severe disease (unwell patient)
        • Antibiotics for 5-7 days
          • Piperacillin/Tazobactam IV 4.5g TDS
          • Step down to Co-trimoxazole PO 960mg BD to finish course if clinically improved (half dose if renal impairment)
      • In incidental diagnosis (i.e. routine ascitic tap)
        • Cotrimoxazole PO 960mg BD for 5-7 days
      • In hospitalised patients who have had SBP, prophylactic Co-trimoxazole PO 960mg OD should be given during the rest of the hospital stay
      • NB in patients with variceal bleeding, prophylactic antibiotics should be given
    • Intra-abdominal sepsis following surgery
      • IV Amoxicillin 1g TDS + IV Metronidazole 500mg TDS + IV Gentamicin or Aztreonam
        • If suspected staphylococcus, IV Flucloxacillin may be of use
  • Surgery
    • If, for example, there is a small anastomotic leak, localised peritonitis with good drainage, surgery can be avoided
    • In patients with widespread peritonitis (note not in SBP), surgery is often required to remove the source of infection.

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