Definition: inflammation of the peritoneal lining of the abdominal cavity, which may be localised or generalised. Generalised peritonitis can be primary or secondary.

Aetiology/risk factors:

Localised- common causes are appendicitis, cholecystitis, salpingitis, diverticulitis, abscess

Primary generalised- bacterial infection of the peritoneal cavity without obvious focus responsible

-primary pneumococcal peritonitis can occur in children

-Spontaneous Bacterial Peritonitis = ascites with neutrophils > 250/mm³, associated with cirrhosis and ascites, nephrotic syndrome. Common organisms are E.coli, Klebsiella and streptococci.

-renal failure patients on peritoneal dialysis

Secondary generalised- peritonitis spreads from a localised infective focus

-polymicrobial (usually)-  appendicitis, cholecystitis, salpingitis, diverticulitis

                      – Intra-abdominal abscess +/- rupture

-non-bacterial- spillage of bile, blood, gastric contents

-GI perforation- peptic ulcer, diverticulum, appendix, bowel, gallbladder

-Pancreatic secretions (chemical peritonitis that often becomes secondarily infected)

-Bile duct injury (gallstones, post-op)


Other causes:

Strangulated, obstructed bowel

Mesenteric ischemia (can lead to septic peritonitis)

Familial Mediterranean Fever (periodic fevers and serositis- peritonitis & pleurisy)



Epidemiology: primary generalised peritonitis is rare, whilst localised and secondary generalised peritonitis are very common



-localised or generalised abdominal pain

-pain usually sharp, continuous, exacerbated by movement and coughing


Localised- signs localised to a region of the abdomen

-abdominal guarding = involuntary tensing of abdominal muscles on palpation

-rebound tenderness = greater pain on removing hand than on depressing abdomen

-percussion tenderness = pain on percussion

-positive cough test = abdominal pain when they cough


Generalised- signs generalised over abdomen

-systemic signs of toxaemia or sepsis: fever, tachycardia

-lying still

-generalised guarding, rebound tenderness, percussion tenderness, positive cough test

-board-like abdominal rigidity

-bowel sounds reduced or absent (paralytic ileus)

-shock (sepsis, circulatory failure, hypovolaemia)


Spontaneous Bacterial Peritonitis– patient with ascites that deteriorates suddenly, but may be asymptomatic


Depends on cause.

Bloods:  FBC (↑WCC), U&Es, LFT (cholecystitis?), amylase (pancreatitis?), CRP, clotting, Group & Save or Crossmatch (for transfusion), blood cultures, pregnancy test (ectopic?), ABG (metabolic acidosis? lactate? respiratory failure?)

Ascitic tap- to confirm Spontaneous Bacterial Peritonitis (neutrophils > 250/mm³), gram stain and culture

Erect CXR- air under diaphragm, if GI perforation

AXR- local peritoneal inflammation can cause localised ileus (paralytic bowel) with a ‘sentinel loop’ of intraluminal gas visible


Image result for abdominal x ray sentinel loop

Sentinel loop secondary to pancreatitis


Look for bowel obstruction

CT abdomen or laparoscopy- to diagnose cause of peritonitis

Management: depends on cause

-Urgent laparotomy/ laparoscopy may be needed to identify and treat cause, remove infected or necrotic tissue and perform copious peritoneal lavage e.g. GI perforation, appendicitis (appendicectomy)

-In acute abdomen presentation, if patient is peritonitic, they should be given antibiotics e.g. CEFUROXIME (1.5g/8h IV) + METRONIDAZOLE (500mg/8h IV/PR) (e.g. cholecystitis, salpingitis, acute diverticulitis)

-Drainage of abscesses, percutaneous (U/S or CT guided) or by laparotomy

Generalised peritonitis– IV fluid resuscitation, correction of volume and electrolyte imbalances, IV antibiotics, urinary catheter, NG tube, CVP line -as risk of sepsis and shock

Spontaneous Bacterial Peritonitis

Antibiotics: e.g. cefotaxime (2g/6h) or tazocin (4.5g/8h) for 5 days, or until sensitivities known. Add metronidazole (500mg/8h IV) if there  has been recent instrumentation to ascites.


-Septic shock, respiratory or multi-organ failure

-Paralytic ileus

-Wound infection

-Tertiary peritonitis (persistence of intra-abdominal infection)

-Abscesses, portal pyaemia

-Incisional hernias (post-op), adhesions


Localised peritonitis usually resolves with treatment of cause.

Generalised peritonitis has a much higher mortality, 30-50%, increased with septic shock and multi-organ dysfunction, >70%.

Primary peritonitis has good prognosis with appropriate antibiotic therapy.

SBP overall mortality rate may exceed 30% with delayed diagnosis and treatment.

References: Rapid Surgery, Cheese & Onion

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