How should I manage a patient with acute abdominal pain who presents with signs of peritonitis?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

For a patient presenting with acute abdominal pain and signs of peritonitis, the immediate and critical step is to arrange emergency hospital admission for specialist assessment and management ,,. This is crucial because peritonitis indicates a serious underlying condition, such as bowel perforation, which is associated with increased morbidity and mortality ,.

Signs such as abdominal rigidity and guarding on examination suggest bowel perforation and peritonitis, particularly in cases of suspected complicated acute diverticulitis . Urgent hospital admission is also indicated if pelvic peritonitis is suspected in a woman with suspected pelvic inflammatory disease (PID) . A very low threshold for admission should be maintained for people with suspected complications of appendicitis, pregnant women, elderly people, infants, and young children .

Upon hospital admission, specialist management may include:

  • Investigations: For suspected complicated acute diverticulitis, offer a full blood count, urea and electrolytes test, and C-reactive protein test . If inflammatory markers are raised, a contrast CT scan should be offered within 24 hours to confirm diagnosis and help plan management . If contrast CT is contraindicated, a non-contrast CT, MRI, or ultrasound scan may be performed . Imaging studies, such as ultrasonography, abdominal CT, and MRI, are commonly used for suspected acute appendicitis .
  • Surgical Management: For diverticular perforation with generalised peritonitis, offer either laparoscopic lavage or resectional surgery, after discussing the risks and benefits . If faecal peritonitis is identified intraoperatively, resectional surgery should be performed . Urgent surgery is also considered for people with acute complicated diverticulitis with peritonitis and sepsis . For progressive or persistent pain where acute appendicitis is suspected, explorative laparoscopy is recommended to establish or exclude the diagnosis .

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