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

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 ¹,²,³. This is crucial because peritonitis indicates a serious underlying condition, such as bowel perforation, which is associated with increased morbidity and mortality ¹,².

Signs such as abdominal rigidity and guarding on examination suggest bowel perforation and peritonitis, particularly in cases of suspected complicated acute diverticulitis ². Urgent hospital admission is also indicated if pelvic peritonitis is suspected in a woman with suspected pelvic inflammatory disease (PID) ³. A very low threshold for admission should be maintained for people with suspected complications of appendicitis, pregnant women, elderly people, infants, and young children ¹.

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 ². If inflammatory markers are raised, a contrast CT scan should be offered within 24 hours to confirm diagnosis and help plan management ². If contrast CT is contraindicated, a non-contrast CT, MRI, or ultrasound scan may be performed ². Imaging studies, such as ultrasonography, abdominal CT, and MRI, are commonly used for suspected acute appendicitis ¹.
• Surgical Management: For diverticular perforation with generalised peritonitis, offer either laparoscopic lavage or resectional surgery, after discussing the risks and benefits ². If faecal peritonitis is identified intraoperatively, resectional surgery should be performed ². Urgent surgery is also considered for people with acute complicated diverticulitis with peritonitis and sepsis ⁴. For progressive or persistent pain where acute appendicitis is suspected, explorative laparoscopy is recommended to establish or exclude the diagnosis ¹.