Acute Abdomen, Appendicitis & Peritonitis
Interpret evolving pain and peritoneal signs while recognising mimics and the need for timely source control.
Quick revision ↓ Medical Dictionary
01Follow the evolution of pain
Visceral pain is often poorly localised; parietal irritation can make pain more focal and movement-sensitive. Migration from central abdominal pain to the right lower quadrant supports appendicitis but is not universal. Ask about urinary, bowel and reproductive symptoms, prior surgery and medications. Older, pregnant or immunosuppressed patients may have less typical findings, so a textbook pattern should not be required before taking concern seriously.
02Recognise peritoneal irritation
Guarding, rigidity, rebound or pain with movement can suggest peritonitis. Distinguish voluntary tensing from involuntary guarding and interpret the whole examination. Generalised peritonitis, shock or rapidly worsening pain needs urgent surgical review. Investigations can clarify the source when safe, but waiting for every marker to rise can delay treatment of perforation, ischaemia or another serious intra-abdominal process.
03Assess suspected appendicitis
Use history, examination, laboratory findings and appropriate imaging together. Clinical scores support risk stratification rather than replace judgement. Ultrasound, CT or MRI selection depends on age, pregnancy, probability and local expertise. A normal white-cell count does not alone exclude appendicitis. Discuss operative and selected non-operative approaches with the surgical team according to disease complexity, patient preference and the applicable pathway.
04Consider important alternatives
Ectopic pregnancy, ovarian pathology, renal colic, gastroenteritis, inflammatory bowel disease and mesenteric ischaemia can mimic common surgical conditions. Pain out of proportion to early examination in a patient with vascular risk is concerning for intestinal ischaemia. Appropriate pregnancy assessment is essential when relevant. A urinary abnormality can accompany adjacent inflammation and should not automatically end the abdominal differential.
05Resuscitate and obtain source control
Provide appropriate analgesia, intravenous support and antimicrobials when indicated while arranging definitive treatment. Source control may require surgery or drainage, with timing dictated by physiology and pathology. Reassess after treatment and explain possible escalation. If observation is selected for an uncertain stable case, record the review plan and warning signs rather than giving an unqualified benign label.
High-Yield Revision
- Appendicitis can occur without its classical sequence.
- Normal inflammatory markers do not independently exclude urgent disease.
- Peritonitis with deterioration needs rapid surgical assessment.
Common Pitfalls
- Do not assume urinary findings explain every lower abdominal presentation.
- Do not dismiss disproportionate pain in a patient at risk of mesenteric ischaemia.
References & Further Reading
Read the relevant guideline sections alongside these original clinical teaching cases. Local pathways, available services and individual patient factors determine care.
Reference review: 27 September 2026. Consult current local protocols for prescribing, procedures and escalation.