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Surgery

Acute Appendicitis

Obstruction of the appendiceal lumen leads to distension, ischaemia and bacterial invasion. Classic migratory RLQ pain, fever and leukocytosis; untreated causes perforation and peritonitis.

Last reviewed 27 May 2026 - MedicoMedics editorial team

Acute appendicitis with a distended, inflamed appendix

Pathophysiology

Luminal obstruction by faecolith (adult), lymphoid hyperplasia (children/teens), tumour or parasite causes intraluminal pressure rise, venous congestion, ischaemia and bacterial overgrowth (E. coli, Bacteroides). Progression: catarrhal → phlegmonous → gangrenous → perforated appendicitis with localised abscess or generalised peritonitis.

Sources: WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27); CODA Trial (NEJM 2020;383:1907)

Clinical presentation

Periumbilical pain migrating to McBurney point in 12-24 h, anorexia, nausea, vomiting, low-grade fever. Signs: RLQ tenderness, guarding, Rovsing (LLQ palpation causes RLQ pain), psoas (retrocecal), obturator (pelvic). Retrocecal or pelvic position may present atypically. Perforation: high fever, generalised peritonitis, sepsis.

Sources: WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27); CODA Trial (NEJM 2020;383:1907)

Diagnosis

Clinical scoring: Alvarado score aids selection for imaging. Bloods: leukocytosis with left shift, elevated CRP. Ultrasound is first-line in children and pregnancy (non-compressible tubular blind-ending structure >6 mm). CT abdomen with contrast is preferred in adults (>90% sensitivity). Diagnostic laparoscopy for equivocal cases in women of childbearing age.

Sources: WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27); CODA Trial (NEJM 2020;383:1907)

Management

IV fluids, analgesia, IV antibiotics (piperacillin-tazobactam or ceftriaxone + metronidazole) and laparoscopic appendectomy within 24 h. Non-operative antibiotic-only management can be considered in selected uncomplicated cases but has 30-40% one-year recurrence and misses appendiceal tumour. Perforation with abscess: percutaneous drainage + antibiotics, interval appendectomy 6-8 weeks later; some centres now avoid interval appendectomy in adults.

Sources: WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27); CODA Trial (NEJM 2020;383:1907)

Complications

Wound infection, intra-abdominal abscess, ileus, small-bowel obstruction, stump appendicitis, tubo-ovarian involvement in women. Missed appendiceal tumours (neuroendocrine, mucinous adenocarcinoma) - always send appendix for histology.

Sources: WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27); CODA Trial (NEJM 2020;383:1907)

Sample USMLE-style MCQs

Try 5 questions on this topic. Practice hundreds more free with a trial.

Question 1

Which physical sign is elicited by palpating the LLQ and observing pain in the RLQ?

Question 2

A 24-year-old woman has 24 h of RLQ pain, temp 37.8 °C, WBC 15 x 10^9/L and Alvarado 8. Best imaging?

Question 3

Which pathogen combination is most commonly implicated in appendicitis?

Question 4

The definitive treatment for uncomplicated acute appendicitis is?

Question 5

Which is a recognised complication after perforated appendicitis?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 27 May 2026 by MedicoMedics editorial team.

  1. WSES Jerusalem Guidelines Acute Appendicitis 2020 (World J Emerg Surg 2020;15:27)
  2. CODA Trial (NEJM 2020;383:1907)

Frequently asked

Where is McBurney point?

One-third the distance from the anterior superior iliac spine to the umbilicus.

Which imaging is preferred in a pregnant patient?

Graded-compression ultrasound first; MRI without contrast if inconclusive to avoid radiation.

Is antibiotic-only therapy an option?

It can be considered in selected uncomplicated cases but recurrence is 30-40% at one year and may miss appendiceal neoplasms.

Why still send the appendix for histology?

To detect neuroendocrine tumours (most common appendiceal neoplasm), mucinous neoplasms and other pathology (e.g. Crohn, tuberculosis, endometriosis).

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