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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Most common surgical emergency in the UK. Peak incidence age 10–20 years
- Classic history: periumbilical pain migrating to RIF over 12–24 hours + anorexia + nausea/vomiting + low-grade fever
- McBurney point tenderness (2/3 from umbilicus to ASIS) with localised peritonism
- Diagnosis: clinical ± CT abdomen/pelvis (sensitivity >95%). USS preferred in children and pregnant women
- Treatment: laparoscopic appendicectomy within 24 hours of diagnosis (or sooner if signs of perforation/sepsis)
Overview
Acute appendicitis is inflammation of the vermiform appendix, usually caused by luminal obstruction (faecolith, lymphoid hyperplasia, foreign body, or rarely carcinoid tumour). Obstruction leads to bacterial overgrowth, mucosal ischaemia, and progressive inflammation through the appendiceal wall. Without treatment, this progresses to gangrene, perforation, and either localised abscess or generalised peritonitis. It is the most common cause of the acute surgical abdomen.
Epidemiology
Lifetime risk is approximately 7–8%. Peak incidence is between ages 10 and 20 years. Approximately 50,000 appendicectomies are performed annually in the UK. Males are slightly more commonly affected than females. Perforation is more common at the extremes of age (children <5 and elderly >65) due to delayed/atypical presentation. Negative appendicectomy rate has decreased with improved CT imaging.
Clinical Features
Symptoms
Periumbilical pain migrating to the RIF over 12–24 hours (classic "visceral to somatic" pain migration)
Anorexia (almost universal — absence should raise diagnostic doubt)
Nausea and vomiting (usually after pain onset — NOT before)
Low-grade fever (37.5–38.5°C)
Pain worse on movement (coughing, walking, bumps in car)
Diarrhoea (if pelvic appendix irritating rectum)
Diffuse abdominal pain and high fever (suggests perforation)
Signs
McBurney point tenderness (1/3 of way from ASIS to umbilicus)
Localised guarding and rebound tenderness in RIF
Rovsing sign: pain in RIF on palpation of LIF (peritoneal irritation)
Psoas sign: pain on passive extension of right hip (retrocaecal appendix)
Obturator sign: pain on internal rotation of flexed right hip (pelvic appendix)
PR tenderness (pelvic appendix)
Generalised peritonitis with rigidity (perforation)
Investigations
First-line
FBCLeucocytosis (WCC >10 × 10⁹/L) with neutrophilia. Normal WCC does not exclude appendicitis
CRPRaised (>10 mg/L). CRP may be normal in early appendicitis (<12 hours)
UrinalysisExclude UTI and renal colic (mild pyuria/haematuria can occur if appendix lies adjacent to ureter)
Pregnancy test (β-hCG)Essential in all women of reproductive age — exclude ectopic pregnancy
Second-line
CT abdomen/pelvisGold standard imaging in adults — sensitivity >95%. Shows enlarged appendix (>6 mm), periappendiceal fat stranding, appendicolith, free fluid
UltrasoundFirst-line imaging in children and pregnant women (avoids radiation). Operator-dependent, sensitivity ~85%
Alvarado scoreClinical scoring: Migratory RIF pain, Anorexia, Nausea/vomiting, RIF tenderness, Rebound, Temperature, Leucocytosis, Left shift. Score ≥7 = highly likely appendicitis
Specialist
MRI abdomenAlternative in pregnant women when USS inconclusive
Diagnostic laparoscopyIf diagnosis uncertain despite imaging — allows direct visualisation and therapeutic appendicectomy
1
Surgical (definitive treatment)
- Laparoscopic appendicectomy: gold standard — within 24 hours of diagnosis
- Open appendicectomy (Lanz incision): alternative if laparoscopic not available
- Perioperative IV antibiotics (e.g. co-amoxiclav 1.2 g or cefuroxime + metronidazole)
- If perforation/peritonitis: emergency appendicectomy with peritoneal washout
2
Appendiceal mass/abscess
- If presentation delayed (>5 days) with localised phlegmon/abscess on CT: conservative management with IV antibiotics
- If abscess >3 cm: percutaneous drainage ± antibiotics
- Interval appendicectomy: 6–8 weeks later (debated — many centres now offer this only if symptoms recur)
- In patients >40 with appendiceal mass: follow-up colonoscopy or CT to exclude underlying caecal malignancy
3
Antibiotics-first approach
- Non-operative management with IV then oral antibiotics is an option for UNCOMPLICATED appendicitis in select patients who wish to avoid surgery
- However, ~25–30% will have recurrence within 1 year requiring appendicectomy
- Surgery remains standard of care in most UK units
Complications
- Perforation: ~20% at presentation (higher in <5 and >65 years). Leads to localised abscess or generalised peritonitis
- Appendiceal abscess: Walled-off perforation — tender RIF mass, swinging fever
- Wound infection: 5–10% post-appendicectomy
- Intra-abdominal abscess: Post-operative complication — pelvic or subphrenic
- Adhesional small bowel obstruction: Late complication (lower risk with laparoscopic approach)
UKMLA Exam Tips
- 1Classic pain sequence: periumbilical (visceral, midgut) → RIF (somatic, parietal peritoneum). This migration is the most discriminating feature
- 2Pain BEFORE vomiting = appendicitis. Vomiting BEFORE pain = gastroenteritis (Murphy's sequence)
- 3Anorexia is almost universal — if the patient is hungry, reconsider the diagnosis
- 4In women of reproductive age, ALWAYS exclude ectopic pregnancy (β-hCG) and ovarian torsion
- 5Retrocaecal appendix: may lack typical RIF signs — can present with flank pain and positive psoas sign
- 6In elderly patients, presentation is often atypical with minimal signs — lower threshold for CT scanning
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