Acute appendicitis is inflammation of the vermiform appendix, usually triggered by luminal obstruction and bacterial overgrowth. It is a common cause of acute abdominal pain requiring emergency surgical assessment. Untreated, it can progress to gangrene, perforation, peritonitis, sepsis, and abscess. Because symptoms overlap with gastroenteritis, urinary, and gynaecological disease, diagnosis relies on a combination of clinical assessment + symptom trajectory supported by targeted investigations.

Epidemiology

📊 Lifetime risk: ~7–8%; higher in men (~8.6%) than women (~6.7%).
👥 Age: Peak in teens/early adulthood; extremes of age have higher perforation rates and atypical presentations.
🔍 Diagnostic reality: Negative appendicectomy historically 10–20%, now reduced with modern imaging.

Anatomy of the Appendix

📍 Blind-ended tube from caecum near the ileocaecal valve; variable length (~6–10 cm).
🧭 Positions: retrocaecal (most common), pelvic, pre-/post-ileal, paracaecal – affects symptom localisation.
🩸 Blood supply: appendicular artery (end-artery branch of ileocolic) → rapid ischaemia if obstruction rises.

Pathophysiology

Sequence: obstruction → mucus accumulation → ↑ intraluminal pressure → venous congestion → bacterial proliferation → mural ischaemia → gangrene → perforation. Visceral pain starts peri-umbilically; once parietal peritoneum is involved, pain localises to RIF. Key teaching: appendicitis is dynamic; a single exam can be misleading, so re-examination and escalation are essential.

Aetiology / Causes

🚧 Luminal obstruction: faecolith, lymphoid hyperplasia (children), rarely tumour.
🦠 Infective triggers: viral illness → lymphoid hyperplasia; gut flora contribute after obstruction.
🐛 Parasites: Enterobius occasionally implicated.

Risk Factors

👶 Children & 👵 older adults: higher risk of delayed diagnosis/perforation.
💊 Immunosuppression/steroids: blunted inflammatory response (normal WCC/fever misleading).
🤰 Pregnancy: atypical localisation; broader differential.

🩺 Clinical Features

➡️ Pain: peri-umbilical → RIF; worsens with movement/cough.
🤢 GI: anorexia, nausea; vomiting follows pain (vs gastroenteritis).
🌡️ Systemic: low-grade fever, tachycardia; severe sepsis suggests perforation/abscess.
💩 Bowel/urinary: diarrhoea/tenesmus (pelvic appendix), dysuria (bladder/ureter irritation).

Typical vs Atypical Presentations

✅ Typical: migration, RIF tenderness, anorexia, rising inflammatory markers.
⚠️ Atypical: retrocaecal (flank/back pain), pelvic (suprapubic pain, diarrhoea, urinary), elderly (subtle), pregnancy (pain shifts cephalad), immunosuppressed (few signs).

Pain Migration & Neuroanatomy

Early visceral pain via sympathetic afferents → peri-umbilical (T10). Parietal peritoneum involvement → sharper localised RIF pain. This links exam findings with disease stage and complication risk.

Examination Findings

👆 RIF tenderness (McBurney’s), percussion/cough tenderness, guarding, rebound.
↪️ Rovsing’s sign: LLQ palpation → RIF pain.
🦵 Psoas sign (retrocaecal), obturator sign (pelvic).
🩺 Male: testicular exam; Female: gynae assessment as appropriate.

Special Populations

👶 Children: mimic gastroenteritis; perforate earlier; use paediatric scores, USS-first.
👵 Elderly: subtle pain/fever; early imaging advised.
🤰 Pregnancy: pain may shift; USS first, MRI if equivocal; do not ignore strong clinical suspicion.
💊 Immunocompromised: low threshold for imaging/senior review.

Differential Diagnosis

🦠 Gastroenteritis, mesenteric adenitis, constipation.
🧻 UTI/pyelonephritis, ureteric stone.
🩸 Gynae: ectopic, ovarian torsion/cyst, PID.
🧠 IBD (terminal ileitis), Meckel’s diverticulitis, right-sided diverticulitis.
🔁 Older adults: consider caecal/appendiceal tumour.

🔎 Investigations

Blood Tests

🩸 FBC, CRP, U&E, LFTs, amylase/lipase (broader acute abdomen screen).
🧪 Lactate/VBG if sepsis or concern for ischaemia/perforation.
🧾 Group & save / crossmatch if operative likelihood.

Urinalysis

💧 Identify UTI; mild haematuria possible from ureteric irritation.

Pregnancy Testing

🤰 β-hCG for all females of reproductive potential – ectopic pregnancy until excluded.

Imaging

🖥️ CT A/P (adults): high accuracy, identifies complications and alternative diagnoses.
🩻 Ultrasound: first-line in children/pregnancy; operator dependent.
🧲 MRI (pregnancy): when USS inconclusive and clinical suspicion persists.

Sources: WSES 2020 pregnancy imaging recommendations.

Risk Stratification / Clinical Scoring

📐 Alvarado, AIR, paediatric scores guide observation vs imaging vs urgent surgery.
⚠️ Scores are adjuncts – do not override clear peritonism or deterioration.

Initial Management

⚡ Initial Management
🏥 ABCDE: vitals, IV fluids if hypovolaemic/septic; O₂ if hypoxic. 💉 2 large-bore cannulas if unwell; bloods + cultures if sepsis suspected. 💊 Early analgesia + antiemetics. 🥛 NBM; early surgical referral. 🧴 NG tube if persistent vomiting/obstruction. 🧦 VTE prophylaxis per local policy.

Antibiotic Therapy

💊 Follow local guidance; start promptly if complicated appendicitis suspected.
✅ Simple/uncomplicated: peri-op prophylaxis; no post-op antibiotics often needed.
💥 Complex/perforated/abscess/sepsis: IV broad-spectrum, step-down guided by clinical response (~3–7 days).

Surgical Management

🔪 Laparoscopic appendicectomy: standard, faster recovery, fewer wound infections.
🟠 Open appendicectomy: selected cases (dense adhesions, complex disease).
🕒 Timing: urgent intervention for unstable/septic/peritonitic; elective/urgent window for stable uncomplicated cases.

Non-operative (Antibiotics-First) Management

🟡 Selected, uncomplicated, imaging-confirmed cases with shared decision-making and follow-up.
🔁 Counsel on recurrence risk; appendicolith increases failure risk.
🚫 Not for peritonism, sepsis, perforation, abscess, or diagnostic uncertainty.

WSES 2020: non-operative guidance.

Appendix Mass / Abscess

🧱 Tender RIF mass, persistent fever, raised CRP; CT shows phlegmon ± collection.
🛡️ IV antibiotics, bowel rest; IR drainage if drainable.
🔎 Colonic assessment in older adults to exclude malignancy.

⚠️ Complications

💥 Perforation → peritonitis, septic shock.
🛡️ Abscess/phlegmon, wound infection, intra-abdominal collections.
🧵 Adhesions → late SBO (rare).
🩸 VTE risk from inflammation/immobility.

Post-operative Care

🚶 Early mobilisation, analgesia, antiemetics, diet as tolerated.
🩺 Monitor fever, pain, ileus, wound; low threshold for imaging if deteriorating.
🧪 Review histology (rare neoplasm alters follow-up).
🏠 Discharge: clear safety net for worsening symptoms.

Outcomes / Prognosis

✅ Prompt uncomplicated appendicitis → excellent outcomes, short admission.
⏱️ Delayed diagnosis → higher perforation, abscess, prolonged antibiotics, longer stay.
👶👵 Children/older adults → higher complication rates from diagnostic delay/atypical features.

Common Pitfalls / Missed Diagnoses

⚠️ Normal early CRP/WCC, especially <12 h or immunosuppressed.
⚠️ Mistaking appendicitis for gastroenteritis; ignore focal/progressive pain/peritonism.
⚠️ Women: exclude ectopic pregnancy/ovarian pathology.
⚠️ Older adults: consider tumour-associated appendicitis.

Case-Based Examples

Case 1 (classic): 21-year-old, peri-umbilical → RIF pain, anorexia, low-grade fever, guarding; WCC/CRP raised; CT confirms uncomplicated appendicitis → fluids, analgesia, peri-op antibiotics, laparoscopic appendicectomy.

Case 2 (pregnancy): 22 weeks, RUQ/right flank pain, vomiting; USS equivocal; MRI confirms appendicitis → early surgical management with obstetric awareness.

Case 3 (mass/abscess): 55-year-old, 5 days symptoms, RIF mass; CT: phlegmon + small collection → IV antibiotics ± drainage; follow-up colonic evaluation, selective interval surgery.

Key Learning Points / Exam Pearls

🧠 Appendicitis is trajectory-based: repeat exams and escalation with deterioration are critical.
🧭 Appendix position explains atypical symptoms (retrocaecal = flank/back; pelvic = urinary/diarrhoea).
🤰 Pregnancy: USS first, MRI if equivocal; do not ignore strong clinical suspicion.
🩺 Early analgesia is safe and does not invalidate the exam.
🟡 Antibiotics-first = selected uncomplicated cases; perforation/sepsis/peritonism = surgical pathway.

Additional related clinical topics

Acute Appendicitis (OSCE focused)

Candidate Instructions:You are the medical student in the Emergency Department. A 22-year-old patient presents with abdominal pain. Take a focused history and outline your most likely diagnosis, differential diagnoses, and initial management plan. You do not need to perform an examination at this station.

Key Areas to Cover ✅

📍 Site: Initially central/periumbilical, later localising to right iliac fossa.
🕒 Onset/Duration: Typically gradual over hours.
🔥 Character: Dull → sharp pain, worse on movement/coughing.
🤢 Associated Symptoms: Anorexia, nausea, vomiting, low-grade fever.
🚽 Bowel/Urinary: Constipation, diarrhoea, dysuria (pelvic appendix can irritate bladder).
📜 Risk factors: Young age, male sex, family history (weak association).

Examiner Prompts 💬

“How would you differentiate appendicitis from other causes of RIF pain?”
“What would be your immediate investigations?”
“How would you manage this patient overnight?”

Differential Diagnoses 🔎

Condition	Distinguishing Features
Appendicitis	Periumbilical → RIF migration, anorexia, nausea
Meckel’s diverticulitis	Similar to appendicitis, diagnosed at laparoscopy
Renal colic	Colicky, radiates to groin, haematuria
Ovarian torsion / cyst rupture	Acute RIF pain in female, USS pelvis helps
Ectopic pregnancy	Reproductive-age female, +ve pregnancy test
Gastroenteritis	Diffuse pain, diarrhoea, systemic upset

Mark Scheme (10 points) 📝

Domain	Marks	Details
Pain history	3	SOCRATES, migration of pain
Associated GI & systemic symptoms	2	Nausea, anorexia, bowel change, fever
Red flags in females	2	Exclude ectopic pregnancy, ovarian pathology
Risk factors/PMH	1	Relevant past episodes, surgeries
Summary & plan	2	Diagnosis + differential + safe next steps

Investigations 🔬

Bedside: Obs, urinalysis, pregnancy test (all women of childbearing age).
Bloods: FBC (WCC/CRP), U&E, LFT, amylase, clotting, group & save.
Imaging: Ultrasound (pelvis in females), CT abdo/pelvis if diagnostic doubt.

Management 🩺

Resuscitation: IV access, fluids, analgesia, antiemetics.
Nil by mouth pending surgical review.
Antibiotics: IV broad-spectrum (e.g., co-amoxiclav or cefuroxime + metronidazole).
Surgical: Laparoscopic appendicectomy is standard of care.
If appendix normal at laparoscopy → look for Meckel’s diverticulum, ovarian pathology, ileitis.

Teaching Commentary 📚

This OSCE is testing your ability to identify a classic surgical emergency. Key marks come from recognising pain migration, always doing a pregnancy test in women, and suggesting IV fluids + antibiotics + urgent surgical review. Examiners reward clarity: say “This is most likely appendicitis, but in a female patient I would also urgently rule out ectopic pregnancy and ovarian torsion.” That phrase alone shows safety and scores very well.

🧑‍⚕️ Case Examples - Acute Appendicitis

Case 1 (Typical Presentation): 🚨 A 19-year-old man presents with 24 hours of abdominal pain that began centrally and migrated to the right iliac fossa. He has nausea, low-grade fever, and guarding in the RIF. Bloods show raised WCC and CRP. Diagnosis: Classic acute appendicitis. Teaching point: Migratory pain (central → RIF) with local peritonism is highly suggestive; requires urgent appendicectomy.
Case 2 (Perforated Appendicitis): 💥 A 30-year-old woman presents late with 4 days of abdominal pain, worsening fevers, and diffuse tenderness with rebound. She is tachycardic and hypotensive. CT abdomen shows perforated appendix with localised abscess. Diagnosis: Perforated appendicitis with peritonitis. Teaching point: Delayed presentation can lead to rupture; requires IV antibiotics, fluid resuscitation, and urgent surgery or percutaneous drainage if abscess walled off.
Case 3 (Atypical Appendicitis in Pregnancy): 🤰 A 28-year-old woman at 22 weeks’ gestation presents with right-sided abdominal pain and nausea. The pain is more in the right upper quadrant due to upward displacement of the appendix. Ultrasound suggests appendicitis. Diagnosis: Acute appendicitis in pregnancy. Teaching point: Pregnancy alters appendix position; diagnosis can be delayed. Prompt surgical management is needed to prevent maternal and fetal complications.

The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms.

Acute Appendicitis ✅

Overview / Definition