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Acute Appendicitis

1. Classification

Pathological (Morphological) Classification

Clinical-Anatomical Classification

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2. Clinical Presentation

Symptoms

• Classic sequence: periumbilical or poorly localised colicky pain → anorexia/nausea/vomiting → migration of pain to the right iliac fossa (RIF) within 4–12 hours (due to parietal peritoneal involvement)
• Low-grade fever (37.5–38.5 °C); high fever suggests perforation or abscess
• Nausea, anorexia, occasionally vomiting (vomiting typically follows pain onset — if vomiting precedes pain, consider alternative diagnoses)
• Constipation is common; diarrhoea occurs when inflamed appendix contacts the rectum (pelvic position)

Signs

Positional Variants

• Retrocaecal (most common, ~65%): psoas sign, flank tenderness; atypical presentation
• Pelvic: suprapubic pain, urinary symptoms, diarrhoea; rectal exam reveals tenderness
• Pre-ileal / post-ileal: mimics bowel obstruction or Crohn's disease
• Subhepatic: RUQ pain — mimics cholecystitis (especially in pregnancy)

Special Populations

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3. Diagnosis

Laboratory Investigations

Scoring Systems

• Score 1–4: Appendicitis unlikely; discharge with follow-up
• Score 5–6: Equivocal; imaging recommended
• Score 7–10: High probability; operate

Bailey & Love (p. 1363): "The diagnosis of acute appendicitis is essentially clinical; however, a decision to operate based on clinical suspicion alone can lead to the removal of a normal appendix in 15–30% of cases."

Imaging

• Non-compressible appendix >6 mm in diameter
• Wall thickness >3 mm
• Periappendiceal fluid or hyperechoic fat
• Appendicolith with acoustic shadowing
• Sensitivity ~75–90%; operator-dependent; limited by obesity and bowel gas

• Dilated appendix (>6 mm), wall enhancement, periappendiceal fat stranding
• Appendicolith (hyperdense faecolith, as shown in imaging below)
• Free fluid, free air (perforation), abscess formation
• Sensitivity ~94–98%, Specificity ~95%

• T2-weighted shows dilated appendix with surrounding inflammation

Differential Diagnosis

• Mesenteric lymphadenitis, Meckel's diverticulitis, Crohn's ileitis
• Right-sided ovarian pathology (cyst, torsion, ruptured ectopic)
• Pelvic inflammatory disease (PID)
• Right ureteric colic
• Caecal carcinoma (elderly), caecal diverticulitis

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4. Management

Preoperative Preparation

• IV fluid resuscitation (correct electrolyte imbalances)
• Analgesia (IV opioids — do NOT withhold; does not mask signs and improves examination cooperation)
• Antibiotic prophylaxis: single-dose IV cefuroxime + metronidazole (covers gram-negatives and anaerobes) 30–60 min before incision
• NG tube if bowel obstruction or ileus
• Urinary catheter for pelvic/advanced cases

Non-operative Management (select cases)

• Uncomplicated appendicitis: growing evidence that antibiotics alone (e.g., IV amoxicillin/clavulanate or ertapenem) can successfully treat ~70% of cases, with ~20–30% recurrence at 5 years
• Periappendiceal phlegmon/abscess: per Harrison's (p. 9192) — IV broad-spectrum antibiotics + drainage of abscess >3 cm + bowel rest; interval appendectomy at 6–12 weeks
• Not suitable for: perforation with diffuse peritonitis, appendicolith present (high recurrence), failure to respond within 24–48 h

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5. Surgical Approaches

A. Open Appendectomy (McBurney/Gridiron incision)

• Incision: at McBurney's point, perpendicular to a line joining ASIS to umbilicus
• Alternative: Lanz (transverse) incision for better cosmesis
• Steps: split-muscle (grid-iron) approach → identify caecum → deliver appendix → ligate and divide mesoappendix → ligate base with absorbable suture (e.g., Vicryl) → divide appendix → stump invagination (optional, not mandatory) → lavage → closure in layers
• Advantages: simple, universally applicable, low cost
• Indications where open preferred: haemodynamic instability, unavailability of laparoscopic equipment, prior surgery, generalised peritonitis (relative)

B. Laparoscopic Appendectomy (standard of care in most centres)

• Setup: 10 mm umbilical port (camera) + 2× 5 mm working ports (suprapubic and LIF)
• Steps: CO₂ pneumoperitoneum → identify appendix → dissect mesoappendix (harmonic scalpel/LigaSure/clips) → double ligation of base with Endoloops or stapler → transect → specimen in retrieval bag → peritoneal lavage if contaminated → drain placement if indicated → port-site closure
• Advantages over open: reduced wound infection, less postoperative pain, shorter hospital stay, faster return to activity, superior for obese patients and women of childbearing age (diagnostic advantage)
• Disadvantages: longer operative time, greater cost, higher risk of intra-abdominal abscess in some studies of perforated cases

C. Single-Incision Laparoscopic Surgery (SILS) / Robotic

• Cosmetically superior (hidden umbilical scar)
• No proven clinical outcome benefit over standard laparoscopy
• Used in specialised centres

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6. Types of Anaesthesia

• Rapid sequence induction (RSI) mandatory — patients assumed to have full stomach
• Avoid succinylcholine in crush-injury or prolonged immobility (hyperkalemia risk)
• Temperature management important for children
• Pneumoperitoneum in laparoscopy increases intra-abdominal pressure → raises CO₂, reduces venous return, worsens pulmonary compliance

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7. Indications for Drainage and Tamponade of the Abdominal Cavity

Drainage

1. Periappendiceal abscess: drainage (percutaneous CT/US-guided or intraoperative) is indicated for abscesses >3 cm — Harrison's (p. 9192)
2. Perforated appendicitis with localised purulent collection: drain placed in RIF/pelvis at time of surgery
3. Diffuse faecal peritonitis (perforated, with gross contamination): peritoneal lavage + drain(s) (pelvic and/or subhepatic)
4. Persistent contamination or clinical uncertainty about adequacy of source control

• Warm saline irrigation of the peritoneal cavity, especially pelvis and paracolic gutters, when perforation with soiling is present
• Routine lavage in laparoscopic appendectomy for perforated appendicitis is recommended to reduce postoperative abscess formation

Tamponade of the Abdominal Cavity

• Control diffuse oozing from inflamed peritoneal surfaces when haemostasis is difficult
• Damage control laparotomy: in haemodynamically unstable patients with diffuse peritonitis where a full-definitive repair is not immediately safe — abdomen is packed and temporarily closed; patient resuscitated in ICU; relook surgery in 24–48 h for pack removal and definitive repair
• Walling off of the peritoneal cavity with gauze packs was historically used when the appendix base was oedematous and ligation was unsafe, to prevent faecal fistula

• Haemodynamic instability despite resuscitation
• Coagulopathy, hypothermia, acidosis (lethal triad)
• Inability to achieve adequate contamination control in one setting
• Massive faecal peritonitis with septic shock

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8. Complications of Acute Appendicitis

Complications of the Disease Itself

Postoperative Complications

Mortality

• Uncomplicated appendicitis: <0.1%
• Perforated appendicitis: 0.5–2% overall; 5–10% in the elderly
• Main causes of death: septic shock, multi-organ failure, pulmonary embolism

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Summary Algorithm

Suspected Appendicitis
        ↓
Clinical assessment + labs + Alvarado score
        ↓
Score ≥7  →  Operate (laparoscopic appendectomy, GA)
Score 5-6 →  Imaging (USS/CT) → confirm → operate
Score <5  →  Observe, reassess, alternative diagnosis
        ↓
Perforated / abscess?
  → Abscess >3 cm → Drainage (percutaneous or surgical) + IV antibiotics
                    → Interval appendectomy 6–12 weeks
  → Diffuse peritonitis → Emergency surgery, lavage, drains
  → Unstable + contaminated → Damage control (pack, temporary closure, ICU, relook)

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• Bailey and Love's Short Practice of Surgery, 28th Edition, p. 1363
• Harrison's Principles of Internal Medicine, 21st Edition, p. 9192