Acute appendicitis

Red Flags

Suspected perforation, generalised peritonitis, or appendicular abscess — emergency surgery; broad-spectrum antibiotic; admit^[1]
Sepsis or septic shock — sepsis pathway with broad-spectrum IV antibiotic within 1 h, fluids, lactate, urgent source control^[1]
Pregnancy with suspected appendicitis — laparoscopic appendicectomy at any trimester; expedite imaging and surgery to reduce fetal loss from delay^[1]
Right iliac fossa pain in elderly with weight loss or anaemia — exclude colorectal malignancy presenting as appendiceal obstruction^[1]

First-line treatment

Interventions

Laparoscopic appendicectomy as gold standard^[1]
Preferred over open in adults, children, obese, elderly, complicated, and pregnancy; lower wound infection, shorter stay, faster recovery; expert-dependent in resource-limited settings
Antibiotic-only management for selected uncomplicated cases^[1]
Adults with uncomplicated appendicitis (no appendicolith, no abscess, no perforation): 7–10 day antibiotic course as alternative; 30–40% recurrence at 1 year requiring delayed appendicectomy; shared decision-making
Appendicular mass / abscess management^[1]
Phlegmon: conservative IV antibiotic (Ochsner-Sherren); abscess: percutaneous drainage + IV antibiotic; interval appendicectomy debated (omit in adults without persistent symptoms; young patients with appendicolith may benefit)
Pre-operative antibiotics^[1]
Single pre-operative dose for uncomplicated; continue 3–5 days post-op for complicated (gangrenous or perforated); narrow per culture and source-control adequacy

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Co-amoxiclav (mild community-acquired)^[1]	Aminopenicillin + beta-lactamase inhibitor	1.2 g IV pre-op; 1.2 g IV every 8 h × 24–72 h post-op for complicated; switch to oral 625 mg TDS once tolerating diet	30 mg/kg every 8 h amoxicillin component	First-line peri-operative prophylaxis and empirical for mild community-acquired; review at 48 h with cultures
Piperacillin-tazobactam (complicated)^[1]	Beta-lactam + beta-lactamase inhibitor	4.5 g IV every 6–8 h	Per local protocol	Complicated appendicitis (perforated, peritonitis, sepsis); broad gram-positive, gram-negative, anaerobic; renal dose adjustment
Ceftriaxone + metronidazole^[1]	Third-generation cephalosporin + nitroimidazole	Ceftriaxone 1–2 g IV daily + metronidazole 500 mg IV every 8 h	Ceftriaxone 50–80 mg/kg/day; metronidazole 7.5 mg/kg every 8 h	Alternative for uncomplicated and selected complicated; oral switch when improving
Meropenem (severe / ESBL risk)^[1]	Carbapenem	1 g IV every 8 h	20 mg/kg every 8 h	Reserve for severe sepsis or known ESBL; renal dose adjustment

Co-amoxiclav (mild community-acquired)^[1]

Aminopenicillin + beta-lactamase inhibitor

Adult: 1.2 g IV pre-op; 1.2 g IV every 8 h × 24–72 h post-op for complicated; switch to oral 625 mg TDS once tolerating diet
Paediatric: 30 mg/kg every 8 h amoxicillin component

First-line peri-operative prophylaxis and empirical for mild community-acquired; review at 48 h with cultures

Piperacillin-tazobactam (complicated)^[1]

Beta-lactam + beta-lactamase inhibitor

Adult: 4.5 g IV every 6–8 h
Paediatric: Per local protocol

Complicated appendicitis (perforated, peritonitis, sepsis); broad gram-positive, gram-negative, anaerobic; renal dose adjustment

Ceftriaxone + metronidazole^[1]

Third-generation cephalosporin + nitroimidazole

Adult: Ceftriaxone 1–2 g IV daily + metronidazole 500 mg IV every 8 h
Paediatric: Ceftriaxone 50–80 mg/kg/day; metronidazole 7.5 mg/kg every 8 h

Alternative for uncomplicated and selected complicated; oral switch when improving

Meropenem (severe / ESBL risk)^[1]

Carbapenem

Adult: 1 g IV every 8 h
Paediatric: 20 mg/kg every 8 h

Reserve for severe sepsis or known ESBL; renal dose adjustment

Safety-net

After surgery: most return to normal activity within 1–2 weeks (laparoscopic) or 4 weeks (open); persistent fever, increasing pain, or wound discharge — same-day review^[1]
If on antibiotic-only management: complete the full course; recurrence rate is 30–40% within 1 year and may need delayed surgery^[1]
Severe abdominal pain with fever, vomiting, or peritonism — emergency department; perforated appendicitis carries higher complication rate^[1]

Referral criteria

All suspected acute appendicitisGeneral surgery for evaluation and management^[1]
Perforation, peritonitis, sepsis, or appendicular abscessEmergency department with surgery and ICU^[1]
Pregnancy with suspected appendicitisJoint surgery and obstetric clinic; expedite^[1]
Elderly with right iliac fossa mass or atypical featuresSurgery with imaging and colonoscopy to exclude malignancy^[1]

Clinical summary

Diagnosis with risk-scoring + imaging, antibiotic vs surgical management, and special situations (children, pregnancy, complicated) for acute appendicitis.

References

1.WSES Jerusalem Guidelines for Diagnosis and Treatment of Acute Appendicitis (2020 update) (2020)