Acute Appendicitis

Introduction

Acute appendicitis is one of the most common causes of acute abdominal pain requiring surgery in children and adults alike. The appendix is a small, finger-like blind-ended structure arising from the caecum of the large bowel. It does not contribute significantly to the digestive function of the human gastrointestinal system but is believed to house bacteria for immune regulation.

Causes and Risk Factors

Acute appendicitis is thought to be caused by an obstruction of the appendiceal lumen, although the exact etiology of such obstruction is often unknown. Obstruction in the appendiceal lumen may be caused by hardened faeces (faecaliths), swollen lymphatic tissues or rarely parasites or tumours, leading to accumulation of secretion, bacterial proliferation, inflammation of appendiceal wall and potentially gangrenous changes or rupture in the later stage. It may occur in individuals across all ages but is most common among adolescents and young adults. The estimated lifetime risk of developing acute appendicitis is 7-12%.

Signs and Symptoms

Classical symptoms of acute appendicitis include vague abdominal pain which migrates to the right lower quadrant, loss of appetite, nausea and vomiting, and low-grade fever. Localized tenderness at the McBurney's point and signs of peritoneal irritation may be elicited on physical examination. However, diagnosis is often challenging in young children as symptoms may be atypical or non-specific. Patients with perforated appendicitis and generalized peritonitis may present with peritoneal signs, a toxic appearance, persistent high fever or diarrhoea.

Diagnosis

Diagnosis of acute appendicitis involves a combination of clinical assessment, blood tests and diagnostic imaging. Inflammatory markers such as white blood cell count and C-reactive protein (CRP) are often elevated signifying an inflammatory reaction. Ultrasonography (USG) is the preferred imaging modality in most children as it is radiation-free. Computed tomography (CT) may be required if USG is inconclusive or in cases with a delayed presentation. In selected cases, diagnostic laparoscopy may be considered as the definitive diagnostic tool to avoid delays due to urgent clinical condition, or if diagnostic uncertainty remains despite non-invasive imaging.

Treatment and Management

Appendicectomy

Surgical removal of the appendix (appendicectomy) is the standard treatment of choice for most children with acute appendicitis. The procedure is often performed laparoscopically but open conversion may be required in a small proportion of cases if severe inflammation limits the safety of the minimally invasive approach. Potential complications include wound infection, injury to abdominal structures, intra-abdominal abscess, and adhesive bowel obstructions. Short recovery from surgery in 1-2 days may be possible in children with early appendicitis, yet patients with perforation or intra-abdominal abscess may require post-operative antibiotics for up to 10-14 days depending on clinical condition.

Non-operative management (NOM)

In selected cases of early, uncomplicated appendicitis, NOM with antibiotics alone may be an option to avoid surgery. Surgery may be required if the condition fails to improve with antibiotics or if appendicitis recurs in the future. Patients with a delayed presentation and the formation of a well-formed intra-abdominal abscess may benefit from initial NOM with antibiotics and image-guided drainage of the abscess, as surgery may be difficult in advanced cases. A delayed elective laparoscopic appendicectomy may be arranged after the acute infective episode is treated to prevent future recurrence of acute appendicitis.

The most appropriate treatment of choice may differ from patient to patient depending on individual clinical conditions. Shared decision making among the medical team, patients and families is encouraged.

Follow-up Care

Most children with appendicitis recover smoothly without significant long-term problems. In patients treated with NOM, the option of delayed elective appendicectomy will be discussed at the clinic after discharge on a case-by-case basis. Following discharge after surgical appendicectomy, clinic visits will be arranged to follow up on any post-operative complications such as any residual infection and wound conditions. Long-term follow-up is often not required after complete resolution of the episode and smooth recovery from surgery.

References

• Bansal S, Banever GT, Karrer FM, et al. Appendicitis in children less than 5 years old: influence of age on presentation and outcome. Am J Surg. 2012;204(6):1031-5. [PMID:23231939]
• Addiss DG, Shaffer N, Fowler BS, etal. The epidemiology of appendicitis and appendectomy in the United States. Am J Epidemiol. 1990;132(5):910-25. [PMID:2239906]
• Carr NJ. The pathology of acute appendicitis. Ann Diagn Pathol. 2000; 4(1):46-58. [PMID:10684382]
• Svensson JF, Patkova B, Almström M, et al. Nonoperative treatment with antibiotics versus surgery for acute nonperforated appendicitis in children: a pilot randomized controlled trial. Ann Surg. 2015;261(1):67-71. [PMID:25072441]

Acknowledgement

Principal author: Dr To Hoi Man on behalf of Department of Paediatric Surgery, HKCH

Initial posting: Oct 2026

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