Appendicitis

Introduction

Appendicitis is inflammation of the appendix and is the most common indication for emergency surgery in paediatric patients.^1,2

Paediatric appendicitis is a common cause of acute abdominal pain in children. Approximately 20 – 30% of children presenting with acute abdominal pain will be diagnosed with acute appendicitis.²

Aetiology

Anatomy

The appendix is an intraperitoneal hollow outpouching of the gut which arises from the caecum.³

It is suspended, by the mesoappendix, from the terminal portion of the ileum and commonly sits retrocaecally.

The appendix is thought to act as a reservoir for intestinal flora which allows the gut to replenish its microbiome after gastroenteritis, but there are usually no long-term consequences to removing it.²

Pathophysiology

Although the exact pathophysiology is unknown, the typical cause of inflammation is obstruction of the opening of the appendix, as a result of either a faecolith (hardened stool) or lymphoid hyperplasia.⁴

Risk factors

Appendicitis most commonly presents in the second decade of life and there is a slight predominance in males versus females (M:F 1.4:1).⁵

Children breastfed for less than six months and those exposed to tobacco smoke are at an increased risk of appendicitis.⁴

Clinical features

History

Typical symptoms of paediatric appendicitis include:⁶

• Nausea and vomiting
• Low-grade fever
• Umbilical pain
• Right iliac fossa pain
• Diarrhoea
• Anorexia

Other important areas to cover in the history include:

• Urinary symptoms such as dysuria, frequency or haematuria
• Recent illnesses
• Pain history (looking for a history of migratory abdominal pain)

Clinical examination

In the context of suspected appendicitis, a thorough abdominal examination is required. 

Typical clinical findings include:

• Right iliac fossa tenderness
• Right lower quadrant peritonism

Additional tests suggestive of appendicitis include:

• Rovsing sign: palpation of the left iliac fossa causes right iliac fossa pain
• Psoas sign: extension of the right thigh, in the left lateral position, causes right iliac fossa pain
• Obturator sign: internal rotation of the flexed right thigh causes pain
• Hop test: hopping or jumping causes abdominal pain

Differential diagnoses

Differential diagnoses of paediatric appendicitis include:

• Mesenteric adenitis: presents similarly to appendicitis, but usually preceded by a sore throat
• Meckel’s diverticulitis: presents similarly to appendicitis, but symptoms include rectal bleeding
• Gastroenteritis: general abdominal pain may be present but it will not typically migrate to the right iliac fossa
• Urinary tract infection: presents with urinary symptoms such as dysuria, frequency and urgency, and urinalysis will commonly show nitrites and white blood cells

Investigations

Bedside investigations

Relevant bedside investigations for appendicitis include:

• Urinalysis: to rule out urinary tract infection
• Capillary blood glucose: nausea, vomiting and anorexia may have cause hypoglycaemia. Hyperglycaemia would be more suggestive of diabetic ketoacidosis and further investigation of this would be required.
• Baseline vital signs: a low-grade fever may be present

Laboratory investigations

Relevant laboratory investigations for appendicitis include:

• Full blood count: raised white cell count
• Urea & electrolytes: anorexia, nausea and vomiting may cause deranged renal function in severe cases
• CRP: suggestive of inflammation
• Group and save: appendicitis management is typically operative and so this test is important as a transfusion may be required if there is a significant intra-operative blood loss

Imaging

Appendicitis is a clinical diagnosis, but imaging helps to determine the extent of appendix inflammation, as well as showing its exact anatomical location.

Imaging can help to determine whether or not operative management is required and in what timeframe.

The accepted first-line imaging for appendicitis is ultrasound, followed by cross-sectional imaging in the form of CT or MRI scanning.

Ultrasound imaging

Typical ultrasound findings in appendicitis include:⁸

• Non-compressible appendix (> 6mm in diameter)
• Appendicolith presence within the appendix
• Wall thickening (≥ 3mm) with associated hyperaemia

Ultrasound diagnoses can be made even more reliable by looking for secondary sonographic signs which are useful when the appendix cannot be properly visualised.

Secondary sonographic signs include:⁹

• Free fluid within the right iliac fossa
• Echogenicity of the mesenteric fat: this is especially useful in ruling out differential diagnoses such as mesenteric adenitis where inflammation would be limited to the lymph nodes

Cross-sectional imaging

The ionising radiation involved in CT scanning makes it a less favourable choice for cross-sectional imaging, particularly in children.⁹

MRI is a preferable choice in paediatrics, and recent research has shown that fast-acquisition scanning can be performed in under 15 minutes and provides a more accurate diagnosis than ultrasound alone.¹⁰

Scoring systems

Although appendicitis is a clinical diagnosis, there are several clinical decision tools that can help with this process. These include:¹² 

• Appendicitis Inflammatory Response (AIR) score
• Paediatric Appendicitis Risk Calculator (pARC)
• Paediatric Appendicitis Score (PAS)
• Alvarado score

These prediction tools give different weighting to signs, symptoms and blood results, to provide a score that determines the likelihood of a patient having appendicitis.^13,14,15,16

pARC and AIR have been shown to be the most reliable decision tools in validation studies. Significantly, there were fewer false-positive scores with both of these tools.¹⁷

However, appendicitis is a clinical diagnosis, and no scoring system can replace the clinical signs picked up from serial abdominal examinations.

Management

Appendicectomy is the most common management strategy for appendicitis, although there are a few cases where this is not the immediate treatment:¹⁸

• Stable patients who present overnight are generally not operated on overnight, with the severity of their systemic inflammatory response guiding time to theatre
• In some cases of appendix masses, antibiotic therapy is commenced and appendicectomy is delayed by several months to allow inflammation to settle
• Children with large intraperitoneal abscesses are more commonly managed with percutaneous drainage than surgery

A laparoscopic approach is preferred for appendicectomy, and pre-operative antibiotic therapy is usually given in both simple and perforated appendicitis.¹⁸

Active observation

Active observation is a new concept in the management of appendicitis in children with an appendiceal mass, and involves antibiotics and fluid therapy, without a planned interval appendicectomy.

During a recent trial, less than 25% of children randomised into the active observation pathway had to undergo an appendicectomy, and the overall healthcare cost was less than the traditional interval appendicectomy approach.¹⁹

These findings may lead to a change in practice in paediatric surgery to favour a more conservative management style.

Complications

If there is a delay in presentation with appendicitis, complications can include:

• Perforation, leading to generalised peritonitis
• Abscess formation, usually requiring drainage

Complications of surgery include:

• Bleeding
• Wound infection

Key points

• Appendicitis is inflammation of the appendix and is the most common indication for emergency surgery in paediatric patients.
• Although the exact pathophysiology is unknown, the typical cause of inflammation is obstruction of the opening of the appendix.
• Appendicitis most commonly presents with Murphy’s triad of nausea and vomiting, low-grade fever and right iliac fossa pain.
• Appendicitis is a clinical diagnosis, but white cell count, ultrasound and cross-sectional imaging can be used to confirm the diagnosis and plan management.
• Management is typically a combination of antibiotics and appendicectomy. In some cases, appendicectomy can be delayed in favour of antibiotics and active observation.
• Complications include perforation and abscess formation in delayed presentations, as well as bleeding and surgical wound infection.

Reviewer

Ms Sameera Sharma

Higher trainee in general surgery

Editor

Dr Chris Jefferies

References

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