Part of the TeachMe Series

Acute Appendicitis

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Last updated: April 14, 2020
Revisions: 36

Last updated: April 14, 2020
Revisions: 36

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Appendicitis refers to inflammation of the appendix.

It is caused by direct luminal obstruction, usually secondary to a faecolith (Fig. 1) or lymphoid hyperplasia, impacted stool or, rarely, an appendiceal or caecal tumour. It typically affects those in their second or third decade and there is a lifetime risk of 7-8%.

In this article, we shall look at the clinical features, investigations and management of acute appendicitis.

Figure 1 – A faecolith obstructing the appendiceal lumen, resulting in acute appendicitis

Risk Factors

  • Family history
    • Twin studies suggest that genetics account for 30% of risk*
  • Ethnicity
    • More common in Caucasians, yet ethnic minorities are at greater risk of perforation if they do get appendicitis
  • Environmental
    • Seasonal presentation during the summer

*No gene has been identified specifically but the risk is roughly three times higher in members of families with a positive history.

Clinical Features

The main symptom of appendicitis is abdominal pain. This is initially peri-umbilical, dull, and poorly localised, but later migrates to the right iliac fossa, where it is well-localised and sharp.

Other possible symptoms include vomiting (typically after the pain, not preceding it), anorexia, nausea, diarrhoea, or constipation.

On examination, patients may be tachycardic, tachypnoeic, and pyrexial. There is likely rebound tenderness and percussion pain over McBurney’s point (Fig. 2), as well as potential guarding (especially if perforated). An appendiceal abscess may also present with a RIF mass.

Specific signs that may be found on examination include*:

  • Rovsing’s sign: RIF fossa pain on palpation of the LIF
  • Psoas sign: RIF pain with extension of the right hip
    • Specifically suggests an inflamed appendix abutting psoas major muscle in a retrocaecal position

*Whilst alone they may have a poor predictive value, when combined they can be very sensitive in the conditions diagnosis

Figure 2 – McBurney’s Point (1), two thirds of the way between the umbilicus (2) and the ASIS (3)

Differential Diagnosis

There are a wide spectrum

  • Gynaecological: ovarian cyst rupture, ectopic pregnancy, pelvic inflammatory disease
  • Renal: ureteric stones, urinary tract infection, pyelonephritis
  • Gastrointestinal: mesenteric adenitis, diverticular disease, inflammatory bowel disease, or Meckel’s diverticulum*

*If a normal appendix is found during appendicectomy, an inflamed Meckel’s diverticulum should also be looked for


Laboratory Tests

Urinalysis should be done for all patients with suspected appendicitis to help exclude any renal or urological cause*. For any woman of reproductive age, a pregnancy test is also essential.

Routine bloods, importantly FBC and CRP, should be requested to assess for raised inflammatory markers, as well as baseline blood tests required for potential pre-operative assessment. A serum β-hCG may also be taken, if ectopic pregnancy still has not been excluded.

*Leucocytes can be present in the urine in low levels for those with an appendicitis, especially if the appendix lies on the bladder


Imaging is not essential to diagnose an appendicitis, as cases can be a clinical diagnosis.

Ultrasound scan or CT imaging (Fig. 3) is often requested if the clinical features are inconclusive and an alternative diagnosis is sought:

  • Ultrasound –  good first line investigation (especially transvaginal approach) if the differential includes gynaecological pathology
    • Also useful in children as can minimise radiation exposure
  • Computed Tomography – Good sensitivity and specificity, able to delineate multiple differentials including gastrointestinal and urological causes
Fig 2 - CT scan showing an acute appendicitis, measuring 17.1mm diameter

Figure 3 – CT scan showing an acute appendicitis, measuring 17.1mm diameter

Risk Stratification Scores

Several risk stratification scores have been developed in an attempted to assist in the diagnosis of appendicitis, based on clinical and radiological evidence.

The RIFT study compared multiple risk prediction models, showing the best predictors for acute appendicitis were:

  • Men – Appendicitis Inflammatory Response Score
  • Women – Adult Appendicitis Score
  • Children – Shera score

A risk score calculator using these parameters can be found here and can be used to aid clinical decision making


The current definitive treatment for appendicitis is laparoscopic appendicectomy (Fig. 4).

There is some debate surrounding the use of conservative antibiotic therapy in uncomplicated appendicitis; a recent Cochrane analysis found that appendicectomy should remain the standard treatment for acute appendicitis.

Indeed, primary antibiotic treatment for simple inflamed appendix can be successful, but has a failure rate of 25-30 % at one year.

Surgical Intervention

Laparascopic appendectomy* (Fig. 4) still remains the gold standard for treating appendicitis, due to a low morbidity from the procedure. In females it also allows for better visualisation of the uterus and ovaries, for assessment of any gynaecological pathology.

The appendix should routinely be sent to histopathology to look for malignancy (found in 1%, typically carcinoid, adenocarcinoma, or mucinous cystadenoma malignancy). As per any laparoscopic procedure, the entirety of the abdomen should be inspected for any other evident pathology, including checking for any Meckel’s diverticulum present.

*An open approach may be used in pregnancy and is still used globally in some healthcare systems, yet the laparoscopic approach has been shown to reduced hospital stay and permit earlier return to baseline activity

Fig 4 - Laparoscopic appendicectomy.

Figure 4 – Stages of a laparoscopic appendicectomy


The mortality associated with appendicitis in developed health systems is low (0.1% to 0.24 %). The complications of acute appendicitis include:

  • Perforation, if left untreated the appendix can perforate and cause peritoneal contamination
  • Surgical site infection
    • Rates vary depending on simple or complicated appendicitis (ranging 3.3-10.3 %)
  • Appendix mass, where omentum and small bowel adhere to the appendix
    • Traditional management for an appendix mass involves conservative approach with antibiotics, yet much debate remains surrounding the role of surgical intervention
  • Pelvic abscess
    • Presents as fever with a palpable RIF mass, can be confirmed CT scan for confirmation; management is usually with antibiotics and percutaneous drainage of abscess

Key Points

  • Appendicitis refers to inflammation of the appendix, most common in those in their second decade
  • The main symptom is abdominal pain, initially dull, peri-umbilical, and poorly localised, before migrating to the right iliac fossa and becomes well-localised and sharp
  • Diagnosis is typically clinical, however ultrasound or CT imaging can help in cases of clinical equipoise
  • Management is typically with laparoscopic appendicectomy, however some cases can be treated conservatively with antibiotics