Acute appendicitis

Acute appendicitis is the most common cause of abdominal pain requiring surgery. The diagnosis of acute appendicitis is often problematic and delays in diagnosis may result in complications. Lifetime risk of appendicitis is 6.7% in females and 8.3% in males.

Traditionally a negative appendectomy rate of 10-20% has been considered acceptable, however appendectomy has low but not insignificant complication rates and imaging is increasingly used in the diagnosis of acute appendicitis.

Non-pregnant adults

Step 1: Pathway Entry

  • Symptoms to consider: Migratory abdominal pain (RLQ typical but not always the case), nausea, anorexia and vomiting
  • Appendicitis may present atypically with indigestion, flatulence, bowel irregularity, diarrhoea, malaise
  • Signs to consider: Low grade fever, Tenderness/ guarding/ rebound in RIF, Rosving’s sign

Step 2: Is the patient stable?

Initial resuscitation if unstable. The patient with acute appendicitis is usually stable but may present in shock/ multi-organ failure from perforation or sepsis.

Differentials to consider in the unstable patient are sepsis from UTI/ diverticulitis, perforated viscus, gut ischaemia, ectopic pregnancy in women of childbearing age, ruptured AAA in older patients. Bedside ultrasound indicated if AAA is a differential.

Step 3: Detailed initial assessment

  • In the stable patient a thorough assessment is the next step including a detailed history, a detailed examination, blood tests including FBC, EUC, LFTs, BSL and urinalysis. Do a pregnancy test in women of childbearing age. Lipase if pancreatitis is a differential. Differential diagnoses to think about include testicular torsion in the male, ectopic pregnancy and PID in females, caecal diverticulitis and incarcerated/ strangulated groin hernias. If an alternative diagnosis is made at this time then the steps further down the pathway can be curtailed.

The Alvarado score (mnemonic MANTRELS) is validated for the diagnosis of appendicitis in adults and may aid the inexperienced physician in their assessment.

M: Migration of pain to right lower quadrant = 1 point

A: Anorexia = 1 point

N: Nausea and vomiting = 1 point

T: Tenderness in right lower quadrant = 2 points

R: Rebound tenderness = 1 point

E: Elevated temperature = 1 point

L: Leukocytosis = 2 points

S: Shift of WBC count to left = 1 point

Appendicitis is probable with a score of 7 or more and is unlikely with a score of less than 4. Patient with a score of 4-6 should have further imaging.

Step 4: Imaging

Imaging is not required in patients with the classic history and physical findings of acute appendicitis. Diagnostic imaging should be performed when the diagnosis of appendicitis is clinically suspected but unclear.

  • AXR is not indicated in the diagnostic workup of appendicitis, however if an AXR is done it may show right lower quadrant appendicolith, localized right lower quadrant ileus, loss of the psoas shadow, deformity of caecal outline, right lower quadrant soft tissue density
  • Ultrasound is the first line test in young patients and pregnant women as it does not expose the patient to radiation or contrast. Pelvic ultrasound is useful where gynaecological pathology is a differential. The ultrasound may be inconclusive, unhelpful in obese patients and is operator dependent. An equivocal ultrasound should be followed by a CT or close observation.
  • Options for CT imaging in appendicitis include CT with contrast and non-contrast CT.

CT with IV and oral contrast is preferred when CT imaging is indicated. Sensitivity and specificity of up to 98 and 93 percent have been reported. It is useful in making an alternative diagnosis for the patient’s presentation. However, it exposes the patient to radiation and contrast. Oral contrast may be omitted where the patient is unable to tolerate oral contrast.

Non-contrast CT is useful where there is a contraindication to contrast. It is however less helpful in making an alternative diagnosis.

ACEM Guidelines on Diagnostic Imaging are available here.

Step 5: Management

Supportive care

  • NBM
  • IV fluids
  • Analgesia

Appendectomy remains standard of care. IV antibiotics should be given, especially if septic.

Medical management with antibiotics only (as in diverticulitis) is currently being investigated as a therapeutic option in patients with uncomplicated appendicitis.

Acute appendicitis in pregnancy

Acute appendicitis is the most common surgical problem in pregnancy. Diagnosis is challenging as abdominal complaints are common in pregnancy, the presentation may be atypical due to displacement of the appendix by the gravid uterus and there is a physiological leucocytosis in pregnancy. Appendiceal rupture occurs more frequently in pregnant women, possibly because of the difficulty in diagnosis and the reluctance to operate in pregnancy.

Step 1: Pathway Entry

Symptoms to consider: Similar to acute appendicitis in the non-pregnant adult, but more often atypical (20% present with RUQ pain)

Signs to consider: Similar to acute appendicitis in the non-pregnant adult, but classical signs more difficult to elicit

Step 2: Is the patient stable?

Initial resuscitation if unstable, if > 20 weeks place wedge under the R hip allows gravitational displacement of the gravid uterus to alleviate aortocaval compression.

Always think of ectopic pregnancy in the pregnant woman with RLQ pain, if there is no previous imaging confirming an intrauterine pregnancy.

Step 3: Detailed initial assessment

Similar to acute appendicitis in the non-pregnant adult, however leucocytosis may be physiological.

Step 4: Imaging

In patients where the diagnosis is equivocal, ultrasound is the investigation of choice. Beyond 35 weeks gestation, ultrasound is less useful because graded compression technique is not easily performed. Ultrasound is often performed even if the diagnosis is clear clinically to assess foetal wellbeing. If ultrasound is non-diagnostic then the next step is CT or close observation. MRI is a potential investigation if available.

Step 5: Management

Supportive care

  • NBM
  • IV fluids
  • Analgesia

IV antibiotics should be given according to local protocol e.g. cefotaxime/ ceftriaxone (pregnancy class B1) and/or metronidazole (pregnancy class B2). Gentamicin (pregnancy class D) should be avoided in the pregnant woman with appendicitis. Definitive treatment is appendectomy.

Walled off perforations

Patients who present with more than five days of symptoms may have a walled-off perforation. An abdominal mass may be present on examination and imaging may reveal a phlegmon or abscess.

Management comprises:

  • IV antibiotics
  • Intravenous fluids
  • Analgesia
  • Bowel rest
  • Admission for close monitoring

In non-pregnant patients, definitive treatment is percutaneous drainage followed by interval appendectomy at 6-8 weeks. Immediate surgery in these patients is associated with increased morbidity due to dense adhesions and inflammation and may result in increased complications. Treatment failure is an indication for appendectomy. The role of conservative treatment, percutaneous drainage and interval appendectomy versus immediate surgery in pregnant women is unclear.

Acute appendicitis - further resources and references

Online resources

  1. EM Cases - discusses and presents appendicitis in different formats including MP3 downloads
  2. American College for Emergency Physicians: Annals of Emergency Medicine 2016 - Clinical Policy: Critical Issues in the Evaluation and Management of Emergency Department Patients With Suspected Appendicitis
  3. BMJ Best Practice - acute appendicitis (subscription required)
  4. Uptodate (requires login) Acute appendicitis in adults: clinical manifestations and diagnosis

Journal articles and textbooks

  1. Hlibczuk V, Dattaro JA, Jin Z, et al. Diagnostic accuracy of non-contrast computed tomography for appendicitis in adults: a systematic review. Ann Emerg Med. 2010;55:51-59.
  2. Vissers RJ, Lennarz WB. Pitfalls in appendicitis. Emerg Med Clin North Am. 2010;28:103-118.
  3. Tintinalli, Judith E, Tintinalli's emergency medicine : a comprehensive study guide, 7TH edition, Chapter 84: Acute Appendicitis

© Agency for Clinical Innovation 2021

Feedback