Authors: Janet Skinner / Editor: Janet Skinner / Reviewer: Michael Perry / Codes: CAP1, HAP1 / Published: 10/11/2017 / Review Date: 10/11/2020

Appendicitis is one of the commonest surgical problems that present to Emergency Departments (ED). It accounts for around 40,000 admissions per year in England, mainly in patients between the ages of 15 and 25 years of age (1). Adults in the Western world have around a 6-8% chance of developing appendicitis in their lives although the incidence seems to be falling somewhat in recent years (1). The mortality of appendicitis rises from 0.8 per 1000 cases to 5.1 per 1000 cases if the appendix perforates (1). Importantly, in the US up to 10% of cases of appendicitis are not picked up on first clinical assessment (2).

Learning Bite

Patients are at much higher risk of significant morbidity and mortality if their appendix perforates.

Appendicitis consists of acute inflammation of the appendix. The appendix is an 8-10cm tube that is attached to the base of the caecum and can lie in various different positions within the abdominal cavity although the retreo-caecal and retro-colic positions are commonest (1,2,3).

Basic Science and Patho-physiology


The classical history in acute appendicitis is that of initial colicky central abdominal pain that moves after 6-12 hours to the right iliac fossa where it is constant in nature (1). This classic history is only normally present in half of the patients that present to the ED with appendicitis (1). Other common symptoms include anorexia (which tends to be present in 80% of patients with appendicitis), nausea, vomiting (which starts after the pain) and constipation (2). Appendicitis often presents with an atypical history particularly in the elderly, children and pregnant patients and can make these a very difficult diagnostic group, where the diagnosis may be made late and the risk of perforation is higher (4).

Why does the pain of appendicitis move?

Remember that the appendix is innervated by the autonomic nervous supply to the mid-gut. Inflammation in the appendix activates afferent sympathetic fibres, which enter the spinal cord at T10 and resulting in referred colicky pain to the peri-umbilical area (3) . Eventually inflammation in the appendix will irritate the surrounding parietal peritoneum, which is innervated by the intercostals nerves resulting in constant local pain in the right iliac fossa.

  • Visceral pain is normally vague, colicky and felt in the mid-line
  • Somatic pain is more constant, and felt at the local site (3,5)

Learning Bite

the classic migrating of pain of appendicitis has a sensitivity and specificity of around 80% (3,5).


The patient can looked flushed, dehydrated and have a furred dry tongue with fetor oris. They may also have a fever and slight tachycardia.

Patients are in pain, want to lie still and have tenderness in the right iliac fossa, maximal over McBurneys point which lies 1/3 of the way along an imaginary line from the anterior superior iliac spine to the umbilicus and indicates where the inflamed appendix normally lies.

What are the signs of localised peritonism in a patient with suspected appendicitis?

  • Direct tenderness press in RIF and patient experiences pain
  • Guarding due to voluntary or involuntary contraction of abdominal muscles
  • Rigidity due to reflex spasm of abdominal wall muscles
  • Rebound press enough to depress peritoneum in the RIF for 30s, suddenly remove hand, patient experiences rebound pain
  • Rovsings sign press deeply in the LIF for 30s, release suddenly, patient experiences rebound tenderness in RIF
  • Psoas sign ask patient to lift flexed thigh against your hand placed just above the knee, patient experiences pain in RIF (4,5)

How do you elicit signs of localised peritonism in a humane way?

While these signs are useful in making a diagnosis a patient in pain will not thank you for trying to elicit them. A kinder way to detect signs of localised peritonism can be

  • Ask the patient to blow their abdomen out fat and then suck it in thin
  • Ask the patient to cough gently
  • Percuss gently over the RIF to elicit guarding and rigidity

Patients may also be tender on digital rectal examination. Although there is some recent evidence to suggest that the finding of a painful PR exam is of little benefit with positive and negative predictive values of 0.44 and 0.54 respectively (6). Certainly multiple rectal examinations should be avoided in patients with suspected appendicitis.

Learning Bite

Appendicitis largely remains a clinical diagnosis based upon piecing together the history and examination.

Risk Assessment

There are no risk assessment tools that predict morbidity and mortality in patients who present with appendicitis. What is know is that patients with a perforated appendix are at higher risk of complications and death, therefore it is vital to try and make the diagnosis in a timely fashion and to recognise that children, elderly patients and pregnant patients are at higher risk because of diagnostic difficulties.

Learning Bite

unnecessary delays to theatre can lead to an increased rate of perforation of the appendix and worse outcomes in patients with appendicitis.

Terminal ileitis
Ruptured ovarian cyst
Renal colic
Mesenteric Adenitis
Ectopic pregnancy
Urinary Tract Infection
Meckels Diverticulitis
Pelvic Inflammatory Disease
Ovarian torsion
Acute cholecystitis
Bowel obstruction
Non-specific abdominal pain
Learning Bite

Appendicitis has a very wide differential diagnosis, particularly in females.

Urinalysis-note up to 30% of patients with appendicitis will have an abnormal urinalysis; send urine for urgent gram stain if in doubt (2)

Urinary beta hCG- to exclude ectopic pregnancy in any female of child bearing age

Full blood count 80-90% of patients with appendicitis will have a raised white cell count (>10 x 105). While helpful, white cell counts will also be raised in other causes of RIF pain and cannot rule in or out the diagnosis (2,7)

C-reactive protein- shows specificity and sensitivities of around 50-60%. Again, CRP is helpful but fairly non-specific but is more useful if interpreted in combination with the WCC (2)

Plain abdominal x-ray there is no role for plain films in patients with RIF pain, unless to look for another diagnosis (such as obstruction)

Learning Bite

The combination of a normal CRP and WCC has a negative predictive value for appendicitis in the region of 80-90% (8).

Predicting the likelihood of appendicitis based on clinical and laboratory findings

Over the years several clinical scoring tools have been proposed. These include the ALVARADO score. (was designed initially as a tool for diagnosing appendicitis in pregnant women) These tools have been shown to be no greater a predictor of acute appendicitis than clinical judgement alone (9).

M=Migration of pain to RIF (1)
A=Anorexia (1)
N=Nausea and vomiting (1)
T=Tenderness in RIF (2)
R=Rebound pain (1)
E=Elevated temperature (1)
L=Leukocytosis (2)
S=shift of WBC to left (1)


A subsequent meta-analysis of 24 studies that looked at the use of clinical and laboratory predictors of appendicitis in terms of their predictive and discriminatory values (10) . Receiver Operator Curves (ROC) were calculated to assess discriminatory power. The ROC is the proportion of true positives (patients with appendicitis) against true negatives (patients without appendicitis) for each value of the test. A value of 0.5 shows no discrimination and a value of 1.0 shows complete discrimination. Positive likelihood ratios (+LR) were calculated to describe predictive value. +LR is the likelihood that a given test result would be present in a patient with appendicitis. A +LR of >1 suggests that the post-test probability of appendicitis is greater that the pre-test probability. The meta-analysis included a number of clinical and laboratory variables. The tables show the variables with the highest +LR and ROC values (10) .

Andersson et al (10). Predictive power of clinical and laboratory values in diagnosing appendicitis (Likelihood ratios of 2 or more shown in increasing order)

Positive Likelihood Ratio
P value
Pain migration
2.06 (1.63, 2.60)
CRP raised
2.39 (1.67, 3.41)
2.48 (1.60, 3.84)
Percussion tenderness
2.86 (1.95, 4.21)
2.96 (2.43, 3.59)
White cell count raised
3.47 (1.55, 7.77)
WCC and CRP raised
23.32 (6.87, 84.79)
None given
Guarding/rebound and WCC raised
11.34 (6.65, 19.56)
None given

Andersson et al (10) . Discriminatory power of clinical and laboratory variables (ROC 0.65 or more in increasing order)

Pooled ROC area
P value
Migration of pain
CRP level
Guarding and WCC raised
None given
WCC and CRP raised
None given

While each of these variables independently has a fairly weak predictive and discriminatory value they are of most use in combination e.g. signs of peritonism and a raised WCC attain high +LRs and ROC values (10).

Learning Bite

Migration of pain, RIF rigidity and guarding with raised inflammatory markers in combination strongly suggest appendicitis (10).

Additional imaging investigations


Graded compression USS has been widely used to look for appendicitis in patients with RIF pain. It has an overall accuracy of about 90% (sensitivity 84% and specificity 88%) but is very operator dependent (7,11,12). An USS can rule in appendicitis but cannot rule it out, i.e. in the presence of a normal scan the patient will still need to be closely observed. USS is of particular value in trying to identify other pathologies, especially in women of childbearing age, when the diagnosis may unclear. It is also of benefit in patients with atypical signs, such as the elderly, children or pregnant patients.


CT has a greater overall accuracy of 94% (sensitivity 94%, specificity 95%) in diagnosing appendicitis compared to USS (12,13,14). However, CT is costly, may not be readily available and can result in significant radiation exposure to the patients. Studies that have shown improved accuracy of CT over USS predominantly utilised helical CT without contrast (13). Similarly to USS, CT can rule in but not rule out appendicitis. CT may be better at identifying other pathologies than USS.

If a patient is felt to have a high likelihood of appendicitis then unnecessary imaging should not delay theatre, remember the mortality and morbidity in appendicitis is higher if the appendix perforates.

Learning Bite

helical CT without contrast is the investigation of choice in patients in whom there are equivocal findings or the diagnosis is not clear.

Diagnostic difficulties

96% of patients will have RIF pain however, atypical pain and diagnostic difficulties are common in the following groups (2)

Atypical symptoms and signs can lead to late presentation
Atypical symptoms and signs can lead to late presentation and 3x increased perforation rate
Pregnant patients
Abnormal position of the appendix due to pregnant uterus can cause atypical signs, perforation associated with foetal mortality
Abnormal positioning of the appendix
Atypical site of pain, e.g. with pelvic appendix
Women of child-bearing age
Extensive differential diagnosis including tubo-ovarian pathologies, higher rates of negative appendicectomies

Learning Bite

maintaining a high index of suspicion in these diagnostic groups may help to prevent missing the diagnosis of appendicitis.

1) Resuscitate – if dehydrated or signs of sepsis

  • Oxygen (high flow, non-rebreather mask)
  • Intravenous access x2
  • IV normal saline 1-2 litres then reassess
  • Give immediate antibiotics if patient has signs of septicaemia or generalised peritonitis (cephalosporin and metronidazole)

2) Analgesia

  • Morphine IV titrated to effect with IV anti-emetic.
  • A Cochrane review states that there is no evidence that opiates mask the signs of peritonism or lead to a delay in diagnosis. Analgesia should never be withheld until the patient has seen the surgeon (15)

3) Keep nil by mouth

4) Involve surgical team

A Cochrane review recommends that once the decision to take the patient to theatre has been made then broad spectrum IV antibiotics (cephalosporin and metronidazole) should be given as they decrease the post-operative rate of wound infection and abscess formation (16).

5) Appendicetomy

Approach to patients with RIF pain
Approach to patients with RIF pain

Learning Bite

Low risk patients who are discharged home need clear advice to return to ED should their symptoms recur.

Surgical Approaches to Management

Surgeons must weigh up the risks and benefits of appendicetomy in patients with RIF pain. Negative appendicetomy rates are often in the region of 10-20% and it is important to try and keep this rate low (1,12)while trying to avoid the risks of perforation with its increase in mortality. Negative appendicetomies have been shown to be associated with female sex, low WCCs, low pulse and age <21 years (17) . A recent study has shown a reduction in the negative appendicectomy rate from 16.3% to 7.65% in a centre in the US where all patients got a CT before theatre (18). Serial clinical examinations performed by a senior surgeon are still invaluable in deciding whether or not a patient with equivocal findings requires theatre for appendicectomy. This wait and see approach is advocated by most although evidence for its benefit is lacking.

Traditionally appendicectomy was always performed as an open procedure but over the last 20 years there has been an increasing vogue for the use of a laparoscopic approach to appendicectomy. There is evidence that a laparoscopic approach reduces post-operative pain and length of hospital stay but at the expense of an increase in abscess formation (1,12,19).

A diagnostic look and see laparoscopy is favoured by some, particularly in women of childbearing age who have a significant incidence of gynaecological pathology.
Appendix masses or abscesses are usually treated conservatively with IV antibiotics, fluids and serial USS to monitor progress. Interval appendicectomy may or may not then be performed at a later date (20).

Learning Bite

A Cochrane review has found the laparoscopic approach to have diagnostic and therapeutic advantages.

Key Learning Points

  • While the mortality from appendicitis is low it increases approximately ten times if the appendix perforates
  • Perforation of the appendix occurs in up to 30% of cases of appendicitis
  • The classic history of pain migrating to the RIF is only present in around 50% of cases of appendicitis
  • The combination of migration of pain with RIF rigidity and guarding strongly suggests appendicitis and despite advances in investigations remains the mainstay in making a diagnosis (grade 1c, B recommendation)
  • A raised WCC and CRP is present in around 90% of patients with appendicitis, although may be raised also in other causes of abdominal pain (grade 1b, A recommendation)
  • In a patient with clinically suspected appendicitis unnecessary imaging should not delay theatre (grade 4, C recommendation)
  • Helical CT is the investigation of choice in patients with equivocal findings, although like USS, it cannot rule out appendicitis (grade 2b recommendation B)
  • Analgesia should never be withheld as there is no evidence that opiates mask the signs of peritonism (grade 1b, A recommendation)
  • Broad-spectrum intravenous antibiotics should be administered as soon as a decision to take the patient to theatre has been made (grade 1a, A recommendation)
  • Patients who are deemed to be at low risk of appendicitis may be discharged home with clear advice to return if their symptoms recur (grade 5, D recommendation)
  • Laparoscopic appendicectomy results in less post-operative pain but more deep infections (grade 1b, A recommendation)
  • A positive urinalysis does not rule out appendicitis as 30-40% of patients will have an abnormal urinalysis
  • Failure to perform a urinary pregnancy test in female patients with abdominal pain can lead to failure to diagnose an ectopic pregnancy with potentially catastrophic consequences
  • An over-reliance on normal blood tests can result in the diagnosis of appendicitis being missed
  • Remember pregnant patients still get appendicitis and may have atypical findings
  • Atypical presentations and late diagnoses are common in the elderly and children
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