Acute appendicitis
Recommendations
Urgent
Suspect appendicitis in any patient with:
Acute severe right iliac fossa pain
Poorly localised central abdominal pain that becomes localised to the right lower quadrant[24]
Anorexia, nausea, and vomiting.[12]
Look for signs of a perforated appendix as this is associated with significant morbidity and mortality; the patient will look unwell and may have signs of shock or sepsis.[2][25] See Shock, Sepsis in adults, and Sepsis in children.
Examine the abdomen; this may show:
Involve early surgical input because emergency appendicectomy is needed. If there is evidence of sepsis, consider escalating to critical care.[26]
Give preoperative resuscitation while waiting for surgery.[27]
Maintain a high level of suspicion of appendicitis in pregnant women because a delay in diagnosis and treatment may result in perforation, which is associated with significant maternal and fetal mortality.[28]
Appendicitis is the most common non-obstetric surgical condition during pregnancy.[28]
After the first trimester, atypical pain such as right upper quadrant or right flank pain can occur.[29]
Refer all children with suspected appendicitis to the paediatric surgery team on call, if available. Where no paediatric surgery team is available, joint care should be managed between paediatrics and surgical teams.
Key Recommendations
History
While taking a history bear in mind that typical symptoms and signs of appendicitis are present in only around 50% of cases.[29]
The most common presenting symptom is poorly localised central abdominal pain that becomes localised to the right lower quadrant as inflammation progresses.[24]
Remember that the location of the appendix varies, and consequently so does the location of the pain.[25]
Examination
Assess for:
Right lower quadrant tenderness[24][25][30]
However, in pregnant women, atypical pain such as right upper quadrant or right flank pain may occur in the later stages of pregnancy[29]
Low-grade pyrexia (>37.8°C [>100.1°F])[2]
Tachycardia
Flushed face and fetor oris[29]
Flexed right hip (psoas sign) in retrocaecal appendicitis.[12]
Risk stratification
In adults, use a scoring system to determine the likelihood or rule out the diagnosis of appendicitis in order to guide further investigations and management (see Risk stratification in the full recommendations section, below).[7]
The most commonly used scoring systems are the Alvarado score, the Appendicitis Inflammatory Response (AIR) score, and the Adult Appendicitis Score (AAS).[7] The AIR and AAS scores perform better as predictors of acute appendicitis than the Alvarado score.
Any one of the three scores can be used to rule out appendicitis in low-risk patients, reducing the need for imaging and the risk of negative appendicectomy. But do not use the Alvarado score to positively confirm an appendicitis diagnosis.[7]
In children and elderly patients, do not make the diagnosis of appendicitis based on clinical scores alone.[4][7]
Initial investigations
Use the results of initial blood tests, in combination with history and examination, to risk stratify patients via a scoring system (AIR or AAS is most accurate); this will determine whether imaging is required.[7] See Risk stratification in the full recommendations section, below.
Consider imaging, along with observation, in intermediate-risk patients. Use either abdominal ultrasound or computed tomography; magnetic resonance imaging may be used in pregnant women if ultrasound is inconclusive.[7] In children, order an ultrasound if an imaging investigation is indicated based on clinical assessment.[7][30] A combination of blood tests (raised white cells and C-reactive protein) and ultrasound is usually enough to confirm the diagnosis. In rare instances of diagnostic doubt in children with an inconclusive ultrasound, choose computed tomography or magnetic resonance imaging based on local availability and expertise.[7]
High-risk patients who are aged <40 years and have strong symptoms and signs of appendicitis may go straight to surgery without imaging. However, if they are >40 years they should generally have imaging before surgery.[7] Check your local protocols as this varies in practice.
Low-risk patients may be safely discharged without diagnostic imaging, as long as they have appropriate safety-netting.[7]
If imaging is required, seek advice from a radiologist to determine the best imaging modality for your patient.
Order a pregnancy test in all women of childbearing age.
Use urinalysis to rule out urinary tract infection (UTI).[25]
However, do not make a diagnosis of UTI on urinalysis alone. A history of urinary symptoms and positive urine microscopy are also required.
Have a high level of suspicion of acute appendicitis because this can be challenging to diagnose.[13]
The clinical presentation can vary from mild non-specific symptoms to a haemodynamically unstable patient with sepsis or shock.[2]
Diagnose appendicitis based on a combination of history, examination, laboratory findings, and imaging. The goals are to:[7]
Ensure diagnoses aren’t missed, particularly in older patients, pregnant women, and children, who are more likely to have an atypical presentation[7]
Minimise the rate of negative appendicectomy (removal of a normal appendix), which is reported to be as high as 15% to 20% and even higher (28%) in young women.[7][13][31]
[Figure caption and citation for the preceding image starts]: Acute appendicitis - intraoperative specimenNasim Ahmed, MBBS, FACS; used with permission [Citation ends].
History
While taking a history bear in mind that typical symptoms and signs of appendicitis are present in only around 50% of cases. In most patients, symptoms start with anorexia, followed by abdominal pain and then vomiting.[12][29]
Abdominal pain is the main presenting symptom:
Anorexia is almost always present.[12]
If the patient is hungry and wants to eat, this is reassuring and makes appendicitis less likely.[25]
Nausea and vomiting are present in 75% of patients.[12]
Always consider intra-abdominal malignancy, particularly in patients aged 50 and over presenting with abdominal pain, weight loss and change in bowel habit.[32]
Practical tip
Some patients may present with diarrhoea or vomiting. Ensure you take a detailed history of the nature, volume, and frequency of these symptoms as the underlying appendicitis is easily missed.
Vomiting may occur in late appendicitis if there is small bowel obstruction due to an appendiceal abscess.[33]
The patient may also pass small volumes of mucus from the rectum if there is a pelvic appendicitis with a collection. The patient may describe this mucus as ‘diarrhoea’ (whereas stool volume is increased in true diarrhoeal illness).[12]
Don’t make the diagnosis of appendicitis in a pregnant woman based on history and examination only; order blood tests including inflammatory markers.[7]
Appendicitis is the most common non-obstetric surgical condition during pregnancy.[28]
A delay in diagnosis and treatment may result in perforation, which is associated with significant maternal and fetal mortality.[28]
Features that are significantly associated with appendicitis in pregnant patients are:[34]
Nausea
Vomiting
Localised peritonitis.
Take a collateral history if communication is a challenge: for example, when there is a language barrier or in patients who are very young, have dementia, have a mental health diagnosis, or have a learning difficulty.[35]
Suspect appendicitis if there is a history of becoming withdrawn or less active, or having reduced oral intake.[35]
Practical tip
Keep an open mind to other diagnoses when examining the patient.[29]
It can be difficult to differentiate appendicitis from other causes of abdominal pain, particularly in older patients, women of childbearing age, and children.[29]
In most patients, symptoms start with anorexia, followed by abdominal pain and then vomiting.[12]
Remember that the location of the pain can vary depending on the position of the appendix.[25]
A retrocaecal appendix can cause flank or back pain.
A retroileal appendix can cause testicular pain due to irritation of the spermatic artery or ureter.
A pelvic appendix can cause suprapubic pain.
A paracolic long appendix with tip inflammation in the right upper quadrant may cause pain in this region.
Examine for the following signs of appendicitis:
Right lower quadrant tenderness[25]
However, in pregnant women, atypical pain such as right upper quadrant or right flank pain may occur after the first trimester due to displacement of the appendix by the gravid uterus[29]
Low-grade pyrexia (>37.8°C [>100.1°F])[25]
However, consider other causes if there is a very high fever[2]
Tachycardia[29]
May be present but remember that this can also indicate a perforated appendix
Flushed face and fetor oris[29]
Flexed right hip (psoas sign) in retrocaecal appendicitis.[12]
Assess for signs of a perforated appendix. The patient will appear unwell and may have:
Signs of shock or sepsis.[2] See Shock, Sepsis in adults, and Sepsis in children.
Localised peritonitis with guarding[25]
Generalised peritonitis; a tense, distended abdomen with guarding or rigidity and absent bowel sounds[25]
This is caused by free perforation in the peritoneal cavity[25]
A palpable mass
This is due to a peri-appendiceal abscess caused by a perforation that is contained by the omentum.[7]
Do not routinely perform a rectal examination; this should be done only if the diagnosis is unclear.[27][36]
Practical tip
Examining children
Consider giving analgesia to children with suspected appendicitis if pain limits the examination.
Ask children to cough or hop to elicit abdominal pain.[9]
Children may need to be distracted by parents, guardians, or a play specialist in order to obtain an accurate examination.
See our topic Assessment of abdominal pain in children.
In adults, use a scoring system to determine the likelihood or rule out the diagnosis of appendicitis in order to guide further investigations and management.[7]
Use either the Appendicitis Inflammatory Response (AIR) score or the Adult Appendicitis Score (AAS) to determine whether your patient is at high, intermediate, or low risk of having appendicitis.[7]
High-risk patients who are aged <40 years, and have strong symptoms and signs of appendicitis, may go straight to surgery without imaging.[7] However, check your local protocols as this varies in practice.
Intermediate-risk patients may undergo further imaging and observation.[7]
Low-risk patients may be safely discharged without diagnostic imaging, as long as they have appropriate safety-netting.[7]
The Alvarado score can be used to rule out appendicitis but do not use it to positively confirm a diagnosis of appendicitis; it is not specific enough for that purpose.[7]
The Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) score is an alternative but is less commonly used. It is not covered in this guidance.[39]
All the scoring systems involve a combination of history, examination findings, and investigation results.[7]
These scoring systems should not be used in place of cross-sectional imaging to make a diagnosis of appendicitis in elderly patients owing to limited evidence in this patient group.[4][5]
In children, do not make the diagnosis of appendicitis based on clinical scores alone.[7]
Children frequently have atypical clinical features and obtaining a reliable history can be challenging.
The diagnosis of acute appendicitis in children should be made on the basis of clinical suspicion, blood tests, and, if needed, imaging (see the Investigations section).
Clinical scores are useful tools in excluding acute appendicitis in children.
Scoring systems used in children include the Alvarado score and the Pediatric Appendicitis Score (PAS). The PAS includes similar clinical findings to the Alvarado score in addition to a sign more relevant in children: right lower quadrant pain with coughing, hopping, or percussion.[7]
Use the following table to calculate the score for your patient, depending on which scoring system you are using:[40][41]
AIR[40] | AAS[41] | PAS*[43] | ||
|---|---|---|---|---|
History | ||||
Vomiting | 1 point | N/A | 1 point for either vomiting OR nausea | 1 point for either vomiting OR nausea |
Anorexia | N/A | N/A | 1 point | 1 point |
Pain in right lower quadrant | 1 point | 2 points | 2 points | N/A |
Migration of pain to the right lower quadrant | N/A | 2 points | 1 point | 1 point |
Examination | ||||
Right lower quadrant tenderness | N/A |
| N/A | 2 points for right lower quadrant tenderness to cough, percussion, or hopping |
Right iliac fossa tenderness | N/A | N/A | N/A | 2 points |
Rebound tenderness or guarding |
|
| 1 point | N/A |
Fever | >38.5℃: 1 point | N/A | >37.3℃: 1 point | >38.0℃: 1 point |
Blood test results | ||||
Leukocytosis shift | N/A | N/A | 1 point | N/A |
Proportion of neutrophils |
|
| N/A | N/A |
Absolute neutrophil count | N/A | N/A | N/A | >7500: 1 point |
White blood cell count (× 10 9/L) |
|
|
|
|
C-reactive protein (mg/L) |
| Symptoms <24 hours
Symptoms >24 hours
| N/A | N/A |
Add up the total number of points for your patient to calculate the risk of appendicitis as follows:[40][41]
High risk
AIR: 9-12 points
AAS: ≥16 points
Alvarado: 9-10 points
PAS: ≥7 points
Intermediate risk
AIR: 5-8 points
AAS: 11-15 points
Alvarado: 5-8 points
PAS: 4-6 points
Low risk
AIR: 0-4 points
AAS: 0-10 points
Alvarado: 0-4 points
PAS: <4 points
*In children, do not make the diagnosis of appendicitis based on clinical scores alone.[7] Children frequently have atypical clinical features and obtaining a reliable history can be challenging. Clinical scores are useful tools in excluding acute appendicitis in children.[7]
Evidence: Scoring systems in adults
Scoring systems are useful to identify adults (>16 years) at low or intermediate risk of acute appendicitis and can reduce the need for imaging.
Guidelines agree that scoring systems are useful to exclude appendicitis and to identify low-risk patients who do not require imaging, although they differ in which score they recommend and the cut-off used.
The World Society of Emergency Surgery (WSES) 2020 guideline concludes that an Alvarado or Appendicitis Inflammatory Response (AIR) score <5 or an Adult Appendicitis (AAS) score <11 can be used to identify adults (>16 years) with a very low likelihood of having acute appendicitis and who therefore do not need further investigation.[7]
However, the WSES states that the Alvarado score cannot be used to diagnose acute appendicitis due to its low specificity, and it seems unreliable in distinguishing complicated from uncomplicated appendicitis in people aged over 75 years.[4]
Therefore the WSES recommends AIR or AAS as the best performing clinical prediction scores for adults with suspected appendicitis.
The European Association for Endoscopic Surgery 2015 consensus statement recommends the use of the Alvarado score to divide patients into:[13]
A low probability group (<4) who do not need imaging
Intermediate (4-8) and high (≥9) probability groups for whom ultrasound scanning is indicated.
A large UK study (n=5345) of adults (16-45 years) also showed that scoring systems may be useful in identifying low-risk patients who are unlikely to have appendicitis. This may reduce the rate of admissions, CT scans, and unnecessary surgeries. This is particularly important in the UK as there is a high rate of normal appendixes removed.[31]
The study found that low-risk patients who are initially discharged and then re-attend with appendicitis had low rates of complications such as perforation.
The study authors proposed a clinical algorithm using an AIR score ≤2 for men and an AAS ≤8 for women to identify people at low risk.
Evidence: Scoring systems in children
Scoring systems are useful to exclude acute appendicitis in children; they should not be used alone to make a diagnosis.
The World Society of Emergency Surgery (WSES) 2020 guideline recommends the Alvarado score or the Pediatric Appendicitis Score (PAS) for excluding acute appendicitis in children.[7] This is based on the following evidence.
A systematic review (search dates January 1950 to January 2012) found that while these scores were the best validated in children (each included in five studies), both failed to meet the performance benchmarks and tended to overdiagnose acute appendicitis.[44]
PAS sensitivity 0.82 to 1 (median 0.93); negative likelihood ratio (LR-) 0 to 0.27 (median 0.1); predicted appendicitis frequency 0.43 to 0.98 (median 0.52); actual appendicitis frequency (median) 0.34; average overdiagnosis 35%.
Alvarado rule sensitivity 0.72 to 0.93 (median 0.88); LR- of 0.09 to 0.34 (median 0.14); predicted appendicitis frequency 0.34 to 0.64 (median 0.6); actual appendicitis frequency (median) 0.41; average overdiagnosis 32%.
These scores are less reliable in preschool-age children due to the presentation often being atypical, and increased risk of rapid progression and complications in this age group.[45]
There is some evidence that the Alvarado score may also help predict postoperative complications in children with acute appendicitis.[46]
Other scores considered in the WSES guideline
A retrospective study of 747 children (mean age of 11 years) with suspected acute appendicitis showed the Appendicitis Inflammatory Response (AIR) score, which includes C-reactive protein (CRP) levels, outperformed the Alvarado score and PAS (area under the receiver-operating curve: AIR 0.90; Alvarado score 0.87; PAS 0.82).[47] Further research is needed validating the AIR score in children.
The Pediatric Appendicitis Laboratory Score (PALabS), which includes CRP and calprotectin levels, has shown some promise in predicting which children are at low risk of acute appendicitis.[48]
Use the results of blood tests, in combination with history and examination, to risk stratify patients using a scoring system (AIR, AAS, or Alvarado); this will determine whether imaging is required.[7] See Risk stratification above.
How to take a venous blood sample from the antecubital fossa using a vacuum needle.
Blood tests
Request a full blood count and C-reactive protein (CRP) in all patients.[27]
Leukocytosis (10-18 x 10 9/L) with neutrophilia is present in 80% to 90% of people with appendicitis.[29]
C-reactive protein is likely to be elevated.[9]
In children, elevated CRP level (≥10 mg/L) on admission and leukocytosis (≥16 x 10 9/L) are strong predictive factors for appendicitis.[7]
Consider a ‘group and save’ for patients having surgery.[27]
Evidence: Blood tests
Blood tests, in combination with a clinical assessment, are sensitive for diagnosing appendicitis.
Imaging
Consider imaging, along with observation, for intermediate-risk patients.[7]
High-risk patients who are >40 years should also have imaging before going to surgery.[7]
Imaging is not always needed.
High-risk patients who are <40 years and have strong symptoms and signs of appendicitis may go straight to surgery without imaging.[7] However, check your local protocols as this varies in practice.
Low-risk patients may be safely discharged without diagnostic imaging, as long as they have appropriate safety-netting.[7]
If imaging is required, seek advice from a radiologist to determine the best imaging modality for your patient.
Ultrasound
Order an ultrasound if radiation risk is a concern; it should be used as first line in pregnant women and children.[7][27][52][53] It is a rapid test and can be performed at the bedside.[7] Check local protocols as guidelines differ in their recommendations on use of ultrasound.
Acute appendicitis can be ruled out if a normal appendix is visualised in its full length.[7][30]
Ultrasound is also useful for detecting alternative causes of abdominal pain (e.g., gynaecological conditions).[7][27]
Order magnetic resonance imaging (MRI) in a pregnant woman if ultrasound is inconclusive.[7][54] MRI has been proven to be a highly accurate diagnostic test for acute appendicitis, with a sensitivity of 0.96 and specificity of 0.97 in pregnant women.[55] However, a negative or inconclusive MRI does not exclude appendicitis and surgery should still be considered if clinical suspicion is high.[7] In children, if there is diagnostic doubt and ultrasound results are inconclusive, choose a second-line imaging technique (computed tomography or MRI) based on local availability and expertise.[7]
Abdominal computed tomography (CT)
Consider contrast-enhanced CT scan if:[7]
Ultrasound is inconclusive and there is ongoing clinical suspicion of appendicitis[7]
Low-dose CT is preferred if negative is ultrasound.[7]
You suspect malignancy[7]
You suspect an appendicular mass or abscess.[7]
A positive CT scan will show wall thickening, wall enhancement, and inflammatory changes in the surrounding tissues.[56][Figure caption and citation for the preceding image starts]: CT abdomen - thickened appendixNasim Ahmed, MBBS, FACS; used with permission [Citation ends].
Evidence: Debate on role of imaging in diagnosis of acute appendicitis
If imaging is required, discuss with a radiologist to determine the best imaging modality for your patient.[7]Use of imaging differs markedly between countries and institutions.
CT has a greater sensitivity and specificity than ultrasound and may reduce normal appendicectomy rates.[31][57][58] However, its use may depend on local resources and patient choice regarding exposure to ionising radiation.
Ultrasound has a sensitivity of 71% to 94% and a specificity of 60% to 98% for acute appendicitis; if ultrasound is unequivocally positive for appendicitis, ultrasound has comparable accuracy to a positive CT or MRI for ruling in appendicitis.[13][59]
In a study based on a large UK dataset (published 2020) the performance of ultrasound imaging for diagnosis of appendicitis was poor in both men and women (women: sensitivity 36%, false negative rate 8·4%; men: sensitivity 38%, false negative rate 18.8%).[31]
CT showed much better accuracy (women: sensitivity 92%, false negative rate 2.1%; men: sensitivity 94%, false negative rate 4.5%).
A Cochrane systematic review (search date June 2017) assessed the diagnostic accuracy of CT based on 71 separate study populations in 64 studies. The sensitivity was 95% (95% CI 93% to 96%), and specificity 94% (95% CI 92% to 95%).[60]
The probability of having appendicitis following a positive CT result was 92% (95% CI 90% to 94%), and following a negative CT result was 0.4% (95% CI 0.3% to 0.5%).
There was little to no difference in sensitivity or specificity for low-dose CT compared with standard‐dose or unspecified‐dose CT.
A CT with contrast has 92% sensitivity compared with 95% sensitivity in non-intravenous contrast-enhanced CT scan (no statistical significance).[61][62][63] Therefore, CT without contrast has equivalent diagnostic utility as a CT with contrast.[64]
Use of imaging differs between Europe and the US.
In Europe, the use of ultrasound for the diagnosis of acute appendicitis is becoming more widespread. However, young men with typical symptoms and signs of appendicitis often proceed straight to surgery without imaging, which might contribute to the rate of negative appendicectomies.[7]
A large UK study (published 2020) found that 73% (2638/3613) of women had preoperative imaging. The vast majority had ultrasound imaging (2289/3613, 63%) with CT performed in only 15% (547/3613).[31]
This compared with only 36% (627/1732) of men who had preoperative imaging (ultrasound 16% [276/1732]; CT 23% [398/1732]).[31]
In the US, it is common practice for all non-pregnant adults to have a CT scan to confirm appendicitis.[7]
Guidelines differ in their recommendations.
The World Society of Emergency Surgery’s 2020 guideline recommends using a combination of clinical parameters (initial assessment and clinical scores) and ultrasound imaging to improve diagnostic sensitivity and specificity and reduce the need for CT scan.[7]
It also makes a weak recommendation that CT scan should not be used for high-risk patients (Appendicitis Inflammatory Response score 9–12, Alvarado score 9–10, or Adult Appendicitis score ≥ 16) younger than 40 years prior to laparoscopy.
The European Association for Endoscopic Surgery 2015 consensus statement recommends ultrasound for any patient with a high or intermediate Alvarado score (≥4). CT or MRI scanning is reserved for patients in whom ultrasound is inconclusive.[13]
In its 2014 commissioning guide, the Association of Surgeons of Great Britain and Ireland recommends either imaging or laparoscopy for any patient suspected of having appendicitis who has an elevated white blood cell and C-reactive protein.[27]
Urinalysis
Use urinalysis to help exclude a urinary tract infection (UTI).[25]
UTI can present with very similar symptoms and signs to appendicitis.
Do not make a diagnosis of UTI on urinalysis alone. A history of urinary symptoms and urine microscopy are also required.
Be aware that urinalysis may be abnormal in about 50% of people with acute appendicitis because of inflammation adjacent to the right-sided urinary tract and bladder.[65]
Pregnancy test
Test all women of childbearing age to exclude pregnancy, including ectopic pregnancy.[66]
Emerging tests
Several novel biomarkers may be of value in the diagnosis and severity assessment of acute appendicitis:
Neutrophil-to-lymphocyte ratio. The simple ratio between neutrophils and lymphocytes measured in peripheral blood has been shown to have moderate predictive power for acute appendicitis and may be a useful adjunctive tool for diagnosis.[67]
Hyponatraemia. Several studies have shown a link between hyponatraemia and acute appendicitis, and as a predictor of complicated appendicitis.[68][69]
Pentraxin 3.[70]
Serum amyloid A. A systematic review and meta-analysis showed that serum amyloid A has a sensitivity and specificity for acute appendicitis of 0.87 and 0.74 respectively.[71]
Platelet indices. Studies suggest that low mean platelet volume is a marker of acute appendicitis.[72][73]
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