Practice Easily Missed?

Appendicitis

BMJ 2011; 343 doi: http://dx.doi.org/10.1136/bmj.d5976 (Published 06 October 2011) Cite this as: BMJ 2011;343:d5976
  1. Sian R R Lewis, locum general practitioner1,
  2. Peter J Mahony, general practitioner2,
  3. John Simpson, associate professor in gastrointestinal surgery3
  1. 1Nottingham, UK
  2. 2Belvoir Health Group, The Surgery, Nottingham, UK
  3. 3Department of General Surgery, University Hospital/Queens Medical Centre, Nottingham NG7 2UH, UK
  1. Correspondence to: J Simpson j.simpson{at}nottingham.ac.uk
  • Accepted 29 August 2011

Acute appendicitis is the most common abdominal condition requiring emergency surgery. It results from inflammation of the vermiform appendix, which is a tubular structure attached to the base of the caecum.

Case scenario

A 50 year old man presented with a 24 hour history of generalised abdominal pain that had become localised in the right loin. He had no urinary symptoms but was feverish (37.8°C). His urine was positive for blood and protein, and a provisional diagnosis of renal colic was made. He was referred to hospital, where computed tomography of the kidneys, ureters, and bladder did not demonstrate any evidence of urinary calculi but did confirm the presence of an inflamed retrocaecal appendix. He underwent an open appendicectomy and made an uneventful recovery.

How common is appendicitis?

  • Appendicitis is the most common abdominal emergency and accounts for more than 40 000 hospital admissions in England every year (approximately 1 per 1500 population)1

  • Appendicitis is most common between the ages of 10 and 20 years, but no age group is exempt

  • There is a male to female ratio of 1.4:1; overall lifetime risk is 8.6% for males and 6.7% for females in the United States2

  • Since the 1940s the incidence of hospital admission for acute appendicitis has been falling, but the reason for this decline is not clear3

Why is appendicitis missed?

The classical presentation of appendicitis appears in only approximately 50% of patients.4 Appendicitis can affect all age groups, and presentation may be influenced by the patient’s age and the anatomical position of the appendix. An accurate history may not be possible from the very young or from older people presenting with confusion.

Pregnancy seems to protect against appendicitis,5 but it is the most common non-obstetric emergency requiring surgery in pregnancy. Presentations in pregnant women may be atypical (due to anatomical displacement of the appendix by the gravid uterus) or mistaken for the onset of labour; tenderness may be located anywhere on the right side of the abdomen or may be minimal if the inflamed appendix is displaced posterolaterally.

The diagnostic accuracy of general practitioners in relation to appendicitis is high (92% of paediatric cases correctly diagnosed) and the non-specificity of symptoms and signs is the predominant reason for a delay in diagnosis.6

Why does this matter?

Appendicitis is a progressive inflammatory process, and the incidence of perforated cases rises with the duration of symptoms. Therefore, prompt diagnosis and treatment are essential for reducing the increased risk associated with advanced inflammation. After the first 36 hours following the onset of symptoms the average rate of perforation is between 16% and 36%, and the risk of perforation is 5% for every subsequent 12 hour period.7 Perforation rates are higher in elderly people and young children,8 possibly because of a delay in diagnosis.9 However, actual perforation rates are difficult to calculate accurately due to the frequency of undiagnosed cases of resolving appendicitis.10

How is appendicitis diagnosed?

Clinical features

Diagnosis of acute appendicitis relies on a thorough history and examination, and the presence or absence of any particular individual symptom or sign cannot be relied upon to diagnose or exclude appendicitis.

In the assessment of a patient with suspected appendicitis, studies have demonstrated that pain migration (positive likelihood ratio 2.06) and evidence of peritoneal irritation (localised direct or indirect tenderness (1.29-2.47), rigidity (2.96), guarding (2.48), rebound (1.99), and percussion tenderness (2.86) are the most useful clinical findings associated with a positive diagnosis.11

Abdominal pain is the primary presenting complaint of patients with acute appendicitis. However, the sequence of vague abdominal pain followed by vomiting with migration of the pain to the right iliac fossa first described by Murphy may be present only in around 50% of patients.4 Typically, the patient describes a periumbilical or epigastric pain that intensifies during the first 24 hours, becoming constant and sharp, and migrates to the right iliac fossa. Loss of appetite is often a predominant feature, and constipation and nausea are frequently present. Profuse vomiting is rarely a major feature in simple appendicitis. The patient can be flushed, with a dry tongue and associated fetor oris. The presence of pyrexia (up to 38°C) with tachycardia is common. Abdominal examination reveals localised tenderness and muscular rigidity after localisation of the pain to the right iliac fossa. The site of maximal tenderness is often said to be over McBurney’s point, which lies two thirds of the way along a line drawn from the umbilicus to the anterior superior iliac spine. Rebound tenderness is present but the test should be used with caution as it can be distressing for the patient. Movement frequently exacerbates the pain, and asking patients to cough will often localise the pain to the right iliac fossa. Demonstration of Rovsing’s sign (palpation of the left iliac fossa causes pain in the right iliac fossa due to peritoneal irritation) may also aid in the diagnosis of appendicitis. In atypical cases, clinical assessment of the right groin and hip is important, particularly in paediatric patients, to rule out pathology in this region.

Scoring systems

Scoring systems have been developed to aid the diagnosis of appendicitis. They aim to estimate the probability of the condition in an individual patient compared with a large number of similar patients from which the system was developed. The best known of the several systems developed is the Alvarado score,12 although more recently the appendicitis inflammatory response (AIR) score correctly classified a higher proportion of patients into low probability and high probability groups. The scores use history and examination findings along with inflammatory markers to achieve a summed numerical score. In a study of 545 patients with suspected appendicitis the receiver operating characteristic area for the AIR score was 0.93 compared to 0.88 for the Alvarado score (P=0.0007).13

Anatomical considerations in the presentation of acute appendicitis

  • Retrocaecal/retrocolic (20%)14—Right loin pain is often present, with tenderness on examination. Muscular rigidity and tenderness to deep palpation are often absent because of protection from the overlying caecum. The psoas muscle may be irritated in this position, leading to hip flexion and exacerbation of the pain on hip extension (psoas stretch sign)

  • Subcaecal and pelvic (51%)14—Suprapubic pain and urinary frequency may predominate. Diarrhoea and tenesmus may be present as a result of irritation of the rectum. Abdominal tenderness may be lacking, but rectal or vaginal tenderness may be present on the right. Microscopic haematuria and leukocytes may be present on urinalysis

  • Pre-ileal and post-ileal (25%)14—Diarrhoea may result from irritation of the distal ileum. A presumptive diagnosis of gastroenteritis may delay a diagnosis of appendicitis8

Investigations

There is no specific laboratory test for appendicitis although simple blood tests may support the diagnosis as the majority of patients with appendicitis will have a neutrophil predominant leukocytosis. Combining C-reactive protein and white cell count can provide a likelihood ratio for appendicitis of up to 23.32 depending on values taken.11 In contrast, when all inflammatory markers are normal, appendicitis is unlikely.11

To assess for obstetric related conditions, pregnancy testing is mandatory in women of child bearing age.

Urinalysis may be abnormal in almost half of patients with acute appendicitis because of inflammation adjacent to the right sided urinary tract and bladder.15

Appendicitis is predominantly a clinical diagnosis that can be supported by simple blood tests—specialist tests aren’t usually required. However, the most frequently used radiological investigations are ultrasonography (sensitivity and specificity of 86% and 81%) and computed tomography (94% and 95%),16 although the latter should be used with caution to minimise radiation exposure.

How is appendicitis managed?

Appropriate resuscitation followed by expedient appendicectomy either by the open or laparoscopic approach is the treatment of choice. All patients should receive broad spectrum perioperative antibiotics as this decreases the incidence of postoperative wound infections and abscess formation.17

Key points

  • Appendicitis is a predominantly clinical diagnosis, and no single individual symptom or sign can be relied upon to diagnose or exclude it

  • A history of fever or pain migration and evidence of peritoneal irritation have been found to be the most useful clinical features in making the diagnosis

  • A raised CRP and white cell count can support the diagnosis

  • The classical presentation can be influenced by the age of the patient and anatomical position of the appendix

Notes

Cite this as: BMJ 2011;343:d5976

Footnotes

  • This is one of a series of occasional articles highlighting conditions that may be more common than many doctors realise or may be missed at first presentation. The series advisers are Anthony Harnden, university lecturer in general practice, Department of Primary Health Care, University of Oxford, and Richard Lehman, general practitioner, Banbury. To suggest a topic for this series, please email us at easilymissed@bmj.com.

  • Contributors: SRRL and JS wrote the first draft. PJM made important revisions. JS is guarantor.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work. JS declares that MA Healthcare paid travel expenses and accommodation fees for speaking at an educational event on the subject of acute appendicitis in September 2010.

  • Provenance and peer review: Commissioned; externally peer reviewed.

  • Patient consent not required (patient anonymised, dead, or hypothetical).

References