oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
Acute appendicitis is sudden inflammation of the appendix, usually caused by obstruction of the lumen resulting in invasion of the appendix wall by the gut flora. If the appendix ruptures, infected and faecal matter enter the peritoneum, producing life-threatening peritonitis. Alternatively, particularly where perforation or gangrene occurs after 24 hours, the peritonitis may be localised, or the inflamed appendix may be surrounded by omentum to form an appendix mass or appendix abscess.
- It is the most common cause of an acute abdomen in the UK. About 10% of the population will develop acute appendicitis.
- Appendicitis is most common between the ages of 10 and 20 years but can occur at any age.
- Appendicitis is more common in men.
- A normal appendix is removed at 10-20% of appendicectomies.
Classic symptoms often do not appear in young children and the elderly and the diagnosis is particularly easy to miss in these age groups:
- Early periumbilical pain moves after hours or sometimes days to the right iliac fossa as the peritoneum becomes involved. Pain which wakes the patient or keeps a child awake is significant.
- Movement and coughing aggravate pain. The patient may lie still with shallow breathing, and coughing hurts.
- Nausea, vomiting, anorexia. The patient is usually constipated but may have diarrhoea. Rapidly progressive cases may have marked vomiting without fever and diarrhoea, which may be marked in post-ileal appendix (which is rare).
- Temperature and pulse are normal at first. Low-grade pyrexia then develops. A rising pulse rate may be an indication of peritonitis.
- Localised tenderness, guarding and rebound tenderness in the right iliac fossa.
- A retrocaecal or pelvic appendix may be missed.
- Rectal examination: localised tenderness and this may be the only sign of an inflamed retrocaecal or pelvic appendix.
- Other methods to demonstrate an inflamed appendix include: the psoas test (extend the hip and abduct the thigh with the patient on the left side) and the obturator test (flex the right thigh and internally rotate the hip).
- Right iliac fossa peritonism:
- Can be demonstrated by percussion tenderness or rebound tenderness.
- Rovsing's sign: pain in the right iliac fossa induced by palpation of the left iliac fossa.
- Stage of illusion: just after perforation, a child may sit up in bed apparently better. A rising pulse rate may be the only indication of perforation, before the obvious signs of peritonitis develop.
- Atypical presentations include:
- Pain and tenderness may be higher in pregnant women but right iliac fossa symptoms are still the main presentation.
- The diagnosis of acute appendicitis is mainly based on clinical assessment and experience.
- However, diagnosis may be difficult and scoring systems have been shown to be useful in determining the need for further investigation and treatment for acute appendicitis.
- One example is the Alvarado scoring system which scores the following indicators:
- Symptoms: migratory right iliac fossa pain (scores 1), nausea or vomiting (1), anorexia (1).
- Signs: tenderness in the right iliac fossa (2), rebound tenderness in the right iliac fossa (1), elevated temperature (1).
- Laboratory findings: leukocytosis (2), shift to the left of neutrophils (1).
- From a total possible score of 10, one study recommended further investigation with CT scan for a score of 4-6, and consideration of appendicectomy for scores of 7 or above.
- Other causes of abdominal pain:
- Gastrointestinal: gastrointestinal obstruction, constipation, intussusception, strangulated hernia, acute cholecystitis, perforated peptic ulcer, mesenteric adenitis, Meckel's diverticulitis, Crohn's disease, diverticulitis, pancreatitis, rectus sheath haematoma, gastroenteritis.
- Urological: testicular torsion, renal calculi, urinary tract infection.
- Gynaecological: ectopic pregnancy, torsion of rupture of an ovarian cyst, pelvic inflammatory disease.
- Others: diabetic ketoacidosis, pneumonia, porphyria, adverse effects from immune modulation therapies (eg panniculitis in the abdomen at the left iliac fossa, associated with beta-interferon injection).
- Other causes of right iliac fossa mass include Crohn's disease, carcinoma of colon, mucocele of the gallbladder, psoas abscess, pelvic kidney and ovarian cyst.
Appendicitis is essentially a clinical diagnosis (see separate article Abdominal Examination) but the following may be useful:
- Urinalysis may exclude urinary tract infection.
- Pregnancy test to exclude ectopic pregnancy.
- Full blood count: there is usually a mild leukocytosis but a normal white cell count does not exclude appendicitis.
- Raised inflammatory markers: C-reactive protein (CRP) may be raised but a normal level does not exclude a diagnosis of appendicitis.
- Ultrasound may help in some patients where the diagnosis is doubtful and in the assessment of an appendix mass or abscess.
- However, CT scanning is more sensitive and specific than ultrasound when diagnosing acute appendicitis. It is becoming increasingly used and this has lowered the rate of negative appendectomies in women under the age of 45 years in some centres.
- Diagnostic laparoscopy should be considered, particularly in young women (perforation may cause infertility in girls later in life, and so there is a lower threshold for surgery in girls).
- All suspected cases should be admitted to hospital. Appendicectomy is the treatment of choice and is increasingly done as a laparoscopic procedure.
- Once a diagnosis is made, appendicectomy should be performed without any delay.
- Spontaneous resolution of early appendicitis can occur, and medical treatment including antibiotics may be an alternative to surgery. However readmission rates are high and, because of relatively low morbidity and mortality associated with appendicectomy, early operative intervention remains the treatment of choice.
- In cases of diagnostic doubt a period of 'active observation' is useful.
- Intravenous fluids and opiate analgesia are required.
- Preoperative antibiotics are associated with a reduction in surgical site infections, but the role of postoperative antibiotics remains unclear.
- Laparoscopic appendicectomy: may be associated with a reduced hospital stay and a more rapid return to normal activity. Young female, obese, and employed patients seem particularly to benefit from laparoscopic appendicectomy.
- Perforation: the average rate of perforation at presentation is between 16% and 30% (significantly higher in elderly people and young children).
- Wound infection: rates of wound infection vary from <5% in simple appendicitis to 20% in cases with perforation and gangrene. Perioperative antibiotics have been shown to decrease the rates of postoperative wound infections.
- Appendix mass:
- Omentum and small bowel adhere to the appendix.
- Usually presents with a fever and a palpable mass.
- Initial treatment is usually conservative with fluids, analgesia and antibiotics but urgent surgical intervention may be required if the mass enlarges or the patient's condition deteriorates.
- Recovery following conservative treatment is usually followed by appendicectomy.
- Appendix abscess: can be shown by ultrasound or CT scan; initial treatment is by percutaneous or open drainage but open drainage also enables appendicectomy.
- Other acute complications include pelvic abscess, subphrenic abscess, paralytic ileus and septicaemia.
- Long-term complications: adhesions may cause intestinal obstruction but this is uncommon.
- Maternal mortality is very low in acute appendicitis in pregnancy but increases to 4% with perforation in late pregnancy. Fetal mortality is less than 1.5% but increases to 20-35% in cases of perforation.
Further reading & references
- Benjamin IS, Patel AG; Managing acute appendicitis. BMJ. 2002 Sep 7;325(7363):505-6.
- Humes DJ, Simpson J; Acute appendicitis. BMJ. 2006 Sep 9;333(7567):530-4.
- McKay R, Shepherd J; The use of the clinical scoring system by Alvarado in the decision to perform Am J Emerg Med. 2007 Jun;25(5):489-93.
- Poulin F, Rico P, Cote J, et al; Interferon beta-induced panniculitis mimicking acute appendicitis. Arch Dermatol. 2009 Aug;145(8):916-7.
- Acute appendicitis, Surgical Tutor
- Craig S, Appendicitis, Medscape, Jul 2011
- Coursey CA, Nelson RC, Patel MB, et al; Making the diagnosis of acute appendicitis: do more preoperative CT scans mean Radiology. 2010 Feb;254(2):460-8.
- Paterson HM, Qadan M, de Luca SM, et al; Changing trends in surgery for acute appendicitis. Br J Surg. 2008 Mar;95(3):363-8.
- Turhan AN, Kapan S, Kutukcu E, et al; Comparison of operative and non operative management of acute appendicitis. Ulus Travma Acil Cerrahi Derg. 2009 Sep;15(5):459-62.
- Le D, Rusin W, Hill B, et al; Post-operative antibiotic use in nonperforated appendicitis. Am J Surg. 2009 Dec;198(6):748-52.
- Shaikh AR, Sangrasi AK, Shaikh GA; Clinical outcomes of laparoscopic versus open appendectomy. JSLS. 2009 Oct-Dec;13(4):574-80.
- Sauerland S, Lefering R, Neugebauer EA; Laparoscopic versus open surgery for suspected appendicitis. Cochrane Database Syst Rev. 2004 Oct 18;(4):CD001546.
- Andersen BR, Kallehave FL, Andersen HK; Antibiotics versus placebo for prevention of postoperative infection after appendicectomy. Cochrane Database Syst Rev. 2005 Jul 20;(3):CD001439.
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Dr Gurvinder Rull
Dr Colin Tidy