Appendicitis is inflammation of the appendix. The peak incidence of appendicitis is in patients aged 10 to 20 years. It can occur at any age but is less common in young children and adults over 50.
Basic Pathophysiology
The appendix is a small, thin tube arising from the caecum. It is located at the point where the three taeniae coli meet (the taeniae coli are longitudinal muscles that run the length of the large intestine). There is a single opening to the appendix that connects it to the bowel, and it leads to a dead end.
Pathogens can get trapped due to obstruction at the point where the appendix meets the bowel. Trapping of pathogens leads to infection and inflammation. The inflammation may proceed to gangrene and rupture.
When the appendix ruptures, faecal contents and infective material are released into the peritoneal cavity. This leads to peritonitis, which is inflammation of the peritoneal lining.
Presentation
The key presenting feature of appendicitis is abdominal pain. This typically starts as central abdominal pain that moves down to the right iliac fossa (RIF) within the first 24 hours, eventually becoming localised in the RIF.
On palpation of the abdomen, there is tenderness at McBurney’s point. McBurney’s point refers to a specific area that is one-third of the distance from the anterior superior iliac spine (ASIS) to the umbilicus.
Other classic features are:
- Anorexia (loss of appetite)
- Nausea and vomiting
- Low-grade fever
- Rovsing’s sign (palpation of the left iliac fossa causes pain in the RIF)
- Guarding on abdominal palpation
- Rebound tenderness in the RIF (increased pain when suddenly releasing the pressure of deep palpation)
- Percussion tenderness (pain and tenderness when percussing the abdomen)
Rebound tenderness and percussion tenderness suggest peritonitis, potentially indicating a ruptured appendix.
Diagnosis
Appendicitis is mostly a clinical diagnosis based on signs and symptoms rather than diagnostic tests. Where the diagnosis is unclear, a period of observation may be used, with repeated examinations to see whether the symptoms resolve or worsen.
Scoring systems can be used to calculate the probability of appendicitis (e.g., Alvarado score and paediatric appendicitis score).
Blood tests show raised white blood cells and inflammatory markers (e.g., CRP).
Ultrasound can help confirm the diagnosis, and exclude ovarian and gynaecological pathology in females patients.
CT scans can help confirm the diagnosis and exclude other pathology but are less suitable in children due to the dose of radiation.
Investigations to exclude differential diagnoses include:
- Urine dipstick for urinary tract infections
- Pregnancy test for ectopic pregnancy
When the clinical presentation suggests appendicitis, the next step is to perform a diagnostic laparoscopy to visualise the appendix directly. An appendicectomy can be performed during the same procedure if indicated.
Key Differential Diagnoses
Ectopic pregnancy needs to be excluded in females of childbearing age. This is a gynaecological emergency with a relatively high mortality if mismanaged. A serum or urine human chorionic gonadotropin (hCG) to exclude pregnancy is essential.
Ovarian cysts can cause pelvic and iliac fossa pain, particularly with rupture or torsion.
Meckel’s diverticulum is a malformation of the distal ileum that occurs in around 2% of the population. It is usually asymptomatic and does not require any treatment. However, it can bleed, become inflamed, rupture or cause a volvulus or intussusception.
Mesenteric adenitis describes inflamed abdominal lymph nodes. It presents with abdominal pain, usually in younger children, and is often associated with tonsillitis or an upper respiratory tract infection. No specific treatment is required.
TOM TIP: When seeing females of childbearing age, assume they are pregnant until proven otherwise with a pregnancy test. This is especially important in patients with abdominal pain (where ectopic pregnancy is a key differential), or where you are requesting x-rays or CT scans. Serum HCG is typically part of the normal abdominal pain blood panel in A&E.
Appendix Mass
An appendix mass occurs when the omentum surrounds and sticks to the inflamed appendix, forming a mass in the right iliac fossa. This is typically managed conservatively with supportive treatment and antibiotics, followed by appendicectomy once the acute condition has resolved.
Management
Patients with suspected appendicitis need emergency admission to hospital under the surgical team. Older children (e.g., above 10 years) will often be managed by adult general surgical teams (with support from paediatrics).
Removal of the inflamed appendix (appendicectomy) is the definitive management for appendicitis. Laparoscopic surgery is associated with fewer risks and faster recovery compared to open surgery (laparotomy).
Complications of appendicectomy include:
- Bleeding, infection, pain and scars
- Damage to the bowel, bladder or other organs
- Removal of a normal appendix
- Anaesthetic risks
- Venous thromboembolism (deep vein thrombosis or pulmonary embolism)
Last updated February 2025
Now, head over to members.zerotofinals.com and test your knowledge of this content. Testing yourself helps identify what you missed and strengthens your understanding and retention.
