Appendicitis is a common and serious gastrointestinal disease that affects many people every year. It can be very acute and painful and if it is not treated quickly, it can be fatal. We will explore the mechanics behind appendicitis, the causes, treatments and complications that can arise. Appendicitis is commonly examined as it is fairly prevalent, acute and can be very serious.
Acute Appendicitis

Image: “Acute Appendicitis” by Ed Uthman. Licence: CC BY 2.0

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Definition and Background

Appendicitis means inflammation (-itis) of the appendix. It occurs when the appendix becomes blocked and infected, causing pain and acute illness. There is gradual swelling as the appendix fills with pus. The appendix is a hollow structure and therefore, it can burst if left untreated. This perforation can rapidly lead to peritonitis (infected abdomen lining) and systemic sepsis, which is a life-threatening condition.

Location of the appendix

The appendix is part of the mid-gut (2nd part of the duodenum to 2/3rds along the transverse colon). The somatic nerve referral is to the periumbilical area, while the arterial supply is from the superior mesenteric artery. The appendix is a small, blind-ended finger-like extension located at the start of the large intestine (caecum) and its surface anatomy is the right iliac fossa.

It is also known as the vermiform process, which means ‘worm-like’ in Latin. The appendix is approximately 5 – 10 cm long and 8 cm wide although sizes can vary.

Digestive appareil

8 = appendix

Function of the appendix

The appendix is a vestigial organ – meaning it has lost most of its original function. Current theories suggest the function of the appendix is to act as a ‘safe harbour’ to commensal gut flora (bacteria) in the event of dysentery/cholera. In such an event, the one-way appendix can repopulate the intestines with normal flora to restore working function.

It was suggested by Charles Darwin that the appendix once harboured bacteria to help our ancestors break down cellulose; there is evidence for this in other animals. Function aside; there are no serious side effects of living without an appendix.

Histology of the appendix

Microscopy of a stained appendix slide reveals a very high density of ‘GALT’ (gut-associated lymphoid tissue), a type of MALT (mucosa-associated lymphoid tissue). The GALT rich appendix harbours many immune cells (T-cells, B-cells, etc.), which protect the body from pathogens and are responsible for antigen detection. The crypts of Leiberkuhn contain many goblet cells which are responsible for the production of mucus.

Acute Appendicitis.

Image: “Acute Appendicitis.” by Patho. Licence: CC BY-SA 3.0


Appendicitis can affect anyone at any age, however, it is more common between the ages of 5 and 40 (median age of 28) and affects males slightly more than females. It is the most common abdominal surgical emergency admission and is more common in the West compared to the East (this is thought to be related to the typical low-fibre western diet). The lifetime risk of appendicitis is around 6 %. In 2013, there were 72,000 deaths globally from appendicitis. 

Age-standardised disability-adjusted life year (DALY) rates from Appendicitis by country

Image: “Age-standardised disability-adjusted life year (DALY) rates from Appendicitis by country” by Lokal_Profil. Licence: CC BY-SA 2.5


It is widely assumed that the majority of cases arise due to a primary obstruction (50 – 80 %). Usually the appendicular wall muscles pushes material back into the large intestines; if this fails, bacteria may thrive and cause an infection. (The appendix can also become inflamed and sterile when no bacteria are present).

Obstructive agents include:

(*Most common causes)

  • *Fecaliths
  • *Lymphoid hyperplasia – lymphadenopathy, infective mononucleosis, measles, respiratory infection (Streptococcal. Spp)
  • Foreign bodies
  • Intestinal worms (usually in a ball)
  • Gallstones
  • Tumours

Common bacterial agents:

  • Escherichia coli
  • Bacteroides fragilis

(These bacteria are commonly found in the gut as part of the normal commensal flora).

Hint: Appendicitis can also be caused by infective spread from lymphatic/haematogenous sources, e.g. Streptococcal-induced appendicitis following a respiratory tract infection causing mesenteric adenitis. It is therefore important to enquire about recent infections. (For example, the patient could present with a concurrent pharyngeal infection with symptoms of appendicitis).


Obstruction of the appendix leads to a build up of goblet cells, which continue to produce large amounts in spite of the obstruction; this causes abdominal pain in the periumbilical area. There is an inflammatory response consisting of swelling and an infection from bacterial overgrowth leading to an accumulation of pus; there is invasion by neutrophils and activation of inflammatory mediators. The main infective organisms are usually Escherichia coli and Bacteroides fragilis.

The infection and swelling causes further distension and an increase in the intra-luminal pressure. The pressure primarily occludes the venous drainage before occluding the arterioles; this leads to engorgement and congestion. This eventually progresses to occlusion and thrombosis of the arteriolar blood vessels and lymphatic drainage. At this point, the pain will localise to the right iliac fossa and surgical intervention will be needed as it rarely resolves past this point. The patient will now have systemic signs of illness such as a fever, tachycardia, nausea and anorexia.

If the appendicitis continues untreated, the lack of blood supply leads to ischemia and eventually to necrosis. The walls of the appendix become weakened and pus begins to spread into the walls (muscularis layer) forming focal abscesses (acute suppurative appendicitis). The pus contains dead lymphocytes from the inflammatory reaction, bacteria, cellular debris and fluid. This can progress further with large haemorrhagic ulceration and gangrene covering the full thickness of the appendix to the serosa (acute gangrenous appendicitis).

If the appendix ruptures, the infection spreads to the abdominal cavity and causes an infection of the lining known as peritonitis (suppurative peritonitis). This widespread infection is very dangerous and can be fatal if it spreads to the bloodstream causing septic shock.

This is a general outline of the pathogenesis. Note, however, that there are variations depending on the causative agent, presence of bacteria and whether the appendicitis resolves or progresses.

The process can be summarised as following:

  • Obstruction
  • Increase in intraluminal pressure
  • Mucosal oedema and ulceration
  • Decreased lymphatic and venous drainage
  • Thrombosis/occlusion of appendicular arteries
  • Bacterial proliferation and inflammation
  • Lymphadenopathy
  • Abscess
  • Gangrene
  • Perforation (1 – 2 days)
  • Peritonitis +/- sepsis


Acute appendicitis has a typical presentation of symptoms:

  • Abdominal pain
  • Nausea
  • Vomiting
  • Anorexia
  • Constipation

Abdominal pain – usually starts periumbilically as the innervation of the appendix enters the spinal cord at the same point as the nerves of the umbilicus. This is because the internal organs and visceral peritoneum do not have any somatic innervation. The abdominal pain is typically very severe and colicky, keeping the patient awake. The pain begins to localise to the right lower quadrant as the appendix irritates the parietal peritoneum (this localisation of pain may not occur in children under 3 years old).

Nausea and vomiting – nausea is almost always present whereas vomiting is less common.

Anorexia – Loss of appetite is common in acute appendicitis.

Bowel habit – The patient may also be constipated and may have reduced bowel movement. Diarrhoea can also be present.

Note: If the appendix is located in the pelvis, it can cause urinary frequency, supra-pubic pain and diarrhoea.


Fever (initially mild) Tachycardia
Furred tongue Foetor (odour)
Flushing Guarding and local tenderness
Rebound (Blumberg´s sign) Percussion tenderness
Abdominal swelling Abdominal rigidity
Tender RIF mass may indicate formation of an appendix mass


Reduced movement Reduced breathing volume
Guarding Rebound and percussion tenderness
Bowel sounds absent Tympanitic (resonance)
Distended abdomen
Dumphy´s sign – Right lower quadrant pain when coughing

Special Tests

  • Location of McBurney's point illustrated on the abdomen of a male subject.

    Image: “Location of McBurney’s point illustrated on the abdomen of a male subject.” by Steven Fruitsmaak. Licence: CC BY-SA 3.0

    McBurney’s sign – Deep tenderness at McBurney’s point is a sign of acute appendicitis. McBurney’s point is the point over the right side of the abdomen, one third of the distance between ASIS (anterior superior iliac spine) and the umbilicus. It is also used to locate the appendix in surgery, as it is the site of the appendix base where it attaches to the caecum.

  • Rovsing’s sign – right iliac fossa pain is worse than in the left iliac fossa when pressure is applied to the left iliac fossa deeply and continuously. This moves gas and bowel contents counter clockwise along the colon towards the ileocecal valve, increasing pressure on the appendix.
  • Obturator sign – pain on flexion and internal rotation of the right hip, due to irritation from obturator internus.
  • Psoas sign – pain when the right hip is passively extended/actively flexed. This movement relies on the iliopsoas muscle that may irritate the appendix or be inflamed itself.
  • Digital rectal examination painful on the right – signs of low-lying pelvic appendix; this may be present without abdominal rigidity.

Atypical Presentations

  • Lack the typical progression and may start with pain in the right lower quadrant.
  • Flank or right upper quadrant pain and right-sided tenderness on digital rectal examination may be signs of retrocaecal/retroperitonitis appendicitis (approximately 2 – 3 %).
  • Children can present with just general abdominal pain and anorexia.
  • 0.1 % of pregnancies experience appendicitis. Caution should be exercised, as there is a higher risk of complications.
  • Pain localises to the left lower quadrant in ‘situs inversus totalis’. 


Diagnosis is usually based on a detailed history and physical examination along with investigations such as blood tests and imaging. The diagnosis must be made quickly to prevent further progression. Some scoring systems may be useful confirming diagnoses:

Alvarado scoring system

  • Right lower quadrant tenderness (+2)
  • Temperature above 37,7 degrees (+1)
  • Rebound tenderness (+1)
  • Migration of pain to the right lower quadrant (+1)
  • Anorexia (+1)
  • Nausea or vomitting (+1)
Lab results
  • Leukocytosis > 10,000 (+2)
  • Leukocyte Left shift (Many immature leucocytes present) (+1)
  • 5/6 – possible
  • 7/8 – probable
  • > 9  – very probable

Typical presentations can be confirmed using blood tests (revealing leucocytosis) and imaging if required. However, atypical presentations almost always require radiological investigations. The most common types of imaging which are used include ultrasound and CT. 


Observations If symptoms are acute, observe: temperature, heart rate, blood pressure, capillary refill, respiratory rate and general appearance
Examinations Full examination of the gastrointestinal system including special tests
Blood Full blodd count (check for signs of infection) Neutrophil leukocytes (70 – 90 % of cases) usually up to 10,000 – 20,000 cells/mm3Leukocyte left shiftElevated inflammatory markers – C-reactive protein (huge increase indicates a gangrenous appendix).
Urinalysis Rule out pregnancy or ectopic pregnancy. Rule out UTI as cause of abdominal pain.
Imaging Ultrasound scan may be useful (preferred in children and pregnant women due to being radiation-free).Useful in the assessment of an appendix mass or abscess.
CT Scan Higher diagnostic accuracy and useful if diagnosis is uncertain. More sensitive and specific than ultrasound.Predictive signs on CT scan – enlarged appendix, appendiceal wall thickening and enhancement and fat stranding around the appendix.
 MRI  Complicated cases where you wish to avoid radiation and where ultrasound is insufficient (pregnancy and children).
 Diagnostic laparoscopy can be considered but there is an increased risk of complications such as perforation.


Neutrophilic infiltration of the muscularis propria of the appendix on a histological micrograph definitely confirms the diagnosis when it is present along with muscularis inflammation. Ulcerations can also be present and evidence of muscular wall inflammation is essential, as exudate from an alimentary tract infection can also cause neutrophilic infiltration of the appendix.

It may be necessary to conduct additional biopsies of any abnormal lymph nodes/masses that may have obstructed the appendix or that are apparent during imaging/surgery. 

Differential Diagnosis

False-positive diagnoses can occur and normal appendices can be occasionally removed, this can be partially avoided with the use of imaging. The following conditions should be considered when the diagnosis is not certain:

  • Pseudoappendicitis – mesenteric adenitis (lymphadenitis caused by Yersinia enterocolitica often preceded by a sore throat) is mostly seen in children, it typically mimicks appendicitis.
  • Infections – gastroenteritis, urinary tract infection, lobar pneumonia, systemic viral infection
  • Gynaecological conditions – testicular torsion, urinary tract infection, ectopic pregnancy, ovarian torsion, salpingitis (PID), endometriosis
  • Other bowel conditions – New-onset inflammatory bowel disease (Crohn’s, Ulcerative Colitis), Meckel’s diverticulitis, diverticulitis, intussusception, intestinal obstruction, colonic carcinoma
  • Other appendix conditions – carcinoid tumour, adenocarcinoma
  • Other – abdominal trauma, renal colic, pancreatitis, peptic ulcer perforation, cholecystitis


All suspected cases warrant hospital admission.

  • If a patient presents in an emergency scenario, life support pathways should be followed: Airways, Breathing, Circulation, etc. to stabilise the patient.
  • Supportive treatments: Intravenous fluids, opiate analgesia (morphine), perioperative Intravenous antibiotics (reduces infective complications).
  • IV Antibiotics: e.g. Metronidazole and Cefuroxime. Administered immediately if sepsis is suspected and perioperatively with IV hydration.
  • Active observation: Can be useful if the diagnosis is uncertain. 
  • Appendectomy: Surgery is the gold standard treatment for appendicitis offering a rapid improvement in symptoms, low recurrence rate and evasion of the life-threatening complications of appendicitis more than any other treatment option. It is important that surgery is carried out as soon as possible; it can be conducted via open surgery or laparoscopically.


Spontaneous resolution can occur, but without surgery there is an increased risk of re-admission. The procedure is usually carried out as an emergency procedure. Laparoscopic surgery offers reduced scarring and quicker recovery time; hence, it is preferred over open surgery. An incision is usually made over McBurney’s point (as discussed earlier), which represents the appendix base.

The procedure was carried out over 300’000 times in the US alone (2011) and represented over 2 % of all procedures.

Contraindications: Inflammatory bowel disease; postoperative healing response is impaired; therefore treat with DMARDs (disease modifying anti-rheumatoid drugs).

Sepsis: If suspected: The sepsis pathway should be followed immediately.

  • High-flow Oxygen
  • Blood cultures
  • IV antibiotics
  • Fluid challenge
  • Measure lactate
  • Measure urine output

Recovery – hospital stays usually last a few days after surgery. However if a complication arises, it can be extended to a few weeks. It also depends on whether the appendix ruptured, as this is an indication of severity. It is advised that the patient rests and avoids physical activity (some movement is encouraged). Full recovery takes 4 – 8 weeks, again depending on severity. 


  • Perforation – Between 16 – 30 % suffer from perforation (higher in the extremes of age and when a fecalith is the cause).
  • Peritonitis – Spread of infection from a perforated appendix can cause peritonitis. It is very serious and can be fatal if the infection spreads to the bloodstream, causing septic shock. Rapid treatment is essential. Signs of peritonitis include increasingly severe abdominal pain, nausea and vomiting, anorexia, fever and oliguria/anuria.
  • Appendix mass – Presentation is usually fever with a palpable mass; the mass is formed when small bowel and omentum cover the inflamed appendix. Surgery is an option along with initial conservative management (nil by mouth with antibiotics). Need to rule out other causes of such masses like colonic cancer.
  • Appendix abscess – Can result from an unresolved appendicular mass that enlarges. Ultrasound and CT scans can reveal abscesses which usually can be treated by drainage during open appendectomy or percutaneously with radiological guidance.
  • Wound infection – Risk depends on the severity of the case. Perioperative antibiotics reduce the risk. 


The surgical procedure is relatively safe with a mortality of 0.8/1000 (non-perforated) and 5/1000 for perforated cases. This relies on early detection, management and rapid surgical treatment to avoid further complications.

If the patient presents with a severe appendicitis with perforation, the prognosis is significantly worse, as there is a risk of life-threatening peritonitis and sepsis.


There is no way to prevent appendicitis. However, there is a lower occurrence in people with a fibre-rich diet. Early detection and treatment is essentially a cure and prevents further progression of the disease.

Popular Exam Questions Regarding Appendicitis

The correct answers can be found below the references.

1. A 17-year-old male is brought to the emergency department complaining about severe right iliac fossa pain. It has been going on for 1 – 2 days and has started in the umbilical region. He now has a temperature of 100.5 Fahrenheit (38.1 degrees celcius) and is very nauseous. He has not vomited but has not eaten in over a day. You diagnose appendicitis and begin fluids and basic supportive measures (e.g. pain relief). What is the next step?

  1. Observe the patient
  2. Refer to a surgeon for an appendectomy
  3. Start on IV antibiotics
  4. Send home
  5. X-ray abdomen

2. The patient is consequently referred to surgery. The surgeon performs laparoscopic surgery to remove the appendix. Which one of the following is not an advantage of laparoscopic surgery over open surgery?

  1. Faster recovery time
  2. Less invasive
  3. Less scarring
  4. Reduced post-operative disability
  5. Longer operating time

3. A 35-year-old female presents with worsening abdominal pain in the right iliac fossa and the physician demonstrates rebound tenderness. He suspects acute appendicitis. The doctor proceeds to perform another test; with the patient supine, he flexes the knee and hip at 90 degrees and then internally rotates the right hip (holding and moving ankle away from her body, whilst allowing her knee to move inwards only). During this procedure, the doctor observes the patients face and notices that she grimaces in pain. It is repeated with the left hip but there is no pain noted. Which muscle is coming into contact with the inflamed pelvic appendix and has an irritating effect on it?

  1. Superior gemellus
  2. Obturator externus
  3. Piriformis
  4. Obturator internus
  5. Gluteus minimus 
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