|

Appendicitis

Last updated:

Overview

Appendicitis describes the acute inflammation of the appendix, a small, narrow tube connected to the caecum. It is one of the most common causes of acute abdominal pain in children and adults and requires urgent management due to the risk of complications including peritonitis.

The function of the appendix is not fully understood and was once considered a vestigial organ, however, recently, it has been proposed to act as a reservoir for normal gut flora, allowing the colon microbiome to recover after infection. The appendix has a high concentration of gut-associated lymphoid tissue.

Pathophysiology

Around 50% of cases are thought to be due to obstruction of the lumen of the appendix. Obstruction can occur due to hard masses of faeces (faecolith) or lymphoid hyperplasia secondary to infection which can lead to bacterial invasion of the appendix. This results in infection and inflammation which can result in perforation of the appendix and faecal matter escaping into the peritoneal cavity, producing potentially fatal peritonitis. 

Epidemiology

  • In the UK, appendicitis is the most common cause of acute abdominal pain requiring surgery
  • Appendicitis is most common between 10-20 years of age but can happen at any age
  • Interestingly, a normal appendix is removed in up to 20% of appendicectomies

Presentation

Overview

Features include:

  • Acute abdominal pain – has key features in appendicitis:
    • Starts in the centre and localises in the right iliac fossa after a few hours:
      • Initially, the pain is generalised and periumbilical (central)
      • After a few hours, the pain localises in the right iliac fossa. This is because as the appendix becomes more inflamed, the parietal peritoneum near the appendix becomes irritated
    • Certain movements may worsen the pain:
      • For example, coughing, deep breathing, driving over bumps on the road
      • In children, jumping or hopping may exacerbate pain
  • Anorexia – very common, it is very unusual for someone with appendicitis to be hungry
  • Nausea and vomiting
  • Fever – usually mild to begin with

Other presentations

Around 50% of people have the typical periumbilical abdominal pain localising to the right lower quadrant with anorexia and nausea. In some patients, the presentation may differ:

  • Some people may have different appendix positioning:
    • They may have low back pain, rectal pain, or pain in the suprapubic area or left side
  • Pregnant people – appendicitis is the most common non-obstetric surgical disorder in pregnancy
    • The pain may be higher up than the right iliac fossa, such as the right flank or right upper quadrant. This is because the uterus ‘pushes’ the appendix upward.
  • Infants and young children:
    • They may present with very non-specific symptoms such as diarrhoea, vomiting, and vague abdominal pain
  • Elderly patients:
    • They may present with confusion and may not report pain

Examination findings

  • Features of peritonitis may be present, see Peritonitis
  • Palpable abdominal masses – suggest appendix mass/abscess
  • Absent bowel sounds – suggests ileus associated with perforation
  • Signs associated with appendicitis:
    • Rovsing’s sign – applying pressure to the left lower quadrant elicits pain in the right lower quadrant:
      • This ‘pushes’ abdominal contents to the right and stretches the peritoneum (which is irritated by appendicitis), resulting in right lower quadrant pain
    • Psoas sign – passive right thigh extension while the patient is lying on their left side elicits right lower quadrant pain:
      • Appendicitis can irritate the peritoneum overlying the psoas muscles, which can become irritated themselves. This manoeuvre stretches the psoas muscles which if irritated, causes pain
    • Obturator sign – passive internal rotation of the flexed right thigh while lying flat elicits right lower quadrant pain:
      • This manoeuvre may make the obturator internus muscle come into contact with the inflamed appendix, causing pain

It is important to note that an examination may be more difficult in overweight people and people of female sex (due to pelvic organ pathologies being possible differential diagnoses).

Investigations

Overview and risk stratification

In general, blood tests showing inflammation and a typical history and examination are generally enough to diagnose and treat appendicitis. This may vary in different hospitals.

Scoring systems to stratify risk may be used, such as the Appendicitis Inflammatory Response (AIR) score, which places patients into the following groups:

  • High-risk – may go straight to surgery without imaging 
  • Intermediate-risk – may undergo further imaging
  • Low-risk groups – may not need imaging and treatment

These scoring systems should not be relied upon as definitive evidence of appendicitis.

Investigations

  • Full blood count (FBC):
    • Around 80-90% have a neutrophil-predominant leukocytosis
  • Urinalysis:
    • Useful to screen for a urinary tract infection
    • Up to 40% of people may have leukocytes in their urine (due to the appendix lying close to the urinary tract)
  • Pregnancy test – must be ordered for all people of childbearing potential:
    • To exclude ectopic pregnancy
  • C-reactive protein (CRP):
    • Non-specific marker of inflammation, may be elevated
  • Ultrasound – useful in scenarios where the diagnosis is not entirely clear, but not always necessary:
    • Can identify appendicitis, but also screens for alternative diagnoses such as gynaecological disorders (e.g. ectopic pregnancy, ovarian torsion etc.)

Unlike in the USA, CT scanning is not routinely used in the UK due to the risk of radiation exposure in children and younger adults.

Differential Diagnoses

Overview

The differential diagnoses for appendicitis are broad and can include gastrointestinal disorders, hepatobiliary disorders, urological disorders, gynaecological disorders etc.

See Acute Abdominal Pain: History Taking and Differential Diagnoses for more. 

Management

Overview

  • 1st-line: Laparoscopic appendicectomy + prophylactic IV antibiotics before surgery
    • Laparoscopic appendicectomy is the treatment of choice, however, in some cases, an open appendectomy may be performed
    • Prophylactic IV antibiotics reduce the risk of wound infections

In some cases, non-operative conservative therapy with IV fluids and antibiotics may be considered in uncomplicated cases, however, this is associated with longer hospital stays and many people go on to have an appendicectomy shortly within 12 months.

Complications

  • Perforation – which can lead to peritonitis, sepsis, and death
  • Appendix mass:
    • The appendix may become walled off by the omentum and form an inflammatory mass leading to a relatively long history of right lower quadrant pain
  • Appendix abscess:
    • Presents with right lower quadrant tenderness and a fluctuant mass and a swinging fever
    • Treated with IV antibiotics and image-guided abscess drainage
  • Bowel obstruction:
    • May be due to perforation itself or due to the formation of abdominal adhesions after surgery
  • Pregnancy complications:
    • Increased risk of foetal loss and prematurity

Prognosis

  • Mortality rates for non-perforated appendicitis are about 0.8 per 1,000 which increases to 5.1 per 1,000 if perforation occurs 
  • In most cases of uncomplicated appendicitis treated with a laparoscopic appendicectomy, people are usually discharged 1 day after the operation
    • For complicated appendicitis or those requiring open surgery, they may be discharged after a week
  • Mortality rates increase significantly in the elderly as symptoms may be more subtle leading to delayed diagnosis and treatment

Author