Acute Appendicitis

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 abscess.

• Commonest cause of an acute abdomen in the UK. About 10% of the population will develop acute appendicitis.¹
• Appendicitis is most common between the ages of 10 and 20 years but can occur at any age.²
• The incidence is falling.
• A normal appendix is removed at 10-20% appendicectomies.¹

Risk Factors

• Appendicitis is more common in men.
• Appendicectomy is performed more often in women. A women is more likely to have a normal appendix removed.

Classic symptoms often do not appear in young children and the elderly and the diagnosis is particularly easy to miss in these age groups.

• Pain:
  • Early peri-umbilical 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. Patient may lie still with shallow breathing, coughing hurts.
• Nausea, vomiting, anorexia. Usually constipated but may have diarrhoea. Rapidly progressive cases may have marked vomiting without fever, and in diarrhoea 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 retro-caecal or pelvic appendix may be missed.
  • Rectal examination: localised tenderness and may be the only sign of an inflamed retro-caecal or pelvic appendix.
  • Other methods to demonstrate an inflamed appendix include: the Psoas test (extend the hip and abduct the thigh with patient on left side) and the Obturator test (flex the right thigh and internally rotate the hip).
• Right iliac fossa peritonism.
  • Percussion tenderness is a kinder sign of peritonism than rebound.
  • Rovsing's sign: pain in right iliac fossa on 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:
  • Infant with watery diarrhoea and vomiting
  • Child with vague abdominal pain and anorexia
  • Shocked and confused elderly patient not in pain
• Pain and tenderness may be higher in pregnant women but right iliac fossa symptoms are still the main presentation.

• Other causes of abdominal pain:
  • Mesenteric adenitis
  • Testicular torsion, strangulated hernia (examination must include a look at genitals and hernial orifices)
  • Urinary tract infection, renal stones
  • Pelvic inflammatory disease, ectopic pregnancy
  • Constipation, cholecystitis, Crohn's disease, diverticulitis, perforated peptic ulcer
• Other causes of right iliac fossa mass:
  • Crohn's disease
  • Caecal carcinoma
  • Mucocele of the gallbladder
  • Psoas abscess
  • Pelvic kidney
  • Ovarian cyst

Appendicitis is essentially a clinical diagnosis (see abdominal examination) but the following may be useful:

• Urinalysis may exclude urinary tract infection.
• Pregnancy test to exclude ectopic pregnancy.
• A normal white cell count does not exclude appendicitis.
• Abdominal x-ray is of little value.
• 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.²
• 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).
• Scoring systems and computer-aided diagnosis my be helpful. Meta-analysis suggest the following to be useful predictors of appendicitis in patients with abdominal pain:
  • Raised inflammatory markers
  • Clinical signs of peritoneal irritation
  • Migration of abdominal pain

• All suspected cases should be admitted to hospital.
• In cases of diagnostic doubt a period of 'active observation' is useful. Active observation reduces negative appendicectomy rate without increased risk of perforation.
• Intravenous fluids and analgesia should be given. Opiate analgesia does not mask the signs of peritonism.
• Antibiotics should not be given until a decision to operate has been made.
• Whether a 'normal' appendix should be removed following laparoscopy is unclear.

Appendicectomy

• Give antibiotic prophylaxis with single dose rectal metronidazole 1 hour preoperatively.
• Consider a midline incision in elderly patients.
• If normal appendix removed need to look for:
  • Meckel's diverticulum
  • Acute salpingitis
  • Crohn's disease
• 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 to particularly benefit from laparoscopic appendicectomy.³

• The average rate of perforation at presentation is between 16% and 30% (significantly higher in elderly people and young children).²
• 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.⁴
• Appendix mass:
  • Omentum and small bowel adhere to the appendix.
  • Inflammation localised to the right iliac fossa by the omentum.
  • Usually presents with a several day history; usually pyrexial with a palpable mass.
  • Initial treatment should be conservative with fluids, analgesia and antibiotics.
  • Continue conservative whilst there is clinical improvement.
  • Operate if mass enlarges or patient deteriorates (increasing pain, pulse, temperature, white cell count), otherwise consider interval appendicectomy after about 3 months.
• Appendix abscess
  • Appendix mass enlarges and high fever fails to settle.
  • Abscess should be surgically or percutaneously drained.
  • Appendicectomy at initial operation can be difficult.
  • Need for appendicectomy after abscess drainage is unclear.
• Other acute complications include pelvic abscess, subphrenic abscess, paralytic ileus and septicaemia.
• Long term complications: adhesions may cause intestinal obstruction but this is uncommon.
• Surgery is well tolerated in pregnancy but perforation leads to a miscarriage rate of about 30%.

• Appendicectomy is relatively safe with a mortality rate for non-perforated appendicitis of 0.8 per 1000 and mortality after perforation of 5.1 per 1000.²