Investigations

Acute appendicitis is usually a clinical diagnosis, however several general investigations should be performed:

• full blood count - leukocytosis is generally present
• urea and electrolytes - assessment of dehydration

The differential diagnosis of acute appendicitis is extensive. Further investigations may be helpful if the diagnosis is equivocal:

• pregnancy test
• serum amylase - if pancreatitis suspected
• abdominal radiology - helpful to distinguish:
  • volvulus
  • intussusception
  • renal stones (90%)
  • gallstones (10%)
  • localised ileus

Generally, urine analysis is unhelpful in differentiating appendicitis from a urinary tract infection. Irritation of the bladder or ureter by an unusually-sited appendix can both cause pyuria.

There is no place for barium enema in the diagnosis of appendicitis. Occasionally, ultrasound and CT scanning are used to investigate suspected appendicitis where the story is atypical.

Notes:

• in head-to-head comparison studies of diagnostic imaging, CT had a better test performance than did graded compression US in diagnosing appendicitis (1)

Reference:

• 1. van Randen A et al. Acute appendicitis: meta-analysis of diagnostic performance of CT and graded compression US related to prevalence of disease.Radiology. 2008 Oct;249(1):97-106.