Acute appendicitis

Acute appendicitis follows obstruction of the appendiceal lumen, typically by a faecolith or lymphoid hyperplasia, leading to distension, inflammation and, if untreated, perforation.

Clinical presentation

Classically, periumbilical pain that migrates to the right iliac fossa, with anorexia, nausea and low-grade fever. Presentation is often atypical in young children, pregnant women and the elderly. Scores such as Alvarado or AIR help stratify risk.

Radiographic features

Ultrasound

First-line in children and pregnancy. Using graded compression, an inflamed appendix appears as a blind-ending, non-compressible tube more than 6 mm in diameter, with hyperaemia on Doppler and echogenic surrounding fat. An appendicolith casts an acoustic shadow.

CT

• Dilated appendix (over 6 mm) with wall thickening and enhancement
• Periappendiceal fat stranding
• Appendicolith in many cases
• Complications: abscess, extraluminal gas, phlegmon

MRI

A useful alternative in pregnancy when ultrasound is non-diagnostic.

Treatment and prognosis

Appendicectomy remains standard. Selected uncomplicated cases can be treated with antibiotics alone, accepting a recurrence risk. Perforated appendicitis with abscess may be drained first.

Differential diagnosis

• Mesenteric adenitis
• Terminal ileitis (Crohn's disease, infection)
• Ovarian torsion, ruptured cyst or ectopic pregnancy
• Right ureteric colic
• Epiploic appendagitis