How to diagnose acute appendicitis: ultrasound first

Abstract

Acute appendicitis (AA) is a common abdominal emergency with a lifetime prevalence of about 7 %. As the clinical diagnosis of AA remains a challenge to emergency physicians and surgeons, imaging modalities have gained major importance in the diagnostic work-up of patients with suspected AA in order to keep both the negative appendectomy rate and the perforation rate low. Introduced in 1986, graded-compression ultrasound (US) has well-established direct and indirect signs for diagnosing AA. In our opinion, US should be the first-line imaging modality, as graded-compression US has excellent specificity both in the paediatric and adult patient populations. As US sensitivity is limited, and non-diagnostic US examinations with non-visualization of the appendix are more a rule than an exception, diagnostic strategies and algorithms after non-diagnostic US should focus on clinical reassessment and complementary imaging with MRI/CT if indicated. Accordingly, both ionizing radiation to our patients and cost of pre-therapeutic diagnosis of AA will be low, with low negative appendectomy and perforation rates. Main Messages • Ultrasound (US) should be the first imaging modality for diagnosing acute appendicitis (AA). • Primary US for AA diagnosis will decrease ionizing radiation and cost. • Sensitivity of US to diagnose AA is lower than of CT/MRI. • Non-visualization of the appendix should lead to clinical reassessment. • Complementary MRI or CT may be performed if diagnosis remains unclear.

Keywords: Appendicitis; Computed tomography; Diagnostic algorithm; Magnetic resonance imaging; Ultrasound.

Fig. 1

Longitudinal real-time US scan of a normal appendix. Diameter 0.3 cm. ** psoas muscle, * rectus muscle, x caecum, + terminal ileum

Fig. 2

Longitudinal (a) and transverse (b) real-time US scan of acute appendicitis with thickening of the wall (crosses 2), target–sign, diameter > 6 mm (crosses 1) and free fluid surrounding the appendix (+)

Fig. 3

US and CT in acute appendicitis. 45-year-old male patient with pain in the right lower quadrant and increased inflammation parameters (white blood cell count and C-reactive protein elevation). a US real-time scan: local pain in combination with some fluid and thickened appendix, only seen in part (between crosses). b contrast-enhanced CT: thickened appendix, mesenteric infiltration around the appendix, inflammatory thickening of the sigmoid colon

Fig. 4

T1-weighted, fat-suppressed axial MRI after intravenous MRI contrast (gadoterate) in acute appendicitis: thickened appendix with Gd enhancement, minimal periappendiceal stranding