Diagnostic Performance of Ultrasound in Adult Appendicitis. A Retrospective Review of 331 Cases

Definitive and accurate diagnosis of acute appendicitis is essential to reduce morbidity, yet ultrasound demonstrates variable performance which has generally improved over time with advancing technology and user expertise. This study aimed to evaluate the diagnostic accuracy of ultrasound for appendicitis in adults in our institution and document alternative diagnoses detected.

We conducted a retrospective review of all abdominal ultrasound examinations performed between January 2021 and December 2021 for patients ≥ 16 years where appendicitis was a clinical query. Reports were categorised as positive or negative based on standardised interpretive phrases. Clinical records, operative findings, histology and follow-up determined true outcomes. Inconclusive examinations (non-visualised appendix) were classified as negative for analysis.

The cohort comprised 331 patients (92% female; mean age 28 years). Appendicitis prevalence was 16% (53/331). For the detection of appendicitis, ultrasound demonstrated sensitivity of 60%, specificity 98%, PPV 82% and NPV 93%. Alternative diagnoses (n = 108) were more frequent than appendicitis by 2:1 and included haemorrhagic ovarian events, hydrosalpinx, mesenteric adenitis and other gynaecological or abdominal pathologies.

Ultrasound demonstrated modest sensitivity but high specificity for diagnosing appendicitis in adults, consistent with international data when inconclusive cases are included. This shows that in the absence of any ultrasound features, appendicitis is unlikely. Alternative findings were twice as common as appendicitis, highlighting the value of ultrasound as a primary imaging modality for the assessment of patients with right lower quadrant pain.