Ultrasonography for suspected mild-to-moderate acute left colonic diverticulitis: a prospective head-to-head study with computed tomography

Background The preferred imaging modality for acute left colonic diverticulitis (ALCD) remains controversial. This prospective study compares ultrasonography (US) and computed tomography (CT) in selected patients with clinically suspected mild-to-moderate localised ALCD. Materials and methods Consecutive patients presenting to the emergency department with suspected localised mild-to-moderate ALCD underwent both US and CT within 1 h and before treatment initiation. US and CT examinations were performed and interpreted by three trained abdominal radiologists. A multidisciplinary consensus panel established the reference (“final”) diagnosis, against which both tests were compared. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each modality. Agreement between US and CT for severity stratification was also assessed. This study was not designed as a non-inferiority or equivalence analysis. Results Sixty-three patients were included in the study; 50 (79.4%) had a final diagnosis of ALCD. US correctly identified 47/50 patients with ALCD, yielding a sensitivity of 97.9%, specificity of 91.7%, PPV of 97.9%, and NPV of 91.7%, while CT showed a sensitivity of 98.0%, specificity of 92.3%, PPV of 98.0%, and NPV of 92.3%. A moderate agreement was found between the two treatment modalities for differentiating stage 0 (mild-to-moderate) from stage >0 (severe) localised ALCD ( κ = 0.568, p < 0.001), which increased when US was performed by a more experienced operator ( κ = 0.70, p < 0.001). Higher C-reactive protein levels were associated with higher radiological severity ( p = 0.014). Conclusion In this selected prospective cohort, ultrasonography performed by experienced abdominal radiologists showed diagnostic estimates similar to CT and identified most ALCD cases. Given the limited sample size, operator dependence, and non-independent reference standard, these findings should be interpreted cautiously and are most applicable to specialised centres with dedicated ultrasound expertise. Clinical Trial Registration : ClinicalTrials.gov, NCT05323968.