Diagnostic accuracy of acute diverticulitis with unenhanced low‐dose CT

BACKGROUND: The aim of this study was to evaluate the diagnostic accuracy of unenhanced low‐dose CT (LDCT) in acute colonic diverticulitis in comparison with contrast‐enhanced standard‐dose CT (SDCT). METHODS: All patients with clinically suspected diverticulitis who underwent LDCT followed by SDCT between January and October 2017 were evaluated prospectively. CT examinations were assessed for signs of diverticulitis, complications and other differential diagnoses by three independent radiologists (two consultants and one fourth‐year resident) using SDCT as the reference method. Sensitivity and specificity were calculated and Cohen's κ coefficient was used for agreement analyses. RESULTS: Of the 149 patients included (mean age 66·7 years, M : F ratio 0·4), 107 (71·8 per cent) had imaging consistent with diverticulitis on standard CT. Sensitivity and specificity values for a diverticulitis diagnosis using LDCT were 95–99 and 86–100 per cent respectively, and respective values for identification of complications were 58–73 and 78–100 per cent. The corresponding κ values among the three readers for diagnosis were 0·984, 0·934 and 0·816, whereas κ values for complications were 0·680, 0·703 and 0·354. Of the 26 patients who presented with other causes of abdominal symptoms identified on standard CT, 23 were diagnosed correctly on LDCT. Missed cases included splenic infarction (1) and segmental colitis (2). CONCLUSION: The diagnostic accuracy of LDCT was high for the presence of acute diverticulitis. However, as signs of complicated disease can be missed using the low‐dose protocol, use of LDCT as a primary examination method should not preclude SDCT when complications may be suspected.