Development of an Ultrasound-Based Clinical Decision Rule to Rule-out Diverticulitis

Abstract The concern for diverticulitis often leads to the use of computed tomography (CT) scans for diagnosis. We aim to develop an ultrasound-based clinical decision rule (CDR) to confidently rule-out the disease without requiring a CT scan. We analyzed data from a prospective study of adult emergency department (ED) patients with suspected diverticulitis who underwent both bedside ultrasound (US) and CT. Patient history, physical examination, laboratory findings, and US results were used to create a CDR via a recursive partitioning model designed to prioritize sensitivity, with a loss matrix that heavily penalized false negatives. We calculated test characteristics for the CDR (TICS-Rule) and assessed the potential reduction in CT scans and ED length of stay. Data from 149 patients (84 female; mean age 58 ± 16) were used to develop the TICS-Rule. The final model integrates US diagnosis of simple and complicated diverticulitis with variables of heart rate, age, history of diverticulosis, vomiting, and leukocytosis. Negative US findings and a heart rate below 100 effectively excluded diverticulitis. The sensitivity increased from 54.5% (32.2–75.6) in the US alone to 100% (84.6–100%) for complicated diverticulitis in the model. The TICS-Rule missed no cases of complicated diverticulitis but one case of simple diverticulitis. The median time from ED greeting to US interpretation was 103 minutes (IQR 62–169), compared to 285 minutes (IQR 229–372) for CT. The TICS-Rule, developed using patient history, labs, and US findings, effectively excludes diverticulitis without the need for CT scans. With high sensitivity and reduced time compared to CT, it offers a promising approach to enhancing clinical decision-making, leading to CT and ED length of stay reductions.