Comparing the Sensitivity and Specificity of Computed Tomography and Ultrasound in the Diagnosis of Acute Cholecystitis in a Rural Setting

Abstract

Background Acute cholecystitis (AC) is a common inflammatory disease of the gallbladder, primarily caused by gallstones or sludge blockage. Early diagnosis and treatment are crucial for reducing morbidity and mortality. Ultrasound (US) and computed tomography (CT) are commonly used imaging methods, with US being considered the gold standard. However, recent studies have shown that CT has higher sensitivity and specificity for diagnosing AC in large hospital settings. Objective This study aims to determine the sensitivity and specificity of US and CT for AC in a community hospital and to assess the sensitivity and specificity of specific signs seen on US and CT for AC. Methods A retrospective cohort study was conducted, including patients who underwent US of the right upper quadrant (RUQ) and/or CT of the abdomen and pelvis, followed by pathological evaluation of the gallbladder after surgical removal between May 1, 2019, and April 30, 2023. Data collected included patient demographics, laboratory values, symptoms, US findings, CT findings, and pathology results. Imaging signs were recorded based on radiology reports and were considered positive if any sign was present. A true positive for CT and US was recorded if imaging was positive for AC and the pathological report confirmed AC. Results A total of 187 patients who underwent cholecystectomy for AC, with a median age of 60.6 years, were included in the final analysis. Abdominal pain was the most common presenting symptom (176/187, 94.1%), followed by nausea (114/187, 61.0%) and vomiting (75/187, 40.1%). White blood cell (WBC) counts were elevated in all groups, with median levels of 11.3 (US only), 15.8 (CT only), and 12.3 (both US and CT) (p<0.001). Most patients (169/187, 90.4%) received an RUQ US, and 123/187 (65.8%) underwent a CT scan prior to surgery. The sensitivity of US and CT was found to be similar (98.6% and 93.4%, respectively) when following a one-sign criterion. US was more sensitive than CT (80.9% and 70.0%, respectively) when a two-sign criterion was used. In a direct comparison between CT and US, US was more sensitive in detecting cholelithiasis and a thickened gallbladder wall (95.9% and 92.3%, respectively), while CT was more sensitive in detecting pericholecystic fluid and gallbladder distension (83.6% and 95.7%, respectively). Conclusion In a community emergency department, US had higher sensitivity than CT for detecting AC when a two-sign criterion was used. Based on these results, US should continue to be the first-line imaging modality in patients suspected of having AC.

Keywords: cholecystitis; computed tomography; sensitivity; specificity; ultrasound.