Diagnostic Accuracy of Gallbladder Dimensions on Ultrasound for Acute Cholecystitis

INTRODUCTION: Acute cholecystitis is commonly evaluated with ultrasound using established sonographic features. The Tokyo Guidelines 2018 recognise gallbladder enlargement as a characteristic imaging finding; however, the diagnostic value of quantitative gallbladder dimensions remains uncertain. This study evaluated whether gallbladder length (GBL), width (GBW), and volume (GBV) provide additional diagnostic value beyond conventional ultrasound features. METHODS: This retrospective case-control study included 176 patients undergoing abdominal ultrasound between 2019 and 2024: 88 with histopathologically confirmed acute calculous cholecystitis and 88 age- and sex-matched controls. Gallbladder dimensions were independently measured by two blinded readers, with GBV approximated using an ellipsoid formula. Logistic regression, nested model comparisons, interobserver reliability and receiver operating characteristic analyses were performed. RESULTS: All conventional sonographic features and gallbladder measurements were significantly associated with cholecystitis on univariate analysis. After adjustment for age, sex, weight and conventional sonographic features, GBL remained independently associated with cholecystitis (adjusted OR 1.045, 95% CI 1.014-1.077; p = 0.004) and improved model fit. GBV also provided incremental value (p = 0.020), whereas GBW did not (p = 0.44). Interobserver reliability was excellent for GBL (ICC 0.94), GBW (0.91) and GBV (0.93). GBL demonstrated the highest diagnostic performance (AUC 0.76), followed by GBV (0.74) and GBW (0.63). A 71-mm GBL cutoff yielded 72% sensitivity and 71% specificity. CONCLUSION: GBL and GBV provide incremental diagnostic information beyond conventional sonographic features. GBL is the strongest quantitative marker and may serve as a reproducible adjunct to established ultrasound findings. External validation of the proposed thresholds is required before broader clinical implementation.