Lindsay Cefalu, MD, CPT, Robert McMurray, MD, CPT, Gerald Bieniek, MD, CPT, Christopher Yheulon, MD, MAJ. Tripler Army Medical Center
Background: Right upper quadrant ultrasound is the standard initial diagnostic imaging modality for evaluating gallbladder pathology, although it has great variability in both sensitivity and specificity. The quality of ultrasound can be influenced by a variety of factors. As distance traveled by ultrasonic waves increases, there is greater absorption and dispersion of energy into the surrounding tissues. Adipose tissue also attenuates ultrasound energy, particularly at higher frequencies. As Body Mass Index (BMI) increases, both abdominal wall thickness and adiposity also tend to increase. The purpose of this study was to determine whether ultrasonography underestimates true gallbladder wall thickness in obese patients as defined by a BMI>30.
Methods: A retrospective review of 601 adult patients who underwent elective and urgent cholecystectomy was performed, comparing gallbladder wall thickness measured on ultrasound with the findings on final pathology. The results were analyzed in relation to patients’ BMI, as well as several other secondary factors including age, presence of diabetes, sex, and urgent vs elective intervention.
Results: Findings were analyzed based on the ability of the ultrasound report to accurately predict wall thickness within a +/- 1mm margin of error. There was no statistical difference in the accuracy of ultrasound in determining wall thickness based on BMI (p=0.291). However, there were significant differences for several secondary subsets of the data. Increasing age showed a negative correlation with the accuracy of ultrasound in predicting gallbladder wall thickness with a marked drop in accuracy over the age of 50 (p<0.001). Ultrasound was more accurate in determining wall thickness in females than in males (p=0.040). Ultrasonography was more predictive of final pathologic gallbladder wall thickness in patients undergoing elective cholecystectomy when compared to patients undergoing urgent cholecystectomy (p<0.001). Finally, negative correlation was present between actual gallbladder wall thickness and accuracy of ultrasound. As wall thickness increased above the upper limits of normal (0.3cm), evaluation on ultrasound became less accurate in identifying actual pathologic thickness (p<0.001).
Conclusion: We conclude that BMI does not impact the accuracy of ultrasound in determining gallbladder wall pathology. However, factors such as advanced patient age, patient gender, timing of repair (urgent vs elective), as well as size parameters (i.e. underestimation of thickened walls) should be further investigated for their impacts on accurate ultrasonography of the gallbladder.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 79776
Program Number: MSS01
Presentation Session: Full-Day Military Surgical Symposium – General Surgery Presentations
Presentation Type: MSSPodium