Normal Gallbladder Wall Thickness
The normal gallbladder wall thickness on a fasting ultrasound is less than 3 mm, measured on the anterior wall between the lumen and hepatic parenchyma. 1, 2, 3
Measurement Technique
Measure the anterior gallbladder wall only, positioned between the gallbladder lumen and the adjacent hepatic parenchyma, as the posterior wall is frequently obscured by bowel gas and yields unreliable measurements. 1, 2
Use the transverse (axial) plane for the most accurate wall thickness assessment, optimizing gain, frequency, and focal zone settings to ensure clear visualization of wall boundaries. 1, 2
Ensure adequate patient preparation with 6-8 hours of fasting before imaging, as post-prandial gallbladder contraction produces physiologic wall thickening that can mimic pathology. 2
Confirm adequate gallbladder distension with a transverse diameter greater than 2 cm, as measurements in underdistended gallbladders are unreliable and may falsely suggest wall thickening. 3, 4
Clinical Validation
The 3 mm threshold has been validated in multiple prospective studies, with 99% of normal fasting patients demonstrating wall thickness ≤3 mm and 96% of patients with acute cholecystitis showing thickness >3 mm. 3, 4
Ultrasonic measurements correlate closely with direct surgical measurements, agreeing within 1 mm in 95% of cases, confirming the accuracy of this imaging modality. 4
Pathologic Threshold
Any measurement >3 mm is abnormal and warrants systematic evaluation for acute or chronic cholecystitis, though wall thickening alone is insufficient for diagnosis without additional sonographic and clinical features. 1, 2, 3
Wall thickness >3 mm occurs in 38% of acute calculous cholecystitis and 41% of chronic calculous cholecystitis cases, but also appears in non-biliary conditions including congestive heart failure, renal failure, hypoalbuminemia, and ascites. 2, 5
Common Pitfalls
Never measure the posterior wall, as bowel gas interference produces unreliable measurements and leads to diagnostic errors. 2
Do not diagnose cholecystitis based solely on wall thickening—correlation with gallstones, pericholecystic fluid, sonographic Murphy's sign, and clinical presentation is mandatory. 1, 2
Recognize physiologic thickening in the post-prandial state or with inadequate fasting, which mimics pathology but represents normal gallbladder contraction. 2
Document technical limitations including patient obesity, excessive bowel gas, or patient tenderness that could compromise measurement accuracy. 1, 2