Do gallstones always appear on ultrasound?

Do Gallstones Always Show Up on Ultrasound?

No, gallstones do not always show up on ultrasound—while ultrasound is highly accurate for detecting gallbladder stones with approximately 96-99% sensitivity, it can miss 1-3% of cases, particularly small stones, cholesterol stones, and stones in the gallbladder neck. 1, 2, 3

Ultrasound Performance for Gallbladder Stones

Ultrasound remains the gold standard initial imaging test for gallbladder stones despite its limitations. 4, 5

• Sensitivity for gallbladder stones is approximately 96-99%, meaning it correctly identifies stones in the vast majority of cases 1, 3
• The false-negative rate is approximately 1.3%, even with modern ultrasound technology 2
• Ultrasound is the preferred initial imaging technique due to its cost-effectiveness, wide availability, lack of radiation exposure, and high accuracy for gallstone disease 4

Specific Scenarios Where Gallstones May Be Missed

Small Stones

• Stones smaller than 3-4 mm may not always show the characteristic acoustic shadowing that makes gallstones easily identifiable 6
• Small gallstones may be overlooked or mistaken for gas in adjacent bowel loops 4

Cholesterol Stones

• Cholesterol stones are often small, less echogenic, may float, and may demonstrate "comet tailing" rather than typical shadowing 4
• These atypical appearances can lead to missed diagnoses 4

Stones in the Gallbladder Neck

• Small stones in the gallbladder neck may easily be overlooked or mistaken for lateral cystic shadowing artifact (edge shadows) 4
• Imaging this area from several directions may be necessary to avoid missing these stones 4

Adherent Stones and Mimics

• Adherent gallstones can mimic gallbladder polyps, leading to misdiagnosis 2
• In cases where ultrasound missed gallstones, 5 cases showed polyps, 5 showed sludge, and 1 showed both sludge and a polyp on the initial scan 2

Large Common Bile Duct Stones

• Large common bile duct stones may not show characteristic features of gallstones and can be misdiagnosed as tumor masses 6

Common Bile Duct Stones: A Different Story

Ultrasound is significantly less sensitive for common bile duct stones compared to gallbladder stones. 7, 8

• Sensitivity for common bile duct stones is only 73% (range 44-90%), with specificity of 91% 7, 8
• Direct visualization of common bile duct stones on ultrasound is a very strong predictor when seen, but many stones are simply not visualized 4, 7
• Common bile duct stones may only be identified by the shadowing they cause 4
• Many patients may have common bile duct stones despite having a negative ultrasound, necessitating further testing with MRCP (93% sensitivity) or EUS (95-98.5% sensitivity) when clinical suspicion is high 4, 7, 8

Technical Factors That Limit Detection

Several technical factors can prevent adequate ultrasound examination and lead to missed stones: 4

• Bowel gas obscuring the gallbladder 4
• Patient body habitus 4
• Abdominal tenderness limiting adequate scanning 4
• When these limitations prevent adequate examination, they should be documented and alternative imaging considered 4

Clinical Implications

When ultrasound is negative but clinical suspicion for gallstones remains high, consider: 8

• Repeating the ultrasound with optimal technique, including scanning from multiple directions and repositioning the patient to check for stone mobility 4
• Optimizing gain settings to better identify shadowing 4
• Recognizing that the absence of gallstones on ultrasound has a 97% negative predictive value for acute cholecystitis, making the diagnosis unlikely but not impossible 4
• Pursuing alternative imaging or clinical follow-up if symptoms persist despite negative ultrasound 8