What Does "Gallbladder is Normally Distended" Mean on Ultrasound?
A "normally distended" gallbladder on ultrasound indicates a gallbladder that is appropriately filled with bile in the fasting state, without pathologic enlargement, and represents a normal physiologic finding that allows adequate visualization and assessment for stones or disease. 1
Normal Gallbladder Appearance
The normal gallbladder is highly variable in size, shape, and axis, making standardized measurements less clinically useful in routine practice. 1 Key characteristics of a normally distended gallbladder include:
- Adequate visualization: The gallbladder contains sufficient bile to allow systematic scanning through all tissue planes in both long and short axis views 1
- Normal wall thickness: Anterior wall measures ≤3 mm when measured between the lumen and hepatic parenchyma 1
- Absence of pathologic features: No pericholecystic fluid, no wall irregularity, and preservation of the normal trilaminar mural structure 1
- Physiologic distension: The gallbladder fills with bile during fasting states, which is the expected normal finding 2
Clinical Context Matters
The term "normally distended" specifically distinguishes physiologic filling from pathologic distension:
- Pathologic distension occurs when the transverse diameter exceeds 5 cm, which may indicate cholecystitis or hydrops 1, 3
- Contracted gallbladder after fasting may actually represent abnormal chronic cholecystitis, though the gallbladder can appear either contracted or distended in this condition 1
- Post-prandial state: A completely contracted gallbladder after fasting that then distends after a fatty meal is actually a normal physiologic response 2
What to Look for Beyond "Normal Distension"
When a gallbladder is described as normally distended, the radiologist is confirming adequate visualization to assess for:
- Gallstones: Mobile, echogenic structures with posterior shadowing (96% accuracy for detection) 1
- Wall abnormalities: Thickening >3 mm, irregularity, or heterogeneous echogenicity suggesting cholecystitis 1
- Pericholecystic fluid: Hypo- or anechoic regions suggesting acute inflammation 1, 4
- Sonographic Murphy's sign: Probe-induced tenderness directly over the gallbladder reproducing the patient's pain 1, 4
Common Pitfalls to Avoid
- Don't confuse normal distension with hydrops: True gallbladder hydrops is characterized by acute distension >5 cm with a thin wall and association with systemic illness, particularly in pediatric patients 3
- Fasting status affects interpretation: The gallbladder should be examined after overnight fasting for optimal assessment; post-prandial contraction is normal and expected 2
- Wall thickness measurement location: Always measure the anterior wall adjacent to hepatic parenchyma, as the posterior wall measurement may be unreliable due to adjacent bowel 1
- Non-biliary causes of wall thickening: Hypoproteinemia, congestive heart failure, and post-prandial states can cause wall thickening without representing biliary pathology 1
Clinical Significance
A normally distended gallbladder is reassuring and indicates the examination was technically adequate to exclude acute gallbladder pathology. 1 The American College of Radiology emphasizes that a normal appearance of the gallbladder, especially the wall, makes acute gallbladder pathology very unlikely. 1 This finding allows clinicians to confidently pursue alternative diagnoses for the patient's symptoms when clinical suspicion for biliary disease exists but ultrasound findings are normal.