What happens to a distended gallbladder, is it due to inappropriate food or drink intake prior to a test or does the gallbladder contract in response to food?

Gallbladder Distension: Causes and Clinical Significance

A distended gallbladder on imaging is most commonly due to fasting status before the test, but can also indicate pathology such as cystic duct obstruction in acute cholecystitis. 1

Normal Gallbladder Physiology

The gallbladder naturally contracts in response to food intake, particularly fatty meals, through the following mechanism:

• Food in the duodenum stimulates cholecystokinin (CCK) release
• CCK causes gallbladder contraction and sphincter of Oddi relaxation
• This results in bile release into the duodenum to aid digestion
• During fasting, the gallbladder gradually fills and becomes distended

Causes of Gallbladder Distension

Non-Pathological Causes

• Fasting state: Most common reason for gallbladder distension on imaging
• Pre-procedural preparation: NPO (nothing by mouth) status before tests
• Inadequate patient preparation: Eating or drinking inappropriately close to the test can actually result in gallbladder contraction, not distension

Pathological Causes

• Acute cholecystitis: Distended gallbladder with wall thickening, pericholecystic fluid, and often gallstones impacted in the cystic duct 1
• Acalculous cholecystitis: Gallbladder distension without stones, often in critically ill patients 1
• Gallbladder hydrops: Extreme distension due to prolonged obstruction
• Gallbladder volvulus: Torsion causing distension with abnormal positioning 2

Imaging Findings in Distended Gallbladder

Normal Distension (Non-Pathological)

• Thin-walled gallbladder (≤3mm)
• No pericholecystic fluid
• No tenderness on sonographic Murphy's sign
• Normal contour and position

Pathological Distension

• Wall thickening >3-4mm
• Pericholecystic fluid
• Positive sonographic Murphy's sign
• Gallstones (especially impacted in cystic duct)
• Abnormal wall enhancement or edema 1

Clinical Implications

For Diagnostic Testing

• Ultrasound is the first-line imaging modality for suspected gallbladder pathology 1
• Patient preparation instructions should include:
  • Fasting for 8-12 hours before abdominal ultrasound if gallbladder evaluation is needed
  • Avoiding fatty meals which would trigger gallbladder contraction
  • Following NPO guidelines precisely

For Pathological Distension

• Acute cholecystitis requires prompt treatment:
  • Early laparoscopic cholecystectomy (within 7-10 days of symptom onset) 1
  • Antibiotic therapy targeting biliary pathogens
  • Percutaneous cholecystostomy for high-risk surgical patients 3

Common Pitfalls in Interpretation

• Mistaking normal fasting distension for pathology
• Failing to recognize acalculous cholecystitis in critically ill patients
• Overlooking gallbladder distension as a sign of cystic duct obstruction
• Not correlating imaging findings with clinical presentation (pain, fever, leukocytosis)

Key Points to Remember

• Gallbladder distension is expected in fasting patients
• Inappropriate food/drink intake before imaging causes gallbladder contraction, not distension
• Pathological distension is accompanied by additional findings (wall thickening, pericholecystic fluid)
• The sonographic Murphy's sign (focal tenderness over the gallbladder during ultrasound) helps differentiate pathological from physiological distension 1

In summary, while gallbladder distension is often a normal finding in fasting patients, it can indicate serious pathology when accompanied by other concerning features. Proper patient preparation before imaging and careful correlation with clinical symptoms are essential for accurate interpretation.