Ultrasound Indication for Floating Stools with Positive Murphy's Sign
Yes, order an abdominal ultrasound immediately—this patient has a positive Murphy's sign suggesting gallbladder pathology, and ultrasound is the first-line imaging modality for suspected biliary disease regardless of the atypical presentation with floating stools. 1
Primary Recommendation
Ultrasound of the abdomen is the investigation of choice for any patient with a positive Murphy's sign, even when other symptoms are atypical. 1 The ACR Appropriateness Criteria explicitly state that ultrasound is the first choice of investigation for biliary symptoms or right upper quadrant findings, with 96% accuracy for detecting gallstones and the ability to identify acute cholecystitis. 1
Clinical Reasoning
Why Ultrasound is Indicated
Murphy's sign is a specific clinical finding that warrants imaging evaluation of the gallbladder, even when "slight" or when accompanied by unusual symptoms like floating stools. 1
Ultrasound can be elicited during the examination itself (sonographic Murphy's sign), which increases diagnostic accuracy when combined with imaging findings such as gallbladder wall thickening, pericholecystic fluid, or gallstones. 1
The three-month duration of symptoms does not exclude significant gallbladder pathology—chronic cholecystitis can present with subtle findings and may show a contracted or distended gallbladder without pericholecystic fluid. 1
Addressing the Floating Stools
Floating stools are typically related to fat malabsorption or increased gas content, not directly to gallbladder disease. [@General Medicine Knowledge@]
However, chronic biliary obstruction or gallbladder dysfunction can impair bile flow, potentially contributing to fat malabsorption and steatorrhea (which can cause floating stools). [@General Medicine Knowledge@]
The ultrasound will evaluate both the gallbladder AND the biliary tree, including assessment for bile duct dilation that might explain malabsorptive symptoms. 1, 2
What the Ultrasound Should Evaluate
The radiologist should specifically assess for:
Gallstones or sludge (sensitivity approaching 100% for cholelithiasis). 1, 3
Gallbladder wall thickening (>3mm suggests inflammation). 1
Pericholecystic fluid (indicates acute inflammation). 1
Gallbladder distention or hydrops (may suggest chronic obstruction). 4
Intrahepatic and extrahepatic bile duct caliber (to exclude biliary obstruction that could explain malabsorption). 1
Sonographic Murphy's sign (focal tenderness over the visualized gallbladder). 1
Important Clinical Caveats
When Ultrasound May Be Insufficient
If ultrasound is negative or equivocal but clinical suspicion remains high, consider MRCP (magnetic resonance cholangiopancreatography) for superior evaluation of the biliary tree and detection of choledocholithiasis (sensitivity 85-100%). 1
CT with IV contrast is valuable if ultrasound findings are equivocal or if complications of cholecystitis (emphysematous, hemorrhagic, gangrenous, or perforated) are suspected. 1, 2
Red Flags Requiring Urgent Evaluation
Re-evaluate immediately and consider urgent surgical consultation if the patient develops:
Fever or signs of systemic infection (suggests acute cholecystitis requiring intervention within 7-10 days). 1
Worsening right upper quadrant pain or more pronounced Murphy's sign (indicates progression to acute inflammation). 4
Jaundice or elevated bilirubin (suggests common bile duct obstruction requiring MRCP or ERCP). 1
Laboratory evidence of inflammation (elevated WBC, inflammatory markers). 1
Additional Diagnostic Considerations
Evaluate for other causes of fat malabsorption if ultrasound is normal, including pancreatic insufficiency, celiac disease, or small bowel disorders. [@General Medicine Knowledge@]
The combination of gallbladder findings and floating stools may indicate chronic biliary dysfunction affecting fat digestion, which ultrasound can help clarify by assessing bile duct patency. 1