Will a right upper quadrant (RUQ) ultrasound (US) show signs of cholecystitis?

Will RUQ Ultrasound Show Cholecystitis?

Yes, RUQ ultrasound will show cholecystitis in most cases and is the first-line imaging test of choice, though it misses approximately 25% of acute cholecystitis cases and over half of chronic cholecystitis cases. 1, 2

Diagnostic Performance of RUQ Ultrasound

Ultrasound remains the initial imaging modality for suspected cholecystitis despite having moderate sensitivity. 1

Sensitivity and Specificity

• Acute cholecystitis: Sensitivity of 75.7-88% and specificity of 80-86% 1, 2
• Chronic cholecystitis: Sensitivity of only 34.6%, making diagnosis particularly difficult 2
• Overall cholecystitis detection: Sensitivity of 42.7% across all types 2
• Gallstone detection: 96% accuracy, which is excellent 1

Key Sonographic Findings to Look For

When ultrasound is positive for cholecystitis, it will demonstrate: 1, 3

• Gallbladder wall thickening >4 mm
• Pericholecystic fluid
• Gallbladder distension (AP diameter >4 cm)
• Gallstones or sludge
• Sonographic Murphy sign (focal tenderness over the gallbladder)
• Sonolucent areas in or around the gallbladder wall

Important Clinical Limitations

When Ultrasound May Miss Cholecystitis

The sensitivity of ultrasound degrades significantly over time and has important diagnostic blind spots. 2

• Time-dependent degradation: Sensitivity falls below 50% when ultrasound is performed >140 days before definitive diagnosis 2
• Optimal timing: Diagnostic accuracy is best when ultrasound is performed <27 days before cholecystectomy 2
• Chronic cholecystitis: Particularly difficult to diagnose on anatomic imaging, with the gallbladder appearing either contracted or distended and pericholecystic fluid usually absent 1

Sonographic Murphy Sign Limitations

The sonographic Murphy sign has relatively low specificity and can be unreliable. 1, 4

• Low specificity for acute cholecystitis 1
• Unreliable when negative if the patient received pain medication prior to imaging 1, 4
• May be absent in elderly, diabetic, or immunocompromised patients despite severe disease 4

Special Populations with Limited Utility

Ultrasound usefulness is significantly limited in critically ill patients. 1, 5

• Gallbladder abnormalities are common in critically ill patients even in the absence of acute cholecystitis 1
• This limits diagnostic specificity in the ICU setting 5

When to Pursue Additional Imaging

If Ultrasound is Negative or Equivocal

When clinical suspicion remains high despite negative or equivocal ultrasound, cholescintigraphy (HIDA scan) is the next appropriate test. 1

• Cholescintigraphy performance: Sensitivity of 96-97% and specificity of 90% for acute cholecystitis 1
• Superior to ultrasound for detecting cystic duct obstruction 1
• Particularly valuable when ultrasound findings are equivocal and clinical suspicion is high 1

Alternative Advanced Imaging Options

MRI with MRCP provides comprehensive biliary evaluation when ultrasound is inconclusive. 1, 5

• MRI sensitivity: 50-91% for acute cholecystitis with specificity of 79-89% 1
• Advantages over ultrasound: Better visualization of cystic duct and common bile duct, can distinguish acute from chronic cholecystitis based on T2 signal characteristics 1
• MRCP excels at detecting choledocholithiasis with sensitivity of 85-100% and specificity of 90% 5

CT with IV contrast is appropriate when complications are suspected or the patient is critically ill. 1

• Can detect emphysematous cholecystitis, perforation, hemorrhage, and gangrenous changes 1
• Useful for evaluating alternative diagnoses when cholecystitis is excluded 1

Clinical Algorithm

Follow this stepwise approach: 1, 4, 5

1. Start with RUQ ultrasound as the first-line test for all patients with suspected cholecystitis 1, 4
2. If ultrasound is positive and clinical picture fits, proceed with appropriate management 1
3. If ultrasound is negative or equivocal but clinical suspicion remains high:
   • Order cholescintigraphy (HIDA scan) for suspected acute cholecystitis 1
   • Consider MRI with MRCP if biliary obstruction or ductal pathology is suspected 1, 5
4. If complications are suspected (emphysematous, gangrenous, perforated cholecystitis), consider CT with IV contrast 1

Key Clinical Pitfalls to Avoid

• Do not rely on negative ultrasound alone to exclude cholecystitis when clinical suspicion is high—ultrasound misses 25% of acute cholecystitis cases 2
• Do not interpret sonographic Murphy sign in isolation—it has low specificity and is unreliable after pain medication 1, 4
• Do not delay repeat imaging if symptoms persist—sensitivity degrades significantly over time 2
• Do not use ultrasound as the sole diagnostic tool in critically ill patients—consider cholescintigraphy earlier in this population 1