What further investigations should be performed if an ultrasound (USG) shows chronic cholecystitis?

Further Investigations for Chronic Cholecystitis Diagnosed on Ultrasound

When ultrasound shows chronic cholecystitis, laboratory tests including liver function tests, complete blood count, and pancreatic enzymes should be performed, followed by MRCP or HIDA scan if there is suspicion of common bile duct involvement or to confirm gallbladder function. 1

Initial Laboratory Investigations

Following the ultrasound diagnosis of chronic cholecystitis, these blood tests should be performed:

• Liver Function Tests:

  • Bilirubin (total and direct)
  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
  • Alkaline phosphatase (ALP)
  • Gamma-glutamyl transferase (GGT)

• Complete Blood Count (CBC) - to evaluate for leukocytosis which may indicate inflammation 2, 1

• Other Blood Tests:

  • Serum calcium - to rule out hypercalcemia as a cause
  • Triglyceride levels - to assess for hypertriglyceridemia
  • Pancreatic enzymes (amylase, lipase) - to rule out pancreatic involvement 2

Advanced Imaging Studies

If initial ultrasound and laboratory tests are inconclusive or suggest complications:

• MRCP (Magnetic Resonance Cholangiopancreatography):

  • Indicated when there is suspicion of common bile duct stones or biliary obstruction
  • Particularly useful when liver enzymes are elevated 2, 1

• HIDA Scan (Hepatobiliary Iminodiacetic Acid Scan):

  • Useful to assess gallbladder function and confirm chronic cholecystitis
  • Gold standard diagnostic test when ultrasound results are equivocal
  • Can determine gallbladder ejection fraction (GBEF) - values <35% are considered abnormal 3, 4

• Endoscopic Ultrasound (EUS):

  • Considered when there is suspicion of small common bile duct stones missed on other imaging
  • More accurate than transabdominal ultrasound for detecting choledocholithiasis 2

Special Considerations

• For patients over 40 years of age: CT or EUS should be performed to rule out underlying pancreatic malignancy that might be causing biliary symptoms 2

• For patients with recurrent symptoms: Consider ERCP (Endoscopic Retrograde Cholangiopancreatography) if other imaging is inconclusive 2

• For elderly patients (>65 years): Liver biochemical tests and abdominal ultrasound should be performed to assess the risk for common bile duct stones 2

Algorithm for Investigation

1. Initial diagnosis: Ultrasound showing chronic cholecystitis
2. Basic laboratory workup: LFTs, CBC, calcium, triglycerides, pancreatic enzymes
3. If laboratory tests normal: Consider HIDA scan to confirm gallbladder dysfunction
4. If laboratory tests abnormal:
   • Elevated liver enzymes → MRCP to evaluate biliary tree
   • Elevated pancreatic enzymes → CT abdomen to evaluate pancreas
5. If age >40 or recurrent unexplained symptoms: Consider EUS or CT to rule out malignancy

Common Pitfalls to Avoid

• Relying solely on ultrasound findings without laboratory confirmation
• Missing common bile duct stones which may be present in 3-10% of patients with gallbladder disease 5
• Failing to consider other diagnoses that may mimic biliary colic (peptic ulcer disease, irritable bowel syndrome)
• Not investigating further in patients with persistent symptoms despite normal ultrasound findings 6

By following this systematic approach to investigating chronic cholecystitis, you can confirm the diagnosis, identify any complications, and guide appropriate management decisions.