What is the most appropriate initial investigation for an elderly man with progressive jaundice, deep yellow sclera, dark urine, pale stool, a distended gallbladder (GB) with stones, and a dilated common bile duct (CBD)?

Diagnostic Approach for Elderly Man with Obstructive Jaundice

Ultrasound (US) is the most appropriate initial investigation for an elderly man with progressive jaundice, deep yellow sclera, dark urine, pale stool, distended gallbladder with stones, and dilated CBD. 1, 2

Rationale for Initial Ultrasound

Ultrasound is recommended as the first-line imaging modality for several reasons:

• It is non-invasive, rapid, and cost-effective
• It effectively evaluates for obstructive jaundice with sensitivities of 32-100% and specificities of 71-97% for detecting biliary obstruction 1
• It can confirm the obstructive process by showing dilatation of the biliary tree
• It can localize the site of obstruction (CBD, gallbladder, biliary bifurcation)
• It can differentiate between likely benign causes (choledocholithiasis, cholecystitis) and malignant causes (pancreatic head mass, Klatskin tumor) 1
• It is specifically recommended by the American College of Gastroenterology as the first investigation for patients with obstructive jaundice 2

Diagnostic Algorithm for Obstructive Jaundice

1. Initial US evaluation

   • Confirms biliary dilatation
   • Identifies gallstones in the gallbladder (already noted in this case)
   • May visualize CBD stones (though sensitivity is limited to 22.5-75% for distal CBD stones) 1, 2
   • Evaluates for mass lesions

2. If US is inconclusive or further characterization is needed:

   • MRCP should be performed next
     • Superior to US for determining both site and cause of obstruction
     • Highly sensitive for detecting ductal calculi (77-88% sensitivity) 1, 2
     • Non-invasive alternative to ERCP for diagnostic imaging
     • Can visualize the entire biliary tree

3. If malignancy is suspected or US is inconclusive:

   • CT may be considered
     • Better than US at determining site and cause of obstruction
     • High sensitivity (74-96%) and specificity (90-94%) for biliary obstruction 2
     • Limited sensitivity for non-calcified gallstones

4. For therapeutic intervention after diagnosis:

   • ERCP should be reserved primarily for therapeutic intervention
     • Has 4-5.2% risk of major complications (pancreatitis, cholangitis, hemorrhage)
     • 0.4% mortality risk 2
     • Should not be used as an initial diagnostic tool unless immediate intervention is needed for cholangitis

Clinical Pitfalls and Caveats

• False-negative US studies can occur due to:

  • Inability to visualize the extrahepatic biliary tree (from interposed bowel gas or large body habitus)
  • Absence of biliary dilation in acute obstruction 1
  • Limited sensitivity for distal CBD stones

• ERCP should not be used as a first-line diagnostic tool despite its high accuracy, as it carries significant risks of complications and should be reserved for therapeutic intervention after diagnosis is established 2

• While MRI/MRCP has superior diagnostic accuracy compared to US, it is more time-consuming (typically requiring 30 minutes) and may not be as readily available as US in emergency settings 1

• EUS has excellent diagnostic accuracy but has a limited field of view and cannot detect pathology beyond adjacent regions, with complications in up to 6.3% of patients 1, 2

In this case with classic signs of obstructive jaundice (progressive jaundice, deep yellow sclera, dark urine, pale stool) and already identified gallbladder stones with dilated CBD, ultrasound is the most appropriate initial investigation to confirm the diagnosis and guide further management.