What is the most appropriate initial investigation for an elderly man with progressive jaundice, icteric (yellow) sclera, dark urine, and pale stool, suspected of having a distended gallbladder (GB) with gallstones 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, suspected distended gallbladder with stones, and dilated CBD. 1

Rationale for Ultrasound as First-Line Investigation

Ultrasound is recommended as the initial imaging modality for several compelling reasons:

• High diagnostic accuracy with sensitivities of 32-100% and specificities of 71-97% for detecting biliary obstruction 1
• Excellent accuracy for detecting:
  • Gallbladder stones (87% accuracy)
  • Common bile duct dilatation (82% accuracy)
  • Potential mass lesions (80% accuracy for pancreatic masses) 1
• Non-invasive nature with no radiation exposure
• Widely available and cost-effective
• Can rapidly confirm the obstructive process by showing dilatation of the biliary tree
• Can help localize the site of obstruction and differentiate between likely benign and malignant causes 1

Diagnostic Algorithm After Initial Ultrasound

Based on ultrasound findings, the subsequent investigations should follow this pathway:

1. If US confirms obstruction but is inconclusive about cause:

   • MRCP should be performed next, as it has superior sensitivity (77-88%) for detecting ductal calculi 1

2. If malignancy is suspected:

   • Contrast-enhanced CT may be useful (sensitivity 74-96%, specificity 90-94% for biliary obstruction) 1

3. For definitive diagnosis and therapeutic intervention:

   • ERCP should be reserved primarily for therapeutic intervention after diagnosis is established, due to its 4-5.2% risk of major complications 1

Why Not Choose Other Options First?

• ERCP (Option B): While ERCP has excellent diagnostic capabilities, it carries significant risks including pancreatitis, cholangitis, hemorrhage, and perforation (4-5.2% risk of major complications). It should be reserved for therapeutic intervention after diagnosis is established through less invasive means. 1, 2

• CT (Option A): Although CT has high sensitivity and specificity for biliary obstruction, it has limited sensitivity for non-calcified gallstones (which represent up to 80% of stones) and involves radiation exposure. 1

• MRCP (Option D): While MRCP has superior diagnostic accuracy compared to US, it is more time-consuming and may not be as readily available as US in emergency settings. It is more appropriate as a second-line investigation after US has confirmed obstruction. 1, 2

Limitations of Ultrasound to Be Aware Of

• False-negative findings can occur due to:

  • Inability to visualize the extrahepatic biliary tree
  • Absence of biliary dilation in acute obstruction
  • Limited sensitivity (22.5-75%) for detecting distal CBD stones 1

• Overreliance on ultrasound alone may not identify the exact cause of obstruction, particularly in the distal CBD 1

In this clinical scenario with classic signs of obstructive jaundice (progressive jaundice, deep yellow sclera, dark urine, pale stool) and suspected gallstone disease, ultrasound provides the most appropriate initial investigation to confirm the diagnosis and guide further management.