In an adult without prior medical history presenting with 12‑hour upper abdominal pain, nausea, normal skin and sclera, deep abdominal tenderness, and ultrasound showing multiple gallstones, normal gallbladder wall, no pericholecystic fluid, and a common bile duct stone, what is the most likely diagnosis?

Diagnosis: Obstructive Jaundice (Answer C)

The most likely diagnosis is obstructive jaundice (choledocholithiasis) because ultrasound directly visualized a common bile duct stone causing obstruction, which is the defining pathologic finding in this case. 1

Clinical Reasoning

Why Obstructive Jaundice is Correct

Direct visualization of a CBD stone on ultrasound is a very strong predictor of choledocholithiasis and represents the primary pathology requiring intervention. 2, 3 The British Society of Gastroenterology guidelines specifically categorize this presentation as "high likelihood of CBDS" when a CBD stone is positively identified on ultrasound, warranting proceeding directly to ERCP or surgical extraction. 1

The key diagnostic features present are:

• CBD stone directly visualized on imaging - this is the most specific finding 3, 4
• Upper abdominal pain with nausea - consistent with biliary obstruction 5
• CBD obstruction documented - the pathologic process causing symptoms 1

Why the Absence of Clinical Jaundice Doesn't Exclude This Diagnosis

The absence of visible jaundice (normal sclera and skin) does NOT rule out obstructive jaundice as a diagnosis, because biochemical obstruction precedes clinical jaundice. 1 Many patients with CBD stones present before bilirubin rises sufficiently to cause visible icterus. The term "obstructive jaundice" refers to the pathophysiologic process of biliary obstruction, not merely the clinical sign of yellow discoloration. 1

At only 12 hours of symptoms, this patient may not yet have developed:

• Elevated total bilirubin sufficient for clinical jaundice (typically requires >2-3 mg/dL) 4
• Dark urine or pale stools (which develop later in the disease course) 5

Why Other Diagnoses Are Less Likely

Cholecystitis (Answer B) is excluded because the ultrasound shows:

• Normal gallbladder wall thickness (acute cholecystitis requires >3mm) 2, 5
• No pericholecystic fluid 2, 5
• No sonographic Murphy sign mentioned 2

The American College of Radiology specifies that acute cholecystitis requires gallbladder wall thickening >3mm, pericholecystic fluid, sonographic Murphy sign, and/or gallbladder distension - none of which are present here. 2

Pancreatitis (Answer A) is less likely because:

• The primary pathology is the CBD stone, not pancreatic inflammation 1
• No mention of lipase/amylase elevation or pancreatic imaging findings 5
• While CBD stones can cause pancreatitis, the question asks for the "most likely diagnosis" based on the imaging findings showing CBD obstruction as the primary pathology 6

Small bowel obstruction (Answer D) is excluded by the clinical presentation showing no changes in bowel habits and imaging focused on biliary pathology. 1

Critical Management Implications

This patient requires urgent ERCP for stone extraction because direct visualization of a CBD stone on ultrasound places them in the "high likelihood" category, and further imaging is not routinely required before proceeding to therapeutic intervention. 1

Common Pitfalls to Avoid

• Do not wait for clinical jaundice to develop before diagnosing biliary obstruction - the CBD stone is already documented 3, 4
• Do not order additional imaging (MRCP/EUS) when a CBD stone is directly visualized on ultrasound - proceed directly to ERCP 1
• Do not delay intervention - even without fever or cholangitis, CBD stones require removal to prevent serious complications including ascending cholangitis, biliary sepsis, and pancreatitis 1, 3, 6

The interval between ERCP and subsequent cholecystectomy should be at least 24 hours but less than 6 weeks to exclude complications from the endoscopic procedure. 3