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Difficulty: HardOrdering Imaging Studies

A 68-year-old man presents to the outpatient clinic with a 4-week history of progressively worsening yellowing of his skin and eyes, generalized pruritus, and a 15-lb (6.8 kg) unintentional weight loss. He reports that his urine has become dark brown and his stools are pale and malodorous. He has no significant past medical history and takes no medications. Vital signs are within normal limits. Physical examination reveals marked scleral icterus and jaundice. Abdominal examination is notable for a palpable, non-tender, rounded mass in the right upper quadrant.

Laboratory studies show:
Total bilirubin: 14.2 mg/dL
Direct bilirubin: 11.5 mg/dL
Alkaline phosphatase: 520 U/L
Aspartate aminotransferase (AST): 85 U/L
Alanine aminotransferase (ALT): 92 U/L
Lipase: 45 U/L

A transabdominal right upper quadrant ultrasound is performed, revealing a significantly dilated common bile duct measuring 16 mm, intrahepatic biliary ductal dilation, and a markedly distended gallbladder without evidence of gallstones. A vague, hypoechoic region is noted near the head of the pancreas.

Which of the following is the most appropriate next step in the diagnostic imaging evaluation of this patient?

  1. Multiphasic contrast-enhanced computed tomography of the abdomenAnswer
  2. B
    Endoscopic retrograde cholangiopancreatography
  3. C
    Endoscopic ultrasound with fine-needle aspiration
  4. D
    Magnetic resonance cholangiopancreatography without intravenous contrast
  5. E
    Positron emission tomography-computed tomography

Answer

Multiphasic contrast-enhanced computed tomography of the abdomen
The patient's presentation of painless jaundice, weight loss, and a palpable, non-tender gallbladder (Courvoisier sign) is highly suspicious for a malignant biliary obstruction, specifically pancreatic head adenocarcinoma. While the initial ultrasound confirmed extra- and intra-hepatic biliary dilation without stones, the next essential step in the diagnostic evaluation is a multiphasic contrast-enhanced CT (pancreatic protocol). This imaging modality provides high-resolution, multiphase (arterial, pancreatic, and portal venous) cross-sectional images. These are absolutely critical for detecting the primary mass, determining its relationship to surrounding vasculature (superior mesenteric artery/vein, celiac axis), and identifying distant metastases (liver, peritoneum). Accurate non-invasive staging must be completed before any invasive procedures are performed to determine surgical resectability.

Step-by-Step Solution

1
Analyze the clinical presentation and physical examination findings.
The patient has painless jaundice, weight loss, and a palpable, non-tender gallbladder (Courvoisier sign).
These findings are highly specific for a malignant biliary obstruction distal to the cystic duct, most commonly pancreatic head adenocarcinoma.
2
Interpret the initial imaging results.
Right upper quadrant ultrasound confirms a dilated biliary tree and distended gallbladder without stones, alongside a vague pancreatic mass.
Ultrasound is the correct initial test to rule out choledocholithiasis, but it lacks the resolution to adequately stage a suspected pancreatic malignancy.
3
Determine the optimal next step in the diagnostic sequence.
Select multiphasic contrast-enhanced CT (pancreatic protocol).
Before any invasive procedures (like ERCP or EUS) are performed, accurate non-invasive cross-sectional staging must be obtained to determine tumor size, vascular involvement, and the presence of distant metastases, which ultimately dictates surgical resectability.

Key Concept

In patients with suspected pancreatic cancer based on initial ultrasound, multiphasic contrast-enhanced CT of the abdomen must be performed prior to any invasive biliary procedures (ERCP or EUS) to ensure accurate staging and avoid imaging artifacts.
Estimated Time:1m 30s
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Ordering Imaging Studies

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