A 65-year-old woman presents with a 5-week history of yellow skin and sclera, anorexia, and epigastric pain. Her past medical history is significant for insulin-dependent diabetes mellitus. She smoked one pack of cigarettes a day for the past 20 years. Physical examination reveals jaundice and a palpable gallbladder. Laboratory studies show a serum bilirubin level of 10 mg/dL, mostly in the conjugated form, and an elevated alkaline phosphatase (260 U/L). A CT scan of the abdomen discloses a mass in the head of the pancreas and multiple nodules in the liver measuring up to 3 cm. Which of the following is the most likely cause of jaundice in this patient?

**Core Concept**
The patient's presentation of jaundice, anorexia, epigastric pain, and a palpable gallbladder, along with laboratory studies showing elevated conjugated bilirubin and alkaline phosphatase, suggests a diagnosis of obstructive jaundice. This condition occurs when a blockage prevents bilirubin from flowing from the liver into the intestine, leading to its accumulation in the blood and tissues.

**Why the Correct Answer is Right**
The patient's CT scan reveals a mass in the head of the pancreas, which is likely a pancreatic cancer causing the obstruction. The multiple nodules in the liver are also consistent with metastasis from the primary pancreatic tumor. The elevated alkaline phosphatase suggests bile duct obstruction, which is a hallmark of pancreatic cancer. The presence of a palpable gallbladder (Courvoisier's sign) is a classic sign of pancreatic cancer causing obstructive jaundice.

**Why Each Wrong Option is Incorrect**
**Option A:** Cholangiocarcinoma is a primary malignancy of the bile ducts, which may also cause obstructive jaundice. However, the presence of a palpable gallbladder and the mass in the head of the pancreas make pancreatic cancer a more likely diagnosis.

**Option B:** Gallstones are a common cause of obstructive jaundice, but the patient's age, smoking history, and the presence of a palpable gallbladder make pancreatic cancer a more likely diagnosis.

**Option C:** Chronic pancreatitis can cause obstructive jaundice, but the patient's presentation of a palpable gallbladder and the CT scan findings of a pancreatic mass and liver nodules are more suggestive of pancreatic cancer.

**Option D:** Hepatitis is an inflammatory condition of the liver, which may cause elevated liver enzymes, but the patient's presentation of obstructive jaundice, a palpable gallbladder, and the CT scan findings make pancreatic cancer a more likely diagnosis.

**Clinical Pearl / High-Yield Fact**
Remember that Courvoisier's sign (a palpable gallbladder) is a classic sign of pancreatic cancer causing obstructive jaundice, and it should prompt further investigation to rule out this diagnosis.

**Correct Answer:** C. Pancreatic cancer

✓ Correct Answer: C. Extrahepatic biliary obstruction