A 70-year-old man presents with sudden onset of severe abdominal pain. He has a history of atrial fibrillation. Physical examination reveals a soft abdomen with minimal tenderness. What is the most likely diagnosis?

Correct Answer: B

Rationale: The most likely diagnosis in this case is B: Mesenteric ischemia. Given the sudden onset of severe abdominal pain in an elderly patient with atrial fibrillation, mesenteric ischemia is a crucial consideration due to the risk of thromboembolism from the heart condition leading to inadequate blood supply to the intestines. Acute pancreatitis (A) typically presents with epigastric pain radiating to the back and elevated serum amylase/lipase levels. Peptic ulcer disease (C) usually presents with a history of dyspepsia and is less likely to cause sudden severe abdominal pain. Diverticulitis (D) commonly presents with left lower quadrant pain and tenderness, which contrasts with the soft abdomen and minimal tenderness seen in this case.

Correct Answer: A

Rationale: The most likely diagnosis for a 50-year-old man with jaundice, dark urine, pruritus, and a mass in the head of the pancreas is pancreatic cancer. Pancreatic cancer commonly presents with obstructive jaundice due to compression of the common bile duct by the tumor in the head of the pancreas. This leads to dark urine (due to increased bilirubin) and pruritus. Chronic pancreatitis typically presents with recurrent abdominal pain, not progressive jaundice. Gallstones can cause obstructive jaundice but are not associated with a mass in the pancreas. Primary sclerosing cholangitis presents with jaundice, but it typically involves intrahepatic and extrahepatic bile ducts, not the pancreas.

Correct Answer: B

Rationale: The correct answer is B: Esophageal cancer. Given the patient's age, symptoms of difficulty swallowing and weight loss, along with a history of chronic heartburn not responding to proton-pump inhibitors, esophageal cancer is the most likely diagnosis. Esophageal cancer commonly presents with dysphagia, weight loss, and a history of chronic reflux. Peptic stricture (A) typically presents with dysphagia but is less likely given the worsening symptoms despite treatment. Achalasia (C) presents with dysphagia and regurgitation, but not typically with weight loss. Esophageal spasm (D) presents with chest pain and dysphagia, but not typically with weight loss or chronic heartburn.

Correct Answer: A

Rationale: The most likely diagnosis is Primary biliary cirrhosis (PBC). PBC typically presents with jaundice, pruritus, and dark urine due to impaired bile flow. Elevated bilirubin and alkaline phosphatase levels are common in PBC. Imaging findings of dilated intrahepatic bile ducts and a normal common bile duct support the diagnosis of PBC. Primary sclerosing cholangitis (Choice B) would show strictures and beading of bile ducts on imaging. Gallstones (Choice C) would typically present with a common bile duct obstruction. Pancreatic cancer (Choice D) may present with similar symptoms but is less likely given the specific imaging findings in this case.

Correct Answer: C

Rationale: The most likely diagnosis is primary sclerosing cholangitis (PSC) based on the patient's symptoms of fatigue, pruritus, jaundice, and elevated bilirubin and alkaline phosphatase levels. PSC is commonly associated with inflammatory bowel disease, such as ulcerative colitis. The characteristic findings of elevated alkaline phosphatase and bilirubin levels are indicative of cholestasis, which is a key feature of PSC. Additionally, PSC is characterized by fibrosis and inflammation of the bile ducts, leading to bile duct strictures and subsequent liver damage. Hepatitis B would present with viral hepatitis symptoms and different lab findings. Primary biliary cirrhosis typically presents with elevated alkaline phosphatase and antimitochondrial antibodies. Autoimmune hepatitis would have elevated transaminases and autoantibodies. Therefore, based on the clinical presentation and lab results, PSC is the most likely diagnosis.