USMLE Step 1 Question 293

Question:

A 58 year old woman with a long history of alcoholism presents with diarrhea, general weakness, and a 9lb weight loss in the past 3 months. Further history reveals that she has been having difficulties driving at night as well as episodic upper abdominal pain not relieved with antacids or proton pump inhibitors. Laboratory studies reveal a serum ionized calcium of 3.5mg/dL (N=4.5-5.6mg/dL); PT of 30 seconds (N=11-15seconds); PTT of 60 seconds (N=25-40seconds). What is the most likely etiology of this patient’s diarrhea?

Correct Answer: C.  Chronic pancreatitis

The patient’s clinical picture most likely reflects a malabsorption syndrome. Chronic pancreatitis (choice C) resulting in chronic pancreatic insufficiency is the most likely diagnosis. Chronic inflammation of the pancreas can result in a critical amount of damage to both the endocrine and exocrine functions of the pancreas. Without the exocrine function of the pancreas, dietary lipids cannot be digested and absorbed nor can the fat-soluble vitamins D, A, K, E. Malabsorption of lipids will result in an osmotic steatorrhea. Malabsorption of vitamins D, A, K, E will result in their respective deficiency symptoms (D=hypocalcemia; A=night blindness; K=prolonged PT/aPTT)

Carcinoid tumor (choice A) can cause carcinoid syndrome which is characterized by secretory diarrhea, flushing, and right-sided heart failure.

Pancreatic cancer (choice B) involving the head of the pancreas can produce a similar clinical picture; however, one would also expect to see signs of obstructive jaundice and elevated LFTs.

Chronic gastritis (choice D) is common in alcoholic patients and can explain the epigastric pain; however, it does not commonly cause malabsorption.

Celiac sprue (choice E) is a common cause of malabsorption. The condition is associated with hypersensitivity to dietary gluten; however, in the setting of an alcoholic, pancreatic insufficiency secondary to chronic pancreatitis is a more likely diagnosis.