A 46-year-old man had profuse diarrhea for two months. He notes that the diarrhea continues throughout the day. Fasting does not decrease the diarrheal episodes. He has tried using loperamide, but the relief is temporary. He notes a 10-pound weight loss over the last two months. He notes that he is not taking any medications except for the loperamide. Upon questioning, he recently quit smoking and has been chewing a lot of sugarless gum. You measure his stool electrolytes. The results are as follows: Na+ 40 mmol/L, K+ 90 mmol/L, Cl- 15 mmol/L, HCO3- 18 mmol/L. What is the most likely diagnosis?

Correct Answer: C

Rationale: This patient has chronic diarrhea that does not improve with fasting. This is a key feature in distinguishing between osmotic and secretory diarrhea. Additionally, his stool electrolytes do not reveal an osmolar gap (as seen with osmotic diarrhea). His osmolar gap is $290-[(40+90) \times 2]=30$, which is normal. An osmolar gap of greater than 50 is suggestive of osmotic diarrhea. Lactase deficiency, sucrase deficiency, and sorbitol ingestion would all cause an osmotic diarrhea. A VIPoma is the only one of the choices that causes a secretory diarrhea.

Correct Answer: B

Rationale: Patients with acute infection outside the liver, severe cardiac or pulmonary disease, or metastatic cancer are not eligible for liver transplantation. Patients with HIV, however, are candidates for transplant if they do not have advanced disease (CD4 <200, viral load >400 copies/mL).

Correct Answer: A

Rationale: Antibiotics (e.g., amoxicillin, clarithromycin) are essential to eradicate H. pylori, a primary cause of PUD, as part of combination therapy.

Correct Answer: B

Rationale: Stress can increase gastric acid secretion via the hypothalamic-pituitary-adrenal axis, worsening PUD symptoms, though it's not the primary cause.

Correct Answer: B

Rationale: A CT scan definitively identifies free air and fluid in the peritoneal cavity, confirming a perforated peptic ulcer.