1. A 30-year-old male presents with profuse, watery diarrhea that does not cease with fasting. Stool analysis shows a low osmotic gap (<50 mOsm/kg). Which type of diarrhea is most likely?
2. The mechanism of action of Vibrio cholerae toxin involves the activation of which intracellular signaling molecule, leading to massive fluid secretion?
3. A patient develops diarrhea after a course of clindamycin. Stool assay for toxins A and B is positive. What is the most likely causative organism?
4. Which of the following is a key characteristic of osmotic diarrhea, such as that caused by lactase deficiency?
5. Oral Rehydration Solution (ORS) is effective in treating dehydration from secretory diarrhea because it utilizes which transport mechanism in the small intestine?
6. A child presents with acute watery diarrhea and vomiting. The most common viral cause of severe gastroenteritis in young children worldwide is:
7. Which of the following pathogens is a common cause of traveler’s diarrhea and produces both a heat-labile (LT) and a heat-stable (ST) enterotoxin?
8. A patient presents with bloody diarrhea, abdominal cramps, and fever. Stool microscopy reveals numerous leukocytes. Which of the following organisms is LEAST likely to cause this type of inflammatory diarrhea?
9. A patient with a neuroendocrine tumor presents with episodic watery diarrhea, flushing, and bronchospasm. These symptoms are characteristic of excess secretion of which substance?
10. Hemolytic Uremic Syndrome (HUS) is a severe complication characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It is most commonly associated with which pathogen?
11. A camper returns from a trip with foul-smelling, fatty stools (steatorrhea), bloating, and flatulence. Microscopic examination of a stool sample is likely to reveal cysts or trophozoites of which organism?
12. Chronic diarrhea is defined as diarrhea lasting for more than:
13. The “rice water” appearance of stool is a classic sign of infection with which pathogen?
14. A patient with AIDS and a CD4 count of 40 cells/mm³ develops chronic, profuse watery diarrhea. Acid-fast staining of the stool reveals oocysts. What is the most probable etiologic agent?
15. The use of antibiotics is generally NOT recommended for uncomplicated E. coli O157:H7 infection because it may increase the risk of:
16. Which of the following is the most appropriate first-line treatment for non-severe Clostridioides difficile infection?
17. A patient presents with chronic diarrhea, weight loss, arthralgia, and neurological symptoms. A small bowel biopsy reveals PAS-positive macrophages in the lamina propria. What is the diagnosis?
18. Fecal calprotectin is a useful non-invasive marker for which type of diarrhea?
19. A 25-year-old female reports chronic abdominal pain that is relieved by defecation, associated with alternating periods of diarrhea and constipation. There are no alarm features like weight loss or rectal bleeding. This clinical picture is most consistent with:
20. What is the mechanism of the heat-stable (ST) toxin of ETEC?
21. Diarrhea caused by VIPoma (vasoactive intestinal peptide-secreting tumor) is characterized by:
22. Which of these pathogens is known for causing diarrhea that can mimic appendicitis due to mesenteric adenitis?
23. Sorbitol, a sugar alcohol used in “sugar-free” products, can cause diarrhea through which mechanism?
24. The stool osmotic gap is calculated using the formula: 290 – 2 * ([Stool Na+] + [Stool K+]). A value greater than 125 mOsm/kg is highly suggestive of:
25. Brainerd diarrhea is a syndrome of acute-onset, chronic watery diarrhea lasting for months, typically following an outbreak. What is its key characteristic?
