Irritable bowel syndrome US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Irritable bowel syndrome. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Irritable bowel syndrome US Medical PG Question 1: A 31-year-old woman visits the clinic with chronic diarrhea on most days for the past four months. She also complains of lower abdominal discomfort and cramping, which is relieved by episodes of diarrhea. She denies any recent change in her weight. Bowel movements are preceded by a sensation of urgency, associated with mucus discharge, and followed by a feeling of incomplete evacuation. The patient went camping several months earlier, and another member of her camping party fell ill recently. Her temperature is 37° C (98.6° F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Her physical examination is unremarkable. A routine stool examination is within normal limits and blood test results show:
Hb% 13 gm/dL
Total count (WBC): 11,000/mm3
Differential count:
Neutrophils: 70%
Lymphocytes: 25%
Monocytes: 5%
ESR: 10 mm/hr
What is the most likely diagnosis?
- A. Giardiasis
- B. Ulcerative colitis
- C. Crohn’s disease
- D. Irritable bowel syndrome (Correct Answer)
- E. Laxative abuse
Irritable bowel syndrome Explanation: ***Irritable bowel syndrome (IBS)***
- The patient's symptoms of chronic diarrhea, abdominal discomfort relieved by defecation, urgency, and incomplete evacuation, without significant weight loss or alarming signs, are highly characteristic of **Irritable Bowel Syndrome** meeting **Rome IV criteria**.
- The camping history suggests possible infectious gastroenteritis, but the **chronic duration (4 months)**, **normal stool examination**, and **absence of systemic illness** make infectious causes unlikely.
- The mild WBC elevation and normal ESR are non-specific findings; IBS is a **functional disorder** without inflammatory markers.
*Giardiasis*
- While giardiasis can cause chronic diarrhea, it often presents with **malabsorption symptoms** such as fatty stools, weight loss, and nutrient deficiencies.
- The routine stool examination being within normal limits makes giardiasis less likely, as **Giardia cysts or trophozoites** would typically be detected on microscopy.
*Ulcerative colitis*
- Ulcerative colitis is an **inflammatory bowel disease** typically characterized by bloody diarrhea, abdominal pain, and systemic symptoms like fever and weight loss.
- The patient's symptoms include the absence of blood in stools and no weight loss, with **normal ESR**, which makes ulcerative colitis unlikely.
*Crohn's disease*
- Crohn's disease is another **inflammatory bowel disease** that can affect any part of the GI tract and presents with chronic diarrhea, abdominal pain, and often systemic symptoms like weight loss, fever, or perianal disease.
- The lack of weight loss, systemic inflammation markers (normal ESR), and absence of blood or inflammatory markers in the stool make Crohn's disease less probable.
*Laxative abuse*
- Laxative abuse can cause chronic diarrhea, but it's typically associated with a history of **eating disorders** (anorexia nervosa, bulimia nervosa) or other psychological conditions, which are not mentioned in this case.
- The patient's description of abdominal discomfort relieved by defecation, urgency, and incomplete evacuation is more consistent with **IBS** (a functional bowel disorder) rather than solely laxative-induced diarrhea.
Irritable bowel syndrome US Medical PG Question 2: A 32-year-old female comes to the physician because of recurrent episodes of abdominal pain, bloating, and loose stools lasting several days to a couple weeks. She has had these episodes since she was 24 years old but they have worsened over the last 6 weeks. The site of the abdominal pain and the intensity of pain vary. She has around 3–4 bowel movements per day during these episodes. Menses are regular at 31 day intervals with moderate flow; she has moderate pain in her lower abdomen during menstruation. She moved from a different city 2 months ago to start a new demanding job. Her mother has been suffering from depression for 10 years. She does not smoke or drink alcohol. Her own medications include multivitamins and occasionally naproxen for pain. Temperature is 37.4°C (99.3°F), pulse is 88/min, and blood pressure is 110/82 mm Hg. Abdominal examination shows no abnormalities. Laboratory studies show:
Hemoglobin 14.1 g/dL
Leukocyte count 8100/mm3
Erythrocyte sedimentation rate 15 mm/h
Serum
Glucose 96 mg/dL
Creatinine 1.1 mg/dL
IgA anti-tissue transglutaminase antibody negative
Urinalysis shows no abnormalities. Further evaluation is most likely to show which of the following in this patient?
- A. Abdominal pain at night
- B. Cutaneous flushing
- C. Bright red blood in the stool
- D. Weight loss
- E. Relief of abdominal pain after defecation (Correct Answer)
Irritable bowel syndrome Explanation: ***Relief of abdominal pain after defecation***
- This is a key diagnostic criterion for Irritable Bowel Syndrome (IBS), as the symptoms in this patient are highly suggestive of **IBS-diarrhea predominant**.
- The patient's history of recurrent abdominal pain, bloating, and loose stools (3-4 bowel movements/day), absence of alarm symptoms, and worsening with stress (new job) are consistent with IBS.
*Abdominal pain at night*
- **Nocturnal abdominal pain** or bowel movements are considered **alarm symptoms** that warrant further investigation for organic causes such as inflammatory bowel disease (IBD) or malignancy.
- The symptoms described are typical of functional GI disorders like IBS, where pain usually improves with defecation and does not typically awaken the patient from sleep.
*Cutaneous flushing*
- **Cutaneous flushing** is a common symptom associated with **carcinoid syndrome**, often accompanied by diarrhea, wheezing, and right-sided heart valve disease.
- Other common causes of flushing include *rosacea*, *mastocytosis*, and *medication-induced flushing*; none of these fit the patient's primary GI symptoms.
*Bright red blood in the stool*
- The presence of **bright red blood in the stool** is an **alarm symptom** that suggests a structural gastrointestinal problem such as hemorrhoids, anal fissures, diverticulosis, or inflammatory bowel disease (IBD), or malignancy.
- This symptom would prompt more invasive diagnostic procedures (e.g., colonoscopy) to rule out serious conditions.
*Weight loss*
- Unintentional **weight loss** is an **alarm symptom** in the context of gastrointestinal complaints, indicating a potential organic cause such as inflammatory bowel disease, celiac disease (which was ruled out by negative anti-tTG antibodies), malabsorption, or malignancy.
- Patients with IBS typically do not experience significant weight loss, and their symptoms are often functional rather than structural.
Irritable bowel syndrome US Medical PG Question 3: A 24-year-old man comes to the physician with a 2-day history of fever, crampy abdominal pain, and blood-tinged diarrhea. He recently returned from a trip to Mexico. His temperature is 38.2°C (100.8°F). Abdominal examination shows diffuse tenderness to palpation; bowel sounds are hyperactive. Stool cultures grow nonlactose fermenting, oxidase-negative, gram-negative rods that do not produce hydrogen sulfide on triple sugar iron agar. Which of the following processes is most likely involved in the pathogenesis of this patient's condition?
- A. Dissemination via bloodstream
- B. Overactivation of adenylate cyclase
- C. Flagella-mediated gut colonization
- D. Invasion of colonic microfold cells
- E. Inhibition of host cytoskeleton organization (Correct Answer)
Irritable bowel syndrome Explanation: ***Inhibition of host cytoskeleton organization***
- The patient's symptoms (fever, crampy abdominal pain, blood-tinged diarrhea) and the microbiological findings (**nonlactose fermenting, oxidase-negative, gram-negative rods** that do not produce hydrogen sulfide) are characteristic of **Shigella infection**.
- **Shigella** invades colonic epithelial cells and manipulates the host cell's **actin cytoskeleton** through effector proteins (IpaA, IpaB, IpaC) delivered via a **Type III secretion system**.
- This cytoskeletal disruption enables **intracellular movement** via actin-based motility and **cell-to-cell spread**, allowing Shigella to evade immune defenses while causing characteristic inflammatory dysentery.
*Dissemination via bloodstream*
- While some bacterial infections cause bacteremia, **Shigella** infections are typically localized to the **gastrointestinal tract** and do not commonly disseminate systemically via the bloodstream.
- **Bacteremia** due to *Shigella* is rare and usually occurs only in immunocompromised individuals or young children with severe disease.
*Overactivation of adenylate cyclase*
- **Overactivation of adenylate cyclase** producing **cyclic AMP** and leading to **secretory diarrhea** is characteristic of toxins like **cholera toxin** or **heat-labile enterotoxin of E. coli**.
- **Shigella** primarily causes **inflammatory dysentery** through mucosal invasion and damage, not through this mechanism of fluid secretion.
*Flagella-mediated gut colonization*
- Many bacteria use **flagella** for motility and colonization, but **Shigella** species are notably **non-motile** and **lack flagella**.
- Their pathogenesis relies on invasion and intracellular spread rather than flagella-driven colonization.
*Invasion of colonic microfold cells*
- While **Shigella does initially invade through M cells (microfold cells)** in the colonic epithelium to gain entry into the lamina propria, this is just the **initial entry step**, not the primary pathogenic mechanism that causes disease.
- The key pathogenic process that leads to the characteristic symptoms is the **disruption of the host cytoskeleton** that enables intracellular replication and lateral spread through epithelial cells, causing the inflammatory dysentery seen in this patient.
Irritable bowel syndrome US Medical PG Question 4: Which neurotransmitter primarily mediates slow synaptic transmission in the enteric nervous system?
- A. Substance P
- B. Serotonin
- C. Acetylcholine
- D. Nitric oxide (Correct Answer)
Irritable bowel syndrome Explanation: **Nitric oxide**
- **Nitric oxide (NO)** is a key **non-classical neurotransmitter** in the **enteric nervous system (ENS)**, mediating **slow synaptic transmission** due to its gaseous nature allowing for diffusion and longer-lasting effects.
- It is involved in **smooth muscle relaxation**, **vasodilation**, and diverse gastrointestinal functions, including **peristalsis** and **sphincter relaxation**.
*Substance P*
- **Substance P** is a **neuropeptide** that acts as an **excitatory neurotransmitter** in the ENS, primarily mediating **fast synaptic transmission** and smooth muscle contraction.
- It is involved in pain perception, inflammation, and is released by sensory neurons and some enteric neurons.
*Serotonin*
- **Serotonin (5-HT)** is a major neurotransmitter in the ENS, largely mediating **fast excitatory or inhibitory synaptic transmission** depending on the receptor subtype.
- It plays a crucial role in regulating gut motility, secretion, and visceral sensation, and is involved in both rapid signaling and neuromodulation.
*Acetylcholine*
- **Acetylcholine (ACh)** is the primary **excitatory neurotransmitter** of the **parasympathetic nervous system** within the ENS, mediating **fast synaptic transmission** by binding to nicotinic and muscarinic receptors.
- It is crucial for stimulating **smooth muscle contraction** (promoting peristalsis), increasing glandular secretions, and generally enhancing gut motility.
Irritable bowel syndrome US Medical PG Question 5: A 63-year-old woman comes to the physician because of diarrhea and weakness after her meals for 2 weeks. She has the urge to defecate 15–20 minutes after a meal and has 3–6 bowel movements a day. She also has palpitations, sweating, and needs to lie down soon after eating. One month ago, she underwent a distal gastrectomy for gastric cancer. She had post-operative pneumonia, which was treated with cefotaxime. She returned from a vacation to Brazil 6 weeks ago. Her immunizations are up-to-date. She is 165 cm (5 ft 5 in) tall and weighs 51 kg (112 lb); BMI is 18.6 kg/m2. Vital signs are within normal limits. Examination shows a well-healed abdominal midline surgical scar. The abdomen is soft and nontender. Bowel sounds are hyperactive. Rectal examination is unremarkable. Which of the following is the most appropriate next step in management?
- A. Dietary modifications (Correct Answer)
- B. Stool PCR test
- C. Octreotide therapy
- D. Metronidazole therapy
- E. Stool microscopy
Irritable bowel syndrome Explanation: ***Dietary modifications***
- This patient's symptoms (diarrhea, weakness, palpitations, sweating, and urge to defecate soon after meals) following a **distal gastrectomy** are classic for **dumping syndrome**. **Dietary modification** is the first-line treatment.
- Recommended modifications include **smaller, more frequent meals**, avoiding high-sugar foods, increasing protein and fiber, and separating solids from liquids during meals.
*Stool PCR test*
- While diarrhea is present, the patient's symptoms are strongly linked to her recent gastrectomy and meal ingestion rather than an infectious cause.
- A stool PCR test would be appropriate if there were other signs of infection, such as fever or severe abdominal pain, or if dietary modifications failed to resolve symptoms.
*Octreotide therapy*
- **Octreotide**, a somatostatin analog, is reserved for **severe cases of dumping syndrome** that do not respond to dietary modifications.
- It works by inhibiting the release of gastrointestinal hormones and slowing gastric emptying, but it is not the initial management step.
*Metronidazole therapy*
- **Metronidazole** is an antibiotic used to treat bacterial and parasitic infections. There is no evidence suggesting an infection in this patient.
- The timing of symptoms immediately post-meal points away from an infection and towards post-gastrectomy complications.
*Stool microscopy*
- Similar to a stool PCR, **stool microscopy** is used to identify parasites or other pathogens.
- Given the classic presentation of dumping syndrome following gastrectomy, an infectious cause is less likely, and other diagnostic tests should be pursued if dietary measures fail.
Irritable bowel syndrome US Medical PG Question 6: A 25-year-old woman presents with abdominal pain and discomfort for the past 3 days. She was diagnosed with irritable bowel syndrome (IBS) a couple of years ago, managed until recently with imipramine, psyllium, and loperamide. 5 days ago, because she had developed alternating diarrhea and constipation, bloating, and abdominal pain on her medication, she was started on alosetron. Her current temperature is 39.0°C (102.2°F), the heart rate is 115/min, the blood pressure is 90/60 mm Hg and the respiratory rate is 22/min. Abdominal examination shows diffuse tenderness to palpation with guarding but no rebound. Bowel sounds are hypoactive on auscultation. A fecal occult blood test is positive and laboratory tests show her white cell count to be 15,800/µL. Arterial blood gas (ABG) analysis reveals a metabolic acidosis. Which of the following is the most likely diagnosis in this patient?
- A. Perforated duodenal ulcer
- B. Pseudomembranous colitis
- C. Appendicitis
- D. Crohn’s disease
- E. Ischemic colitis (Correct Answer)
Irritable bowel syndrome Explanation: ***Ischemic colitis***
- The patient's presentation with **abdominal pain**, **fever**, **tachycardia**, **hypotension**, **diffuse tenderness with guarding**, **positive fecal occult blood**, **leukocytosis**, and **metabolic acidosis** after starting **alosetron** is highly suggestive of ischemic colitis. Alosetron, a 5-HT3 antagonist, can cause severe constipation and, rarely, **ischemic colitis**.
- The **hypoactive bowel sounds** and signs of **systemic inflammatory response** (fever, tachycardia, leukocytosis) further support a diagnosis of ischemic bowel compromise leading to colitis.
*Perforated duodenal ulcer*
- A perforated duodenal ulcer typically presents with sudden onset, **severe, sharp epigastric pain** that rapidly generalizes, often with a rigid, board-like abdomen and **rebound tenderness**, which is not seen here.
- While it can cause peritonitis and systemic signs, the history of recent medication change and more diffuse abdominal tenderness points away from an isolated perforation.
*Pseudomembranous colitis*
- Pseudomembranous colitis is primarily associated with **Clostridium difficile infection**, often following antibiotic use, and typically presents with severe watery diarrhea, not necessarily with a metabolic acidosis or overt signs of ischemia as seen in this case.
- While it can cause abdominal pain and systemic symptoms, the acute onset with severe tenderness and shock-like picture makes ischemic colitis more likely given the drug history.
*Appendicitis*
- Appendicitis typically presents with **periumbilical pain** that migrates to the **right lower quadrant**, often with localized tenderness at McBurney's point and rebound tenderness.
- The patient's **diffuse abdominal tenderness**, associated with such severe systemic symptoms and a history of specific medication use, is inconsistent with typical appendicitis.
*Crohn’s disease*
- Crohn's disease is a **chronic inflammatory bowel condition** characterized by transmural inflammation, often with intermittent abdominal pain, diarrhea, and weight loss, but it is less likely to present acutely with such severe, systemic signs and shock-like features without a clear exacerbating factor like acute ischemia.
- While Crohn's can cause complications like strictures or fistulas, an acute presentation resembling ischemic colitis with a clear provoking drug history is less common for an initial severe flare.
Irritable bowel syndrome US Medical PG Question 7: A 23-year-old woman presents with flatulence and abdominal cramping after meals. For the last year, she has been feeling uneasy after meals and sometimes has severe pain after eating breakfast in the morning. She also experiences flatulence and, on rare occasions, diarrhea. She says she has either cereal or oats in the morning which she usually consumes with a glass of milk. The patient is afebrile and vital signs are within normal limits. Physical examination is unremarkable. Which of the following drugs should be avoided in this patient?
- A. Pantoprazole
- B. Cimetidine
- C. Sucralfate
- D. Loperamide
- E. Magnesium hydroxide (Correct Answer)
Irritable bowel syndrome Explanation: ***Magnesium hydroxide***
- Magnesium hydroxide is an **osmotic laxative**, and its side effects include **diarrhea**, which the patient already experiences.
- In a patient presenting with symptoms suggestive of **lactose intolerance** (abdominal cramping, flatulence, and occasional diarrhea after consuming milk with cereal), a laxative intensifying these symptoms should be avoided.
*Pantoprazole*
- **Pantoprazole** is a proton pump inhibitor primarily used to reduce stomach acid, which is not indicated for the patient's symptoms.
- It would not worsen the patient's current symptoms of **flatulence** and **occasional diarrhea**.
*Cimetidine*
- **Cimetidine** is an H2 receptor antagonist used to decrease stomach acid, which is not relevant to the patient's symptoms of **lactose intolerance**.
- Its side effects generally do not include significant changes in **bowel habits** that would exacerbate the patient's presentation.
*Sucralfate*
- **Sucralfate** is a cytoprotective agent that forms a protective barrier in the stomach, primarily used for ulcers.
- It works locally in the gastrointestinal tract and is not known to cause symptoms like significant **flatulence** or **diarrhea**.
*Loperamide*
- **Loperamide** is an anti-diarrheal medication, which would be used to treat diarrhea, not avoided.
- It would likely alleviate the patient's occasional diarrhea rather than exacerbate it.
Irritable bowel syndrome US Medical PG Question 8: A 24-year-old man presents to the emergency department for severe abdominal pain for the past day. The patient states he has had profuse, watery diarrhea and abdominal pain that is keeping him up at night. The patient also claims that he sees blood on the toilet paper when he wipes and endorses having lost 5 pounds recently. The patient's past medical history is notable for IV drug abuse and a recent hospitalization for sepsis. His temperature is 99.5°F (37.5°C), blood pressure is 120/68 mmHg, pulse is 100/min, respirations are 14/min, and oxygen saturation is 98% on room air. On physical exam, you note a young man clutching his abdomen in pain. Abdominal exam demonstrates hyperactive bowel sounds and diffuse abdominal tenderness. Cardiopulmonary exam is within normal limits. Which of the following is the next best step in management?
- A. Vancomycin (Correct Answer)
- B. Mesalamine enema
- C. Metronidazole
- D. Clindamycin
- E. Supportive therapy and ciprofloxacin if symptoms persist
Irritable bowel syndrome Explanation: ***Vancomycin***
- The patient's history of **IV drug abuse**, recent **hospitalization for sepsis**, and severe abdominal symptoms with **bloody diarrhea** and **weight loss** are highly suggestive of **Clostridioides difficile infection (CDI)**.
- **Oral vancomycin** is the recommended first-line treatment for **severe C. difficile infection**, especially with signs like systemic illness (tachycardia) and marked abdominal tenderness.
*Mesalamine enema*
- **Mesalamine** is an **anti-inflammatory drug** primarily used for **mild to moderate ulcerative colitis**, particularly when the disease is limited to the rectum or rectosigmoid colon.
- While inflammatory bowel disease can cause bloody diarrhea, the acute presentation with recent hospitalization and IV drug use makes **infectious etiologies**, particularly CDI, much more likely.
*Metronidazole*
- **Metronidazole** is an antibiotic that was previously used for uncomplicated **C. difficile infection**.
- However, **oral vancomycin** is now preferred for **initial CDI episodes** due to superior efficacy, especially in severe cases, and metronidazole is generally reserved for non-severe cases if vancomycin is unavailable or not tolerated.
*Clindamycin*
- **Clindamycin** is an antibiotic notorious for being a common cause of **antibiotic-associated C. difficile infection**.
- Giving clindamycin in this scenario would likely **worsen the patient's condition** if C. difficile is indeed the cause, as it promotes C. difficile overgrowth.
*Supportive therapy and ciprofloxacin if symptoms persist*
- While **supportive care** (hydration, electrolyte management) is essential, it is **insufficient as the sole treatment** for severe C. difficile infection.
- **Ciprofloxacin** is an antibiotic that is **ineffective against C. difficile** and could potentially exacerbate the infection by disrupting the normal gut microbiota.
Irritable bowel syndrome US Medical PG Question 9: A 26-year-old woman presents with sudden-onset pain in her lower back. She says she was exercising in the gym several hours ago when she felt a sharp pain. The pain is radiating down the side of her leg and into her foot. On physical exam, her vital signs are as follows: HR 95, BP 120/70, T 37.2 degrees C. She has extreme pain shooting down her leg with a straight leg raise. Her sensation to light touch and pin-prick is intact throughout. Which of the following is the most likely diagnosis?
- A. Cauda equina syndrome
- B. Ankylosing spondylitis
- C. Osteomyelitis
- D. Spinal stenosis
- E. Disc herniation (Correct Answer)
Irritable bowel syndrome Explanation: ***Disc herniation***
- The sudden onset of **sharp back pain** radiating down the leg (**radiculopathy**) after physical exertion, coupled with a positive **straight leg raise test**, is highly indicative of a disc herniation.
- Radiating pain suggests nerve root compression, and the straight leg raise test stretches the sciatic nerve, aggravating the pain in cases of disc herniation.
*Cauda equina syndrome*
- This is a neurological emergency characterized by **saddle anesthesia**, bowel or bladder dysfunction, and progressive motor weakness in both legs.
- These severe neurological deficits are not present in the patient's presentation; sensation is intact, and no mention of bowel/bladder issues.
*Ankylosing spondylitis*
- Typically presents with **chronic inflammatory back pain** that improves with exercise and worsens with rest, often in younger males.
- It is a systemic inflammatory condition, and the acute, exertion-related onset of pain with radiculopathy described here is not characteristic.
*Osteomyelitis*
- This is an **infection of the bone**, usually accompanied by fever, localized tenderness, and systemic signs of infection.
- The patient's vital signs are stable, and there is no indication of infection, making osteomyelitis less likely.
*Spinal stenosis*
- Characterized by **neurogenic claudication**, where leg pain and numbness worsen with walking and improve with sitting or leaning forward.
- The acute onset of pain after an intense activity and the presence of a positive straight leg raise are not typical features of spinal stenosis.
Irritable bowel syndrome US Medical PG Question 10: A 52-year-old woman presents to the clinic with several days of vomiting and diarrhea. She also complains of headaches, muscle aches, and fever, but denies tenesmus, urgency, and bloody diarrhea. Past medical history is insignificant. When asked about any recent travel she says that she just came back from a cruise ship vacation. Her temperature is 37°C (98.6° F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Physical examination is non-contributory. Microscopic examination of the stool is negative for ova or parasites. What is the most likely diagnosis?
- A. Traveler’s diarrhea due to ETEC
- B. Irritable bowel syndrome
- C. Norovirus infection (Correct Answer)
- D. Giardiasis
- E. C. difficile colitis
Irritable bowel syndrome Explanation: ***Norovirus infection***
- The combination of **vomiting** and **diarrhea** along with a history of **cruise ship travel** is highly suggestive of norovirus. Norovirus is a common cause of gastroenteritis outbreaks in crowded settings like cruise ships, schools, and nursing homes.
- While fever, headaches, and muscle aches can be present, the absence of **bloody diarrhea** and **tenesmus** points away from bacterial dysentery.
*Traveler’s diarrhea due to ETEC*
- **Enterotoxigenic *E. coli* (ETEC)** is a common cause of traveler's diarrhea, but the primary symptom is typically **watery diarrhea** often without significant vomiting.
- While travel is a risk factor, **cruise ship outbreaks** are more characteristic of norovirus due to its highly contagious nature and short incubation period.
*Irritable bowel syndrome*
- **Irritable bowel syndrome (IBS)** is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain associated with altered bowel habits.
- It does not typically present with an acute onset of **vomiting, diarrhea, fever, and muscle aches** following a specific exposure like a cruise.
*Giardiasis*
- **Giardiasis** is caused by the parasite *Giardia lamblia* and typically presents with **prolonged watery diarrhea**, abdominal cramps, bloating, and malabsorption.
- The acute, self-limiting nature and prominent **vomiting** in this case are less typical for giardiasis, and stool microscopy was negative for ova or parasites.
*C. difficile colitis*
- ***C. difficile* colitis** is primarily associated with **recent antibiotic use** and symptoms include **severe watery diarrhea**, abdominal pain, and fever.
- There is no history of antibiotic use, and the cruise travel context and prominent vomiting are not typical for *C. difficile* infection.
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