Differential Diagnosis for Nausea, Vomiting, and Diarrhea

The patient presents with a 10-day history of nausea and vomiting followed by 2 weeks of diarrhea, without any recent introduction of new medications or supplements. The initial considerations to rule out (R/O) include pancreatitis and influenza. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis
  • Viral gastroenteritis: This is a common cause of nausea, vomiting, and diarrhea, especially given the sequence and duration of symptoms. The lack of recent travel, antibiotic use, or exposure to sick contacts does not rule out viral gastroenteritis, as it can be spread through various means including contaminated food and water or person-to-person contact.
• Other Likely Diagnoses
  • Food poisoning: Although the patient denies new medications or supplements, food poisoning could still be a consideration, especially if the patient has consumed undercooked or contaminated food.
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis could present with chronic diarrhea and intermittent nausea and vomiting, though they typically have a more gradual onset and are accompanied by other symptoms like abdominal pain and weight loss.
  • Irritable bowel syndrome (IBS): This is a functional gastrointestinal disorder that could explain the patient's symptoms, especially if there's a pattern of bowel habits and associated bloating or abdominal pain.
• Do Not Miss Diagnoses
  • Pancreatitis: As mentioned, pancreatitis is a critical diagnosis to consider, especially if the patient has severe abdominal pain, though the primary symptoms here are gastrointestinal without specific mention of pain.
  • Inflammatory or infectious causes: Conditions like appendicitis, diverticulitis, or intestinal infections (e.g., Clostridioides difficile) could present with similar symptoms and require prompt diagnosis and treatment.
  • Cancer: Although less likely, gastrointestinal cancers (e.g., gastric, pancreatic, or colorectal cancer) can cause chronic symptoms like nausea, vomiting, and changes in bowel habits.
• Rare Diagnoses
  • Whipple's disease: A rare, systemic bacterial infection that can cause chronic diarrhea, weight loss, and abdominal pain.
  • Tropical sprue: A rare condition that affects the small intestine's ability to absorb nutrients, leading to chronic diarrhea and malabsorption, typically seen in individuals who have traveled to or live in tropical regions.
  • Giardiasis: An intestinal infection caused by the parasite Giardia lamblia, which can lead to chronic diarrhea, though it's more commonly associated with travel or exposure to contaminated water.

Each of these diagnoses should be considered in the context of the patient's full clinical presentation, including any additional symptoms, physical examination findings, and diagnostic test results.