Differential Diagnosis for Case 8

The patient presents with acute onset of diffuse abdominal pain, watery diarrhea, fatigue, dizziness, palpitations, and a history of pseudomembranous colitis. The following differential diagnoses are considered:

• Single Most Likely Diagnosis
  • C. difficile infection: Given the patient's history of pseudomembranous colitis, recent episodes of diarrhea, and the detection of C. difficile toxin in the stool, this diagnosis is the most likely. The presence of occult blood and many leukocytes in the stool further supports this diagnosis.
• Other Likely Diagnoses
  • Inflammatory bowel disease (IBD): The patient's symptoms of abdominal pain, diarrhea, and presence of leukocytes in the stool could also suggest IBD, such as ulcerative colitis or Crohn's disease.
  • Gastroenteritis: The acute onset of symptoms could be indicative of a viral or bacterial gastroenteritis, although the absence of fever and negative stool tests for common pathogens make this less likely.
• Do Not Miss Diagnoses
  • Ischemic colitis: This condition can present with abdominal pain, diarrhea, and occult blood in the stool. Given the patient's age and symptoms, ischemic colitis is a critical diagnosis not to miss, as it can lead to significant morbidity and mortality if not promptly treated.
  • Infectious colitis (e.g., Salmonella, Shigella, E. coli): Although initial stool tests were negative, it's essential to consider other infectious causes of colitis, as they can have severe consequences if left untreated.
• Rare Diagnoses
  • Microscopic colitis: This condition is characterized by chronic watery diarrhea and can be caused by lymphocytic or collagenous colitis. It's a less common diagnosis but should be considered if other causes are ruled out.
  • Diverticulitis: Although less likely given the patient's symptoms, diverticulitis can cause abdominal pain, diarrhea, and occult blood in the stool, especially in older adults.

To help arrive at a final diagnosis, a cytochemical stain such as Gram stain could be used to identify the presence of bacteria, including C. difficile. Additionally, endoscopy with biopsy could be performed to visualize the colon and obtain tissue samples for histopathological examination, which can help confirm the diagnosis of pseudomembranous colitis or other conditions such as IBD or ischemic colitis.