Differential Diagnosis

The patient presents with a history of diarrhea following junk food consumption, which persisted for 20 days despite a stool test showing no abnormalities. The patient also reports a history of urge and gassiness during periods of stress, such as during board exams, which resolved once the stressor was removed. Based on this information, the following differential diagnoses can be considered:

• Single Most Likely Diagnosis

  • Irritable Bowel Syndrome (IBS): This diagnosis is likely due to the patient's history of stress-induced gastrointestinal symptoms, the onset of diarrhea after a stressful event (consumption of junk food, which can be a trigger), and the chronic nature of the symptoms despite negative stool tests. IBS is a functional gastrointestinal disorder characterized by abdominal pain, bloating, and changes in bowel movements, which can be exacerbated by stress and certain foods.

• Other Likely Diagnoses

  • Inflammatory Bowel Disease (IBD): Although the stool test was negative, IBD (including Crohn's disease and ulcerative colitis) could still be considered, especially if the patient has persistent symptoms. However, the absence of blood in the stool, weight loss, or other systemic symptoms makes this less likely.
  • Functional Dyspepsia: Given the patient's history of gassiness and urge to have a bowel movement during stressful periods, functional dyspepsia could be a contributing factor, especially if the patient experiences upper gastrointestinal symptoms like bloating or discomfort.
  • Food Intolerance: The patient's symptoms started after consuming junk food, which could indicate a food intolerance (e.g., lactose intolerance, fructose malabsorption). However, the persistence of symptoms for 20 days makes a simple food intolerance less likely.

• Do Not Miss Diagnoses

  • Infectious Causes: Although the stool test was negative, it's crucial not to miss infectious causes like giardiasis or other parasitic infections, which can have negative initial tests but still cause chronic diarrhea.
  • Celiac Disease: An autoimmune reaction to gluten, which can cause chronic diarrhea, abdominal pain, and malabsorption. It's essential to consider this diagnosis due to its potential for long-term complications if left untreated.
  • Colon Cancer: Although rare in young individuals, if the patient has a family history or other risk factors, colon cancer should be considered, especially with persistent diarrhea.

• Rare Diagnoses

  • Microscopic Colitis: A condition characterized by chronic, watery diarrhea, which can be diagnosed through a colonoscopy and biopsy. It's more common in older adults but should be considered in cases of chronic, unexplained diarrhea.
  • Bile Acid Diarrhea: A condition where the body produces too much bile acid, leading to chronic diarrhea. It's a rare cause of diarrhea but can be considered if other diagnoses are ruled out.
  • Hormonal Imbalances: Certain hormonal imbalances, such as those seen in thyroid disorders, can cause gastrointestinal symptoms, including diarrhea. However, these would typically be accompanied by other systemic symptoms.