Differential Diagnosis

The patient presents with a history of diarrhea triggered by junk food and alcohol, with persistent symptoms despite a normal stool test. The symptoms have been ongoing for a year, with a previous episode of similar symptoms during a stressful period (10&12 board exams) that resolved on its own. Here's a differential diagnosis based on the provided information:

• Single most likely diagnosis:
  • Irritable Bowel Syndrome (IBS): The patient's symptoms of diarrhea, gas, and increased urge to have a bowel movement after eating certain foods, along with a history of stress-induced exacerbation, are consistent with IBS. The normal stool test and the chronic nature of the symptoms also support this diagnosis.
• Other Likely diagnoses:
  • Lactose intolerance or other food intolerances: The patient's symptoms are triggered by specific foods (junk food, alcohol), which could indicate an intolerance to certain components of these foods.
  • Inflammatory Bowel Disease (IBD): Although the stool test was normal, IBD (such as Crohn's disease or ulcerative colitis) can present with similar symptoms and should be considered, especially if the symptoms persist or worsen over time.
  • Small Intestine Bacterial Overgrowth (SIBO): This condition can cause similar gastrointestinal symptoms, including diarrhea, gas, and bloating, and can be triggered by food intake.
• Do Not Miss diagnoses:
  • Infectious causes (e.g., giardiasis, amoebiasis): Although the stool test was negative, it's essential to consider infectious causes, especially if the patient has a history of travel or exposure to contaminated food or water.
  • Celiac disease: This autoimmune disorder can cause chronic diarrhea, abdominal pain, and other gastrointestinal symptoms, and can be triggered by gluten intake.
  • Colon cancer: Although rare in young adults, colon cancer can present with changes in bowel habits, including diarrhea, and should be considered if other symptoms such as weight loss, blood in stool, or abdominal pain are present.
• Rare diagnoses:
  • Microscopic colitis: A rare condition characterized by chronic diarrhea, often with a normal colonoscopy and stool tests.
  • Bile acid diarrhea: A condition where the body produces too much bile acid, leading to chronic diarrhea.
  • Hormonal imbalances (e.g., thyroid disorders): Certain hormonal imbalances can cause changes in bowel habits, including diarrhea.