Differential Diagnosis for Sudden Onset of IBS-like Symptoms

• Single most likely diagnosis:
  • Post-Infectious IBS (PI-IBS): This is the most likely diagnosis for sudden onset of IBS-like symptoms. PI-IBS occurs after a bout of gastroenteritis, which can trigger the onset of IBS symptoms in some individuals. The sudden onset is consistent with the history of a recent infection.
• Other Likely diagnoses:
  • Classic IBS with sudden exacerbation: Although classic IBS typically has a gradual onset, it's possible for symptoms to suddenly worsen due to various factors such as stress, dietary changes, or hormonal fluctuations.
• Do Not Miss:
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with sudden onset of symptoms similar to IBS, including abdominal pain, changes in bowel habits, and weight loss. Missing this diagnosis could lead to delayed treatment and potentially severe complications.
  • Gastrointestinal infections: Certain infections, such as Clostridioides difficile (C. diff), can cause sudden onset of symptoms that mimic IBS. Failing to diagnose and treat these infections promptly can lead to severe outcomes.
• Rare diagnoses:
  • Carcinoid syndrome: A rare condition caused by a neuroendocrine tumor that can produce substances leading to diarrhea, abdominal pain, and other symptoms similar to IBS. Although rare, it's a diagnosis that should be considered in the differential to avoid missing a potentially treatable condition.
  • Small intestine bacterial overgrowth (SIBO): While not as rare as carcinoid syndrome, SIBO can cause IBS-like symptoms and should be considered, especially if there's a history of abdominal surgery, diabetes, or other conditions that predispose to SIBO.