Differential Diagnosis for Adult with 3 Week History of Diarrhea
Single Most Likely Diagnosis
- Infectious gastroenteritis: This is the most common cause of acute and sometimes prolonged diarrhea in adults, often due to viral, bacterial, or parasitic infections. The 3-week duration could represent a prolonged infection or a post-infectious complication.
Other Likely Diagnoses
- Irritable Bowel Syndrome (IBS): Although IBS typically presents with a longer history of symptoms, it could be considered if the diarrhea started recently and has been persistent. The diagnosis would require ruling out other causes and fitting the Rome criteria.
- Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can present with chronic diarrhea. The 3-week history might be an initial presentation, especially if the disease is mild.
- Medication-induced diarrhea: Various medications, including antibiotics, can cause diarrhea as a side effect. The history of starting a new medication around the time of symptom onset would support this diagnosis.
Do Not Miss Diagnoses
- Clostridioides difficile infection: This bacterial infection can cause severe diarrhea and is often associated with antibiotic use. It's crucial to consider this diagnosis due to its potential severity and the need for specific treatment.
- Giardiasis: Infection with Giardia lamblia can cause prolonged diarrhea and is a consideration, especially in individuals with exposure to contaminated water or travel history.
- HIV infection: Diarrhea can be a presenting symptom of HIV infection, particularly in the acute phase. Given the potential for severe immunocompromise, missing this diagnosis could have significant consequences.
Rare Diagnoses
- Microscopic colitis: This condition involves inflammation of the colon and can cause chronic, watery diarrhea. It's more common in older adults and those with a history of certain medications.
- Whipple's disease: A rare, systemic bacterial infection that can cause diarrhea among other symptoms. It's essential to consider in cases where diarrhea is accompanied by weight loss, arthralgias, and neurological symptoms.
- Lymphocytic colitis: Similar to microscopic colitis, it's a rare condition causing chronic diarrhea, often associated with a history of smoking and certain autoimmune diseases.