Differential Diagnosis for Watery Diarrhea in a 68-Year-Old Male
Single Most Likely Diagnosis
- Viral Gastroenteritis: This is a common cause of watery diarrhea in adults, often presenting with a sudden onset of symptoms without blood, abdominal pain, fever, or vomiting. The duration of 10 days could be consistent with a viral etiology, especially if the patient has been exposed to a viral gastroenteritis outbreak or has recently traveled.
Other Likely Diagnoses
- Bacterial Overgrowth: This condition can cause chronic watery diarrhea, especially in older adults. It might be considered if the patient has a history of abdominal surgery, diabetes, or uses medications that slow gut motility.
- Irritable Bowel Syndrome (IBS): Although IBS can present with a variety of symptoms, the subtype IBS-D (diarrhea-predominant) could be a consideration, especially if the patient reports a long-standing history of similar symptoms.
- Medication-Induced Diarrhea: Many medications can cause diarrhea as a side effect. Given the patient's age, he may be on multiple medications, one of which could be contributing to his symptoms.
- Lactose Intolerance or Other Carbohydrate Malabsorption: These conditions can lead to watery diarrhea after consuming lactose or other poorly absorbed carbohydrates.
Do Not Miss Diagnoses
- Clostridioides difficile (C. diff) Infection: Although the patient does not have fever or abdominal pain, C. diff infection can sometimes present atypically, especially in older adults. It's crucial to consider this diagnosis due to its potential severity and the need for specific treatment.
- Giardiasis: This parasitic infection can cause prolonged watery diarrhea. It might be less likely but is important to consider, especially if the patient has been camping, drinking untreated water, or has had exposure to someone with giardiasis.
- Colorectal Cancer: While less likely to present solely with watery diarrhea, it's a critical diagnosis not to miss, especially in an older adult. Chronic blood loss could lead to iron deficiency anemia, but the primary symptom here is diarrhea.
Rare Diagnoses
- Whipple's Disease: A rare, systemic bacterial infection that can cause chronic diarrhea among other symptoms. It's very uncommon but could be considered if other diagnoses are ruled out and the patient has systemic symptoms like weight loss or arthralgias.
- VIPoma: A rare endocrine tumor that secretes vasoactive intestinal peptide (VIP), leading to a syndrome of profound watery diarrhea, hypokalemia, and achlorhydria. It's an extremely rare cause of diarrhea but is mentioned due to its distinct clinical presentation.