Differential Diagnosis for Diarrhea in a Healthy 50-Year-Old

Single Most Likely Diagnosis

• Viral Gastroenteritis: This is the most common cause of acute diarrhea in adults, often caused by norovirus or rotavirus, and typically presents with non-bloody diarrhea, vomiting, and abdominal cramps. The duration of symptoms can range from a few days to over a week, which aligns with the 5-day duration in this case.

Other Likely Diagnoses

• Bacterial Gastroenteritis: While less common than viral causes, bacterial infections such as those from Salmonella, Campylobacter, or E. coli can cause non-bloody diarrhea. These infections are often foodborne or waterborne.
• Food Poisoning: Similar to bacterial gastroenteritis, food poisoning from consuming contaminated or spoiled food can lead to non-bloody diarrhea.
• Medication-Induced Diarrhea: Certain medications, including antibiotics, antacids, and laxatives, can cause diarrhea as a side effect.
• Irritable Bowel Syndrome (IBS): Although IBS is a chronic condition, an acute exacerbation could present with a short-term increase in diarrhea symptoms.

Do Not Miss Diagnoses

• Inflammatory Bowel Disease (IBD): While less likely, conditions like Crohn's disease or ulcerative colitis can present with diarrhea. Although they typically cause bloody diarrhea, early stages or certain types might present with non-bloody diarrhea.
• Celiac Disease: An autoimmune reaction to gluten can cause chronic diarrhea, but the onset can sometimes appear acute.
• Giardiasis: Infection with Giardia lamblia can cause prolonged diarrhea and is a consideration, especially if the patient has been camping, drinking untreated water, or has had exposure to someone with the infection.
• Ischemic Bowel: Although rare, ischemia to the bowel can cause acute diarrhea and is a medical emergency.

Rare Diagnoses

• Microscopic Colitis: A condition characterized by chronic, watery diarrhea, often without blood, and diagnosed by colonoscopy and biopsy.
• Whipple's Disease: A rare, systemic bacterial infection that can cause diarrhea among other symptoms.
• Lactose Intolerance or Other Carbohydrate Malabsorption: Conditions where the body cannot digest certain sugars, leading to diarrhea after consuming these substances.
• Hormone-Producing Tumors: Rare tumors like VIPomas can cause chronic, watery diarrhea due to the excessive production of vasoactive intestinal peptide (VIP).