Differential Diagnosis for Diarrhea in a Patient Returning from Mexico

Single Most Likely Diagnosis

• Traveler's Diarrhea (most commonly caused by Enterotoxigenic Escherichia coli - ETEC): This is the most common cause of diarrhea in travelers to Mexico, often due to consumption of contaminated food or water. The symptoms typically include watery diarrhea, abdominal cramps, and occasionally fever.

Other Likely Diagnoses

• Norovirus: Highly contagious and can cause outbreaks, especially in areas with poor sanitation. Symptoms include diarrhea, vomiting, and stomach cramping.
• Giardiasis (Giardia lamblia): A common intestinal parasite that can be contracted through contaminated water. Symptoms include diarrhea, abdominal cramps, and weight loss.
• Shigellosis (Shigella spp.): Bacterial infection causing diarrhea, often with blood and mucus, abdominal pain, and fever.
• Salmonellosis (Salmonella spp.): Bacterial infection leading to diarrhea, fever, and abdominal cramps, often associated with food poisoning.

Do Not Miss Diagnoses

• Cholera (Vibrio cholerae): Although less common, it's critical to consider due to its potential for severe dehydration and high mortality if not treated promptly. It's characterized by profuse, watery diarrhea.
• Amoebic Dysentery (Entamoeba histolytica): Can cause severe diarrhea with blood and mucus, and if not treated, can lead to complications like liver abscess.
• Cyclosporiasis (Cyclospora cayetanensis): A parasitic infection that can cause prolonged diarrhea, weight loss, and fatigue. It's often associated with imported produce.

Rare Diagnoses

• Cryptosporidiosis (Cryptosporidium spp.): A parasitic infection that can cause diarrhea, more commonly seen in immunocompromised patients.
• Viral Gastroenteritis (e.g., Rotavirus, Adenovirus): While common in children, these viruses can also affect adults, especially in areas with poor sanitation.

Appropriate Antibiotic

For the treatment of bacterial causes of diarrhea, such as ETEC, Shigella, or Salmonella, antibiotics like Azithromycin or Ciprofloxacin may be prescribed, depending on the suspected pathogen and local resistance patterns. However, antibiotic treatment should be guided by stool test results and medical consultation, as not all causes of diarrhea require antibiotic therapy.