Viral Gastroenteritis: This is the most common cause of diarrhea and vomiting, often accompanied by an elevated white blood cell (WBC) count due to the body's inflammatory response. Viruses such as norovirus, rotavirus, and adenovirus are frequent culprits.

Bacterial Gastroenteritis: Bacteria like Salmonella, Shigella, and Campylobacter can cause severe diarrhea and vomiting, with an elevated WBC count indicating a significant inflammatory response.
Food Poisoning: Similar to bacterial gastroenteritis, food poisoning from consuming contaminated food can lead to these symptoms, with the elevated WBC count reflecting the body's response to the toxin or pathogen.
Inflammatory Bowel Disease (IBD) Flare: Conditions like Crohn's disease and ulcerative colitis can cause diarrhea, vomiting, and an elevated WBC count during a flare-up, due to increased inflammation in the gastrointestinal tract.

Appendicitis: Although it primarily presents with abdominal pain, appendicitis can sometimes cause diarrhea and vomiting, especially if the appendix ruptures. The elevated WBC count is a key indicator of the infection. Missing this diagnosis can lead to severe complications, including peritonitis and sepsis.
Intussusception: A condition where a part of the intestine slides into an adjacent part, intussusception can cause bowel obstruction, leading to vomiting and diarrhea. It's a medical emergency that requires prompt intervention.
Mesenteric Ischemia: Reduced blood flow to the intestines can cause severe abdominal pain, diarrhea, and vomiting. The elevated WBC count indicates tissue injury. This condition is life-threatening and requires immediate medical attention.

Whipple's Disease: A rare, systemic bacterial infection caused by Tropheryma whipplei, which can lead to malabsorption, diarrhea, weight loss, and joint pain. The diagnosis is often delayed due to its rarity and nonspecific symptoms.
Eosinophilic Gastroenteritis: A condition characterized by the infiltration of eosinophils into the gastrointestinal wall, leading to inflammation, diarrhea, and sometimes vomiting. It's more common in individuals with a history of atopic diseases.
Giardiasis: An intestinal infection caused by the Giardia lamblia parasite, which can result in chronic diarrhea, weight loss, and malabsorption. While not extremely rare, it's less common in developed countries and might be overlooked in the differential diagnosis.