What is the diagnosis for an 8-year-old patient presenting with abdominal pain, diarrhea, and a history of vomiting, who recently received a single dose of prednisone (corticosteroid) for an asthma (chronic obstructive airway disease) exacerbation, with symptoms worsening postprandially and accompanied by a subjective feeling of feverishness?

Viral Gastroenteritis: This is the most likely diagnosis given the symptoms of stomach pain, diarrhea, and vomiting, which are classic for a viral gastrointestinal infection. The fact that symptoms worsen after eating and the patient feels feverish also supports this diagnosis.

Food Poisoning: Given that symptoms are worse after eating, food poisoning is a plausible diagnosis. The recent history of taking prednisone could potentially mask some symptoms or alter the immune response, but it's less likely to be directly related to the gastrointestinal symptoms.
Inflammatory Bowel Disease (IBD) Exacerbation: Although less common in children, IBD (such as Crohn's disease or ulcerative colitis) could present with similar symptoms. The recent use of prednisone for an asthma exacerbation might complicate the diagnosis, as corticosteroids are also used to treat IBD.
Irritable Bowel Syndrome (IBS): This could be considered, especially if the symptoms persist and no infectious cause is found. However, the acute onset and presence of fever make this less likely as a primary diagnosis.

Appendicitis: Although the symptoms do not perfectly align with classic appendicitis (which typically presents with pain migrating to the right lower quadrant), it's crucial not to miss this diagnosis due to its potential for severe complications if not promptly treated.
Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause bowel obstruction and ischemia. It's more common in younger children but should be considered, especially with symptoms of abdominal pain and vomiting.
Infectious Diarrhea due to Bacterial or Parasitic Causes: Certain bacterial (e.g., Salmonella, Shigella) or parasitic infections can cause severe diarrhea and abdominal pain. These infections might require specific treatments and can have serious complications if not addressed.

Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, which could be considered given the patient's history of asthma (an atopic condition) and recent corticosteroid use.
Celiac Disease: An autoimmune reaction to gluten, leading to small intestine damage. While it can cause chronic diarrhea and abdominal pain, its acute presentation would be unusual.
Giardiasis: A parasitic infection that can cause diarrhea, abdominal cramps, and dehydration. It's less common but should be considered, especially if the patient has been exposed to contaminated water or has traveled to areas where Giardia is prevalent.