Differential Diagnosis for Vomiting/Nausea and Associated Symptoms

Single Most Likely Diagnosis

• Viral Gastroenteritis: The patient's symptoms of vomiting, nausea, upset stomach, and episodes of diarrhea, along with a history of fever at the onset, are consistent with viral gastroenteritis. The fact that the symptoms have been intermittent and the patient has had periods of feeling better also supports this diagnosis.

Other Likely Diagnoses

• Inflammatory Bowel Disease (IBD): Although less common, the chronic nature of the symptoms (2-3 weeks) and the presence of diarrhea could suggest early signs of IBD, such as Crohn's disease or ulcerative colitis.
• Gastritis: The upset stomach and vomiting could be indicative of gastritis, possibly exacerbated by the use of over-the-counter medications like Dimetapp.
• Viral Pharyngitis: The sore throat and cough, worse in the morning and night, could be due to a viral pharyngitis, which is common in children and can coexist with gastrointestinal symptoms.

Do Not Miss Diagnoses

• Appendicitis: Although the patient's symptoms do not classically present as appendicitis (e.g., no specific mention of abdominal pain migrating to the right lower quadrant), it is crucial to consider this diagnosis due to its potential for severe consequences if missed.
• Food Poisoning: Certain types of food poisoning can cause prolonged gastrointestinal symptoms and must be considered, especially if the patient has recently consumed high-risk foods.
• Infectious Mononucleosis (Mono) Reconsideration: Despite a negative mono test, the presence of sore throat, fever at the onset, and general malaise could warrant reconsideration of this diagnosis, as false negatives can occur, especially early in the disease.

Rare Diagnoses

• Cyclic Vomiting Syndrome: A condition characterized by recurrent episodes of severe vomiting, which could be a consideration if other diagnoses are ruled out and the pattern of vomiting is cyclic.
• Giardiasis: An intestinal infection caused by the parasite Giardia, which can lead to chronic diarrhea and gastrointestinal upset, especially if the patient has been exposed to contaminated water or has traveled recently.
• H. pylori Infection: A bacterial infection that can cause gastritis and peptic ulcers, leading to symptoms like vomiting and abdominal pain, although this is less common in children without specific risk factors.