Differential Diagnosis for a 9-Month-Old Female with Fever, Vomiting, Diarrhea, and Congestion

• Single Most Likely Diagnosis
  • Viral gastroenteritis: This is the most likely diagnosis given the symptoms of fever, vomiting, and diarrhea, which are common presentations of viral gastroenteritis in infants. The mild congestion could be a concurrent viral upper respiratory infection.
• Other Likely Diagnoses
  • Upper respiratory tract infection (URTI): The patient's mild congestion and history of fever could suggest a URTI, possibly caused by a virus. The vomiting and diarrhea could be secondary to the URTI or due to a viral gastroenteritis.
  • Bacterial gastroenteritis: Although less common than viral causes, bacterial gastroenteritis (e.g., caused by Salmonella, Shigella, or E. coli) could present similarly and should be considered, especially if the diarrhea is bloody or if there's a high fever.
• Do Not Miss Diagnoses
  • Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause intestinal obstruction. It's a medical emergency and can present with vomiting, diarrhea, and sometimes a history of fever. Although rare, it's critical to consider due to its severe consequences if missed.
  • Urinary tract infection (UTI): UTIs can present with nonspecific symptoms in infants, including fever, vomiting, and sometimes diarrhea. It's crucial to consider UTI, especially if the patient has a fever without an obvious source.
  • Meningitis: Although the patient does not have specific symptoms like neck stiffness or severe irritability, meningitis is a life-threatening condition that can present subtly in infants and must always be considered in the differential diagnosis of fever, especially if the fever is high or persistent.
• Rare Diagnoses
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis are rare in infants but could present with chronic diarrhea, vomiting, and sometimes fever.
  • Food allergy or intolerance: Certain food allergies or intolerances (e.g., lactose intolerance) could cause gastrointestinal symptoms, although they are less likely to cause fever.
  • Systemic infections (e.g., sepsis, osteomyelitis, or pneumonia): While these conditions are serious and can present with fever and nonspecific symptoms, they are less likely given the patient's current presentation but should be considered if the patient's condition worsens or if specific risk factors are present.