Differential Diagnosis for Abdominal Pain, Urticarial Rash, Diarrhea, and Shock
Single Most Likely Diagnosis
- Anaphylaxis: This condition is characterized by a severe, whole-body allergic reaction that can cause abdominal pain, diarrhea, urticarial rash, and potentially life-threatening shock. The combination of these symptoms, especially the presence of an urticarial rash and shock, strongly suggests anaphylaxis as the most likely diagnosis.
Other Likely Diagnoses
- Food Allergy: A severe food allergy can cause anaphylaxis, but it can also present with gastrointestinal symptoms like abdominal pain and diarrhea, along with a rash. The key would be identifying a recent ingestion of a common allergenic food.
- Insect Sting Allergy: Similar to food allergy, an allergic reaction to an insect sting can cause a range of symptoms from mild to severe anaphylaxis, including abdominal pain, rash, and shock.
- Medication Allergy: An allergic reaction to certain medications can manifest with these symptoms, especially if the medication is known to cause allergic reactions.
Do Not Miss Diagnoses
- Septic Shock: Although the presence of a rash and abdominal pain might suggest an allergic reaction, septic shock due to a bacterial infection (e.g., meningococcemia) can present with a rash (petechial or purpuric), abdominal pain, diarrhea, and shock. Missing this diagnosis could be fatal.
- Toxic Shock Syndrome: Caused by bacterial toxins, this condition can present with sudden onset of fever, vomiting, diarrhea, abdominal pain, and shock, along with a rash. It's crucial to consider this diagnosis, especially in menstruating women using tampons or anyone with a focal infection.
Rare Diagnoses
- Hereditary Angioedema: A rare genetic disorder that causes swelling of the face, extremities, and gastrointestinal tract, which can lead to abdominal pain and diarrhea. Although it doesn't typically cause urticaria, it can cause a rash and potentially life-threatening airway obstruction.
- Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, which can cause abdominal pain, diarrhea, and potentially an urticarial rash, though shock would be an uncommon presentation.
- Mastocytosis: A condition where there's an accumulation of mast cells in one or more organs, which can cause a range of symptoms including abdominal pain, diarrhea, rash, and potentially anaphylaxis-like episodes. However, the full spectrum of symptoms described would be unusual for this condition.