mrcem2-0660

mrcem2-0660

A 5 year old male is brought into the emergency department by his parents. They inform you that the patient started experiencing diarrhea and vomiting 3 days ago. The vomiting stopped yesterday, but the diarrhea has persisted and the parents are worried because the patient seems restless and not acting like himself. There is no recent history of traveling abroad, no significant medical history, the patient is up to date with vaccinations, and the parents have not noticed any blood or mucus in the stool. During the clinical examination, you observe jittery movements in the limbs and head, increased muscle tone, and exaggerated reflexes in the limbs. There is some tenderness upon deep palpation of the abdomen, but no guarding. The central and peripheral capillary refill time is approximately 3 seconds, and the extremities feel warm.

What investigation would be most beneficial for this patient?