This document presents several case studies of pediatric patients with fluid and electrolyte disorders. It discusses the differential diagnoses, diagnostic evaluations and treatment approaches for conditions such as Syndrome of Inappropriate Antidiuretic Hormone (SIADH), diabetes insipidus, adrenal insufficiency, and hypokalemia. Through a series of questions and answers, it aims to teach learners how to recognize, diagnose and manage common fluid and electrolyte emergencies in critically ill children.