By Dr. Zahoor 1

A 23 year old male was seen in an emergency department after suffering a head injury from a motor vehicle accident. Patient was stabilized in emergency department and transferred to ICU for observation. Patient had CT scan of the head which revealed small amount of cerebral edema but was otherwise normal. During 2 nd day in ICU, the nurse informed that the patient had large amount of urine output in last 24 hours. The nurse record reported urinary output was over 5000 ml per previous 24 hours. 2

Patient had not been given any diuretic medication. Urine Osmolality was ordered and was found to be low. His physician remarked that the kidneys were not concentrating urine normally. Questions  1. What is differential diagnosis?  2. What is most likely diagnosis for increased dilute urine output?  3. How will you confirm the diagnosis? 3

Answers: Answer 1: - Central Diabetes Insipedious [DI] - Nephrogenic DI Answer 2: - Central Diabetes Answer 3: - Plasma and Urine Osmolality - Water deprivation test - Response to ADH 4

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