Causes of Polyuria - Differential Diagnosis Algorithm
Polyuria - Urine Output > 3L/day, Increased Urine Volume (>2ml/min)
Osmotic Diuresis
Urine Osmolality > Serum Osmolality
• Hyperglycemia (Uncontrolled Diabetes Mellitus)
• Mannitol administration
• Increased urea concentration (e.g. Recovery from Acute Renal Failure, increased protein feeds, Hypercatabolism [Burns, Steroids], GI Bleed)
• NaCl administration
Hypertonic Urine Following Water Deprivation Test
• Primary polydipsia
Hypotonic Urine Following Water Deprivation Test - Excessive Loss
- DDAVP -> Uosm Increased by >50% - Proper kidney response
• Central Diabetes Insipidus
- DDAVP -> Uosm unchanged or increased by <50% - Unresponsive Kidney
• Nephrogenic Diabetes Insipidus
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