AM renal report PEARLS 12/18: approach to polyuria (>3L UOP/day)

Take-home point: for new polyuria, think about whether it is APPROPRIATE (eg fluid shifts, including post-ATN or post-obstructive diuresis), or INAPPROPRIATE (particularly osmotic diuresis to glucose or mannitol; or diabetes insipidus, either central or nephrogenic). Also think about polydipsia!!


More PEARLS from the case:

  • For DI: often will see Na>140
    • For nephrogenic DI, some causes include hypercalcemia, hypokalemia, medications multiple myeloma
    • For central DI, think about panhypopituitarism (including Sheehan’s!), subarachnoid hemorrhage
  • For polydipsia, often see lower Na
  • For work-up: primarily, water restriction + DDAVP while monitoring UOP and osms
    • Corrects with water restriction = primary polydipsia
    • Corrects with DDAVP = central DI
    • Does not correct with either water restriction or DDAVP administration = nephrogenic DI


And thank you to Jake for bringing in a molecular medicine PEARL:

  • FGF23: fibroblast growth factor 23: one of the first hormones that goes up in renal injury! It regulates systemic phosphate homeostasis, vitamin D metabolism, and more and could explain some of the complex endocrinopathies that happen with CKD.
  • Here is a picture:



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