Evaluation of Polyuria: The Roles of Solute Loading and Water Diuresis

Am J Kidney Dis. 2016 Mar;67(3):507-11. doi: 10.1053/j.ajkd.2015.10.021. Epub 2015 Dec 11.


Polyuria, defined as daily urine output in excess of 3.0 to 3.5L/d, can occur due to solute or water diuresis. Solute-induced polyuria can be seen in hospitalized patients after a high solute load from exogenous protein administration or following relief of urinary obstruction. Similar clinical scenarios are rarely encountered in the outpatient setting. We describe a case of polyuria due to high solute ingestion and excessive water intake leading to a mixed picture of solute and water diuresis. Restriction of the daily solute load and water intake resulted in complete resolution of polyuria. Determination of the daily excreted urinary osmoles may yield important clues to the cause of polyuria and should be included in the routine workup of polyuria.

Keywords: Polyuria; hypernatremia; solute excretion; urinary osmoles; water diuresis.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Diagnosis, Differential
  • Dietary Proteins* / analysis
  • Dietary Proteins* / metabolism
  • Disease Management
  • Diuresis / physiology
  • Drinking / physiology*
  • Female
  • Humans
  • Osmolar Concentration
  • Polyuria* / etiology
  • Polyuria* / metabolism
  • Polyuria* / physiopathology
  • Polyuria* / therapy
  • Potassium* / analysis
  • Potassium* / metabolism
  • Sodium* / analysis
  • Sodium* / metabolism
  • Treatment Outcome
  • Water-Electrolyte Imbalance* / etiology
  • Water-Electrolyte Imbalance* / therapy
  • Water-Electrolyte Imbalance* / urine


  • Dietary Proteins
  • Sodium
  • Potassium