II. Pathophysiology
- 
                          Edematous State reduces effective circulating volume- Decreased flow to nephron diluting segment stimulates hormonal response
 
- Stimulates Antidiuretic Hormone (ADH) release- Results in water retention
 
- Stimulates Renin-Angiotensin-Aldosterone system- Increases thirst drive and free water intake (outweighs any increased Sodium retention)
 
III. Causes
- 
                          Urine Sodium < 10-15 meq/L (if no Diuretic use)- Urine Osmolality >350 mOsm/kg water
- Edematous States- Cirrhosis
- Congestive Heart Failure
- Nephrotic Syndrome
- Hypoalbuminemia
 
 
- Urine Sodium > 20 meq/L
IV. Diagnostics (consider)
- Chest XRay
- Electrocardiogram
- Echocardiogram
- 
                          IVC Ultrasound for Volume Status
                          - Ultrasound may also demonstrate Ascites in Cirrhosis
 
V. Labs
- Urinalysis
- Urine Protein to Creatinine Ratio
- Comprehensive metabolic panel (Renal Function tests, Liver Function Tests)
- Brain Natriuretic Peptide (BNP)
VI. Management
- See Hyponatremia Management
- 
                          Congestive Heart Failure
                          - Salt Restriction <2 to 3 grams/day
- Water restriction <1 Liter per day
- Decrease contributing Diuretics
- Optimize Cardiac Output
 
- 
                          Cirrhosis
                          - Water restriction <750 ml per day
- Loop Diuretics may be used cautiously in mild Hyponatremia (avoid in moderate to severe Hyponatremia)
 
- Severe Renal Insufficiency- Consider Hemodialysis
 
VII. References
- Edwards, Yang and Mehta (2025) Crit Dec Emerg Med 39(9): 25-33
- Kone in Tisher (1993) Nephrology, p. 87-100
- Levinsky in Wilson (1991) Harrison's IM, p. 281-84
- Rose (1989) Acid-Base and Electrolytes, p. 601-38
- Braun (2015) Am Fam Physician 91(5): 299-307 [PubMed]
- Miller (2023) Am Fam Physician 108(5): 476-86 [PubMed]
