From the Research
Hyponatremia in urate nephropathy occurs primarily due to impaired renal function and altered water handling, as evidenced by the most recent and highest quality study 1.
Pathophysiology of Hyponatremia in Urate Nephropathy
When uric acid crystals deposit in the renal tubules and interstitium, they cause inflammation, obstruction, and progressive kidney damage. This compromises the kidney's ability to dilute urine and excrete free water appropriately. The damaged kidneys cannot adequately clear free water, leading to water retention that dilutes serum sodium levels. Additionally, the inflammatory response triggered by urate crystal deposition can increase antidiuretic hormone (ADH) release, further promoting water retention. Reduced glomerular filtration rate from kidney injury also contributes to sodium and water imbalance.
Clinical Manifestations and Diagnosis
Hyponatremia can lead to a wide spectrum of clinical symptoms, from mild to severe or even life-threatening, and is associated with increased mortality, morbidity, and length of hospital stay 2. The diagnosis of hyponatremia involves categorizing patients according to their fluid volume status (hypovolemic hyponatremia, euvolemic hyponatremia, or hypervolemic hyponatremia) and identifying the underlying cause.
Treatment and Management
Treatment focuses on addressing the underlying hyperuricemia with medications like allopurinol or febuxostat, while carefully managing fluid intake and sometimes using salt supplementation to correct the sodium imbalance 1. The principles of fluid restriction should be clearly understood and followed, and treatment methods specific to various categories of hyponatremia should be used. Rapid correction of chronic hypotonic hyponatremia may lead to osmotic demyelination syndrome, which has severe clinical manifestations, and may lead to permanent neurological disability or death 3.
Key Considerations
- Hyponatremia is a secondary cause of osteoporosis, and even mild hyponatremia is associated with increased hospital stay and mortality 1.
- The net result of urate transport in the proximal tubule is determined by the dominance of transporters between reabsorption and secretion 4.
- Urate and vaptans can be effective treatments for the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure, but have adverse effects 1.