Osmoregulation Performance and Kidney Transplant Outcome

Area of Science:

• Nephrology
• Transplantation
• Physiology

Background:

• Kidney transplant recipients (KTRs) exhibit impaired urine dilution but rarely present with hyponatremia before end-stage renal disease (ESRD).
• Hyponatremia is a known risk factor for adverse events in chronic kidney disease (CKD) and KTRs.
• The association between subtle osmoregulation impairments and outcomes in KTRs remains unclear.

Purpose of the Study:

• To assess osmoregulation performance in kidney transplant recipients using a water-loading test.
• To determine the association between osmoregulation performance and transplantation outcomes, including mortality and allograft loss.
• To evaluate the correlation between osmoregulation performance and subsequent kidney function, measured by glomerular filtration rate (GFR).

Main Methods:

• A prospective cohort study of 1258 KTRs 3 months post-transplant.
• A water-loading test was administered to assess osmoregulation capacity.
• Measured GFR (mGFR) and outcomes were evaluated, with 164 healthy kidney donors as controls.

Main Results:

• Most KTRs (83%) failed to maintain plasma sodium levels during water loading, unlike controls.
• A steeper decrease in plasma sodium during the test independently predicted a composite outcome of all-cause mortality and allograft loss (HR 1.73).
• Impaired osmoregulation also independently predicted allograft loss (HR 2.04) and was associated with lower mGFR at 12 months.

Conclusions:

• Reduced osmoregulation performance is common in KTRs.
• Osmoregulation impairment is an independent predictor of adverse renal outcomes, including graft loss and reduced GFR.
• These findings highlight the importance of assessing osmoregulation in KTR management.