The effect of fluid intake on chronic kidney transplant failure: a pilot study.
OBJECTIVE
Transplant recipients are generally instructed to increase their daily fluid intake so as to preserve kidney function. However, studies supporting this hypothesis are lacking.


SETTING
Prospective, randomized study at a tertiary care university hospital.


PATIENTS
Patients with chronic kidney transplant failure.


INTERVENTION
Assignment to normal fluid intake (NFI: 2 L/day) or high fluid intake (HFI: 4 L/day) for 12 months.


MAIN OUTCOME MEASURE
The effect of fluid intake on the decrease in estimated glomerular filtration rate (eGFR) was estimated by a mixed-effects general linear model. The analysis was adjusted for the observation period, age, intake of angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers, diuretics, and transplant duration.


RESULTS
A total of 33 patients were randomized to NFI and 29 to HFI. After 12 months, the mean eGFR had decreased to a similar extent in both groups (NFI: 44 ± 9 mL/min vs. 41 ± 9 mL/min; HFI: 46 ± 15 mL/min vs. 44 ± 15 mL/min). In the multivariate analysis, only the observation period had a significant effect on the decrease in eGFR. Randomization to NFI or HFI nor any other variable was associated with kidney function. The association between urine volume and urine osmolality was lost after 12 months.


CONCLUSIONS
Recommendation of higher fluid intake does not seem to improve chronic kidney transplant failure. However, the lack of association between urine osmolality and reported urine volume at a later stage implies a loss of adherence to fluid intake over time.