Dietary Sodium Restriction Reduces Nocturnal Urine Volume and Nocturnal Polyuria Index in Renal Allograft Recipients With Nocturnal Polyuria.

OBJECTIVE:To investigate whether sodium restriction alters the nocturnal urine volume (NUV) and the ratio of NUV to 24-hour urine of renal allograft recipients (RARs). MATERIALS AND METHODS:This prospective, single-center study analyzed 38 of the 59 RARs who were followed up for more than 6 months in our hospital. All patients underwent 3 sessions of dietary counseling performed by a board-certified dietitian. Before and after these 3 sessions, 24-hour urine samples were collected, along with voiding frequency volume charts. RESULTS:Of the 38 included RARs, 23 (60.5%) were diagnosed as having nocturnal polyuria (NP, NUV >10 mL/kg). After counseling the RARs with NP, their 24-hour sodium excretion was reduced from 169.5 to 125.6 mEq (P = .0066), their NUV from 862 to 709 mL (P = .021), and the ratio of NUV to 24-hour urine volume from 38.9% to 33.0% (P = .023). In contrast, these parameters were not significantly changed by dietary counseling in RARs without NP. Reduced sodium excretion and decreased NUV were significantly correlated (Spearman rho = 0.45, P = .005). CONCLUSION:Excess intake of sodium is considered a cause of NP in RARs. Dietary counseling on sodium restriction is effective in reducing NUV in RARs. Prospective studies are needed to evaluate the general population with NP.