The Prevalence of Nocturia and Nocturnal Polyuria After Renal Transplantation and Associated Factors

Background: Although uncontrolled systemic hypertension is associated with poor survival and allograft outcomes in patients after renal transplant, nondipping systolic blood pressure at night is not identified as an independent factor for deterioration of renal function after renal transplant. Therefore, in this study, we aimed to evaluate the prevalence of nocturia and nocturnal polyuria in renal transplant patients. Methods: This cross sectional study included 114 renal transplant patients above 18 years, who were referred to the nephrology clinics of Rasht, Iran in 2016. The patients were asked to collect 24-hour urine samples twice at home, once during the day and once at night. Urine volume, creatinine, sodium, osmolarity, and creatinine clearance of resting and working periods were measured. Monitoring of ambulatory 24-hour blood pressure was performed simultaneously, and findings including the mean arterial pressure (MAP) were evaluated during the day and night. Moreover, dimensions of the transplanted kidney, postvoid residual (PVR) urine, and prostate size were evaluated by ultrasonography. Results: The analyses showed that 81 (71.1%) patients had nocturia, while 77 (67.5%) patients had nocturnal polyuria. The mean age of the patients with nocturia was significantly higher than that of patients without nocturia (P = 0.003). MAP in patients with nocturnal polyuria was higher than that of patients without nocturnal polyuria. Blood pressure nondipping at night was significantly more common among patients with nocturia and nocturnal polyuria (P < 0.001). The increased level of urine sodium at resting time (night) was associated with nocturnal polyuria and nocturia (P < 0.001). In addition, the increase in creatinine clearance at resting time was associated with nocturnal polyuria and nocturia (P = 0.04 and P < 0.001, respectively). A higher level of creatinine clearance was reported during the day in patients without nocturnal polyuria or nocturia (P < 0.001). Conclusions: Since nondipping blood pressure is associated with more tissue damage and deterioration of renal transplant outcomes, control of hypertension and changes in the time of antihypertensive drug administration (for improving blood pressure dipping at night) may prevent the adverse effects of nondipping blood pressure.