What question did this study set out to answer?

This research aims to investigate the connection between nighttime blood pressure and diurnal sodium excretion in kidney transplant recipients (KTRs).

June 3, 2026

Relationship Between Diurnal Urine Sodium Excretion and Nocturnal Blood Pressure in Kidney Transplant Recipients

Key Points

This research aims to investigate the connection between nighttime blood pressure and diurnal sodium excretion in kidney transplant recipients (KTRs).
120 KTRs with stable graft function underwent 24-h ambulatory blood pressure monitoring and 24-h urine collection.
Patients were divided into tertiles based on the nighttime-to-daytime urinary sodium excretion ratio.
Patients were also divided into two groups by nighttime systolic blood pressure thresholds (>=120mmHg and <120mmHg).
Nighttime SBP was significantly increased with higher nighttime-to-daytime sodium excretion ratio (mean values 122.0±10.4 vs 128.5±14.7mmHg, p=0.034).
Patients with nighttime SBP >=120mmHg had a significantly higher N/D sodium ratio (0.7±0.4 vs 0.6±0.3, p=0.032).
Numerical differences in 24-h and daytime sodium excretions were observed but not statistically significant (p=0.465 and p=0.084, respectively).

Abstract

Objective: Hypertension in chronic kidney disease (CKD) is characterized by sodium sensitivity and disturbance of the normal circadian rhythm of kidney sodium excretion, leading to loss of the normal dipping pattern of blood pressure (BP) and development of nocturnal hypertension. Kidney transplant recipients (KTRs) also exhibit sodium sensitivity and disturbances in sodium excretion with a high prevalence of nocturnal hypertension; however, the relationship between nocturnal BP levels and diurnal sodium excretion in KTRs has not been previously studied. This study examined the relationship between nighttime-to-daytime (N/D) urinary sodium excretion ratio and diurnal BP in KTRs. Design and method: 120 KTRs with stable graft function underwent 24-h ambulatory BP monitoring with ABPMpro device and 24-h urine collection, divided in two distinct periods (daytime 7:00-23:00 and nighttime 23:00-7:00). For analysis, patients were divided by tertiles of N/D urine sodium excretion ratio and by 2 groups based on nighttime SBP (>=120mmHg and =120mmHg exhibited significantly higher N/D ratio (0.7±0.4 vs 0.6±0.3, p=0.032) and numerically higher (48.0± 35.3vs 41.7±22.0mEq, p=0.230) nighttime sodium excretion. In contrast, they showed numerically lower 24-h (126.1±61.7 vs 133.8±53.6mEq, p=0.465) and daytime (78.1±38.5vs 92.2±47.0mEq, p=0.084) sodium excretion compared to those with SBP <120mmHg. Conclusions: In KTRs, impaired circadian renal sodium handling is associated with higher nighttime BP. Assessment of nighttime and N/D urine sodium excretion may help identify sodium-sensitive nocturnal hypertension and guide treatment strategies.

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