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Abstract: PO1781

Single-Nephron Salt Excretion and Nighttime Hypertension: A Cross-Sectional Study in Patients with IgA Nephropathy

Session Information

Category: Hypertension and CVD

  • 1402 Hypertension and CVD: Clinical, Outcomes, and Trials

Authors

  • Tsuboi, Nobuo, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Marumoto, Hirokazu, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Haruhara, Kotaro, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Sasaki, Takaya, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Okabayashi, Yusuke, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Kanzaki, Go, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Koike, Kentaro, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
  • Yokoo, Takashi, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan, Tokyo, Japan
Background

Abnormalities in diurnal blood pressure variability and renal salt handling may contribute to poor disease outcomes in patients with IgA nephropathy (IgAN). This study examined the relationships between diurnal blood pressure variability and single-nephron urinary salt excretion (SNUSE) in IgAN patients.

Methods

The subjects were IgAN patients who underwent ambulatory blood pressure (ABP) monitoring and 24-h urine collection during hospitalization for a diagnostic biopsy. In all patients, dietary salt intake was restricted to 6 g/day during hospitalization. Daytime and nighttime hypertension were defined as daytime ABP ≥135/85 mmHg and nighttime ABP ≥120/70 mmHg, respectively. The total nephron number per kidney was estimated by a combined cortical volume assessment of unenhanced computed tomography images and stereology-based measurements of non-sclerotic glomerular density in a biopsy. SNUSE was calculated by dividing urinary salt excretion per day by the total nephron number of both kidneys.

Results

Among the 112 patients (42 years old, 63.4% male, estimated glomerular filtration rate [GFR] 62.4 mL/min/1.73 m2) included, daytime and nighttime hypertension were noted in 33.0% and 50.9%, respectively. There was no marked difference in the total nephron number or SNUSE in relation to the daytime hypertension. In patients with nighttime hypertension, the total nephron number per kidney was lower (490,000 vs. 796,000/kidney, p = 0.01) and SNUSE was higher (6.53 vs. 4.22 µg/day, p=0.003) than in normotensive patients during nighttime. An increase in SNUSE in patients with nighttime hypertension was associated with advanced tubulointerstitial injury, defined as a T score in the Oxford histopathological classification of IgAN. The single-nephron GFR was comparable among patient groups with and without hypertension both during the daytime and nighttime and was not associated with a T score.

Conclusion

These results provide evidence that salt excretion per nephron is increased in IgAN patients presenting with nighttime hypertension. The difference in SNUSE was identified in relation to the tubulointerstitial injury without producing a difference in single-nephron GFR values among ABP categories, indicating compensatory changes in tubular salt handling at the single-nephron level.

Funding

  • Other U.S. Government Support