Circadian variations in renal hemodynamics in healthy volunteers ő preliminary findings (692.8)

Renal blood flow is tightly controlled by at least two different intrinsic mechanisms, which should guarantee a stable blood flow. However, it is currently unknown if renal hemodynamics is influenced by circadian rhythm like many other tissues. Therefore, we measured total and cortical renal blood flow using completely non‐invasive magnetic resonance technique in six healthy male volunteers every fourth hour for a total of 24 hours (six measurements in total). Total renal blood flow was measured using standard phase contrast technique in renal arteries, whereas cortical renal blood flow was measured using the newly developed arterial spin‐labeling technique. Total renal blood flow averaged 13.3±1.4 and 13.0±1.0 ml/min for right and left kidney, respectively, with a circadian variation of 18±5 and 14±3%. Cortical renal blood flow in the right kidney averaged 323±17 ml/min/100g with a variation of 10±2% between the different measurements. None of these variations reached statistical significance. In conclusion, neither total nor cortical renal blood flows display circadian variations. Thus, circadian variations in renal hemodynamics seem less likely to affect the results from studies investigating renal blood flow and related parameters.