Felix W. Wehrli

Purpose Renal metabolic rate of oxygen (rMRO 2 ) is a potentially important biomarker of kidney function. The key parameters for rMRO 2 quantification include blood flow rate (BFR) and venous oxygen saturation (SvO 2 ) in a draining vessel. Previous approaches to quantify renal metabolism have focused on the single organ. Here, both kidneys are considered as one unit to quantify bilateral rMRO 2 . A pulse sequence to facilitate bilateral rMRO 2 quantification is introduced. Methods To quantify bilateral rMRO 2 , measurements of BFR and SvO 2 are made along the inferior vena cava (IVC) at suprarenal and infrarenal locations. From the continuity equation, these four parameters can be related to derive an expression for bilateral rMRO 2 . The recently reported K‐MOTIVE pulse sequence was implemented at four locations: left kidney, right kidney, suprarenal IVC, and infrarenal IVC. A dual‐band variant of K‐MOTIVE (db‐K‐MOTIVE) was developed by incorporating simultaneous‐multi‐slice imaging principles. The sequence simultaneously measures BFR and SvO 2 at suprarenal and infrarenal locations in a single pass of 21 s, yielding bilateral rMRO 2 . Results SvO 2 and BFR are higher in suprarenal versus infrarenal IVC, and the renal veins are highly oxygenated (SvO 2 >90%). Bilateral rMRO 2 quantified in 10 healthy subjects (8 M, 30 ± 8 y) was found to be 291 ± 247 and 349 ± 300 (μmolO 2 /min)/100 g, derived from K‐MOTIVE and db‐K‐MOTIVE, respectively. In comparison, total rMRO 2 from combining left and right was 329 ± 273 (μmolO 2 /min)/100 g. Conclusion The present work demonstrates that bilateral rMRO 2 quantification is feasible with fair reproducibility and physiological plausibility. The indirect method is a promising approach to compute bilateral rMRO 2 when individual rMRO 2 quantification is difficult.