Unilateral obstructive uropathy (UUO) is a cause of acute kidney injury and can also lead to chronic kidney diseases. A common cause for UUO is kidney stones and is also often the cause of end-stage renal diseases in children because of congenital development defects. Here we used a unilateral obstruction model with obstruction release after 5 days, and injection of co-polarized 13C-pyruvate and 13C-urea 2 days after release. We saw a marked elevation in lactate/pyruvate ration in the UUO kidney of the animals and also a reduction of approx. 50% in kidney blodflow measured by 13C-urea. The mechanisms involved must be investigated further. We believe that injection of co-polarized 13C-pyruvate and 13C-urea can be used as a clinical tool to follow kidney metabolic status and blodflow after surgical release of ureter obstruction.