Evaluation of intrarenal oxygenation in patients after receiving a kidney from non-heart-beating and living donors by BOLD MRI on a 3.0 T scanner 1 day after surgery.

Renal blood flow, a quarter of the cardiac output and the highest in the body
in relation to organ weight, is directed mostly to the cortex to optimize
glomerular filtration rate and the reabsorption of solute. In the physiologic
situation, blood flow to the hairpin loops of the renal medulla, in contrast,
is low, to preserve osmotic gradients and enhance urinary concentration. The
medullary partial pressure of oxygen is in the range of 10 to 20 mm Hg,
contrasting with the partial oxygen pressure of approximately 50 mmHg in the
cortex. Medullary hypoxia may have important implications in renal failure
after transplantation which is associated with variable periods of ischemia.

Animal studies strengthen the view that ischemic insults leads primarily to
disturbance of the medullary perfusion [5, 6]. We have observed similar results
in our ischemia/reperfusion mouse model in which we find a highly hypoxic
medulla in de ischemic injured kidney in contrast to the contra lateral kidney
until 24 hours after reperfusion (E.E. de Vries, M.G.J. Snoeijs, W.H. Backes,
unpublished observations). It can be concluded that the outer medulla is
particularly vulnerable for ischemic/reperfusion injury and this ongoing
hypoxia and impaired perfusion could lead to ischemic organ failure in humans.

The current study is designed to test the hypothesis that the medulla in
transplanted kidneys is still hypoxic at 1 day after transplantation using a
non-invasive method: BOLD MRI.
By studying two groups a comparison can be made between patients after
transplantation of kidneys with various degrees of ischemia. This information
may improve the rational selection of interventional strategies to attenuate
renal ischemia/reperfusion injury and to improve post-operative kidney
function. Furthermore, it may provide a new diagnostic tool for application in
future clinical trials or setting in acute ischemic renal failure and kidney
transplantation.

Observational study

One day postoperatively patients will get an extra MRI examination. Through a
peripheral venous line (standard care) furosemide is administered, after which
a small amount of Gadovist will be administered. Old versions of this contrast
agent bear a small risk of a serious skin disorder (NSF), however this new
agent Gadovist has no reported cases of NSF so far. Urine can be taken from the
katheter already in situ.
After 3 months this procedure will be repeated. Because of the absence of a
peripheral venous line, we will have to apply one. We will ask patients to
collect some (50 mL) urine.