Noninvasive assessment of early kidney allograft dysfunction by blood oxygen level-dependent magnetic resonance imaging.
BACKGROUND
Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) is a noninvasive method to assess tissue oxygen bioavailability, using deoxyhemoglobin as an endogenous contrast agent. We hypothesized that BOLD-MRI could accurately discriminate different types of rejection early after kidney transplantation.


METHODS
Twenty-three patients underwent imaging in the first four months posttransplant. Five had normal functioning transplants and 18 had biopsy-proven acute allograft dysfunction (acute tubular necrosis [ATN, n=5] and acute rejection [n=13] including borderline rejection: n=3; IA rejection: n=4; IIA rejection: n=6: C4d(+) rejection: n=9).


RESULTS
Mean medullary R2* (MR2*) levels (a measure directly proportional to tissue deoxyhemoglobin levels) were significantly higher in normal functioning allografts (R2*=24.3/s+/-2.3) versus acute rejection (R2*=16.6/s+/-2.1) and ATN (R2*=20.9/s+/-1.8) (P<0.05). The lowest MR2* levels were observed in acute rejection episodes with vascular injury i.e. IIA and C4d (+). Similarly, the lowest medullary to cortical R2* ratios (MCR2*) were present in allografts with IIA (1.24+/-0.05) and C4d(+) rejection (1.26+/-0.06). ROC curve analyses suggested that MR2* and MCR2* values could accurately discriminate acute rejection in the early posttransplant period.


CONCLUSIONS
BOLD-MRI demonstrated significant changes in medullary oxygen bioavailability in allografts with biopsy-proven ATN and acute rejection, suggesting that there may be a role for this noninvasive tool to evaluate kidney function early after transplantation.
Djamali
Arjang
A
Department of Medicine, University of Wisconsin Madison, Madison, WI, USA. axd@medicine.wisc.edu
Sadowski
Elizabeth A
EA
Samaniego-Picota
Millie
M
Fain
Sean B
SB
Muehrer
Rebecca J
RJ
Alford
Sara K
SK
Grist
Thomas M
TM
Becker
Bryan N
BN
D000328:Adult; D001706:Biopsy; D005260:Female; D006084:Graft Rejection / Q000453:epidemiology; D006085:Graft Survival / Q000502:physiology; D006801:Humans; D007677:Kidney Function Tests; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000473:pathology / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011183:Postoperative Complications / Q000097:blood / Q000473:pathology / Q000503:physiopathology*; D014184:Transplantation, Homologous
D010100:Oxygen