Diffusion-weighted MRI depicts early adaptations in nontransplanted kidneys

Diffusion-weighted MRI has been shown to depict early adaptations in the remaining nontransplanted kidneys of donors after nephrectomy, according to a study published in the March issue of Radiology.

Those who donate kidneys have a long-term, increased risk for a multitude of maladies, such as higher blood pressure, proteinuria, and loss of renal function. Lead author Ute Eisenberger, MD, of the University Hospital of Bern in Switzerland, and colleagues performed diffusion-weighted MRI measurements in living kidney donors and their recipients to assess the technology’s ability to monitor potential changes in the remaining kidney due to unilateral nephrectomy. They also strove to identify which parameters were correlated in the same kidney prior to and after transplantation.

The study included 13 kidney donors and their allograft recipients. Donors underwent MRI exams within three weeks of the donation. Donors and recipients then underwent MRI exams eight days, three months and 12 months after donation. In total, 87 exams were performed. The researchers determined total apparent diffusion coefficient values, quantified microcirculation contribution in perfusion fraction, compared the longitudinal changes of diffusion parameters and tested correlations.

Results showed that the total apparent diffusion coefficient values in the nontransplanted kidney of donors increased from 188 to 202 mm2/sec in medulla. In cortex, the values increased from 199 to 210 mm2/sec one week after donation. The medullary values remained at an increase for up to a year in the study’s subjects, while the values in allografts retained stability.

Additionally, the corticomedullary difference was reduced in allografts. Cortical apparent diffusion coefficient values correlated with estimated glomerular filtration rate in recipients, but not donors. Cortical values in the same kidney before transplantation in donors correlated with those in recipients on day eight after transplantation. Lastly, perfusion fraction did not show significant changes.

“The present investigation demonstrates that DW MR imaging has the capability to help detect early adaptations in the remaining nontransplanted kidney of donors after nephrectomy,” wrote Eisenberger and collleagus. “Our results suggest that there is a potential monitoring utility of the method. However, the assessment of the potential clinical relevance of functional MR imaging in renal transplantation deserves further clinical studies.”