Nuclear Medicine Test Identifies Kidney Transplant Infection

A novel positron emission tomography/magnetic resonance imaging (PET/MRI) test can determine whether a kidney transplant patient has developed infection in the transplanted tissue, according to a new study.

Researchers at Hannover Medical School (Germany) conducted a study involving 13 kidney transplant recipients with complicated urinary tract infections (UTIs) in order to determine whether molecularly targeted PET/MRI could enable the detection of leukocytes in renal allografts. The patients underwent both PET with a specific CXCR4 ligand (68Ga-pentixafor), and diffusion-weighted MRI. The spatial distribution and intensity of CXCR4 upregulation in the kidney transplants were analyzed and compared with urinalysis, clinical chemistry and bacteriology, and biopsy (if available).

The study showed that PET/MRI detected acute infection in the transplanted kidneys of nine patients, and lower UTI/non-urological infections in the remaining four patients. Leukocyte infiltration was identified by areas of CXCR4 upregulation versus unaffected parenchyma in PET, corresponding to areas with increased cell density under MRI. Transplant CXCR4 signal was mirrored by similar upregulation in lymphoid organs, and histopathology supported a correlation between CXCR4 signal and presence of leukocytes. The study was published in the November 2017 issue of The Journal of Nuclear Medicine.

“This work establishes CXCR4-targeted PET as a novel approach for imaging of infection, and it strengthens the role of nuclear medicine for renal imaging,” said lead author Thorsten Derlin, MD, of the department of nuclear medicine. “It demonstrates the potential of integrating state-of-the art imaging approaches - i.e., diffusion-weighted MRI and novel, highly specific PET tracers - for a comprehensive assessment of kidney disease, and has the potential to be translated into other settings of difficult-to-diagnose infections, such as cholangitis in transplanted patients and bone infections.”

CXCR-4 is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1), a molecule with potent chemotactic activity for lymphocytes. After attachment to SDF-1, the CXCR4 protein activates signaling pathways inside the cell that help regulate cell growth and proliferation. CXCR4 is also involved in cell migration, especially that of hematopoietic stem cells in the bone marrow.

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