Diffusion-weighted MR imaging of transplanted kidneys: Preliminary report

Abstract

SummaryBackgroundAn aim of this study was to assess the feasibility of DWI in the early period after kidney transplantation. We also aimed to compare ADC and eADC values in the cortex and medulla of the kidney, to estimate image noise and variability of measurements, and to verify possible relation between selected labolatory results and diffusion parameters in the transplanted kidney.Material/MethodsExaminations were performed using a 1.5 T MR unit. DWI (SE/EPI) was performed in the axial plane using b-values of 600 and 1000. ADC and eADC measurements were performed in four regions of interest within the renal cortex and in three regions within the medulla. Relative variability of results and signal-to-noise ratio (SNR) were calculated.ResultsThe analysis included 15 patients (mean age 52 years). The mean variability of ADC was significantly lower than that of eADC (6.8% vs. 10.8%, respectively; p<0.0001). The mean variability of measurements performed in the cortex was significantly lower than that in the medulla (6.2% vs. 11.5%, respectively; p<0.005). The mean SNR was higher in the measurements using b600 than b1000, it was higher in ADC maps than in the eADC maps, and it was higher in the cortex than in the medulla. ADC and eADC measured at b1000 in the cortex were higher in the group of the patients with eGFR ≤30 ml/min./1.73 m2 as compared to patients with eGFR >30 ml/min./1.73 m2 (p<0.05).ConclusionsDiffusion-weighted imaging of transplanted kidneys is technically challenging, especially in patients in the early period after transplantation. From a technical point of view, the best quality parameters offer quality ADC measurement in the renal cortex using b1000. ADC and eADC values in the renal cortex measured at b1000 present a relationship with eGFR.

Acute pyelonephritis in transplanted kidneys: can diffusion-weighted magnetic resonance imaging be useful for diagnosis and follow-up?

“…DW-MRI with ADC allows functional evaluation of renal lesions and was proved to be reliable for diagnosing APN in native kidneys by several authors [14][15][16][17]. On the contrary, there are still relatively few studies in the literature on the use of DWI in transplanted kidneys, even if the initial results on its use for the assessment of early graft deterioration encountered in nearly 30% of renal allografts seem encouraging [21][22][23][24]. In particular, despite the pressing need of these patients for contrast-free MR imaging, to our knowledge there are no studies in which the feasibility and reproducibility of DW-MRI in detection and follow-up of APN in transplanted kidneys were analyzed.…”

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“…2 Dysfunction could be due to allograft rejection, infection, urinary or vascular obstruction, drug nephrotoxicity, delayed graft function, acute tubular necrosis, or dehydration, with each requiring different treatment modalities. 1,3 Accurate differentiation between causes of allograft dysfunction is based on the combination of clinical findings and histopathologic examination of an allograft biopsy. 1 In practice, biopsy is the only method that allows identification of parenchymal abnormalities of the allograft.…”

“…1 In practice, biopsy is the only method that allows identification of parenchymal abnormalities of the allograft. 3 However, a needle biopsy from an allograft may be associated with serious morbidity, such as hematuria requiring transfusion, obstruction of the allograft by clots, hypovolemic shock, and massive bleeding that may lead to graft nephrectomy. 1 An additional important problem associated with allograft biopsy is the substantial number of nondiagnostic and false results.…”

“…1 An additional important problem associated with allograft biopsy is the substantial number of nondiagnostic and false results. 3 Long-term monitoring using biopsy is controversial. 3 Unfortunately, there is no efficient and noninvasive method to assess graft function and to diagnose the cause of allograft dysfunction.…”

“…3 Long-term monitoring using biopsy is controversial. 3 Unfortunately, there is no efficient and noninvasive method to assess graft function and to diagnose the cause of allograft dysfunction. 1,3 Doppler ultrasonography is a noninvasive diagnostic method for hemodynamic assessment of renal allograft, but it is not specific for renal graft dysfunction because there is no reliable difference between acute rejection and other parenchymal pathologies.…”