Selection for biopsy of kidney transplant patients by diffusion-weighted MRI

Objectives

To assess retrospectively whether diffusion-weighted magnetic resonance imaging (DW-MRI) allows physicians to determine the severity of histopathologic findings in biopsies of renal allograft patients with deteriorating renal function.

Methods

Forty consecutive kidney transplant patients underwent DW-MRI and biopsy. Patients were assigned to one group with severe and to another group with normal or mild histopathologic findings. These two groups were compared based on a qualitative DW-MRI assessment (homo-/heterogeneity) and the combination of qualitative and quantitative DW-MRI parameters (ADC, and intravoxel incoherent motion, IVIM, parameters: D, f, D*). Sensitivity, specificity, and accuracy were determined for each parameter.

Results

Biopsy findings were severe in 25 patients and normal or mild in 15 patients. Qualitative DW-MRI led to a sensitivity of 44.0% and a specificity of 93.3%. Combined qualitative and quantitative DW-MRI led to an accuracy of 80% for both the minimal ADC (ADCmin) and the minimal perfusion fraction (fmin) with a sensitivity of 84.0% and 92.0% and a specificity of 73.3% and 60.0%, respectively.

Conclusion

Combined qualitative and quantitative DW-MRI might allow physicians to determine the severity of histopathologic findings in biopsies of a high number of kidney transplant patients.

Key points

• Qualitative DW-MRI is highly specific when predicting the severity of kidney transplant biopsy.

• Allografts appearing heterogeneous on ADC are associated with severe histopathologic findings.

• Combining qualitative and quantitative DW-MRI parameters improves the classification’s sensitivity and accuracy.

• Kidney transplant biopsies might be spared by combining qualitative and quantitative DW-MRI.