Complex posttransplantation abnormalities of renal allografts: Evaluation with MR imaging

PURPOSE: To assess the efficacy of magnetic resonance (MR) imaging in the evaluation of complex abnormalities of renal allografts. MATERIALS AND METHODS: Clinical and radiologic findings were retrospectively reviewed in 24 patients who underwent MR imaging of a renal allograft because ultrasonographic (US) findings were inconclusive or discordant with clinical findings. The final diagnoses were established with histopathologic analysis (n = 16) or clinical and imaging follow-up (n = 8). RESULTS: MR imaging diagnoses were correct in 16 patients (67%), whereas US diagnoses were correct in six patients (25%) (P < .05). Five cases of allograft involvement by posttransplantation lymphoproliferative disorder (PTLD) were found at histopathologic analysis; at MR imaging, PTLD appeared as hypointense masses on T1- and T2-weighted images with minimal enhancement. In four of the five cases of PTLD, the masses occurred at the renal hilum and encased hilar vessels. Normal morphology was correctly diagnosed with MR imaging in five patients in whom a mass was suspected at US. CONCLUSION: MR imaging results are often diagnostic in cases of complex abnormalities of renal allografts. Renal allograft involvement by PTLD appears to have a relatively characteristic MR imaging appearance. Normal MR imaging findings in cases of suspected masses at US may obviate biopsy.