Immunosuppression with sirolimus and low-dose tacrolimus has facilitated successful clinical islet transplantation (CIT). Because the long-term effects on the kidney are unknown and immunosuppressant drugs can be nephrotoxic, CIT is currently restricted to patients with preserved renal function or a functioning renal transplant. The impact of CIT on the native kidney of islet-alone recipients was assessed with magnetic resonance imaging (MRI). After successful CIT, MRI revealed perinephric edema (PNE) in 10 of 30 recipients. PNE was associated with a mild degree of renal impairment but was not associated with preexisting diabetic nephropathy, albuminuria, microscopic hematuria, graft function, or other clinical and metabolic parameters. The presence of PNE on MRI after CIT seems to be a common but benign finding, most likely an adverse effect of sirolimus. Although this novel observation does not seem to be of concern, further studies are required to examine the long-term impact of CIT and immunosuppression on renal function.