Rectal malacoplakia in renal transplantation: MR features.

This report describes the CT and MRI features of rectal malacoplakia in a renal transplant recipient. The lesion appeared strongly hyperdense (105 HU) on unenhanced CT and demonstrated hypointense signal on T1- and T2-weighted MR imaging with slight homogeneous enhancement after gadolinium injection. These characteristics distinguish this lesion from other more common neoplastic, inflammatory rectal lesions that are typically isointense on T1-weighted imaging and enhance variably after gadolinium injection. Characteristic intracytoplasmic siderocalcific spherules in malacoplakia can produce suggestive features on unenhanced CT and MRI.