Renal allograft malakoplakia mimicking malignancy: the value of combined morphological and functional imaging

Background: Malakoplakia is a rare, chronic granulomatous inflammatory condition that primarily affects the genitourinary tract, albeit rarely renal allografts. This article highlights the clinical presentation and radiological features of renal allograft malakoplakia and aims to identify knowledge gaps by a pooled analysis of case reports. Methods: This study contains a detailed case report focusing on the presentation and radiological evolution of renal allograft malakoplakia, followed by a pooled analysis of 38 histologically confirmed cases, extracted from 34 publications. Descriptive statistics were applied. Results: UTIs (87%) and considered at high immunological risk (70%). Acute kidney injury (AKI) was the most common presentation of allograft malakoplakia (84% of cases). Three main patterns can be differentiated on imaging: parenchymal lesions (40%), abscess-like formations (34%), and pseudotumoral masses (26%). Ultrasound, CT, MRI, and FDG-PET-CT can result in initial detection, assess disease extent, and treatment response. However, these imaging modalities cannot reliably differentiate malakoplakia from malignant or other infectious processes, making histopathological confirmation essential for definitive diagnosis. There are no standardized treatment protocols, nor guidelines concerning antibiotic duration, reduction of immunosuppression, and definition of remission. Despite treatment, one-fifth of cases result in graft failure and one-fifth in death. Conclusions: Renal allograft malakoplakia is a rare but serious condition that in worst cases leads to graft loss and death. Prospective studies are needed to establish standardized diagnostic and therapeutic approaches, including the potential role of FDG-PET-CT in monitoring treatment response.