CT and MRI Characterization of a Retroperitoneal Lymphatic Malformation in an Adult.

Lymphatic malformations (LMs) of the abdomen are uncommon congenital vascular anomalies that typically present during childhood. The nonspecific symptoms and radiological overlap with other cystic lesions may present significant diagnostic challenges, as their occurrence in adults is uncommon. We present the case of a 19-year-old male patient with human immunodeficiency virus (HIV) on antiretroviral therapy (ART), who presented with lower abdominal pain and fullness. Computed tomography (CT) imaging revealed a large, retroperitoneal, multiloculated cystic mass characterized by low attenuation and internal septations, resulting in bowel displacement. Magnetic resonance imaging (MRI) further characterized the lesion as complex and cystic, with additional features consistent with a benign vascular anomaly. The diagnosis of lymphatic malformation was confirmed through histopathological examination following a CT-guided biopsy. The patient experienced an uncomplicated recovery following the surgical resection of the lesion. This case highlights the significance of multimodal imaging, specifically how CT and MRI complement each other, in the precise diagnosis of a lymphatic malformation and the enhancement of the differential diagnosis.