The space of Retzius: anatomy, imaging features, and patterns of disease spread

The space of Retzius is a clinically important but often overlooked extraperitoneal compartment that serves as a common site of disease involvement and a key pathway for the spread of pelvic and retroperitoneal pathology. Its complex anatomical relationship with other extraperitoneal/retroperitoneal spaces renders it prone to involvement in different pathologic processes. Most cases represent secondary involvement rather than primary pathology. CT and MRI play a pivotal role in depicting the anatomy of the space of Retzius, characterizing lesions, and identifying routes of disease extension. This review provides a comprehensive imaging-based overview of the anatomy of the space of Retzius and illustrates the imaging findings of a broad spectrum of diseases involving this region. We highlighted the anatomical pathways of disease spread, characteristic imaging features, and surgical considerations relevant to radiologists. Familiarity with these imaging patterns and anatomical relationships can improve diagnostic confidence, facilitate identification of the underlying disease process, and guide appropriate clinical management. KEY POINTS: Question Accurate recognition of diseases involving the space of Retzius is challenging because of its complex anatomy and diverse patterns of disease spread. Findings Most pathologies involving the space of Retzius represent secondary extension from adjacent compartments rather than primary disease. Critical relevance statement By integrating imaging anatomy, patterns of disease spread, and surgical relevance, this review provides a practical framework for evaluating abnormalities involving the space of Retzius, improves diagnostic confidence, facilitates identification of the disease process, and guides clinical and surgical management.