Acute conditions affecting the perinephric space: imaging anatomy, pathways of disease spread, and differential diagnosis

The perinephric space is an important, central compartment of the retroperitoneum which may host various acute conditions. Imaging evaluation of the perinephric space requires an understanding of its anatomy and the pathways of disease spread to and from other retroperitoneal compartments. Numerous acute conditions can affect the perinephric space and may occur in isolation, extend from nearby retroperitoneal structures, or be part of a systemic condition. Familiarity with the key imaging findings of acute conditions affecting the perinephric space is imperative to facilitate diagnosis and guide treatment. The purpose of this article is to review and illustrate the relevant anatomy, pathways of disease spread, and acute pathology encountered during cross-sectional imaging evaluation of the perinephric space.