Abnormal renal morphology Perinephric abscess A perinephric abscess is a collection of suppurative material in the perinephric space (i.e., the connective and adipose tissues surrounding the kidney). Detecting its presence can be diagnostically challenging because, in its chronic form, it usually develops insidiously, and in some cases its appearance can even simulate a renal tumor. The presence of a perinephric collection of purulent material around the kidneys occurs more often insidiously as a secondary phenomenon to upper tract urosepsis, classically in association with an infective staghorn renal calculus.