E3396. Rough Around the Edges: Distinguishing Causes of Loss of Renal Corticomedullary Differentiation on Abdominopelvic CT
  1. Michael McColl; Johns Hopkins Medical Institute
  2. Erin Gomez; Johns Hopkins Medical Institute
  3. Elliot Fishman; Johns Hopkins Medical Institute
The kidneys have a distinct appearance across multiphase postcontrast imaging that is rooted in anatomy and physiology. Loss of normal renal corticomedullary differentiation is a commonly encountered finding on abdominopelvic CT. The two most common causes of loss of the renal corticomedullary interface are infection and infarction. However, numerous additional entities may also contribute to this finding, many of which radiologists fail to consider. In this exhibit we intend to explore the various causes of loss of corticomedullary differentiation and stress that clinical history is of the utmost importance when evaluating this finding on CT.

Educational Goals / Teaching Points
After reviewing our educational exhibit, learners will be able to better understand normal renal physiology, identify imaging characteristics that represent disruption to that normal physiology, produce a wide differential diagnosis for loss of corticomedullary differentiation rather than only infection or infarction, and narrow that differential to a more precise cause with consideration of clinical history.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In this educational exhibit, we will first outline the normal renal anatomy and function including describing the appearance of the kidneys on precontrast, arterial, venous and excretory phase CT and the pathway of contrast through the nephron. We will then provide pointers on identifying loss of corticomedullary differentiation using thin and thick section images and mutliplanar reformats. Next, we will discuss the causes of a loss of corticomedullary differentiation including pyelonephritis, infarction (including renal artery stenosis, renal vein thrombosis, embolic phenomenon, etc.), interstitial nephritis (secondary to drugs, granulomatous disease, IgG4, radiation, etc.), rhabdomyolysis, and neoplasm. Finally, we will emphasize the importance of clinical history in the diagnostic process of this finding with example vignettes of common presentations.

Loss of corticomedullary differentiation in the kidney is a common finding with a wide differential diagnosis that is often underappreciated by radiologists. Understanding the related pathophysiology, the common imaging appearances, and the importance of clinical history in regards to this finding will assist the radiologist in providing more accurate and actionable assessments of renal pathology in their practice.