What is a mildly prominent column of Bertin?

Mildly Prominent Column of Bertin

A mildly prominent column of Bertin is a normal anatomical variant of the kidney that represents unresorbed polar parenchyma between two fused subkidneys, containing normal renal cortex, pyramids, and columns of Bertin, which can sometimes mimic a renal mass on imaging. 1

Anatomical Definition and Characteristics

• A column of Bertin is a projection of normal renal cortical tissue that extends into the renal sinus, appearing isoechoic with the renal cortex on ultrasound 2
• The term "hypertrophic column of Bertin" is actually a misnomer since the tissue is not truly hypertrophied but simply represents normal unresorbed polar parenchyma from the developmental fusion of two subkidneys 1
• More accurately termed "junctional parenchyma," it contains all normal renal tissue elements including cortex, pyramids, and septa 1
• Most commonly located in the middle third of the kidney and more frequently found on the left side 2
• Can be bilateral in approximately 18% of cases 2

Imaging Characteristics

• On ultrasound, a prominent column of Bertin appears as a cortical projection into the renal sinus that is isoechoic with the renal cortex 2
• Key sonographic criteria for identifying a column of Bertin include:
  • Located between overlapping portions of two renal sinus systems 1
  • Indents the renal sinus laterally 3
  • Clearly defined from the renal sinus 3
  • Typically measures less than 3 cm in its largest dimension 3
  • Continuous or contiguous with the adjacent renal cortex 3
  • Echogenicity similar to that of the renal cortex 3
  • Bordered by a junctional parenchymal line and defect 1
  • Smooth renal contour without distortion of the external kidney shape 2

Clinical Significance

• The primary clinical importance of a prominent column of Bertin is that it can mimic a renal mass on imaging, potentially leading to unnecessary interventions 4
• It is a common cause of renal "pseudotumor" that may be difficult to distinguish from neoplasia or cysts in some cases 5
• Proper identification through appropriate imaging can prevent unnecessary biopsies or surgical procedures 4

Diagnostic Approach

• Ultrasound is often sufficient for diagnosis, showing the characteristic appearance of normal cortical tissue projecting into the renal sinus 2
• In cases where ultrasound findings are equivocal, MRI can provide definitive diagnosis by demonstrating:
  • Normal enhancement patterns identical to surrounding renal cortex
  • Absence of mass effect on collecting system
  • Continuity with normal renal parenchyma 4
• Other helpful diagnostic features include:
  • The renal sinus may engulf the column in a claw-like fashion 2
  • The column contains normal renal cortex that is continuous with adjacent renal cortex of the same subkidney 1

Pitfalls to Avoid

• Misdiagnosing a prominent column of Bertin as a renal tumor, which could lead to unnecessary biopsy or nephrectomy 4
• Failure to recognize this normal variant during ultrasound examination, particularly when the column is unusually large 2
• Relying solely on a single imaging modality when findings are atypical or equivocal 4

Understanding the imaging characteristics of a prominent column of Bertin is essential for accurate diagnosis and avoiding unnecessary interventional procedures or surgeries for this benign anatomical variant.