What is the role of renal biopsy in the workup of acute tubular necrosis (ATN)?

Updated: Mar 15, 2021
  • Author: Sangeeta Mutnuri, MBBS; Chief Editor: Vecihi Batuman, MD, FASN  more...
  • Print
Answer

Kidney biopsy is rarely necessary in patients with suspected ATN. An urgent indication for kidney biopsy is in the setting of clinical and urinary findings that suggest renal vasculitis rather than ATN, in which case the diagnosis needs to be established quickly so that appropriate immunomodulatory therapy can be initiated. A biopsy may also be critically important in renal transplant recipients, to rule out rejection. [18, 19]  Otherwise, biopsy should be performed only when the exact renal cause of AKI is unclear and the course is protracted.

Kidney biopsy is performed under ultrasound or CT scan guidance after ascertaining the safety of the procedure. In most circumstances, the histology demonstrates the loss of tubular cells or the denuded tubules. As illustrated in the image below, the tubular cells reveal swelling, formation of blebs over the cellular surface, and exfoliation of the tubular cells into the lumina. The earliest finding could be loss of the cellular brush border.

Acute tubular necrosis. Photomicrograph of a kidney biopsy specimen shows renal medulla, which is composed mainly of renal tubules. Features suggesting acute tubular necrosis are the patchy or diffuse denudation of the renal tubular cells with loss of brush border (blue arrows); flattening of the renal tubular cells due to tubular dilation (orange arrows); intratubular cast formation (yellow arrows); and sloughing of cells, which is responsible for the formation of granular casts (red arrow). Finally, intratubular obstruction due to the denuded epithelium and cellular debris is evident (green arrow); note that the denuded tubular epithelial cells clump together because of rearrangement of intercellular adhesion molecules.

Acute tubular necrosis. Photomicrograph of a kidne Acute tubular necrosis. Photomicrograph of a kidney biopsy specimen shows renal medulla, which is composed mainly of renal tubules. Features suggesting acute tubular necrosis are the patchy or diffuse denudation of the renal tubular cells with loss of brush border (blue arrows); flattening of the renal tubular cells due to tubular dilation (orange arrows); intratubular cast formation (yellow arrows); and sloughing of cells, which is responsible for the formation of granular casts (red arrow). Finally, intratubular obstruction due to the denuded epithelium and cellular debris is evident (green arrow); note that the denuded tubular epithelial cells clump together because of rearrangement of intercellular adhesion molecules.

Although ATN was long considered to be synonymous with acute tubular injury (ATI), frank tubular epithelial necrosis is only 1 histologic pattern observed in clinical ATI. A systematic review of 292 studies comprising a total of 1987 patients identified 16 histologic descriptions of tubular injury, including the following [20] :

  • Tubular cell necrosis: 31.8%
  • Tubular cell sloughing: 39.4%
  • Tubular epithelial flattening/simplification: 37.7%
  • Tubular dilatation: 37.3%

The review found no difference in tubular injury histology between among kidney biopsy, transplant kidney biopsy, and autopsy, among different etiologies, or between biopsy samples taken before or after creatinine peaks in native kidneys. [20]


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!