Taking an arrow to the (Kid)ney.

Q: “Definitive diagnosis for diseases such as Wegener's and Churg Strauss is by renal biopsy. Is there some imaging done to determine where to do the biopsy from or are the granulomas so widespread that any part of the kidney can be biopsied?”

A: So, the simple answer to whether imaging is done in Wegener's/Churg Strauss to determine a specific location in the kidney from where a biopsy is done is no!

Points to keep in mind:

• Granulomatosis with polyangiitis (formerly known as Wegener’s) affects the kidney in approximately 50 % of the cases and present as focal and segmental necrotising granulomas in the kidney. These findings cannot be seen on imaging (CT, MRI) in most cases. Rarely (and I mean very rarely), they present as solitary/ multiple renal masses.

• Eosinophilic Granulomatosis with polyangiitis (formerly Churg-Strauss) affects the kidney in approximately 25% of the cases and presentation is same as that seen in Wegener’s and imaging does not help in identifying these lesions.

• Biopsy in a lung for example (in Wegener’s)  can be based on imaging showing pulmonary nodules/infiltrates but not so in the kidney.

• Histopathological evidence of vasculitis, such as pauci-immune glomerulonephritis or necrotising vasculitis in any organ, remains the gold standard for diagnostic purposes (EULAR recommendations).

So, let’s get a quick idea of how a renal biopsy is done:

The most widely performed biopsy technique is a percutaneous renal biopsy (PRB) under real time ultrasound guidance. (The ultrasound is for locating the kidney and for corticomedullary differentiation in order to get the most number of glomeruli and also, to avoid causing damage to other structures.)

So, this is how it goes:

The patient is kept in prone position and the overlying skin is prepped and draped in a sterile fashion, and a local anesthetic (1% buffered lidocaine) is infiltrated to the depth of the kidney. A  real–time, ultrasound–guided PRB, using an automated, spring–loaded, 14/16-gauge biopsy needle is performed. The biopsy is usually obtained from the lower pole of the kidney to avoid damage to any major vessels. Post-PRB,  bed rest is advised and vital signs are monitored during the observation period. Then, a complete blood count is checked 6–8 hours after PRB, and a urine specimen is evaluated for gross hematuria and also to confirm voiding before discharge.

Image of Ultra-pro II needle guide, Civco, IA, USA, and (B) image of left kidney lower pole with dot marks of guide (arrow)

Real-time ultrasound-guided percutaneous renal biopsy with needle guide by nephrologists decreases post-biopsy complications. Narayan Prasad et al

Clin Kidney J. 2015;8(2):151-156. doi:10.1093/ckj/sfv012

Of course, the diagnostic accuracy of renal biopsy depends on the different parameters such as experience of the operator, mean number of glomeruli in specimen, and extent of renal involvement. As you can see in the image below, the arrows point to the glomeruli. Generally, two or three core biopsies are obtained, for light microscopy, electron microscopy and immunomicroscopy each.

Renal biopsy specimens as seen with a dissecting microscope. Black arrows point to glomeruli (wet prep, ×10).

The Native Kidney Biopsy: UpdatThe Native Kidney Biopsy: Update and Evidence for Best Practice

Jonathan J. Hogan, Michaela Mocanu, and Jeffrey S. Berns Clin J Am Soc Nephrol. 2016 Feb 5; 11(2): 354–362.Published online 2015 Sep 2. doi:  10.2215/CJN.05750515

So, to summarise,  renal biopsy is the gold standard for diagnosis in ANCA associated vasculitis and is done the same way for all renal biopsy indications, unless there is a specific mass seen on imaging( very rare in ANCA associated vasculitis).

By Amrusha Musunuru

References:

1. Real-time ultrasound-guided percutaneous renal biopsy with needle guide by nephrologists decreases post-biopsy complications 

2. Narayan Prasad  Shashi Kumar Revanasiddappa Manjunath  Dharmendra Bhadauria Anupama Kaul Raj K Sharma  Amit Gupta Hira Lal Manoj Jain Vinita Agrawal
Clinical Kidney Journal, Volume 8, Issue 2, 1 April 2015, Pages 151–156, https://doi.org/10.1093/ckj/sfv012
EULAR/ERA-EDTA recommendations for the management of ANCA-associated vasculitis M Yates et al. Ann Rheum Dis: first published as 10.1136/annrheumdis-2016-209133 on 23 June 2016

   3. The Native Kidney Biopsy:Update and Evidence for Best Practice  Jonathan J. Hogan, Michaela Mocanu, and Jeffrey S. Berns Clin J Am Soc Nephrol.2016 Feb 5; 11(2): 354–362.Published online 2015 Sep 2. doi:  10.2215/CJN.05750515

4.  Practice guidelines for the renal biopsy.

Walker PD1, Cavallo T, Bonsib SM; Ad Hoc Committee on Renal Biopsy Guidelines of the Renal Pathology Society.

Mod Pathol. 2004 Dec;17(12):1555-63

5.Renal biopsy: Still a landmark for the nephrologist

Luca Visconti, Valeria Cernaro, Carlo Alberto Ricciardi, Viviana Lacava, Vincenzo Pellicanò, Antonio Lacquaniti, Michele Buemi, and Domenico Santorol

World J Nephrol. 2016 Jul 6; 5(4): 321–327.

Published online 2016 Jul 6. doi:  [10.5527/wjn.v5.i4.321]