Indications

Nephrotic syndrome, acute nephritis, rapidly progressive glomerulonephritis, unexplained AKI, non-nephrotic range proteinuria

Contraindications

Absolute: uncontrolled severe HTN, uncontrolled bleeding

Relative: Solitary native kidney, multiple cysts/masses, small hypoechoic kidneys, active renal infection, skin infection, anatomical anomalies

Technique

Percutaneous needle biopsy under ultrasound guidance to obtain two cores (one formalin fixed for LM and one in saline for IF and EM)

• Cores examined under dissecting microscope and divided while fresh
• Core length minimum 10mm and diameter minimum 1.2mm

Complications

Bleeding, infection, damage to surrounding structures, pain, AV fistulas

Macroscopic appearance

Use of dissecting microscopy or standard light microscopy to assist in sample adequacy

Glomeruli can be difficult to visualize due to lack of blood, significant sclerosis, fragmented biopsy with significant blood staining

Adequacy

Diameter

• Aim 14-16 gauge core for individuals >8 years old, given glomeruli 200-250um

Number

• Generally 8-10 glomeruli, prefer > 10. Likelihood of detecting pathology dramatically increased with > 20 glomeruli
  • If MCD vs FSGS, 25+ glomeruli including juxtamedullary representation

Region:

• Need to also consider diagnostic regions
  • Adequate tubulointerstitial parenchyma to assess interstitial fibrosis & tubular atrophy (IFTA)
  • Juxtamedullary in MCD vs FSGS
  • Subcapsular in hypertension-associated glomerulopathy

Inadequacy not meant as criticism but aimed to ensure interpret biopsy result with caution

Processing of Sample:

Ensure accompanied by clinical datasheet: allows the pathologist to provide a more accurate final diagnosis rather than interpret the pattern

Formalin pot for light microscopy

• Delegation of tissue must occur within minutes to ensure maximum preservation of architecture
• Generally one whole core
• Core placed in cassette -> formalin fixed -> processed to remove water and replace with alcohol -> infiltrated with wax -> frozen -> sections taken (up to 21 levels)
  • Sections 2-3 micron (each section has a dedicated stain, dependent on the laboratory)

Fresh tissue for

• Immunofluorescence
  • Snap frozen
• Electron microscopy
  • Fixed in glutaraldehyde
  • Generally only need a few glomeruli

Elements evaluated:

Cells: mononuclear, PMN, Eosinophils

Hypercellularity

Glomerular:

• • Mesangial: IgAN, SLE II, IgM Nephropathy
  • Endocapillary: PIGN, MPGN, SLE class III-IV

Interstitial: Tubulointerstitial nephritis

Spaces: Capillary lumen, Bowman’s space

Matrix: Basement membrane, mesangial matrix

Stains:

Haematoxylin and Eosin (H&E Stain) (A) (B) (E)

• Allows the first impression of the composition of tissue
• Hematoxylin stains nuclei blue
• Eosin stains all components of glomerular and capillary wall pink (Podocyte, endothelial cells, immune deposits)

Periodic acid Schiff stain (PAS stain) (D)

• Stain allows the assessment of the basement membrane
• Stains carbohydrates in GBM and mesangial matrix but not other components
• GBM appears more distinct
• Can demonstrate nodularity

Jones Methenamine-Silver Stain (C)

• Stain allows the assessment of the basement membrane
• Stains carbohydrates that can be oxidized to aldehydes, appear black (argyrophilic)
• Primarily stains the GBM and areas of sclerosis
• Can demonstrate spikes, double contours

 Masson’s Trichrome Stain (F)

• Stains to assess connective tissue and vessels
• Stains collagen blue, uses three solutions
• Demonstrates subepithelial immune deposits red/pink
• Can show areas of fibrosis and sclerosis in red/pink

Image (with permission): Tyagi et al. Indian Journal of Nephrology 2013

Need to comment on the following:

Number of glomeruli present

Number of globally sclerosed glomeruli (Often non-specific staining pattern)

Positivity and Intensity of staining: 0-3+ (or 4+)

Staining pattern: Granular, linear, semi-linear, smudgy, garland, coarse, confluent

Location: Peripheral capillary wall, mesangium, capillary lumen, bowman space, tubular basement membranes, vascular wall, nuclear staining

Segmental trapping of C3 and IgM

Internal controls

IgA nephropathy/HSP (A) Class IV or diffuse lupus nephritis (B) Membranous nephropathy (C)
Post infectious glomerulonephritis (D) C1q nephropathy (E) Diabetic Nephrology (F)
Image: Singh G et al. World J Nephrol. 2016