Test Catalog

Test ID: RPCWT    
Renal Pathology Consultation, Wet Tissue

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating and managing patients with kidney disease


Following the progression of known renal disease or response to therapy


Determining the cause of dysfunction in the transplanted kidney (allograft)

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

The Renal Pathology Consultation is performed by a Mayo Clinic renal pathologist and entails the performance of appropriate procedures and stains based on the material received, patient information and specific findings on the case in order to determine a diagnosis. Optimal/standard diagnostic interpretation of a medical kidney biopsy requires integration of the light microscopy, immunofluorescence, and electron microscopy findings together with the clinical and laboratory data for the patient. Published standards by the Renal Pathology Society are followed for the diagnostic evaluation and reporting of non-neoplastic renal disease.(1)


Light Microscopy:

Wet/unprocessed tissue submitted for light microscopy routinely includes the preparation of stains, which include hematoxylin and eosin (H and E), periodic acid Schiff (PAS), Masson trichrome, and Jones methenamine silver stains.



Wet/unprocessed tissue submitted for immunofluorescence may include the following stains in order to render an accurate diagnosis. These stains include: IgA, IgG, IgM, C1q, C3, albumin, fibrinogen, kappa light chain, and lambda light chain stains with C4d added if the biopsy is an allograft.


The IgG subtypes (IgG1, IgG2, IgG3, IgG4) are typically only utilized if the biopsy shows features suspicious for a monoclonal/monotypic deposition process involving IgG.


Alport (collagen IV, alpha 2 and alpha 5) staining is performed in the setting of biopsy findings that are consistent with hereditary nephritis/Alport syndrome.


Phospholipase A2 Receptor (PLA2R) staining is performed in the setting of membranous nephropathy/glomerulonephritis to aid in determining whether it is most likely primary/idiopathic or secondary. 


Paraffin-Based Immunofluorescence Stains:

The paraffin-based immunofluorescence stains listed above would only be utilized in the special circumstance when there is no tissue or inadequate tissue available for standard immunofluorescence or if there are findings that raise concern for so-called "masked deposits"


Electron Microscopy:

Wet/unprocessed tissue submitted for electron microscopy will be processed for transmission electron microscopy. A formal interpretive report is issued, incorporating the findings from all tests performed for diagnostic purposes.


See Pathology Consultation Ordering Algorithm in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The Mayo Renal Pathology service is staffed by board-certified pathologists who have a special interest in non-neoplastic diseases of the kidney.


Kidney biopsy has proven to be of value in the clinical evaluation and management of patients with kidney disease, including acute and chronic renal insufficiency, nephrotic syndrome, nephritic syndrome, proteinuria and hematuria, and in the overall management of renal transplant recipients.


Optimal interpretation of a kidney biopsy requires integration of clinical and laboratory results with light microscopic, immunofluorescent histology, and electron microscopy findings.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

Both a verbal report and a faxed report are provided to nephrologists for Mayo Clinic Laboratories cases.


Representative electron microscopy images and significant positive immunofluorescent stain findings can be provided on a CD upon request.


In most cases, the electron microscopy results are reported as an addendum and a final report is issued including these findings. This final report is again faxed to the submitting nephrologist and mailed to the submitting pathology laboratory, along with a representative set of the light microscopy slides.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Accurate and timely interpretation of a kidney biopsy requires integration of light microscopic, immunofluorescent histology, and electron microscopic findings with clinical and laboratory data. Failure to provide the relevant clinical history and laboratory results may result in a delay in the interpretation or the inability to adequately correlate the biopsy findings with the clinical picture.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Chang A, Gibson IW, Cohen AH, et al: A position paper on standardizing the nonneoplastic kidney biopsy report. Clin J Am Soc Nephrol 2012;7:1365-1368

2. Heptinstall RH: Heptinstall's Pathology of the Kidney. Edited by JC Jennette. Lippincott Williams and Wilkins, 2007

Special Instructions Library of PDFs including pertinent information and forms related to the test