OVERVIEW

Nephropathology (Renal pathology) is a subspecialty of anatomic pathology that deals with the diagnosis and characterization of medical diseases (non-tumour) of the kidneys. The department processes the renal biopsies (native and allograft) for light microscopy, immunofluorescence and electron microscopic evaluation by a Nephro-pathologist. Medical kidney diseases present with varied clinical manifestations like Nephrotic Syndrome, Nephritic Syndrome, acute kidney injury, isolated hematuria/proteinuria, and graft dysfunction, in the case of a renal transplant recipient. These diseases may affect the kidney at microscopic level.

The Nephro-pathologist analyses the findings of renal Biopsy on light microscopy, immunofluorescence, and electron microscopy keeping in mind the clinical findings to obtain a definitive diagnosis and to identify the particular renal compartment affected by the disease. In doing so he plays a pivotal role in the management of patients with medical renal disease.

In addition, the nephropathological diagnosis often evolves from a morphological diagnosis to disease diagnosis to etiological diagnosis, which constitutes the key to treatment. which constitutes the key to treatment.

Nephropathological diagnosis is nowadays almost always made on percutaneous needle biopsies. The quality of the information gained from a renal biopsy study depends on numerous factors, including the size and type of renal biopsy sample, its fixation, processing, microtomy, and staining. The thickness of sections, quality of the reagents, and the expertise of the technical staff are of utmost importance for proper evaluation of the morphological lesions. No compromise should be made on the quality of fixative, quality of processing reagents, thin sectioning of the paraffin embedded tissue and the quality of staining reagents, if proper nephropathology is to be practiced.

Renal Biopsy, a relatively safe medical procedure, has gained considerable importance for the diagnosis of kidney diseases.

[Sample transport requirements – For purposes of transport of patient samples, all clinical samples, in accordance with UN guidelines, are generally classified as Category B and assigned to UN3373 (Biological Substance, Category B) and should be packaged in accordance with UN packaging instructions PI650. Triple packaging system for transport of Biopsy samples (with a fixative) to the lab-]

Nowadays, a spring-loaded automated cutting needle, with or without ultrasound guidance, is used for obtaining renal tissue core. The lower pole of the native left kidney and the most visible or accessible pole of the transplanted kidney are utilized for renal Biopsy. In adults, 14- or 16-gauge needles are suitable, considering the internal diameter of 900-1000 microns and 600-700 microns, respectively (average diameter of the normal glomerulus in an adult is 200-250 microns). The finer needle of 18-gauge (internal diameter 300-400 micron) may be used for children younger than 8 years.

Whenever possible, 2-3 cores of renal Biopsy should be taken: one for light microscopy (LM), another for immunofluorescence (IF), and one for electron microscopy (EM), if required. These renal Biopsy cores should be sent in separate vials containing appropriate fixative/transport media for each of these tests (Light microscopy- 10% Formalin, Immunofluorescence- Michel’s transport medium or normal saline, Electron microscopy- 2.5% Glutaraldehyde). The biopsies sent in normal saline should be processed within 6 hours. In cases where taking extra passes is not possible, a cutting protocol may be followed: both the ends of the core are taken for EM, one-third of the core, including some glomeruli, is placed in the transport medium for IF and the rest is kept for LM.

The Nephro-pathologist always works closely with nephrologists and transplant surgeons, who typically obtain diagnostic specimens via percutaneous renal Biopsy. The absence of adequate pertinent clinical information seriously hinders any meaningful evaluation of renal Biopsy. Ideally, the renal Biopsy should be accompanied by pertinent clinical information. Detailed clinical history, including past medical illnesses, recent laboratory values with particular emphasis on urinalysis, biochemical parameters (urea, creatinine, total protein, cholesterol), serological investigations (ANA, dsDNA, ANCA, C3, C4, anti-GBM), viral markers (hepatitis B, hepatitis C, HIV) and other parameters of interest should be included. Details of any therapy administered should also be mentioned. In cases of renal transplant biopsies, information must include the duration of transplant and therapy. Nephro-pathologist, knowledgeable in both renal medicine and pathology, can correlate subtle tissue-derived information with appropriate clinical data. This remains the most important key to the development of an accurate clinicopathologic diagnosis. It needs to be remembered that renal pathology cannot succeed as a standalone practice. Extremely close collaboration and teamwork between a Nephrologist and Nephro-pathologist is the key to achieving the appropriate management of patients.

Given below are the descriptions of the conditions treated

Renal biopsy- A Neuropathologist’s perspective

Renal Biopsy, a relatively safe medical procedure, has gained considerable importance for the diagnosis of medical renal diseases. Nowadays, a spring-loaded automated cutting needle, with or without ultrasound guidance, is used for obtaining renal tissue core. The lower pole of the native left kidney and most visible or accessible pole of the transplanted kidney is utilized for renal Biopsy. In adults, 14-or 16-gauge needles are suitable, considering the internal diameter of 900-1000 micron and 600-700 micron, respectively (average diameter of the normal glomerulus in an adult is 200-250 micron). The finer needle of 18-gauge (internal diameter 300-400 micron) may be used for children younger than 8 years.

Whenever possible, 2-3 cores of renal Biopsy should be taken: one for light microscopy (LM), another for immunofluorescence (IF) and one for electron microscopy (EM), if required. These renal Biopsy cores should be sent in separate vials containing appropriate fixative/transport media for each of these tests (Light microscopy- 10% Formalin, Immunofluorescence- Michel’s transport medium or normal saline, Electron microscopy- 2.5% Glutaraldehyde). The biopsies sent in normal saline should be processed within 6 hours. In cases where taking extra passes is not possible, a cutting protocol may be followed: both the ends of the core are taken for EM, one-third of the core, including some glomeruli, is placed in the transport medium for IF and the rest is kept for LM.

The Neuropathologist always works closely with nephrologists and transplant surgeons, who typically obtain diagnostic specimens via percutaneous renal Biopsy. The absence of adequate pertinent clinical information seriously hinders any meaningful evaluation of renal Biopsy. Ideally, the renal Biopsy should be accompanied by pertinent clinical information. Detailed clinical history, including past medical illnesses, recent laboratory values with particular emphasis on urinalysis, biochemical parameters (urea, creatinine, total protein, cholesterol), serological investigations (ANA, dsDNA, ANCA, C3, C4, anti-GBM), viral markers (hepatitis B, hepatitis C, HIV) and other parameters of interest should be included. Details of any therapy administered should also be mentioned. In cases of renal transplant biopsies, information must include the duration of transplant and therapy. Neuropathologist, knowledgeable in both renal medicine and pathology, can correlate subtle tissue-derived information with appropriate clinical data. This remains the most important key to the development of an accurate clinicopathologic diagnosis. It needs to be remembered that renal pathology cannot succeed as a standalone practice. Extremely close collaboration and teamwork between a Nephrologist and Neuropathologist is the key to achieving the appropriate management of patients

Adequacy of biopsy

The minimum diagnostic sample size varies with the specific diagnosis for instance, only one glomerulus is enough for making diagnoses such as Membranous Glomerulonephritis and Amyloidosis, while 25 glomeruli may be required to make an accurate diagnosis of a focal lesion like FSGS. For most of the light microscopic assessment, 8-10 glomeruli are considered adequate.

Nephropathology at NU Hospitals

Nephropathology Department was started at NU Hospitals in February 2015. A comprehensive evaluation of renal biopsies will be done by a qualified Neuropathologist. The biopsies can be sent either in colour-coded vials provided by the NU Hospitals or in separate vials containing appropriate fixative/transport media for each of these tests (Light microscopy- 10% Formalin, Immunofluorescence- Michel’s transport medium or normal saline, Electron microscopy- 2.5% Glutaraldehyde). Sample sent in normal saline should be accompanied with an ice pack in case the transportation takes more than 6 hours. Courier service can be utilized for the transport of samples from the outstation. The reports will be dispatched via mail with pictures.

Sample transport requirements –

For purposes of transport of patient samples, all clinical samples, in accordance with UN guidelines are generally classified as Category B and assigned to UN3373 (Biological Substance, Category B) and should be packaged in accordance with UN packaging instructions PI650.

Triple packaging system for transport of Biopsy samples (with a fixative) to the lab-

The following procedures should be adopted for the transport of all specimens with fixative to the lab:

Step 1: Primary pack – should be watertight, leak-proof and labeled with patient detail and hospital name.

Step 2: Secondary pack – encloses primary pack(s), leak-proof and watertight and protects the primary sample.

Step 3: Outermost pack - sealable and strong enough to protect contents from physical damage during transport.

Packaging for fresh biopsies (in normal saline without fixative)