[08.02] Review of Renal Histology & Introduction to Renal Pathology V2.2.pdf

Cortex

What is the lighter outer layer of the kidney containing the glomeruli?

Medulla

What is the darker inner layer of the kidney containing the renal pyramids and tubules?

Renal papillae

What are the apices of the renal pyramids called?

Renal pelvis

What is the funnel-shaped center of the kidney that contains fatty tissue and calyces?

Renal cortical tissue

What specific type of tissue is obtained during a kidney biopsy because it contains the glomeruli?

Glomerulus, Tubules, Interstitium, and Blood vessels

What are the four compartments of the normal adult kidney?

Back-to-back arrangement

How are renal tubules normally arranged, making the interstitium difficult to observe?

PCT, loop of Henle, DCT, and collecting ducts

Which specific structures comprise the renal tubules?

Interstitium

What is the space between the renal tubules called?

Light Microscopy (LM), Immunofluorescence (IF) Microscopy, and Electron Microscopy (EM)

What are the three diagnostic modalities used to evaluate medical renal disease?

Fresh renal tissue

What type of specimen preparation is required for Immunofluorescence (IF) microscopy?

Formalin or formaldehyde

Fresh tissue for IF microscopy must not be exposed to which chemicals?

Black and white

What is the color characteristic of images produced by Electron Microscopy (EM)?

Hematoxylin and eosin (H&E)

What is the most common stain used in the usual evaluation of renal slides?

Identifying inflammatory cells (eosinophilic and neutrophilic infiltrates)

What is the primary importance of the H&E stain in renal pathology?

Interstitial nephritis

In which condition are eosinophilic and neutrophilic infiltrates easily seen using H&E?

Periodic Acid-Schiff (PAS)

Which stain is considered the best for evaluating the pathology of a renal biopsy specimen?

Glomerular basement membranes (GBM), tubular basement membranes (TBM), and the mesangium

Which structures are highlighted by the PAS stain?

Brush border

Which specialized structure on the surface of PCTs is uniquely identifiable using the PAS stain?

Masson’s trichrome stain (MTS)

Which stain is used to evaluate areas of fibrosis and stains collagen blue or green?

Silver stain (PAAG)

Which stain highlights basement membranes in dark brown and is used to identify atrophic tubules?

Spikes

What characteristic feature of membranous nephropathy is identified using the PAAG stain?

Simple squamous epithelium

What type of epithelium forms the endothelium lining the glomerular capillaries?

Visceral and parietal epithelium

Which two layers of epithelium invest the glomerular capillary network?

Podocytes

What is another name for the visceral epithelial cells that are part of the capillary wall?

Foot processes

What are the finger-like cytoplasmic extensions of podocytes seen under EM?

Filtration slits

What structures are present between the foot processes of podocytes?

Parietal epithelium

Which layer of epithelial cells lines the Bowman’s space and is attached to the Bowman’s capsule?

Renal corpuscle

What term describes the combination of the glomerulus and the Bowman’s capsule?

Endothelial cells, GBM, visceral epithelial cells, and the mesangium

What four components make up the glomerular capillary wall?

Lamina rara interna, lamina densa, and lamina rara externa

What are the three layers of the Glomerular Basement Membrane (GBM)?

Lamina densa

Which layer of the GBM is the thickest, most prominent, and appears dark gray due to its density?

Lamina rara externa

Which layer of the GBM is located directly under the podocytes?

Mesangial cells

Which cells in the glomerulus are contractile, phagocytic, and capable of laying down matrix and collagen?

2 to 3

How many mesangial cells are typically found within a normal mesangial matrix?

Proliferation

The presence of four or more mesangial cells within a mesangial matrix is indicative of what process?

Water and small solutes

Normal glomerular filtration is characterized by high permeability to which substances?

Proteins (e.g., albumin)

The glomerular barrier function makes the membrane impermeable to which large molecules?

Size-dependent and charge-dependent

On what two factors does the glomerular barrier function rely?

Negative (Polyanionic)

What is the electrical charge of the filtration barrier and the inner layer of podocytes?

Slit diaphragm

What structure between podocytes contains proteins that control glomerular permeability?

Nephrin, Podocin, and CD2-associated protein

Which specific proteins are located in the slit diaphragm?

Nephrotic syndrome

Mutations in the genes encoding slit diaphragm proteins lead to what clinical syndrome?

Fenestrated endothelial layer

Which layer of the capillary wall contains "holes" to facilitate filtration?

Effacement

What term describes the fusion and flattening of podocyte foot processes?

Minimal change disease

In which disease is globally effaced foot processes the only feature seen?

Linear and Granular

What are the two primary patterns observed in Immunofluorescence (IF) microscopy?

Positive

In IF microscopy, what does a green staining pattern indicate?

Negative

In IF microscopy, what does a black or dull result indicate?

0 to 4+

How is the intensity of staining in IF microscopy graded?

IgA nephropathy (Berger’s disease)

Which disease requires an IF intensity grade of at least 2+ for diagnosis?

IgA nephropathy

What is the most common glomerulonephritis (GN) worldwide?

Full house pattern

What term do clinicians use when all IF stains (IgG, IgA, IgM, C3, C1q) are positive in lupus nephritis?

C1q

Positive staining for which specific complement component is a strong indicator of lupus?

Antigen and antibody

An immune complex is composed of which two components?

Anti-IgG, Anti-IgA, Anti-IgM, Anti-C3, Anti-C1q, and Anti-fibrinogen

What are the six usual antibodies added to tissue for IF microscopy?

Fluorochromes

What substances attached to antibodies cause the green-staining reaction under IF?

Dense deposit disease

Which condition is characterized by the activation of the alternative complement pathway?

Electron-dense deposits

How do immune complexes appear under Electron Microscopy?

Subepithelial humps

Which immune deposits are sandwiched between podocytes and the GBM, commonly seen in PSGN?

Epimembranous deposits

Which deposits are situated between podocyte foot processes and are seen in Membranous nephropathy?

Subendothelial deposits

Which deposits are situated underneath the endothelium and are seen in lupus nephritis and MPGN?

Mesangial deposits

In which region are immune complexes located in IgA nephropathy?

Anti-GBM antibody-induced nephritis and Membranous glomerulopathy

What are two forms of "in situ" immune complex deposition?

Alpha 3-chain of collagen type IV

Against which specific component of the GBM are antibodies directed in anti-GBM nephritis?

Goodpasture syndrome

In which syndrome do anti-GBM antibodies cross-react with the alveolar basement membrane in the lungs?

Hemoptysis

Patients with Goodpasture syndrome present with nephritis and what pulmonary symptom?

Diffused linear staining

What IF pattern is characteristic of anti-GBM disease?

Severe crescentic glomerular damage

Anti-GBM disease is histologically characterized by what type of damage?

Rapidly progressive glomerulonephritis (RPGN)

Anti-GBM disease often presents clinically as which syndrome?

Planted antigens

What term describes antigens like DNA or bacterial products that are not normal components of the kidney but localize there?

Granular staining

What IF pattern is produced by antibodies reacting with planted antigens?

Circulating immune complex deposition

In which mechanism are antigen-antibody complexes formed in the blood and then trapped in the glomeruli?

Endogenous (e.g., Lupus) or Exogenous (e.g., post-streptococcal)

What are the two sources of antigens that trigger circulating immune complexes?

Hepatitis B, Hepatitis C, Syphilis (T. pallidum), and Malaria (P. falciparum)

Which microbial infections can cause immune complex-mediated nephritis?

Hypercellularity

Which histological feature of GN involves leukocytic infiltration and the proliferation of mesangial and endothelial cells?

Mesangiolysis

What is the consequence of antibodies attacking mesangial cell antigens?

Intravascular thrombosis

Antibodies to endothelial cell antigens cause endothelial injury and what other complication?

Proteinuria

What is the clinical result of antibodies attacking podocyte components?

Melted Hershey’s Kisses

Effaced podocyte foot processes are described as resembling what under EM?

Detachment of epithelial cells from the GBM

What event following podocyte injury causes protein to leak into the urine?

Hypercellularity, basement membrane thickening, hyalinosis, and sclerosis

What are the four major pathologic responses of the glomerulus to injury?

Endothelial cells

The proliferation of which cells leads to the obliteration of the capillary lumen?

Neutrophils

The influx of which type of white blood cell is a characteristic feature of post-streptococcal GN?

Crescents

What structures are formed by proliferating parietal epithelial cells and infiltrating leukocytes in Bowman’s space?

Fibrin

Which plasma protein triggers the formation of crescents when it leaks into Bowman’s space?

PAS-stained renal tissue

Thickening of capillary walls or the GBM is best seen using which stain and modality?

Increased protein synthesis or additional layers of matrix

Besides immune complexes, what can cause GBM thickening in diabetic glomerulosclerosis?

MPGN

In which disease is a fully duplicated lamina densa (splitting) seen?

Hyalinosis

What is the accumulation of homogeneous, eosinophilic plasma proteins within glomerular structures called?

Sclerosis

What is the accumulation of extracellular collagenous matrix that leads to the collapse of capillary loops?

Focal Segmental Glomerulosclerosis (FSGS)

Sclerosis is a common feature of which specific renal disease?

Nephritic syndrome

Which clinical syndrome is characterized by hematuria, hypertension, and mild proteinuria?

Nephrotic syndrome

Which clinical syndrome is characterized by heavy proteinuria, edema, and hypoalbuminemia?

Isolated urinary abnormalities

What manifestation is defined as hematuria and/or subnephrotic proteinuria without other symptoms?

Diffuse endocapillary proliferation and leukocytic infiltration

What are the light microscopy findings for postinfectious (post-streptococcal) GN?

Subepithelial humps

What is the characteristic EM finding for post-streptococcal GN?

Extracapillary proliferation with crescents and necrosis

What is the light microscopy finding for Crescentic (RPGN) GN?

Diffuse capillary wall thickening and subepithelial spikes

What are the light microscopy findings for Membranous nephropathy?

Minimal change disease

Which disease shows a normal appearance under light microscopy but foot process effacement under EM?