Renal Pathology Flashcards
Function of the Urinary system
Filter blood and produce urine
Important in homeostasis of body fluids
Responsible for altering blood composition and pressure forming urine and regulating bodily fluid pH.
Role of the kidney in the urinary system
Filters waste and maintains fluid balance
Location of kidneys
Upper abdominal cavity on either side of the spine with the right kidney lower than the left.
Ureters role
Transport urine to urinary bladder
role of nephrons in the kidney
Functional unit
alters blood composition
regulates blood pH
affects blood volume and pressure
Gross structure of the kidney: Renal Cortex and Renal colums - location and structure
The outer region of the kidney consists of convoluted tubules, renal corpuscles, blood vessels
Appear granular due to numerous nephrons packed closely together.
Renal Columns: are extensions of the renal cortex that project into the renal medulla separating adjacent renal pyramids and giving stability to the cortex
Gross structure of the kidney: Renal Medulla and Renal Pryamids - location and function
-Inner region of the kideny
- Contains renal pyramids
- Renal pyramids consits of renal tubules and collects urine from nephrons. Cone-shaped structures located within the medulla of the kidney
- Medulla appears striated due to arrangement of renal pyramids
Gross structure of the kidney: Renal Pelvis - Location and function
Funnel-shaped structure
- Located at the innermost part of the kidney where urine from collecting ducts is collected
- Narrows down to form the ureter which transports urine to the urinary bladder
Gross structure of the kidney: Renal Artery and Vein - function
- Blood vessels that supply and drain the kidney
renal artery: oxygenated blood to the kidney for filtration
renal vein: carries deoxygenated blood away for reoxygenation and further transport to the heart
Gross structure of the kidney: Nephrons
- functional units of the kidney responsible for filtering blood and producing urine
- each nephron consits of a renal corpuscle and renal tubule
Constituents of the renal corpuscle and renal tubule in a nephron
renal corpuscle: glomerulus and Bowmans capsule
renal tubules: proximal convoluted tubule, loop of Henle, distal convoluted tubules and collecting duct
Gross structure of the kidney: Renal Capsule - function
-Tough fibrous layer surrounding each kidney
- Maintains its shape
- Protects from injury
- Continuous with the ureter
Gross structure of the kidney: Renal Sinus - structure
Cavity within the kidney containing: renal pelvis, renal calyces, blood vessels, nerves, lymphatic vessels.
Gross structure of the kidney - Renal hilum
- Indented area
- Entrance for: renal artery, renal vein, ureter, nerves, lymphatics
Collecting and papillary ducts gather urine from nephrons
- urine directed to the renal calyx
- then drained into the pelvis and ureter
Nephrons - Cortical / Juxtamedullary
Cortical nephrons: Shorter loops of henle barely penetrating the medulla
Juxtamedullary nephrons: Long loops of henle that extend deep into the medulla, facilitating concentration of urine
Nephron structure and function
Distal Convoluted Tubule (DCT)- located distal (farther away) from the glomerulus. The Proximal Convoluted Tubule (PCT) - proximal (closer) to the glomerulus.
Glomerulus (tuft of capillaries): specialized structure within the kidney nephron responsible for initial blood filtration and the formation of primary urine.
Afferent arterioles deliver blood to the glomerulus, efferent arterioles carry blood away
vasa recta: peritubular capillaries surrounding the nephron loops, facilitating exchange and reabsorption in the kidney
SEM of a glomerulus
- Reveals intracate networks of podocytes, enothelial cells, basement membranes necessary for kidney filtration
- Uses a focus beam of electrons to generate detailed surface images of specimens at a nanometer scale
Glomerulus: Function filtration membrane
filtration of water and ions
preents filtration of blood cells and medium-large proteins
Renal Corpuscle: High-resolution images
Captures delicate genestrations and interdigitations cruical for maintaining glomeruluar function in health.
Overview of filtration membrane structure in glomerulus
Glomeruluar endothelial cells: Large pores (fenestrations) and are leaky. Prevents filtration of blood cells but allows components of blood plasma through.
Basement membrane (basal lamina): lies between endothelium and podocytes. Prevents filtration of larger proteins.
Podocytes: Specialised cells of the bowmans capsule in the kidney. Form pedicles with filtration slits inbetween that prevent filtration of medium-sized proteins.
Lab Investigations to examin kidney tissue samples- Hematoxylin and Eosin (H&E) Staining
standard technique used in histology to visualize cellular morphology and tissue architecture.
Hematoxylin stains nuclei blue-purple,
eosin stains cytoplasm and extracellular matrix pink.
method routinely used in the initial examination of kidney tissue to assess general morphology and identify any abnormalities.
Lab Investigations to examin kidney tissue samples- Special Stains (The Renal Set)
Collection of special stain used in examination of renal biopsies.
Jones (PAAG): Periodic Acid-Silver Stain - visualizes basement membranes (part of the filtration barrier of the nephron).
MSB: Martius Scarlet Blue or other trichrome stains- assesses fibrosis and scarring.
PAS +/- D: Periodic Acid-Schiff with and without diastase, highlighting carbohydrates like glycogen.
Diastase enzyme breaks down complex carbohydrates like glycogen- helps distinguish between true glycogen and other PAS-positive substances by selectively removing glycogen, aiding in the accurate identification of glycogen-rich structures in tissues.
EVG: Elastic van Gieson stain- visualizes elastic fibers in the tissue.
Congo Red: Detects amyloid deposits that can accumulate in kidney tssues disrupting function and contributing to various disease (AD).
Lab investigations: Immunoflourescence Microscopy (IMF)
Immunofluorescence Microscopy (IMF): Detects presence and location of specific protein within a cell.
Uses fluorescent markers such as:
IgG, IgM, IgA, Light Chains (Κ & Λ): Detect immunoglobulins and light chains, which can indicate immune complex-mediated glomerulonephritis.
Light chains in immunoglobulins (antibodies) are components of the antigen-binding region of antibodies and play a crucial role in immune responses - categorized into two types: kappa (κ) and lambda (λ).
CD8, CD4, CD3: Markers for T-cell populations, useful in assessing inflammatory infiltrates.
C3, C1q, C4D: Complement proteins- presence indicates immune complex deposition and complement activation, suggesting conditions like lupus nephritis or antibody-mediated rejection in transplant.
Lab Investigations: Electron Microscopy
Provides high-resolution images of kidney tissue at the ultrastructural level- valuable in diagnosing glomerular diseases and other renal pathologies where ultrastructural changes play a significant role.
Provides ultrastructural details.
Uses a beam of electrons to visualize cellular and subcellular structures, such as podocyte foot processes, basement membranes, and mesangial cells.
Renal Biopsy Evaluation: ‘ish’
“Ish”: Informal term conveying approximation or uncertainty.
‘always (ish@ used to imply occasionalexceptions variations in EM and IMF use for renal biopsy evaluation depending on the specific case/ insitution.
What is a renal biopsy? What does ut at ‘levels’ mean?
Renal biopsies: removal of small piece of tissue to examin under a microscope to diagnose/assess kidney damage.
Cut at “Levels”: Kidney tissue samples cut into thin sections at various levels (superficial, deep , midline) so pathologists can examine different regions of the tissue to asses for variations/abnormalities throughout the sample.
Different types of common renal biopsies
Needle Biopsy: Most common type. Needle inserted through skin into the kidney extracting a small tissue sample.
Native Kidney Biopsy: Biopsy performed on native kidneys (patient’s own kidneys.)
Transplant Biopsy: conducted on a transplanted kidney to assess its function or to diagnose any potential issues ( rejection.)
Tumor Biopsy: biopsy may be performed to obtain a tissue sample for diagnosis and to determine the type of tumor present if one is suspected
Wedge Biopsy: small wedge-shaped piece of tissue is removed from the kidney.
Lobe Biopsy: Refers to a biopsy technique where a lobe of the kidney is specifically targeted for sampling.
Resection Biopsy: Removal of a portion of the kidney tissue for examination, often used in cases where a larger sample.
Explant Biopsy: involves removal of entire kidney (explant) for examination, which may be necessary in cases of severe disease or transplantation.
Indications of Renal Biopsy
- Definitive histological gianosis of glomerular/ interstitial disease
- Severe Proteinuira
- Haematuria not caused by disease of the lower urinary tract: suggests potential renal or glomerular involvement often necessitating renal biopsy for accurate diagnosis.
- Acute renal failure (intrinsic renal disease)
- Glomerulonephritis
- Other glomerular disorders (e.g amyloid and diabetes)
- Interstitial Nephritis
- Renal Transplant ( assessment post-transplant for rejection/complications
Renal biopsy in diagnosing glomerulonephritis
- assesses glomeruluar abnormalities and interstitial diseases by evaluating interstitial inflammation and fibrosis
- Needle core biopsy followed by examination under microscopes e.g electron, light and immunoflourescence microscopy. Allows for comprehensive evaluation of kidney tissue providing valuable diagnostic information for guiding patient care.
Stages of Renal Biopsy - Fixation
Tissue preserved in formalin for light microscopy, glutaraldehyde for electron microscopy (EM), and frozen/Michel’s medium for immunofluorescence microscopy (IMF) to maintain cellular structure and antigen integrity.
-Aldehyde fixatives (e.g formalin and glutaraldehyde), crosslink proteins in tissue samples, preserving cellular structures and preventing degradation for microscopic examination.
-Glutaraldehyde in high concentrations can cause irritation to the respiratory tract, skin, and eyes, and prolonged exposure may lead to sensitization and allergic reactions. Pure morphology, better, slower, lot more toxic
Stages of Renal Biopsy - Processing
Samples embedded :
-paraffin for light microscopy
-resin for electron microscopy
-frozen sections for immunofluorescence microscopy
-Prepares samples for respective microscopic examinations while preserving tissue architecture and antigenicity.
Post-Infectious Glomerulonephritis
Can be global and diffuse
Enlarged, hypercellular glomeruli
Proliferation of enotherlial and messignal cells
Cresent formation in severe cases- impairs kidney function
Immune system reacts to bacterial antigens deposited in the glomeruli causing inflammation, cellular proliferation and formation of crescents.
this inflammation and damage can progress to chronic kidney disease if left untreated.
