Renal Pathology 1

RENAL PATHOLOGY University of the City of Manila

Development of the Kidneys • Intermediate mesoderm a. pronephric kidneys – cords of cells cervical and thoracic regions pronephric duct b. mesonephric kidneys series of tubules and tuft of vessels from the aorta mesonephric duct c. metanephric kidneys ureteric bud metanephric blastema

Congenital Anomalies 1. 2. 3. 4.

Agenesis of the kidneys Hypoplasia Ectopic kidneys Horse shoe kidneys fusion of either the upper pole or the lower poles anterior to the great vessels common

Renal cystic diseases • Importance 1. common diagnostic problem 2. major cause of CRF 3. confused with malignant tumors

Renal cystic diseases

Urinary tract obstruction •

Importance 1. Increased susceptibility to infection 2. Increased susceptibility to obstruction 3. Obstrcution may lead to atrophy Hydronephrosis – dilatation of the renal pelvis and calyces

Urolithiasis •

Four main types of calculi 1. 2. 3. 4.

Calcium containing Struvite stone/triple stones Uric acid Cystine

Staghorn calculi stone in the renal pelvis

Tumours of the Kidney •

Benign 1. 2. 3. 4.

Renal papillary adenoma Renal fibroma Angiomyolipoma Oncocytoma

Tumours of the Kidney •

Malignant 1. Renal cell carcinoma 1. 2. 3. 4.

Clear cell Papillary Chromophobe Collecting duct

2. Urothelial carcinoma of the pelvis 1. Squamous cell carcinoma 2. Transition cell carcinoma

Functions • Filtration of small molecules from blood plasma to form a filtrate • Selective reabsorption of most of the water and other molecules from the filtrate; leaving behind excess and waste materials to be excreted • Secretion of some secretory products directly from blood into filtrate

Important Implications of Blood Supply 3. End-arteries, occlusion of any branch usually results in infarction of the specific area it supplies 5. Glomerular disease that interferes with blood flow through the glomerular capillaries has profound effects on the tubules, within both the cortex and the medulla, because all tubular capillary beds are derived from the efferent arterioles 7. Blood supply to the renal medulla render them especially vulnerable to ischemia

Nephron • Functional unit of the kidney • Consists of – Renal corpuscle • Bowman’s capsule • Glomerulus

– Renal tubule • • • •

Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting tubule

Glomeruli •

•

anastomosing network of 20 to 40 capillary loops arranged in several units or lobules architecturally centered by a supporting mesangial stalk lined by fenestrated endothelium invested by two layers of epithelium a. visceral epithelium is incorporated into and becomes an intrinsic part of the capillary wall, b. parietal epithelium, situated on Bowman's capsule lines the urinary space, the cavity in which plasma filtrate first collects

The glomerular capillary wall is the filtering membrane and consists of the following structures 1. A thin layer of fenestrated endothelial cells each fenestrum being about 70 to 100 nm in diameter.

The glomerular capillary wall is the filtering membrane and consists of the following structures 2. Glomerular basement membrane (GBM) a. lamina densa - a thick electron-dense central layer, b. thinner electronlucent peripheral layers lamina rara interna lamina rara externa

The glomerular capillary wall is the filtering membrane and consists of the following structures GBM

consists of collagen (mostly type IV), laminin, polyanionic proteoglycans (mostly heparan sulfate), fibronectin, entactin, and several other glycoproteins

Type IV collagen forms a network suprastructure to which other glycoproteins attach The building block (monomer) of this network is a triple-helical molecule made up of three αchains determines its permeability characteristics.

The glomerular capillary wall is the filtering membrane and consists of the following structures 3. visceral epithelial cells (podocytes) are structurally complex cells that possess interdigitating processes embedded in and adherent to the lamina rara externa of the basement membrane. Adjacent foot processes (pedicels) are separated by 20to 30-nm-wide filtration slits, which are bridged by a thin diaphragm

The glomerular capillary wall is the filtering membrane and consists of the following structures 4.

mesangial cells supports the entire glomerulus Basement membrane-like mesangial matrix forms a meshwork through which the mesangial cells are centered mesenchymal origin contractile \ phagocytic capable of proliferation can lay down both matrix and collagen secrets a number of biologically active mediators akin to vascular smooth muscle cells and pericytes

H and E

MTS

PAS

PAS

PAAg

Immunofluorescence microscopy • Immunoglobulins – IgG, IgA, IgM

• Complements – C3, C1q

• Fibrinogen • (Albumin, Kappa, lambda)

Electron microscopy • One-micron thick sections (semi-thin sections) – Toluidine blue

• Ultra-thin sections

Compartments • • • •

Glomeruli Tubules Interstitium Blood Vessels

Glomeruli -Hypercellularity (mesangal, endothelial, epithelial, inflammatory cells) -Glomerulosclerosis (segmental, global) -GBM abnormality (thickening, double contour, wire loops, rupture) -Bowman’s capsule

Tubules -Tubulitis -Tubular atrophy -Tubular necrosis -Casts -Inclusion bodies -Vacuolations -Calcifications

Interstitium -Fibrosis -Edema -Inflammatory cells -Hemorrhage

Blood Vessels -Arteries, veins, arterioles, capillaries -Vasculitis -Fibrinoid necrosis -Thrombi -Fibrosis

Definition of Terms

Diffuse

Focal

Global

Segmental