Urinary system pathology 1 Flashcards
Which species have multilobar renal morphology and which have unilobar?
Multi = cow, pig Uni = carnivores, small ruminants, horses
Kidney function is what % of cardiac output?
30%
What are some of the kidneys function?
- Regulation of electrolytes
- Conservation of water
- Excretion of waste products
- Acid-base regulation
- Endocrine roles: erythropoietin, vitamin D, renin
What are the functions of the lower urinary tract?
- Transport and storage of urine
- Controlled expulsion
What is the functional unit of the kideny?
The nephron
What needs to be observes when looking at a kidney grossly?
- Shape, position, size
- Contours
- Adherence of capsule
- Cortex is finely radially striated + dark red / brown (except cats).
- Medulla pale brown
- Ratio of cortex : medulla of ~2:1 to 3:1 in domestic spp
Describe the normal radiographic anatomy of the kidneys
- Dorsal abdomen, retroperitoneal space
- Right kidney is more cranial
- Smooth margins, similar size and shape
- GI tract can hide right kidney
The right kidney lies within which organ?
Within the renal fossa of the caudate liver lobe
Which 5 features make up the specialised structures of the kidney?
- Glomerulus
- PCT
- LOH
- DCT
- CD
Histologically, how can PCT be compare to DCT?
- PCT epithelium is cuboidal and very metabolically active
- The DCT cells are much more flattened and the lumen is larger
What is the response of the glomerulus to injury?
- Severe damage = fibrosis
- Cannot be replaced so loss of the entire nephron
What is the response of tubular epithelium to mild injury?
- Renal tubular epithelium lies on a basement membrane, cells can regenerate if this membrane stays intact
- Mild to moderate damage
What is the response of tubular epithelium when nephrons are lost?
Remaining tubules can undergo compensatory hypertrophy
- limited capacity, which if reached => renal failure
What is the response of tubular epithelium to severe damage?
- Severe damage with disruption to
b. m. eg. diffuse ischaemic necrosis - loss of basement membrane structure so epithelium cant regenerate
- permanent loss of entire nephron functional unit
Why does damage lead to entire loss of the nephron?
Each portion of the nephron is dependant on the others for its function
Give some examples of congenital/inherited kidney diseases
- Ectopic and fused kidneys
- Dysplasia
- Familial renal disease
- Cystic renal disease
Can an animal with ectopic/fused kidneys live normally?
- not a serious defect
- can be fully functional if not obstruction to blood supply or urethral path
What is renal dysplasia?
Abnormal development of the organ, its tissue and components
- can get a dilated ureter (hydroureter)
- one kidney may be hypertrophied to compensate for the other kidney lacking most of its functional ability
Describe familial renal disease
- occurs in families of animals e.g. cocker spaniels
- polyuria, polydipsia
- inflammation of the kidneys
- excessive tubule dilation
- eosinophilic
- proteinuria
Describe cystic renal disease
- Origin blocked tubules => filtrate build up => dilation
- As the cysts enlarge, pressure increases => pressure atrophy of local renal tissues
- normal function compromised
How would cystic renal disease appear histologically?
Large dilated air cavities (blank white spaces)
- Some may have fluid within them
Polycystic renal disease is heritable in which breed?
Persian cats
What are the 4 renal circulatory diseases?
- Haemorrhage
- Infarction
- Papillary necrosis
- Cortical ischaemia
How can renal haemorrhage occur - 3 possibilities?
- Trauma e.g. RTA, dog bite
- Septicaemia e.g. salmonella, herpesvirus
- Disseminated intravascular coagulation (DIC)
How would Salmonella septicaemia with DIC appear grossly on the kidney surface?
Disseminated to coalescing dark red/black areas of haemorrhage
What is renal infarction?
Coagulative necrosis of renal parenchyma secondary to vascular occlusion by an embolus
- A blockage will cause an area of the kidney to be deprived of its blood flow => ischemic necrosis
What does the severity of renal infarction depend on?
- Level of vascular obstruction: The smaller the blood vessel the less damage to that section of the kidney
- Nature of the thrombus
In renal infarction, damaged/non-vascularized sections appear how grossly?
Wedge shaped pale tan sunken tissue with apex pointing to site of vascular obstruction
Describe the branching of the renal blood supply
Same for arteries and veins:
- Renal
- Interlobar
- Arcuate
- Interlobular
- Afferent arterioles
How does a renal infarct appear histologically?
- Congested field: most blood vessels have static blood flow
- Very little inflammatory component
- PCT necrosis at edges though glomeruli often spared
How does a chronic infarct appear grossly?
Replacement of necrotic tissue by fibrosis => contraction and depressed cortical lesion
How does an acute infarct become chronic?
- If the animal goes on to survive (only had one infarct, the other kidney is fully functional, etc), you get invasion of the necrotic tissue by macrophages, fibroblasts
- Fibrous tissue contracts leaving an indented scar
What is renal papillary necrosis?
- occurs secondary to reduced blood flow, often due to NSAIDs (horses)
- decreased blood flow and ischaemic necrosis of the medulla
How does renal papillary necrosis appear grossly?
Green/grey patches of the renal parenchyma – areas of papillary necrosis – they have to be severe to cause significant disease – these areas slough off and block the ureter
What are the two types of cortical ischaemia?
- acute tubular necrosis
- renal cortical necrosis
What is the cause of acute tubular necrosis?
Results from reduced blood flow (ischaemia) or toxins => multifocal to diffuse ischemia
What is the cause of renal cortical necrosis?
G-ve septicaemia or DIC => microthrombi => multifocal to diffuse necrotising damage – rare
Describe the pathogenesis of acute tubular necrosis
- PCT epithelium loss
- As cell debris blocks tubules + urine leaks into interstitium.
- Can regenerate if basement membrane intact
- If not fibrosis or death
Describe the main cause of acute tubular necrosis in sheep
- Copper toxicity
- Tubular epithelial necrosis with cell debris + refractile orange-red granular material (Hb comp) in lumens
How does acute tubular necrosis appear histologically?
- eosinophilic material in tubules
- loss of tubular epithelium
- loss of cell structure and necrosis
How does renal cortical necrosis appear grossly?
Gross - Pale/tan areas are affected – necrotising
How does renal cortical necrosis appear histologically?
- Tubules lack nuclei within their epithelium
- Glomeruli still have some nuclei present
- PCT are all necrotic – no cellular detail
- Lots of eosinophilic material
Give 3 examples of renal degenerative diseases
- Amyloidosis
- Hydronephrosis
- Hypercalcaemic nephropathy
Describe renal amyloidosis
- Modified protein deposits (serum amyloid A)
- Some secondary chronic inflammation or neoplasia
- Deposited in the glomerulus and medulla
What are the consequences of amyloidosis deposition in the glomerulus?
- pressure atrophy of the glomerulus
- Proteinuria (hypoproteinaemia) => CRF (“Nephrotic syndrome”)
How does a kidney with amyloidosis appear grossly?
- uniform colour change to pale tan
- waxy/greasy texture
- diffusely swollen
How does renal amyloidosis appear histologically?
- Enlarged glomeruli
- Protein builds causing a pressure atrophy in the glomerulus
- Lots of eosinophilic material
What is a hydronephrosis?
Dilation of the renal pelvis secondary to PARTIAL obstruction of urine flow
- urine pressure build-up => reduces local medullary blood flow => ischaemia => dilation of pelvis
What can be seen in severe cases of hydronephrosis?
- Cortical atrophy
- Urine filled sac in end stage
Describe the pathogenesis of hydronephrosis
- urine flow is still continuous, despite the partial obstruction, but the pressure builds up over time
- reduces the flow of blood passing through the renal medulla
- ischaemic damage occurs
Give examples of slowly developing partial blockages that could cause a hydronephrosis
- Congenital urethral abnormality
- Ureteral obstruction e.g. Calculi (stones)
- LUT inflammation
- Downstream neoplasia
- Bladder paralysis
Define pyelonephritis
Inflammation of the kidney (specifically of the parenchyma and renal pelvis) as a result of bacterial infection
How would Urethral + bladder calculi with obstructive hydronephrosis appear grossly?
Dilated renal pelvis with calculi throughout urinary tract but especially in the bladder
Hypercalcaemic nephropathy occurs secondary to?
Hypercalcaemia
Describe hypercalcaemic nephropathy and its pathogenesis
- Mineralisation (deposits of calcium salts) of tubular basement membrane, epithelium + glomeruli => necrosis
- Destroys the cells it forms upon
- Tubular obstruction and loss => renal failure
How does hypercalcaemic nephropathy appear grossly?
Depressed crater like structures multifocally/diffusely distributed over the surface of the kidney
How does hypercalcaemic nephropathy appear histologically under different stains?
- Under H & E calcification appears as a purple/black colouration
- More obvious with a Von kossa stain where calcium is highlighted as black
