Urinary - pathology Flashcards
What are the main functions of the kidney?
Formation of urine
Acid-base, water and electrolyte homeostasis
Endocrine - renin-angiotensin-aldosterone, vitamin D
What are the 4 main structural components of the kidney?
Blood vessels
Glomerulus
Tubules
Interstitium
What proportion of the cardiac output goes to the kidneys?
25%
What are the arteries that make up the kidney?
Renal artery
Interlobar arteries
Interlobular arteries
Arcuate arteries
Where are the arcuate arteries located in the kidney?
At the corticomedullary junction - between the cortex and the medulla
What are the names of the vessels going to and from the glomerulus?
Afferent and efferent glomerular arterioles
What makes up the three layers of the glomerular filtration barrier?
Fenestrated capillary epithelium
Glomerular basement membrane
Podocytes
If injury occurs to the glomerular filtration barrier what is likely to start to appear in the urine?
Proteins - proteinuria
What can disrupt tubular function in the kidneys?
Disruption of the close apposition of the tubules and peritubular capillaries
What 4 things can enter the interstitium of the kidneys during disease processes?
Fluid
Cells
Connective tissue - collagen (fibrosis)
Other - calcium, amyloid
What are some potential causes of renal vascular injury?
Embolism
Vascular injury/vasculitis
Loss of autoregulation of renal perfusion - ischaemic injury
Compression of blood vessels
What does renal thromboembolism look like in the kidney?
Dark red area - less old infarction, acute
Regions of pallor - long time ischaemic
Wedge shaped
What is the most common place for thrombi to cause infarction in the kidney?
Interlobular vessels - small end arteries
Cause localised infarction of a segment of the cortex
What is the second most common place for thrombi to cause infarction in the kidney?
Arcuate or interlobar artery
Causes localised infarction of a segment of the cortex AND medulla
What is the most uncommon place for thrombi to cause infarction in the kidney?
Renal artery
Causes total infarction of the kidney or of one half of the kidney
Where are renal thromboemboli most likely to come from?
The heart - left side
e.g from hypertrophic cardiomyopathy or endocarditis
What viruses can cause vascular injury/vasculitis causing kidney damage?
Canine herpesvirus - 2-3 week puppy
African/classical swine fever
Feline infectious peritonitis
What controls perfusion of the kidney by vasodilating afferent arterioles in response to ischaemia to maintain perfusion?
Prostaglandin
What drug can inhibit prostaglandins causing disturbed perfusion and ischaemia in the kidney?
NSAIDs
What are some potential causes of compression of the renal vasculature and medullary necrosis?
Urinary obstruction
Pyelonephritis
Medullary amyloidosis
What does glomerulosclerosis look like?
Fibrosis and thickening of the bowmans capsule
Abnormal glomerulus
How does chronic kidney disease tend to change the gross appearance of the kidneys?
Granular appearance
Swollen with loss of cortical striation
What is the difference between glomerulonephritis and glomerulopathy?
Glomerulonephritis - glomerular disease with secondary changes to the nephron components
Glomerulopathy - glomerular disease without inflammation
What is the main cause of glomerulonephritis?
Glomerular deposition of immune complexes
Causing podocytes to lose foot processes and basement membrane to thicken, increasing permeability
What are the different classifications of glomerulonephritis?
Membranous - changes primarily to the basement membrane
Proliferative - cell components proliferate without changing the basement membrane
Membranoproliferative - both
What are the consequences of glomerulonephritis?
Proteinuria
Interstitial fibrosis
Reduced nephron function
What does glomerular amyloidosis look like on histology?
Pink blobs of amyloid protein inside the glomerulus
What causes glomerular amyloidosis?
Chronic inflammatory diseases
Neoplastic diseases
What is suppurative glomerulitis?
Bacteraemia - bacteria lodging in glomerular capillaries and interstitial capillaries forming microabscesses
What does suppurative glomerulitis look like on histology?
Mass of speckled purple in the glomerulus
Small white foci on cortical surface surrounded by pink hyperaemic area
What are the 3 causes of tubular damage in the kidneys?
Nephrotoxins
Ischaemia
Infectious agents
What are some examples of nephrotoxins?
Drugs - NSAIDs, tetracyclins, aminoglycosides, cisplatin
Antifreeze
Raisins - dogs
Lillies - cats
Haemo/myoglobin
What are 4 tubular epithelial cell responses to tubular injury?
Atrophy
Degeneration
Necrosis
Regeneration
What does acute tubular degeneration and necrosis look like on histology?
Very eosinophilic - pink
Loss of nuclear detail
Very swollen
What is a functional consequence of tubular injury?
Acute decrease in glomerular filtration rate and renal function causing oliguria/anuria - little to no urine production
How does myoglobin and haemoglobin affect the kidneys? What does it look like?
Haemoglobin - from haemolysis
Myoglobin - from muscle injury
They are nephrotoxins, can stain kidneys dark red-black to blue-black
What affects regeneration of tubular epithelial cells?
Whether the basement membrane is damaged or not
If not damaged then tubular regeneration of epithelial cells can occur
If damaged then fibrosis and tubular atrophy occurs
What is the word for disruption of the tubular basement membrane?
Tubulorrhexis
What occurs during epithelial regeneration following degeneration and necrosis of tubular epithelial cells?
Polyuria - limited reabsorption capacity
What does metabolism of ethylene glycol (antifreeze) produce?
Nephrotoxic metabolites and oxalate produced from breaking it down in the liver
What does oxalate cause in the kidney from metabolism of ethylene glycol (antifreeze)?
Tubular obstruction
What causes interstitial injury in the kidney?
Secondary to injury of other renal components
Infectious agents
Toxins
What are some interstitial responses to injury? When do you find them
Oedema
Inflammation - acute (neutrophils) or chronic (lymphocytes, macrophages)
Fibrosis - chronic kidney disease
What is pyelonephritis?
Inflammation of the renal pelvis and the renal tubules/parenchyma (tubulointerstitial nephritis) simultaneously
What causes pyelonephritis?
Ascending bacteria from a lower UTI
What are some predisposing factors for pyelonephritis?
Increased pressure in bladder or ureter - reflux of urine
What does pyelonephritis look like on gross histology?
Renal crest necrosis, hyperaemia
Dilation of renal pelvis
Cortical atrophy
What are simple renal cysts?
Grossly visible thin walled fluid filled cavities in the kidney parenchyma
What can cause simple renal cysts?
Congenital/aquired obstructive lesions of the nephrons
Tubular basement membrane abnormalities
Disorders of tubule epithelial cell growth
What is polycystic kidney disease?
Multiple renal cysts bilaterally on kidneys which grow over time and can cause renal failure
What does polycystic kidney disease look like?
Purple foci with semitransparent capsular surface
What causes polycystic kidney disease? What are predisposed?
Heritable condition in some breeds
eg. bull terrier, persian cat
Can be sporadic
What are juvenile nephropathies? What do they affect?
Variety of familial/hereditary conditions
Cause chronic progressive renal disease in young dogs (between 4-18 months)
What are ectopic ureters?
When ureters dont empty into trigone of the bladder but instead into another area of the bladder eg. neck, urethra, repro tract
What do ectopic ureters predispose to?
Urinary incontinance - steady dribble of urine
Ascending infections
Obstructive disease
What is a retrocaval/circumcaval ureter?
Ureter has an abnormal spiral course around the caudal vena cava that occurs during development
What is a consequence of retrocaval/circumcaval ureter?
Mostly asymptomatic but is predisposed to obstruction
What is cystitis?
Urinary bladder inflammation
What are predisposing factors for cystitis?
Female
Local infections
Obstructive urinary diseases
Diabetes mellitus - glucose in urine
What can cystitis be in cats?
Sterile - feline interstitial cystitis
From stress causing neurogenic inflammation of the bladder wall
What are two different types/appearances of chronic cystitis?
Polypoid cystitis - fibrous tissue and chronic inflammatory cells
Follicular cystitis - nodular proliferation of lymphoid tissue, grey white nodules surrounded by red hyperaemic zone
What is follicular cystitis often seen alongside?
Urolithiasis
What are more common - metastatic kidney tumours, or primary kidney tumours?
Metastatic are more common
Twice as common as primary in dogs
7 times more common than primary in cats
What is the most common type of primary renal neoplasia?
Epithelial - carcinoma
What is a type of embryonal primary tumour found in the kidney?
Nephroblastoma - from residual embryonal cells that would normally differentiate into nephrons
What are the consequences of a nephroblastoma?
Mostly asymptomatic
What is the most common secondary tumour to affect the kidney?
Lymphoma
What is the most common urinary bladder neoplasia?
Urothelial carcinoma (transitional cell carcinoma) - primary tumours are most common in the bladder
Where are urothelial carcinomas (transitional cell carcinoma) usually found?
Bladder trigone
What are the consequences of Urothelial carcinoma (transitional cell carcinoma)?
Invasive and often metastasise
Predispose to infection
Can cause haematuria
What is the definition of the term renal failure?
Failure of the kidneys to be able to carry out their normal excretory, metabolic and/or endocrine functions
What is acute kidney injury?
Abrupt decrease in kidney function
May be reversible
What is chronic kidney disease?
Abnormalities of kidney structure and function for a long time (>3 months)
Usually irreversible and often progressive
What is azotemia?
Biochemical abnormality with elevated blood urea, creatinine
What is uraemia?
Clinical SYNDROME resulting from impaired kidney function
Often accompanied by multisystemic extrarenal lesions
What are the extra-renal lesions/syndromes of uraemia?
Ammonia causing caustic injury to oral and gastric epithelium - ulcer formation
Uraemic toxin causing injury to blood vessel endothelium - vasculitis, thrombosis, oedema
Altered calcium/phosphate metabolism - soft tissue mineralisation, secondary hyperparathyroidism, fibrous osteodystrophy
Reduced erythropoietin production - anaemia
