Renal Pathology Flashcards
Describe the gross appearance of kidneys in chronic renal failure.
Pale and shrunken with irregular depressions of the capsular surface
- contraction of scar tissue causes irregularity
What features on histology may be observed in chronic renal failure?
Glomerulosclerosis
Periglomerular fibrosis
Degeneration and loss of tubules
Interstitial fibrosis
Define glomerulosclerosis
The glomerular tuft can become damaged and replaced by fibrous connective tissue
What is periglomerular fibrosis?
When in disease progression is this seen?
Fibrosis just around the glomerulus
Earlier than glomerulosclerosis
What occurs when tubules have degenerated?
Scar tissue fills the space where tubules are lost
What occurs as a result of interstitial fibrosis?
Presses on tubules causing atrophy
Describe some potential biochemical/clinical features of uraemia
Azotaemia + clinical signs :
- metabolic acidosis,
- other electrolyte imbalances
- oedema (plasma protein loss)
- mild non-regenerative anaemia
Outline secondary renal hyperparathyroidism
-When GFR low, phosphate no longer removed by kidneys enough
-Phosphate binds free calcium + precipitates in the serum - METASTATIC MINERALISATION
-Decrease 1 a-hydroxylase activity and subsequent D3 activation
- reduced calcium absorption and ionised serum calcium
PTH secretion -> chief cell hyperplasia
What occurs as a result of secondary renal hyperparathyroidism?
How does this occur
Fibrous osteodystrophy
Osteoclastic resorption of bone and replacement by fibrous connective tissue
Nephrocalcinosis - deposition of Ca in the kidney
What causes nephrocalcinosis?
Secondary renal hyperparathyroidism
Primary hyperparathyroidism
Vitamin D intoxication
Hypercalcaemia of malignancy
What neoplasias are associated with hypercalcaemia of malignancy?
Lymphomas
Anal sac adenocarcinomas
How does hypercalcaemia of malignancy occur?
Paraneoplastic effect where PTH-rap is mimicking the effect of PTH in the body
What non-renal mechanisms of pathology are associated with uraemia?
VASCULITIS
- endothelial degeneration and necrosis - thrombosis and infarction
Caustic injury to ORAL cavity and STOMACH - ammonia after urea breakdown by bacteria
Describe oral lesions associated with uraemia
Ventral surface on edge of tongue
Often bilateral
Ulcerative glossitis and stomatitis
What gastrointestinal lesions can be attributed to uraemia?
Ulcerative glossitis and stomatitis
Ulcerative and haemorrhagic gastritis/colitis
What CNS lesion is associated with uraemia?
Uraemic encephalopathy (degredation of White matter)
What lesions in the thoracic cavity are associated with uraemia ?
Fibrinous pericarditis
Uraemic pneumonitis and pulmonary calcification
Intercostal mineralisation
What is the underlying pathogenesis behind fibrinous pericarditis, arteritis and uraemic pneumonitis and pulmonary calcification?
Vasculitis
How is acute renal failure defined and what are the consequences?
> 75% loss of function
Oliguria or anuria Azotaemia Hyperkalaemia Hypocalcaemia Metabolic Acidosis Hypertension
How can pathological agents access the kidney?
Haematogenous
Glomerular infiltrate
Ascending from the ureter
What haematogenous agents can cause renal pathology?
Septic embolic nephritis
Ischaemic necrosis post infarction
What glomerular infiltrate can cause pathology?
Substance secreted into the filtrate causing trauma to tubular lining OXYLATE CRYSTALS - ethylene glycol
Filtered preformed toxins or substances processed by tubular lining epithelium
What conditions may predispose a patient to developing an ascending infection from the ureter?
GIT contamination - diarrhoea
Genital tract contamination - pyometra
Dermal contamination - perivulval dermatitis
Name some developmental disorders of the kidney
Renal aplasia/hypoplasia/dysplasia
Ectopic kidneys
Fused kidneys
Progressive juvenile nephropathy
Polycystic kidney disease
When is renal aplasia/hypoplasia/dysplasia a problem?
When it is bilateral
What can be an issue with ectopic kidneys?
Secondary Hydronephrosis due to kinking of ureters
What is the presentation seen with progressive juvenile nephropathy?
What species?
DOG
Present usually less than 2 years with end stage kidney disease typical of what you would see in an older animal
What is polycystic kidney disease?
What is it seen in?
Persian Cats and Bull Terriers
Problem with the tubular epithelium which allows large cystic cavities to form within the kidney
Pressure atrophy and necrosis of normal surrounding tissue
When does immune mediated glomerulonephritis occur?
Persistent infections or prolonged antigenaemias which enhances formation of soluble immune complexes (+complement fixation and damage by leukocytes)
Describe the pathogenesis of immune mediated glomerulonephritis
Soluble immune complexes circulating can be deposited in the capillaries of the glomerular tufts or the basement membrane -> interferes with filtration
When deposited, bind with complement releasing chemo tactic substances
Attract leukocytes which release reactive oxygen species causing more damage
What is glomerular amyloidosis?
When does it occur?
Deposition of extracellular protein
Chronic inflammatory disorders,
Systemic infectious disease,
Neoplasia
What causes acute suppurative glomerulitis?
BACTERAEMIA
Bacteria lodge in glomerular and interstitial capillaries and form microabscesses in the cortex.
What bacteria are associated with acute suppurative glomerulitis in:
Foals
Cows
Pigs
Sheep+goats
Foals - actinobacillus equuli
Cows - Trueperella pyogenes
Pigs - Erisipelothrix rheusiopathiae
Sheep+Goats - Corynebacterium pseudotuberculosis
What is Nephrotic syndrome?
PLN -> NS
Decrease in plasma osmotic pressure and loss of antithrombin III
Oedema and effusions, hypercoagulability and hupercoagulability
What does nephrotic syndrome occur as a result of?
Glomerular damage - PLN
What is the most important cause of acute renal failure?
Acute tubular necrosis
When does acute tubular necrosis occur?
After nephrotoxic or ischaemic injury to the proximal tubular epithelium
Why is oliguria/anuria associated with acute tubular necrosis?
Leakage of tubular filtrate into interstitium
Intratubular obstruction from sloughed epithelium
Why do toxins in blood preferentially damage the kidney?
Kidney recieves 25% of CO
How does nephrotoxin associated ischaemia occur?
Reactive metabolites are produced as they’re being processed by the cells
Stimulate vasoconstriction -> ischaemia
After which insult is the tubular basement membrane more likely to be retained?
How does this relate to prognosis?
TOXIC
Improved - allows for regeneration
What agents can cause acute tubular necrosis?
NSAIDS
Fungal and plant toxins
Ethylene glycol
Bacterial toxins
How do NSAIDs cause acute tubular necrosis?
Decreased PG synthesis (which usually causes vasodilation)
Afferent arteriolar constriction
Decreased renal perfusion
Acute tubular and papillary necrosis
What makes ATN from NSAIDs more likely?
Excessive doses,
Underlying dehydration,
CHF
CRD
What fungal and plant toxins cause ATN?
Mycotoxins - Aspergillus
Lily plants cats
Grapes and raisins dogs
Oak poisoning in cows
How does Ethylene glycol cause ATN?
Dogs cats pigs -> readily absorbed from GIT
Oxidised by the liver to toxic glycolic acid and oxalate
Filtered by glomeruli - direct toxin to tubules
Calcium oxylate crystals precipitate into tubular lumen -> obstruction and damage epithelium
What nephrotoxin is produced by C. Perfringens type D?
What does it cause?
Epsilon
PULPY KIDNEY
How does a small ruminant get pulpy kidney?
Overeating esp. well conditioned lambs
Proliferation of clostridium type D
Epsilon toxin
Pulpy kidney
Describe the pathology of Pulpy Kidney
Acute tubular degeneration and/or necrosis
Interstitial oedema and haemorrhage
What changes in the urine are associated with pulpy kidney?
Glycosuria
What causes disease of the interstitium?
Ascending infection - pyelonephritis
Haematogenous - E.Coli and Leptospira, Canine adenovirus
Secondary to injury of tubules/glomeruli (infectious, toxic, IMD)
Describe the appearance of a kidney with E.coli
White spotted kidney disease
Describe the kidney pathology associated with FIP
Granulomatous necrotising vasculitis
Outline the difference between hyperaemia and congestion
Hyperaemia - increased arterial blood flow e.g. acute inflammation
Congestion - venous blood pooling (cardiac insufficiency, hypovolaemic shock, agonal)
What kidney changes are seen in septicaemia?
Pinpoint petechial haemorrhages
A puppy presents with sudden death and cortical ecchymotic haemorrhage on PM. DDx?
Canine HERPESVIRUS
Causes direct endothelial damage
What area of the kidney will be affected if the interlobular artery is blocked?
CORTEX
What area of the kidney will be affected if the arcuate artery is blocked?
CORTEX+ MEDULLA
What are the sources of renal emboli?
Cardiac mural or valvular
Endarteritis in pancreatic dz - angiostrongylus, strongylus vulgaris
Neoplastic cell emboli
Bacterial or septic emboli
Describe the appearance of an acute embolism in the kidney
Discrete dark wedge
Describe the appearance of a sub-acute embolism in the kidney
Lighter in colour as cells have undergone necrosis
Describe the appearance of chronic embolism in the kidney
Fibrous tissue laid down which contracts - depression
When would a patient with hydronephrosis tend to present clinically?
If bilateral
What predisposes a patient to hydronephrosis?
Congenital malformation
Urethral or urethral blockage (calculi, neoplasia, inflammation)
Neurogenic functional disorders
Iatrogenic (accidentally tying off ureter)
What is pyelonephritis ?
What is the most common cause?
Bacterial infection of the pelvis with extension into tubules and interstitium
Ascending infection
What bacteria can cause pyelonephritis?
Corynebacteria E. coli Staph and Strep Pseudomonas Trueperella
What type of infarction is associated with pyelonephritis?
POLAR
What can cause primary papillary necrosis?
NSAIDs
Ischaemic necrosis of inner medulla
What can cause secondary papillary necrosis?
Decreased blood flow to vasa recta
- glomerular dz, interstitial dz, compression of papilla e.g. stones
What is the most common primary renal neoplasm?
Metastatic?
Renal carcinoma
Highly metastatic
What paraneoplastic effect is associated with renal carcinoma?
Polycythaemia - EPO
What developmental anomalies affect the LUT?
Ureteral aplasia and hypoplasia
Ectopic ureters
Patent Urachus (FOALS)
How can ureteral aplasia/hypoplasia affect the kidneys?
Obstruction -> hydronephrosis
How do patients with ectopic ureters tend to present?
Why?
What problems can they cause?
Urinary incontinence
Empty into urethra, vagina, or bladder neck
Prone to obstruction or infection
What is a patent urachus?
Foetal urachus fails to close -> direct channel between the bladder and umbilicus
What can cause a patent urachus?
Underlying omphalitis or congenital urethral obstruction creating backward pressure.
Increased bladder pressure forces urine out into the urachus therefore dribbles urine from umbilicus
What Uroliths form at alkaline pH?
Struvites and carbonates
What uroliths form at acidic pH?
Oxalates
What stones are Dalmatians predisposed to?
Why?
Urate stones
Uric acid unusually metabolised
How can vitamin A deficiency result in Urolithiasis?
Causes metaplasia of urinary tract epithelium from transitional to keratinised stratified -> DESQUAMATION
This provides a nidus for calculus formation
What factors predispose calculus formation?
Urinary pH
Reduced water intake - mineral supersaturation
Bacterial infection LUT
Abnormal metabolism e.g. dalmations
High dietary levels of substances e.g. Mg
VitA deficiency
What bacteria causes cystitis in many species?
Uropathogenic E. coli
What causes cystitis in cattle?
Corynebacterium renale
What causes cystitis in pigs?
Eubacterium suis
Describe the pathogenesis of cystitis
Hydrolysis of urea by urease producing bacteria
Excessive ammonia
Mucosal damage and increased urine pH
What causes emphysematous cystitis?
E.g DIABETICS
Glycosuria enhances bacteria
E.coli/C.perfringens metabolise and release CO2
CO2 released into bladder Lumen
Absorption of gas into lymphatics ->emphysema
What causes toxic cystitis
Bracken fern -> enzootic haematuria
Cyclophosphamide
What causes Enzootic haematuria?
Chronic ingestion of Bracken fern
Haemorrhage, chronic cystitis, bladder neoplasia
Bladder neoplasia is uncommon but what are the main types?
Epithelial - transitional cell carcinoma
Mesenchymal - rhabdomyosarcoma
