Urinary system pathology 3 Flashcards
Why is the kidney highly susceptible to toxic damage?
- High exposure
- High sensitivity
- PCT has a high level of metabolic activity
Explain different proposed mechanisms of the pathogenesis of toxic disease => acute tubular necrosis
- Toxins later the ion pump in the tubular epithelium membrane causing reduced sodium absorption, Na loss leads to vasoconstriction and ischaemia through the RAAS
- Obstruction of tubular flow by cell debris + interstitial oedema.
- Tubular fluid leakage into interstitium
- Impaired glomerular permeability
How does ethylene glycol toxicity occur?
Found in car antifreeze, it can be ingested by an animal and is multistage metabolised into oxalates – calcium oxalate crystals form in the renal tubules
What are the initial effects of ethylene glycol toxicity?
Initial dulling effects on the CNS
What are the effects of ethylene glycol following GI absorption and liver metabolism breakdown?
- insoluble Ca oxalate crystals form in the PCT tubules => obstruction
- Leads to metabolic acidosis
- Azotaemia, hypocalcaemia, hyperkalaemia, renal failure
How do the kidneys appear grossly with ethylene glycol toxicity?
- Red
- Swollen
- Fine yellow/white striated cortex
- Damage to vessels, leakage of fluid
- pulmonary oedema in the lung
How will ethylene glycol toxicity appear histologically?
- Glomeruli visible
- Some tubules will appear normal
- Other tubules will be dilated and filled with calcium oxalate crystals which block the flow of filtrate through the tubules
Which bacteria causes Enterotoxaemia pulpy kidney disease?
Clostridium perfringens type D
What are the consequences of pulpy kidney disease?
Acute, infectious, non-contagious disease of lambs: convulsions + sudden death
Where is clostridium perfringens found?
Soil
Manure
Intestinal commensal flora of ruminants
What ages of animal are most commonly affected by C.perfringens?
All ages susceptible, but 3-10 week-old fast - growers on high nutritional plane/a sudden change in feed, are commonly affected
What signs of C.perfringens are shown in:
- lambs
- older sheep
Lambs: die peracutely without clinical signs, or after brief neurological signs
Older: few days of mild GI signs. Others survive longer + develop CNS signs: blindness, ataxia + head-pressing
Describe how clostridium perfringens type D is ingested and multiplies in the body
- Ingestion of C.perfringens spores
- Normal peristalsis prevents high concentration of bacteria/toxin accumulating
- Consumption of lush grasses/concentrated grain/large quantities of milk => undigested starches in SI providing substrate for Clostridial overgrowth
Describe how clostridium perfringens type D, now in the SI, causes enterotoxaemia
- Multiplying bacteria in the SI produce toxin
- Toxin decreases intestinal mobility and allows uptake into circulation via portal capillaries
- Toxin acts on endothelium producing widespread oedema, haemorrhages + acute tubular necrosis
Describe the gross appearance of kidneys affected by clostridium perfringens type D enterotoxaemia
From an infected lamb – soft, very friable and break apart easily. Can be confused with autolysis so animals need to get to PM quickly for diagnosis.
We know this toxin damages endothelium and blood vessels so there will be multi-focal, haemorrhages on the serosa of a variety of tissues.
Describe the type of neoplasia that most commonly occurs in the kidneys
- Primary renal neoplasia uncommon
- Metastasis most common: Melanoma, Carcinoma, Lymphoma
What features of the kidney make it susceptible to metastasis?
Fine capillary network
Good blood supply – embolic tumour fragments can pass through the bloodstream and lodge in the kidney
What is an adenoma?
- a type of non-cancerous tumour: benign
- well circumscribed
- cortical mass
Adenocarcinomas form from which cells?
Tubular epithelial cells
How can an adenocarcinoma in the kidneys lead to polycythaemia and hypertension?
- Erythropoietin is the hormone that dictates the speed of RBC production: more erythropoietin production
- Hypertension is caused by the increase in HR due to trying to pump the more viscous blood around the body