Pathology of the Urinary Tract Flashcards
What are the functions of the urinary system?
- Formation of urine to excrete metabolic waste
- Acid-base regulation: reclamation of bicarbonate
- Conservation of water: PCT, ADH, urea gradient in medulla
- Maintenance of normal extracellular K+: passive resorption in PCT and tubular secretion in DCT under the influence of aldosterone
- Endocrine functions: erythropoietin, calcitriol and renin
What are the three categories of renal failure?
- prerenal: compromise of renal perfusion e.g. circulatory shock or local obstruction
- renal: compromised renal function e.g. tubular necrosis by infectious agents, toxins and drugs or emboli disease or ascending pyelonephritis
- postrenal: obstruction of urine outflow e.g. ascending infections, urolithiasis or neoplasia
What physiologically happens in acute renal failure?
Occurs when >75% of renal nephrons abruptly impaired.
Increased in urea and creatinine
Retention of potassium and thus dysrrhythmia
Rention of phosphates which bind to ionised calcium and produces muscular tremor & coma
Disturbances in electrolytes and decreased pH -> metabolic acidosis
Hypertension
Oliguria or anuria
What are the systemic effects of uraemia?
Clinical feature of renal failure.
Insufficient glomerular filtration thus azotemia
Failure of tubular function and water NaCl rention, matbolic acidosis and hyperkalaemia
Plasma protein loss (oedema)
Hyperphosphataemia and secondary renal hyperparathryroidism
Decreased production of erythropoietin creating a non-regenerative anaemia
Hypertension
Explain how renal failure may cause secondary renal hyperparathyroidism..
Low calcium in the blood - GFR <25% phosphates are no longer secreted by the kidneys. Phosphates precipitates ionised calcium in serum and decrease activation of vitamins D and decreased intestinal absorption. Decreased ionised Ca stimulates PTH secretion and releases calcium via osteoclasts activity and causes fibrous osteodystrophy.
What non-renal lesions may be seen with uraemia?
Endothelial degeneration and necrosis causing vascularise with secondary thrombosis and infarction
Caustic injury to epithelium of the oral cavity and stomach as a consequence to production of large concentrations of ammonia.
What are possible causes of glomerular damage?
Immune complexes Entrapment of thromboemboli Viral or bacterial infection Reduced blood flow Chronic loss of tubular function Amyloid deposition
What happens are a consequence of glomerular damage?
Protein losing nephropathy:
Leakage of albumin into the filtrate which overwhelms the reabsortive capabilities of the PCT epithelium. This causes proteinuria and hypoproteinaemia. Prolonged severe renal protein loss results in a reduced plasma colloid osmotic pressure and loss of antithrombin III and therefore nephrotic syndrome.
NS: generalised oedema, aspires, pleural effusions, hypercoagulability and hypercholesterolaemia.
What might cause immune mediated glomerulonephritis?
FeLV and FIP Pyometra or pyoderma Chronic parasitism Autoimmune disease Neoplasia
Why does immune mediated glomerulonephritis occur?
Associated with persistent infections of other disease with prolonged antigenaemia that enhances the formation of soluble immune complex’s.
Explain glomerular amyloidosis
Reactive amyloidosis when disease associated with chronic inflammation, systemic infectious disease or neoplasia. Amyloid despots are composed of fragments of a serum acute phase reactant protein. These deposit on glomeruli and as a consequence PLN and nephrotic syndrome may occur.
What bacteria may cause acute suppurations glomerulitis?
Actinobacillus equuli in foals
Eyrsipelothrix rhusiopathiae in pigs
Corynebacterium psuedotuberculosis in sheep and goats
Arcanobacterium pyogenes in cattle
Give some causes of tubular disease
Blood borne infections Ascending infections Toxins Ischemia Infarction Obstruction Fibrosis External compression
How does the tubules respond to injury?
If the membrane remains intact the repair by proliferation of the remaining viable epithelial cells occurs. The basement membrane is retained more in toxic vs ischemic insult. Sever damage results in necrosis and is replaced by fibrosis.
Give some causes of acute tubular necrosis
Copper toxicity in sheep Babesiosis in cattle Red maple toxicity in horses IMHA in dogs Lead poisoning NSAIDs Lilys in cats Grapes/raisins in dogs Mycotoxins in aspergillosis Oak poisoning in cattle Ethylene glycol toxicity Hypervitaminosis D Clostridium perfringens type D
