Urinary System Flashcards
What is acute kidney injury?
A rapid loss in kidney function
A sudden reduction in GFR
Medical emergency- inability to maintain fluid, acid base and electrolyte balance
What is CKD?
Chronic kidney disease- structural or functional abnormalities of one or both kidneys that have been there for 3 months or longer
What does the GFR show?
Shows the total filtration of functioning nephrons
Best wat to asses kidney function
What is the gold standard of assessing kidney function’?
Clearance of exogenous filtration marker
What is clearance of a solute and what is the total body clearance equal to?
Clearance of suture is the rate at which the drug disappears from the body by excretion and/or metabolism
Body clearance- renal, hepatic and lung clearence
If a drug is not metabolised elsewhere and filtered freely and not reabsorbed what does this show?
Renal clearance= GFR
What is the units and equation of renal clearance?
mls/min
[B] in urine x urine flow
_________________
[B] plasma
What are the idealistic features of filtration markers?
Not metabolised anywhere else in the body
Freely filtered in glomerular capillaries
Not reabsorbed or secreted anywhere
Exogenous
What is the gold standard of GFR filtration markers?
Inulin
What can be used for GFR estimates that are cheap and readily accessible?
Urea- catabolism of deamination of amino acids
Creatine- steady breakdown of creatine phosphate in skeletal muscle
Why is Urea not an ideal measure of GFR?
Urea is partially fat soluble and so reabsorption occurs in the PCT
If GFR is decreased there is more time for reabsorption of urea
Normal continuous high filtration rate prevents excessive high conc of urea in the blood
What is urea production influenced by?
High urea- high protein diet, recent meal, catabolism, GI haemorrhage, dehydration
Low- sever liver disease, low protein diet, aggressive fluid therapy
Why is creatinine a useful measure of GFR?
Freely filtered, not reabsorbed or secreted
Endogenous but steady state
What is the problem of creatinine for measure go GFR?
Up to 75% of kidney function can be lost before serum increases
What are the three broad causes of decreases GFR?
Pre-renal
Renal
Post-renal
What causes pre-renal azotaemia?
Reduced blood supply to the kidney
What causes renal disease?
Intrinsic disease of the kidney
What causes post-renal disease?
Blockage of urine flow below the kidneys- bladder rupture
How can pre-renal and renal disease be distinguished?
Prerenal is occurring upstream of the kidney therefore animal can concentrate urine
Renal is kidney problem so the animal cannot concentrate urine
Would you expect hypovolaemic animals to have low urine specific gravity or high urine specific gravity?
Animals with hypovolaemia should be conserving volume therefore concentrating filtrate and have a high urine specific gravity
What are clinical signs of reduced renal function?
Anorexia and weight loss Dullness and lethargy PUPD Dehydration Vomiting Constipation Poor hair coat Signs related to hypertension
What can be physically examined in cases of CKD?
Dehydration, poor condition, pale mucous membranes, oral ulcerations, uraemic breath
Retinal lesion from hypertension
Osteodystrophy, especially the mandibles (rubber jaw)
Palpate kidneys
How can CKD cause hyperparathyroidism?
Increase in phosphate, binds to calcium and reduces blood calcium and stimulates parathyroid increases, increased phosphate also stimulate PTH release, high phosphate inhibits activated vitamin D which inhibits PTH, causing immobilisation of calcium
How can kidney function be evaluated?
Urinalysis- analysis of volume, physical, chemical and microscopic properties of the urine
Blood tests- urea and creatinine, serum electrolytes
What are the key changes in blood and urine with loss of kidney function?
Blood- increased urea, increases creatinine, phosphate, metabolic acidosis, decreases plasma bircarbonate
Urine- dilute- loss of ability to concentrate, protein in urine, sometimes glucose
How is CKD treated?
Irreversible Combat dehydration Renal diet Control hyperphosphataemia Control hypertension Control constipation Control metabolic acidosis Manage anaemia
What does a therapeutic diet contain?
Low proteins of high biological value Low phosphorus Low sodium Alkalinising agents Feline contains K Omega 3 fatty acids High energy density Water soluble vitamins Fibre
What is the mode of action of angiotensin receptor antagonists and its adverse effects?
Inhibits the effects of angiotensin- sodium and water retention
Adverse effects- rare, minor GI upset
What does potassium supplementation achieve for CKD and what are its adverse effects?
Used to correct hypokalaemia from CKD
IV solutions of KCl, oral potassium gluconate, oral potassium citrate
Adverse effects- IV solution must be diluted, hyperkalaemia- muscle weakness, cardiac arrest
What does phosphate binders do and what are their adverse effects?
Bind to phosphate in the GI tract, must be given with food, passed in faeces
Adverse effects- hypoposphataemia, GI problems
How does sodium bicarbonate help CKD and what are its side effects?
Buffers protons- helps with metabolic acidosis, or hypokalaemia and hypocalcaemia
Adverse effects- oral can alkalinise stomach, may contribute to excess Na, can cause metabolic alkalosis
What does eryhtopoetin replacement do and what are its adverse effects?
Stimulates division and differentiation of RBCs
Adverse effects- production of cross reacting antibodies reducing efficacy
What other drugs can be used for treatment of CKD?
Calcium channel blockers ACE inhibitor H2 agonists Proton pump inhibitors Sucralfate Anti-emetics Appetite stimulants Laxatives Iron supplementation
What is micturition?
Urination
What three muscles control urination?
Detrusor- smooth muscle (ANS)
Internal urethral sphincter- Smooth (ANS)
External urethral sphincter- Striated (Somatic)
How does the parasympathetic, sympathetic and somatic nervous supply control urination?
Sympathetic- relaxation of detrusor (accommodate filling), contraction of internal sphincter
Parasympathetic- contracts detrusor
Somatic- prevents bladder emptying
What are the sympathetic and somatic effects of bladder filling?
Sympathetic effects-
relaxation of detrusor- noradrenaline on beta 2 adrenoreceptors. Contraction of internal sphincter, noradrenaline acting on alpha adrenoreceptors
Somatic-
Continuous excitation of external urethral sphincter- via acetylcholine acting on nicotinic receptors
What are the parasympathetic and somatic effects of the bladder emptying?
Parasympathetic:
Contraction of detrusor- acetyl choline on muscarinic receptors
Somatic motor effects:
inhibition of continuous excitation- acetyl choline on nicotinic receptors
What is the nervous supply to the bladder and what system do they conduct?
Hypogastric nerve- sympathetic motor to internal sphincter and detrusor
Pelvic nerve- parasympathetic motor to detrusor
Pudendal nerve- somatic motor
What happens if the pelvic nerve is damaged?
Lack of parasympathetic motor neurones to detrusor, preventing bladder emptying, will need manually expressing
What happens if the pudendal nerve is damaged?
Detrusor reflex ok so can void urine, external sphincter lacks control so may leak
What will spinal damage in the sacral section of the spinal cord cause for urination?
Will lack parasympathetic supply to detrusor muscle and loss of external sphincter
Sympathetic tone in internal sphincter maybe present
Bladder will be full but will easily express
How can drugs increase the action of the urethral sphincter?
alpha agonists
Increase adrenoreceptor sensitivity
How can drugs decrease the activity of the detrusor?
Muscarinic antagonists
What are muscarinic agonists used to treat and what are there adverse effects?
Treatment of urinary incontinence secondary excessive detrusor activity- GI spasm, nasal congestion
Propantheline
Adverse- Constipation, tachycardia, mydriasis, increased intraocular pressure, urinary retention
What do alpha adrenal-receptro agonists do, what can they treat and what are there adverse effects?
Increase urethral outflow resistance and some peripheral vaso-constrictive effects
Treatment of urinary incontinence secondary to urethral sphincter incompetence
Adverse effects- increased blood pressure, irritability, restlessness
Phenylpropanolamine
What are oestrogen receptor agonists used to treat, when are they contraindicated and what are the adverse effects?
Used in treatment of urethral sphincter mechanism incompetence that develops in spayed bitches- increases muscle tone
Contraindicated in entire bitches
Oestrogen effects are seen in 5-9% bitches
Estriol
What are muscarinic receptor agonists used to treat? and what are its adverse effects and name a drug?
Management of urinary retention associated with reduced detrusor tone
Adverse effects- GI cramping, vomiting/diarrhoea, salivation, bradycardia
Bethanechol
What drug is used for the management of urethral muscle spasm and severe hypertension in animals and what are the adverse effects?
Phenoxybenzamine
Alpha adrenergic receptor antagonists alpha blockers
Adverse effects- hypotension, miosis, tachycardia, nasal congestion
What drug inhibits Ca release from SR in skeletal muscle cells and what is it used for and its adverse effects?
Dantrolene
Used in the management of muscle spasms- urethral muscle spasms
Adverse effects- generalise muscle weakness may affect respiratory muscles
How do sedatives work and how are they used in treatment of urinary system?
Diazepam- enhances activity of the major CNS neurotransmitter, GABA
Used as an anticonvulsant and in the management of muscle spasms
Adverse effects- sedation, muscle weakness and ataxia
What drug us used as a urinary acidifier, for what reason and what is the adverse effect?
Methionine
Used for treating struvite urolithiasis
Adverse effects- metabolic acidosis
What is an example of urinary alkaliniser, what does it treat and what is its adverse effects?
Potassium citrate
Used for urolithiasis
Adverse hyperkalaemia
