Urinary Flashcards
What do diuretics do?
How do they do this?
Increase output of urine, by reducing sodium and water retention
LIst the 5 types of diuretics
Osmotic diuretics Carbonic anhydrase inhibitors Loop diuretics Thiazides Potassium-sparing diuretics
Which hormone stimulates the principal cells in the collecting ducts to reabsorb more Na+ and Cl- and secrete more K+?
Aldosterone
What stimulates aldosterone secretion?
Decreased blood pressure and increased potassium
What is reabsorbed and secreted in the DCT and collecting duct?
Reabsorbed: Na+, Cl-
Secreted: K+
(principal cells)
Intercalated cells: H+ secretion
How would you increase the action of the urethral sphincter muscle?
Alpha or beta agonists, eg phenylpropanolamine
Increased adrenoreceptor sensitivity.
Increased noradrenaline release and activity
How would you decrease the activity of the detrusor muscle (of bladder wall)?
Anticholinergics/muscarinic antagonists eg Propantheline
How would you fix urinary incontinence?
Increase action of the urethral sphincter
Decrease activity of the detrusor (bladder wall) muscle
How does hyper phosphataemia lead to increased parathyroid hormone?
Phosphate inhibits formation of vitamin D3. As vitamin D3 exerts negative feedback on PTH, hyper phosphataemia leads to increased PTH.
Which part of the nephron do osmotic diuretics act in?
Proximal convoluted tubule
Give an example of an osmotic diuretic
Mannitol
Give an example of a carbonic anhydrase inhibitor (diuretic)
Where do they act?
Acetazolamide
Dichlofenamide
(All are sulphonamides)
Act in PCT
Give an example of a loop diuretic
What do they do?
Furosemide
Inhibition of Na+/K+/Cl- co-transporter
Where do thiazides act?
DCT
What do thiazides do?
Inhibit Na+/Cl- co-transport (before aldosterone-stimulated Na+/K+ exchange)
Increase Na+, Cl-, Mg2+ and K+ excretion
Decrease Ca2+ excretion
Decrease urine output in some nephrogenic diabetes insipidus
Inhibits conversion of pro-insulin to insulin
What do carbonic anhydrase inhibitors do?
Reversibly inhibit carbonic anhydrase enzyme, predominantly in PCT.
Causes decreased H+ secretion, and reduced Na+/H+ exchange
Decreased CO2 reabsorption
Increased NaHCO3 excretion
Alkaline urine
What do osmotic diuretics do?
Increase kidney medullary blood flow which reduces interstitial osmotic gradient
Filtered but not reabsorbed, so maintain osmotic pressure within filtrate
What are the key features of principle cells (epithelial cells) in the DCT and collecting duct?
Na+/K+ pump on basolateral membrane
Na+ and K+ leak channels on apical membrane
How is Na+ reabsorption and K+ secretion increased in the principle cells of the renal collecting duct?
Acutely: increased activity of existing channels and pumps
Long-term: synthesis of new channels and pumps
What do potassium-sparing diuretics do?
Do not secrete potassium into urine
Triamterine and amiloride are organic bases, and inhibit active Na+ reabsorption, which decreases Na+/K+ ATPase activity
Spironolactone is a steroid and competitive inhibitor of aldosterone (which reabsorbs Na+ and secretes K+)
Carbonic anhydrase inhibitors cause initial diuresis, but what is their primary function?
To treat glaucoma
What is the most common side effect of using diuretics (except K+-sparing)?
Hypokalaemia (increased K+ loss)
Give an example of a diuretic treatment (i.e. combination of two)
Potassium sparing e.g. amiloride with a loop or thiazide diuretic e.g. hydrochlorothiazide
When using α-agonists to treat urinary incontinence, what can we also use to increase α-adreno-receptor sensitivity?
When might this be contraindicated, why?
A natural, short-acting oestrogen i.e. Estriol
Contraindicated in entire bitches.
Adverse effects: swollen vulva and mammary glands, attracts males
What are the adverse effects of using anticholinergics or muscarinic antagonists?
Increased heart rate, dilated pupils and photophobia, dry mouth, constipation
How do we treat urinary retention?
We want to increase activity of detrusor muscle (muscarinic agonists eg Bethanecol)
Want to decrease activity of urethral sphincter (alpha or beta antagonist)
Give an example of an a-antagonist drug used to decrease activity of the urinary sphincter (in urinary retention)
Phenoxybenzamine
Prazosin
Which 2 drugs can we use to relax the external urinary sphincter?
Central inhibition: Diazepam
Peripheral inhibition: Dantrolene
Adverse effect of general muscle weakness with overdose of Dantrolene
What drug could we give to treat cystine uroliths? How does it work? What form of preparation is it given as?
Penicillamine
Binds to cystine to make a complex that is more soluble than cystine
Oral preparation
What drug could we give to treat urate uroliths? How does it work? What form of preparation is it given as?
Allopurinol
Inhibits xanthine oxidase and decreases formation of Uric acid
Oral preparation
How can you acidify urine pH?
Methionine
Ammonium chloride/sulphate
How can you alkalinise urine pH?
NaHCO3
Sodium/potassium citrate
What are the common clinical signs of renal failure?
Azotaemia (increased blood urea and creatinine) Polyuria and polydipsia Anorexia Metabolic acidosis High blood pressure Anaemia Hyperphosphataemia Hypokalaemia
When managing renal failure, diet should contain increased and decreased what?
Increased potassium
Decreased phosphorus
Name 3 phosphate binders used to bind phosphate in the GI tract
Calcium acetate
Lanthanum carbonate octahydrate
Sevelamer
What is cystitis?
Inflammation (not necessarily infection) of the bladder
If we want to treat a bacterial bladder infection, what sort of drug should we select?
What might we need to manipulate?
One that is excreted, unchanged, in the urine
E.g. amoxicillin, trimethoprim, fluoroquinalones
May need to manipulate urine pH, as different antibiotics work best at different pHs (e.g. penicillins=5.5)
Give an example of a urinary antiseptic
What are its adverse effects?
Methanamine (hexamine). Hydrolysed in urine to release formaldehyde
Bladder irritation
What is a crystalloid?
A water-based solution with small-molecular-weight particles, freely permeable to the capillary ‘membranes’
What do buffered crystalloids contain?
HCO3- or, more often, contain molecules (e.g. acetate, lactate, gluconate) which are metabolised in the liver to produce HCO3-
What do balanced crystalloids contain?
Give an example of one and state its pH
Contain electrolytes in addition to Na+ and Cl- (such as K+ Ca2+ Mg2+ ), making them similar to plasma
Lactated Ringer’s (pH 6.7)
What is the pH of normal saline solution?
5.7
What is a colloid?
A water-based solution with a molecular-weight too large to freely pass across capillary ‘membranes’
Intravascular volume-replacement solution
Give some examples of natural and synthetic colloids
Natural: albumen, plasma, whole blood
Synthetic: gelatines, starches, dextrans
What is the priority when doing fluid therapy?
Restoration of circulating volume
For each litre of ECF volume replacer given, how much remains in the intravascular space?
250mls
Why is it not always appropriate to give fluid replacers with high Na solutions?
Sodium may accumulate over time
How do colloids work
Large molecules thus can’t pass through healthy vascular endothelium.
They therefore increase osmotic pressure of the plasma and ‘pull’ water from the interstitial space.
Plasma volume expanders.
Why should ECF replacers be used concurrently or soon after colloids?
To replace the fluid taken from the interstitial space
How does hypertonic saline work?
7.2% NaCl. Increases blood pressure.
Draws water in by osmosis from the interstitial space. Plasma expanders.
Any effect is transient, so must be followed by administration of isotonic crystalloids
What is the optimum Na concentration of an oral fluid required to achieve optimum rehydration?
120-130mmol/L
What is urine specific gravity?
What do we use to measure it?
Ratio of density of urine compared with density of a reference (water=1)
Refractometer
What is the specific gravity of protein-free plasma?
1.008-1.012
Which values for specific gravity are classed as an ‘inadequate concentration’ in cats and dogs?
Cats
What does isosthenuria refer to?
What does it suggest?
The excretion of urine whose specific gravity is within the range of protein-free plasma, typically 1.008-1.012.
Suggests that the kidneys have not altered the glomerular filtrate. It is likely that the animal has kidney failure
How can you distinguish between renal and pre-renal azotaemia?
Renal-unable to concentrate urine
When might you see ketones in urine?
Not normally Might see them in: -starvation -ketosis in ruminants -poorly controlled diabetes mellitus
What kind of problem do you have if you have glucosuria, but plasma glucose is normal?
PCT problem
How much protein is normally in urine?
None
What is the normal pH range for dogs and cats?
5-9
What percentage of urea is reabsorbed in the kidneys?
50%
What can we measure to estimate GFR?
Creatinine
What are the differences between urea and creatinine?
Urea= nitrogenous waste product, made in liver from ammonia from catabolised proteins. Filtered by glomerulus. Some reabsorbed in PCT Creatinine= Produced constantly by muscles. Filtered by glomerulus. Not reabsorbed in PCT
Why might a patient have high urea in their urine? (7)
High protein diet Decreased GFR Recent meal Catabolism (fever) Blocked/ruptured lower urinary tract GI haemorrhage Dehydration
Why might a patient have low urea in their urine? (3)
Low protein diet
Severe liver disease
Aggressive fluid therapy
How do you evaluate kidney function?
Urinalysis (analysis of volume, physical, chemical, and microscopic properties of urine) Blood tests (urea & creatinine, serum electrolytes)
What waste products are found in urine?
Na+, K+, urea, creatinine
