urinary system

function of the kidneys

• production of urine

• elimination of drugs/toxins, maintenance of normal blood pH

• kidney functional unit nephron

• urinary system includes: paired kidneys, paired ureters, bladder, urethra

how is urine formed

formed in the nephron thru process of glomerular filtration, tubular reabsorption, tubular secretion

Glomerular filtration, how its affect?

filters substances from blood and is affected by BP, plasma osmotic pressure -dehydration?, and capsule pressure - urinary obstruction?

Tubules reabsorb and secrete substances

Reabsorption includes H2O, glucose, amino acids, Na, K,Ca,Cl

Secretion includes K.H. creatinine , NH4, phosphorus

Urinary system clinical signs

1. pollakiuria - increase freq of urinations

2. dysuria - painful urination

3. hematuria

4. inability to urinate

Urinary system disorders

1. UTI

2. inflammation

3. kidney dz - acute or chronic

4. urethral obstruction

what do diuretics do?

increase urine volume

• reduce edema and BP

work by affecting Na and Cl reabsorption

can cause electrolyte imbalances

What do loop diuretics do

inhibit Na reabsorption at Loop of Henle Na pumps

Loop Diuretic

Furosemide

affect reabsorption of Na → more Na in urine → water follows → more urination

• Side effect: hypokalemia and electrolyte imbalances

Potassium Sparing Diuretics

acts to promote Na and water excretion and potassium retention, usually used w other drugs

• spironolactone

Potassium Sparing Diuretic

Spironolactone

a aldosterone receptor antagonist at distal renal tubules in which increases excretion of Na, Cl, H2O and reduce excretion of K, phosphate

• effect: hyperkalemia

• part of RAAS

Is potassium-sparing as strong as furosemide?

no, potassium-sparing has milder diuretic

What happens in the RAAS pathway? what does it stand for?

Renin-Angiotensin-Aldosterone System

activates b/c decr BP → kidney releases renin → angiotensinogen → Ang I → ACE (angiotensin converting enzyme) → Ang II → ↑ BP

Ang II causes vasoconstriction = stimulates aldosterone → Na⁺/H₂O retention and ADH → water retention

Thiazide diuretics

Hydrochlorthiazide

blocks Na reabsorption at distal convoluted tubules and increase K excretion but could lead to hypokalemia w/ chronic use

• not potent as furosemide

Diuretic

Carbonic Anhydrase Inhibitor

reduce formation of H and HCO3 → HCO3 pairs w Na and is excreted

• metabolic acidosis possible

• Methazolamide

Osmotic Diuresis

increase filtrate osmolality

• Mannitol: high osmolality molecule, filtered at glomerulus, can be also used w acute kidney failure to promote urine production

Antihypertensives

reduce blood pressure

Antihypertensives-

ACE inhibitors

inhibit action of ACE

• reduce vasoconstriction and Na reabsorption

• Enalapril (renal) and Benazepril (renal/hepatic elimination)

Antihypertensives

Angiotensin Receptor blocker - Telmisartan and Losartan

Ang II competitive antagonist

• vasodilate and Na excretion

• Telmisartan - FDA approved feline hypertension

• Losartan

Antihypertensives

Calcium Channel Blockers - Diltiazem and Amlodipine

blocks influx of Ca ions in myocardial cells will inhibit smooth/cardiac muscle contractility and decrease BP

• Diltiazem - activity at cardiac myocytes

• Amlodipine - activity at vascular smooth muscle myocytes FIRST choice for feline

Antihypertensives

Arteriole Vasodilators - Hydralazine

Hydralazine - affects intracellular Ca metabolism → smooth muscle relaxation

• for CHF

Antihypertensives

Beta-adrenergic antagonist (beta blockers)

reduce BP via reduce CO

beta-1 → heart

beta-2 → bronchus smooth muscle

• Carvedilol and Atenolol

Beta-adrenergic antagonists

Carvedilol and Atenolol

Carvedilol - non-selective beta blocker and a-1, dilated cardiomyopathy → reduce SNS and reduce afterload

Atenolol - selective beta-1 blockers

Antihypertensives

alpha-adrenergic antagonist

Phenoxybenzamine - used for feline urinary sphincter tone reduction (blocked male cats)

• side effect: hypotension

What drugs might a cat be put on during treatment for a urethral obstruction in order to reduce urethral spasms?

alpha-adrenergic antagonists, relax urethral sphincter

• prezosin and phenoxybenzamine

What do phosphate binders do? what type of drug?

bind to dietary phosphorus to prevent absorption in bloodstream when pt has renal dz

• Aluminum hydroxide: binds dietary phosphorus but give with food

What is the primary curative treatment for uroliths (bladder stones)?

surgery for dogs and cats

What are uroliths made of?

1. struvite - mg, NH4, phosphate = formed in alkaline/higher pH and UTI

2. Calcium oxalate - form in acidic/lower pH urine or genetics

3. urate

4. cystine

Which type of animal is ureter or urethral obstruction less common

in large female dogs which they have shorter urethra

Difference uses for Hills s/d and Purina St/Ox

Hills is used for dissolving struvite stones only for 6 mo max

Purina for dissolving struvites and prevent struvites and Ca oxalates, maintain nor pH

Will a dissolution diet work when UTI is occuring

No because diet cannot treat infection

Potassium Citrate

it is a urine alkalinizing to increase urine pH to prevent Ca oxalate stones

• might be used in a breed that had one and is predisposed

Allopurinol

it is a type of urine alkalinizing that inhibits the enzyme that converts chemicals into uric acid

• used for dissolving or preventing urate stones

• in dalmatians and bulldogs

What is urinary incontinence

the loss of voluntary control of micturition

What are the negative effects and life-threatening risks of a urolith? What are the symptoms?

Effects: Urinary obstruction Inability to urinate and Kidney damage

Symptoms: Pollakiuria , Dysuria Hematuria, and inability to urinate

What roles do the PNS and SNS play on urinary incontinence?

PNS - promotes bladder contraction and sphincter relaxation

SNS - promotes bladder relaxation and sphincter contraction

non-neurologic urinary incontinence

Phenylpropanolamine (Proin)

Phenylpropanolamine (Proin) - a and b receptor agonist increasing sphincter tone

• used for canine female hormonal/stress incontinence

• a-1 may cause hypertension

non-neurologic urinary incontinence

Estriol (incurin)

binds estrogen receptors in female lower urinary tract, may be used to treat hormone-responsive incontinence

• effects: mammary hyperplasia, swollen vulva

urinary incontinence

Bethanechol

cholinergic agonist to induce urination w spinal injury

urinary incontinence

adrenergic antagonist

relax urethral spincter for urinary obstruction

• Prazosin - a-1

• Phenoxybenzamine- non-selective a