Clin Path Lab evaluation Kidney

Volume and rate of production urine depends on

Glomerular filtration, tubular secretion, tubular reabsorption

When looking at Net result of normal renal function on plasma analytes what is reliable as it is all excreted

Creatine

What are the major requirements for kidneys to concentrate urine?

Functional nephrons, concentration gradient, ADH, Epithelium responsive to ADH, Aldosterone, ANP

What percentage of functional nephrons does there need to be for kidneys to concentrate urine

33%

Concentration gradient of urine concentration includes what

Osmolality of tubular fluid-Na,Cl,urea

ADH role in concentrate kidney

response to hyperosmolality increases H2O back to circulation to raise BP

Epithelium of which part of nephron responds to ADH

Distal- produce hyposthenuric urine

Aldosterones role in concentrate urine

Stimulate RAAS- inc Na/Cl reabsorption and K excretion

Atrial naturetic peptide role in concentrate urine

secrete by heart stretch receptors increase Na&H2O excretion and dec ECF volume

Osmolality definition

Concentration of a solution expressed as the total number of solute particles/kg solvent and closely approximates USG

How do you measute USG

REFRACTOMETER

What is the USG to osmolality #

USG-1.010 USG=300

Isothenuria means?

#?

same strength as glomerular filtrate

1.007-1.013

What three things are needed to calculate osmolality

Sodium, Glucose, Urea

If your refractometer reads USGref as 1.00 what does this mean?

it needs to be calibrated- never will be exact 1.00 in real life

Hypersthenuria means?

Dog range?

Cat Range?

Excessive concentration

Dog>1.050

Cat >1.060

Eusthenuria means?

Dog?

Cat?

Large animal?

Adequate concentration (minimum-prerenal)-kidneys are able to concentrate urine to some extent

>1.030dog

>1.035cat

>1.025 Large Animal

Hyposthenuria

Distilled/ deionized water-dilute

1.001-1.007

What must be taken into account when looking at the USG

hydration status, abnormalities reproducible 3 consecutive times= trending

What are urea nitrogen, creatinine?

excretion/waste product not enzyme

BUN

blood urea nitrogen- amount of NITROGEN present in UREA as it enters bloodstream

-will have lower ref interval because only nitrogen in blood

UN

urea nitrogen

Total amount of urea in blood following its production in urea cycle in liver

-will have higher ref interval because whole urea molecule

what does creatinine depend on?

Muscle mass

Decreased serum urea can be?

low protein diets, liver failure, portosystemic shunt, increased excretion

Decreased serum creatinine can be?

low muscle mass or catabolism

underlying renal disease

Azotemia

Retention of nitrogenous metabolic waste products in serum/plasma—>inc UN & or inc Creatinine

Prerenal azotemia

USG

decreased blood flow dec GFR

Animal dehydrated , inc urea production

most causes of decreased perfusion

Dog>1.030

Cat>1.040

Horse and cow>1.025

Renal azotemia/insufficiency

USG

decreased functional nephrons

Dog- 1.014-1.029

Cat-1.014-1.035

postrenal azotemia

obstructive uropathy

When in renal failure what is the USG

isosthenuria- 1.007-1.013

Chronic Kidney disease

too few functional nephrons(solute diuresis & tubules not responding to ADH. dec medullary tonicity)

tubules not responding to ADH/ solute diuretic

Post obstructive diuresis- (K+ buildup, bradycardia, get put on IV)

solute diuresis and ± dec medullary tonicity

Diabetes mellitus/psychogenic polydipsia (CATS-drink more stressed)

dec medullary tonicity

dec plasma osmolality & dec release ADH

Hypoadrenocorticism- addisons

dec medullary tonicity dec aldosterone

Hypo Na, Cl, UN-liver failure

dec medullary tonicity &/or NH4+ interferes with ADH

Central diabetes insipidus

dec release of ADH

Nephrogenic DI, Acute renal failure, canine pyometra. hypokalemia

Tubules not responding to ADH

hypercalcemia

Ca2+ interferes with tubule response to ADH

Hyperadrenocorticism(Cushings) hyperthyroidism (cats)

Cortisol dec release of ADH inhibition of ADH action and inc GFR

Pre non renal causes of increased urea

Catabolic conditions heart failure and hyperthyroidism in cats

Catabolic drugs-steroids

Drugs that reduce protein synthesis

Hemorrhage in GI

Early renal insufficiency/compromise

not azotemic yet ± 66% loss of functional nephrons and dec concentration ability

CKD progressive renal disease

azotemia >75% loss of funcitonal nephrons nad dec concentration ability

Uremia

end stage kidney disease

clinical syndrome associated with polysystemic signs of end stage renal disease

Post renal Azotemia increase in urea/creatinine

caused by obstruction of urinary outflow tract -stones, neoplasia

SDMA

biomarker for calcularion of GFR