Urinary System Flashcards
What are the processes that regulate urine formation?
Glomerular filtration
Tubular absorption
Tubular secretion
How is the GFR assessed?
Assessed by the rate some substances are cleared from the plasma
What does GFR depend on?
Renal plasma flow
How much Na is resorbed in the proximal tubules? Loop of Henle?
75%
It is passively resorbed in the loop of Henle
What stimulates absorption of Na in the loop of Henle?
ADH
What stimulates the absorption of Na in the collecting ducts?
Aldosterone
How much Cl is resorbed in the proximal tubules? Loop of Henle?
75%
Passively resorbed in loop of Henle
How is Cl resorbed in the distal nephron?
Resorbed assively due to a gradient formed by Na
What happens to HCO3 in the proximal tubules?
90% is conserved via H+ secretion
What increases the resorption of HCO3 in the collecting ducts?
Type A intercalated cells
What decreases the resorption of HCO3 in the collecting ducts when there is excess?
Type B intercalated cells
Where is most of the K resorbed?
Prior to the distal tubules
What is K secreted by?
Principal cells in the collecting ducts
What is the secretion of K by the principal cells in the collecting ducts promoted by?
Aldosterone
What promotes the secretion of K in the cortical collecting ducts?
ADH
What is H+ secreted by?
Type A intercalated cells in distal nephron
What promotes the process of H+ secretion?
Aldosterone and acidemia
How much Ca is resorbed in the proximal tubules and loop of Henle?
80 to 85%
What promotes resorption of Ca?
PTH and Vit D
How much PO4 is resorbed in the proximal tubule?
85-90%
What is the resorption of PO4 enhanced by?
Hypophosphatemia and insulin
What is the resorption of PO4 inhibited by?
Hyperphosphatemia and PTH
How much Mg is resorbed in the loop of Henle?
Almost all of it
What stimulates the resorption of Mg?
ADH PTH Glucagon Calcitonin β-agonists
How much glucose is resorbed in the proximal tubules?
All of it
How much of the proteins and amino acids is resorbed in the proximal tubule?
Nearly all of them
How much urea is resorbed in the proximal tubules?
60 to 65%
What enhances the resorption of urea in the distal nephron?
ADH
Where is creatinine excreted in dogs?
In small amounts in the proximal tubules
How much of water is resorbed in the proximal tubules?
75%
What is the concentrating ability?
Ability to resorb water in excess to resorption of solutes
What is the diluting ability?
Ability to resorb solutes in excess to resorption of water
What is isosthenuria?
Urine osmolality is the same as plasma osmolality
USG of 1.007-1.013
What is hyposthenuria?
Urine osmolality is less than isosthenuric values
What is eusthenuria?
Osmolality that is expected for an animal with adequate renal function
What is hypersthenuria?
Very concentrated urine
What must be present for urine concentration?
ADH
What causes chronic renal insufficiency/failure?
Renal tissue is inadequate to maintain health
What is the criteria for staging chronic renal insufficiency/failure?
Diminished renal reserve
What is the GFR in chronic renal insufficiency?
20-50% of normal
What is the GFR in chronic renal failure?
< than 20-25% of normal
What is the GFR of end-stage renal failure?
<5% of normal
What happens when more than 2/3 of the nephrons are lost?
The animal will lose the ability of concentrating the urine
What happens when more than 3/4 of the nephrons are lost?
The animal will become azotemic
What are reasons for loss of concentrating ability?
More solutes are presented to the remaining nephrons
Medullary hypertonicity is not maintained
What is evidence of insufficiency or failure?
Azotemia
Low USG due to loss of concentrating ability
What is evidence of chronicity?
Clinical findings including duration of signs
Lab findings: anemia, hypocalcemia
What is acute renal insufficiency/failure?
Reversible or irreversible, abrupt disease or insult that markedly decreases GFR
Does azotemia occur more rapidly in acute or chronic renal failure?
Acute
What is azotemia?
Increased BUN and/or creatinine
What is uremia?
Urinary in blood
What is pre-renal azotemia?
Any process that decreases RPF
What is renal azotemia?
Any renal disease that leads to major decreased GFR
What is the cause of increased BUN and/or creatinine in post-renal azotemia?
It is distal to the nephron
What is the pathogenesis of azotemia caused by?
Leakage of urine within the body
What is the USG of a dog that is pre-renal?
> 1.030
What is the USG of a cat that is pre-renal ?
> 1.040
What is USG of horses and cattle that are pre-renal?
> 1.025
What does azotemia develop from when it is extrarenal?
Hypovolemia
What sample is needed to measure urea?
Serum or plasma
What are causes of decreased urea nitrogen?
Hepatic insufficiency
Portosystemic shunt
Increased urea excretion
What is the sample needed to evaluate creatinine concentration?
Serum or plasma
What tests are used to look at creatinine concentration?
Dry chemistry and wet
Colorimetric
What are causes of increased creatinine conentration?
Decreased GFR
Increased production and release from myocytes
What does decreased creatinine do to muscle?
Decreased muscle mass
What is the creatinine clearance rate?
Rate by which creatinine is cleared from blood
An indicator of GFR
What are causes of decreased creatinine clearance rate?
Prerenal
Renal
Postrenal
What is the endogenous procedure to check creatinine clearance rate?
Adequate hydration is established and confirmed
All urine is produced during a given period
What is the exogenous procedure to check creatinine clearance rate?
The same as the endogenous but creatinine is injected in the animal
What is the advantage to the exogenous creatinine clearance procedure?
It is a challenge to teh kidneys
What are the disadvantages to the exogenous creatinine clearance procedure?
May increase tubular secretion of creatinine
Lack of standardization methods
What are the 2 parts to a urinalysis?
Physical exam
Chemical exam
What are the methods of collection for urinalysis?
Voided
Cystocentesis
Catheterized
Off surface
What is the problem with voided samples?
Samples may have more bacteria, epithelial cells, and leukocytes from distal urethra adn genital tract
What can cystocentesis cause?
Iatrogenic hemorrhage
What is the problem with catheterized samples?
Epithelial cells, hemorrhage, lubricant, and bacteria
What is the problem with off surface samples?
Contaminated with a variety of microscopic material
What is the normal urine color?
Amber
What does it mean if urine is red?
It has erythrocytes
What does it mean if urine is red-brown?
It contains erythrocytes, Hgb, myoglobin or methemoglobin
What does it mean if urine is brown to black?
Methemoglobin
What does it mean if urine is yellow to orange?
It contains bilirubin
What does it mean if urine is yellow-brown or yellow-green?
It contains bilirubin or biliverdin
What does it mean if urine is cloudy?
Presence of cells, crystals, bacteria, casts, and lipid droplets in the urine
What determines the solute concentration?
Dissolved ions and molecules
What do you use to analyze solute concentration?
Specific gravity
Refractive index
What is the urine pH of dogs and cats?
6.0 to 7.5
What is the urine pH of horses and cows?
7.5 to 8.5
What does aciduria suggest?
Increased secretion of H+
What does alkalinuria suggest?
Decreased excretion of H+
What are the different causes of proteinuria?
Prerenal Glomerular Tubular proteinuria Hemorrhagic Inflammatory
What is the maximum glucose transport ability in dogs?
180-220 mg/dL
What is the maximum glucose transport ability in cats?
290 mg/dL
What are the analytical methods of glucose in urine?
Strip
Copper reduction method
What does it mean if an animal is hyperglycemic?
More glucose in the ultrafilterate that can be resorbed
What will glucosuria cause?
Osmotic diuresis
Decreased concentration ability
Increased urine volume
What are the ketone bodies?
Acetoacetate
β-hydroxybutyrate
Acetone
What are the analytical methods for ketones?
Strip
Acetest table method
What can cause ketonuria?
Increased metabolism of lipids
If a test for heme is positive, what could be seen?
Hematuria
Hemoglobinuria
Myoglobinuria
Methemoglobinuria
What are methods of testing bilirubin in urine?
Strip method
Icotest
What are causes of bilirubinuria?
Hemolytic states or decreased excretion of bilirubin
Concentrated urine from healthy dogs frequently produces a small bilirubin reaction
May be present before hyperbilirubinemia or icterus are present
What is the clinical relevance of urobilinogen?
It is not very clinically relevant
Why is nitrite not very clinically relevant?
Inconsistency of results
What can leukocyte esterase cause in the urinalysis?
False negative in dogs
False positive in cats
How can you get a more accurate and clinically relevant results when looking at urine sediments?
Consistently using the same volume
What are causes of hematuria?
Pathological hemorrhage
Iatrogenic hemorrhage
Urogenital tract (estrus)
Should there be bacteria in the urine?
No, urine is sterile
Because a false negative is possible when looking a bacteria on a urinalysis, what is recommended if infection is suspected?
Urine culture
What are casts?
Cylindrical concretions
Shape mirrors the tubular segment where it was formed
What forms the urinary tract mucosa?
Epithelial cells
What are the type of epithelial cells that form the mucosa?
Renal tubular cells
Transitional cells
Squamous epithelial cells
What is teh clinical significance of epithelial cells on urinalysis?
Present in healthy animals
Inflammation can increase release of cells
Neoplastic cells may be present
What are crystals?
Precipitation of salts
What may dictate the formation or dissolution of crystals?
pH
What is crystalluria a risk factor for?
Urolith formation
What is the shape of calcium oxalate dihydrate and monohydrate crystals?
Envelope shaped
In what animals can you find calcium oxalate dihydrate and monohydrate crystals?
Healthy dogs and cats
Dogs and cats with calcium oxalate uroliths
Dogs intoxicated with ethylene glycol (monohydrate kind is more common)
In what animals can you find calcium phosphate crystals?
Healthy dogs
Dogs with persistent alkaline urine
Dogs with calcium phosphate urolith
Infection induced struvite crystalluria
In what animals can you find cholesterol crystals?
Healthy dogs
What is the shape of cystine crystals?
Hexagonal
Where can find cystine crystals?
Concentrated acidic urine
Dogs and cats with cystinuria
What may cause cytine crystals to dissolve?
Alklaine urine due to infection or contamination with urease-producing bacteria
What is the shape of magnesium ammonium phosphate (struvite) crystals?
Coffin-like prisms
Where can you find stuvite crystals?
Normal dogs and cats
Infection with urease-producing bacteria
Sterile struvite uroliths
Other uroliths
What do urate crystals look like?
Yellow to brown spherules with long irregular profusions
Where can you find urate crystals?
Dogs with portal vascular anomalies
Dogs and cats with ammonium urate uroliths
Uncommon in healthy dogs and cats
What do bilirubin crystals look like?
Needle-like
Yellow to brown
Where can you find bilirubin crystals?
Concentrated urine
Healthy dogs
Cholestatic disease in cats, horses, bovine, and camelids
Where can you find calcium carbonate crystals?
Healthy horses and goats
What organisms, other than bacteria, can be found on urinalysis?
Yeasts
Hyphal structures
Algae
Parasitic structures (may be due to fecal contamination)
