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162 Cards in this Set

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What is needed in order to identify common microscopic structures that can be found in urine sediment?

-a fresh urine sample
Describe the Intact Nephron Hypothesis
-if the glomerulus gets destroyed, the entire nephron will die
-if the tubules get destroyed, the entire nephron will dies
3 Major Physiological processes of the nephron

-Glomerular filtration (passive)
-Tubular Reabsorption (active/passive)
-Tubular Secretion (active/passive)

What happens to water that is in tubules?
-the water that is present is from the glomerular ultrafiltrate
-most of this water is reabsorbed
-NO water is added by tubular cells
In a healthy person, how much water enters the tubules each day, compared to the amount of water that is excreted?
-180 L enters the tubules
-only 1-2 L excreted
Glomerular Filtration Rate (GFR)
-definition
-the rate that substances are cleared from the plasma through the glomerulus
What typically occurs when GFR decreases?
-substances in the blood are cleared slower causing their concentrations in the plasma to increase
-with decreased GFR there is a dec in excretion of metabolic waste through the kidneys
Substances that normally pass through the glomerular filtration barrier
-water
-solutes/proteins smaller than albumin
Why does tubular fluid become more dilute in the ascending loop of henle?
-solutes are being removed from the fluid
Animal that typically has the most concentrated urine (highest osmolality)?
-least concentrated urine
-highest: cats
-lowest: cattle and horses
Osmolality
-definition
-total solute concentration
Solute osmolality that typically isn't increased in the urine compared to the plasma
-glucose
-the body tries to retain glucose
Events in the proximal collecting tubule
No change in concentration due to removal of total volume
-water reabsorbed
-solutes reabsorbed
Events in the descending loop of henle
Increase in solute concentration
-water reabsorbed
Events in the ascending loop of henle
Decrease in solute concentration
-removes solutes
-water volume the same
Events in the distal nephron
Concentration dependent on ADH activity
-increased concentration if water removed
-remains dilute if water is not removed
In order for the nephron to concentrate urine, what must occur?
-all parts of the tubule must be functional
Chronic renal insufficiency
-definition
-when a chronic disease damages the kidneys to an extent that the renal tissue is no longer able to function and maintain health
Chronic renal insufficiency
-categories
-diminished renal reserve
-chronic renal insufficiency
-chronic renal failure
-end-stage renal disease
Diminished renal reserve
-characteristics
-GFR = 50% normal
-animal is clinically healthy
-no azotemia present
Chronic renal insufficiency
-chracteristics
-GFR = 20-50% normal
-azotemia and anemia
-polyuria from a decreased concentration ability
Chronic renal failure
-characteristics
-GFR = < 20-25% normal
-azotemia and anemia
-polyuria from a decreased ability to concentrate
-inability for the kidneys to regulate extracellular fluid volume or electrolyte balance
End-Stage Renal disease
-characteristics
-GFR = < 5% normal
-termial stages of uremia present with oliguria or anuria
How is a cats concentration ability different from other animals?
-most cats are still able to concentrate urine until about 85% functional renal loss
Acute Renal Insufficiency
-definition
-reversible or irreversible renal dysfunction resulting abruptly from renal disease or an insult that markedly decreases the GFR and leads to azotemia
Azotemia
-defintion
-increase in non-protein nitrogen compounds in the plasma (urea/creatinine)
Uremia
-defintion
-increase in non-protein nitrogen compounds in the plasma with the presence of clinical signs reflecting renal failure
3 things to think about concerning azotemia
-prerenal azotemia
-renal azotemia
-postrenal azotemia
Relationship of Renal Plasma Flow and GFR
-blood must flow through the glomerulus in order for there to be plasma filtration
Possible paths of urea in the body
-produced by hepatocytes that convert NH4 (produced by either tissues or bacteria in the intestines) to urea
-pass through the glomerulus and enter renal ultrafiltrate
-some reabsorption by renal tubules
-excretion in urine
-excretion in intestine/feces
Possible paths of creatinine in the the body
-produced from creatine degredation in muscle fibers
-pass through flomerulus and enter renal ultrafiltrate
-NO reabsorption by renal tubules
-excretion in urine
-excretion in intestines
Causes of partial or complete urinary tract obstruction
-urolithiasis
-neoplasms
-injuries
Which substance will diffuse faster from extravascular fluid? urea or creatinine?
-urea
Prerenal Azotemia
-causes
-hypovolemia
-shock
Renal Azotemia
-causes
Chronic:
-Inflammatory
-Amyloidosis
Acute:
-Toxic nephrosis (hypercalcemia, ethylene glycol)
-Renal iscemia/hypoxia
Postrenal Azotemia
-causes
-urinary tract obstruction
-leakage
Decreased [UN]
-causes
-decreased synthesis (hepatic insufficiency)
-increased renal excretion (impaired reabsorption by the proximal tubules)
[UN] vs. [Crt]
-normally parallel eachother
-[Crt] more sensative to decreased GFR than [UN] in horses and ruminants
[UN] is affected by:
-renal tubular reabsorption
-protein catabolism
Although routine urinalysis components vary between labs, what should be the same in all of them?
-the use of fresh urine
Common components analyzed in urine
-physical (color, clarity, USG)
-chemical
-sediment
3 Factors that determine urine composition
-composition of the plasma that is presented to the kidneys
-renal function (filtration, reabsorption, secretion)
-what is added during flow through the renal tubules and post-renally
colorless urine
-meaning
-dilute
light yellow urine
-meaning
-normal
dark yellow urine
-meaning
-normal/concentrated (urochromes)
Red & Clear urine
-meaning
-hemoglobinuria/myoglobinuria
Red & Cloudy urine
-meaning
-Hematuria
Orange to Brown urine
-meaning
-Bilirubin
Coffee-brown urine
-meaning
-myoglobinuria
-methemoglobinuria
Clear urine
-meaning
-expected
-any solutes are dissolved
Hazy to Cloudy urine
-meaning
-suspended particles are present (cells, crystals, etc.)
When is solute concentration in urine expected to change?
-inc. if kidneys are conserving water
-dec. if the kidneys are not conserving water
How is solute concentration in urine measured?
-Refractive index (USG)
What does the refractive index depend on?
-the # of particles/volume
-types of particles (larger particles contribute more)
In health, what is the refractive index primarily due to?
-electrolytes
-urea
-creatinine
How is osmolality determined?
-freezing point osmometer
-the lower the freezing point of the urine, the high [solids] present in the urine
Osmolality
-definition
-# of particles/volume
Why is urine osmolality important?
-the resorption of water is dependent on osmolality not Specific Gravity
When is there not good correlation between USG and Osmolality?
-USG will overestimate solute concentration with a greatly increased [protein] or [glucose]
What does the USGref tell us?
-most of the water concentrating that affects specific gravity occurs in the distal nephron
Hyposthenuria
-USGref
-what does this tell us
- < 1.007
-the urine osmolality is less than the plasma osmolality
Isosthenuria
-USGref
-what does this tell us
- 1.007 - 1.013
-the urine osmolality is about the same as the plasma osmolality
What 3 components must be present in order to produce concentrated urine?
-ADH must be present
-tubules must respond to ADH
-a concentration gradient must be present
What components must be present in order to produce hyposthenuric urine?
-functional loop of henle (remove solute but not water
-NO ADH activity
Concentration of solute in urine depends on:
-amount of solute excreted in the urine over time
-the amount of H2O excreted by the urinary system over the same time interval
When performing a urine chemical analysis by dipstick method, what is important to consider?
Either:
-volume of urine produced per day
or
-USGref
Typical Urine pH
-carnivores
-herbivores
-carnivores: acidic
-herbivores: alkaline
Aciduria
-definition
-pH < 7.0
-kidneys are excreting H+ from the blood
Alkalinuria
-definition
-pH > 7.5
-kidneys are returning H+ to the blood
Protein in urine
-normal findings
-none except for some in dogs (albumin typically)
Methods of measuring protein in urine
-reagent strip method
-SSA turbidity
Proteinuria
-types
-Prerenal
-Glomerular
-Tubular
-Hemorrhagic/Inflammatory
Prerenal Proteinurias
-common conditions
-hemoglobinuria (intravascular hemolysis)
-myoglobinuria (acute muscle necrosis)
-Bence Jones proteinuria (lymphoid neoplasm)
Glomerular Proteinuria
-common conditions
-glomerulonephritis
-glomerular amyloidosis
-Protein losing nephropathy and renal failure
Tubular Proteinuria
-common conditions
-acute tubular toxicity
-congenital disorder
Hemorrhagic or Inflammatory Proteinuria
-common conditions
-hematuria: urinary tract hemorrhage
-pyuria: urinary tract inflammation
Glucose
-expected test reaction
-why?
-negative
-all glucose should be getting reabsorbed in the proximal tubule
Glucose
-testing method
-reagent strip method that uses glucose oxidase to convert glucose to gluconic acid
Glucosuria
-types
-hyperglycemic glucosuria
-renal glucosuria
Hyperglycemic glucosuria
-pathogenesis
-a greatly increased plasma [glucose] causes glucose to filter into the ultrafiltrate. The amount of glucose in the ultrafiltrate exceeds the renal threshold for reabsorption
Animal with the highest renal threshold for glucose reabsorption
-cat
Renal glucosuria
-pathogenesis
-plasma [glucose] is WRI but tubular disease causes defective renal resorption of glucose
Osmotic diuresis due to glucosuria
-pathogenesis
-Inc. [glucose] in tubular fluid
-decreased osmotic gradient
-decreased water reabsorption in tubule
-constant urine volume --> Polyuria
Are proteins osmotic agents?
-No
Ketones
-produced by
-hepatocytes
Ketone bodies
-acetoacetate
-beta-hydroxybutyrate
-acetone
Primary ketone body detected by the reagent strip test
-why
Acetoacetate
-acetone is volatile and is lost very quickly
-beta-hydroxybutyrate is not a ketone
Reasons for increased Ketogenesis
-excess catabolism of fatty acids by hepatocytes
-decreased insulin acitivity or increased glucagon activity
Excess ketogenesis is common in:
-diabetes mellitus
-bovine ketosis
What does ketonuria represent?
-there is excretion of acetoacetate and beta-hydroxybutyrate
-causes a resultant hyponatremia and hypokalemia because the ketones are anions
Heme in urine
-tests
-reagent strip
-hematase tablet
Heme in urine
-tests method of detection
-detect peroxidase activity of heme
Types of heme-uria:
-hematuria
-hemoglobinuria
-myoglobinuria
Hematuria
-causes
-erythrocytes entering urine via hemorrhage into the urinary tract
-renal
-bladder
-urethra
Hemoglobinuria
-causes
-intravascular hemolysis
-hemolysis after erythrocytes enter urine (will not have a concurrent hemoglobinemia)
Myoglobinuria
-causes
-myocyte necrosis or damage
-excessive exertion
-rhabdomyosis in horses
Which type of heme-uria will the patient have concurrent pink plasma?
-hemoglobinuria
What condition needs to be present for hemoglobinuria to occur due to cells bursting in the urine?
-a low specific gravity (<1.015) causing the blood cells to swell and burst in the urine
What animal is expected to have trace levels of bilirubin present in the urine?
-dog
Forms of Bilirubin detected by the reagent strip test
-conjugated bilirubin
-occasional unconjugated bilirubin bound to albumin
Bilirubinuria
-causes
-hemolytic icterus (formation > excretion in bile)
-hepatobiliary disease (cholestasis)
Leukocytes in urine
-vocab
-pyuria
Erythrocytes in urine
-vocab
-hematuria
Bacteria in urine
-vocab
-bacteriuria
Casts in urine
-vocab
-cylinduria
Crystals in urine
-vocab
-crystaluria
Locations for possible sites of pyuria determined by route of sample collection
-voided
-catheter
-cystocentesis
-voided: any genito-urinary tissue
-catheter: urethra, bladder, kidneys, prostate
-cystocentesis: bladder, kidneys, prostate
Types of casts that can be formes
-hyaline
-fine granular
-coarse granular
-epithelial
-leukocyte
-erythrocyte
-waxy
Types of casts indicative of active tubular degeneration
-fine granular
-coarse granular
-epithelial
Epithelial cells in urine
-causes
-few = normal
-iatrogenic
-hyperplastic mucosa from inflammation
-neoplastic mucosal cells
Ions in urine that can combine to form crystals
Cations:
-Ca2+
-Mg2+
-NH4+
-Na+

Anions:
-Phosphates
-Carbohydrates
-Oxalate
-Urate
-Bilirubin
Factors promoting crystal formation in urine:
-concentrations of ions in urine
-pH
-temperature
-inhibitors to crystal formation
Crystals more common in acidic urine
-ammonium biurate
-bilirubin
-calcium oxalate
-cystine
-urate and uric acid
Crystals more common in alkaline urine
-calcium carbonate
-calcium phosphate
-magnesium ammonium phosphate
Ammonium biurate crystalluria
-due to
-urate receptor defect (breed variation: dalmation, bulldogs, russian terrier)
-decreased urate resorption by renal tubules

or

-hepatic dysfunction
-increased renal excretion of NH4 and urate
-decreased urate conversion to allantoin
Urate
-derived from
-breakdown of purines (A, G)
Bilirubin crystalluria
-due to
-healthy dog with concentrated urine
-increased renal excretion of bilirubin from an icteric disorder
Calcium oxalate crystalluria
-due to
-inc. excretion of calcium
-increased excretion of oxalates
Calcium oxalate sources
Calcium oxalate monohydrate:
-ethylene glycol
-ruminant diet

Calcium oxalate dihydrate:
-healthy dog with concentrated urine
-ethylene glycol
-ruminant diet
-horse diet
Urate Crystalluria
-causes
-Breed variation (dalmation, bulldog)
-hepatic dysfunction (decreased conversion to allantoin)
Calcium carbonate crystalluria
-common in
-herbivores
-no pathological significance
Calcium phosphate crystalluria
-due to
-healthy dog with alkaline urine
-UTI
-hypercalcuria
Magnesium ammonium phosphate crystalluria
-aka
-Struvite
Struvite crystalluria
-due to
-degredation of urea from bacteria or delayed urinalysis
Pathogenic Mechanisms of Polyuria
-chronic renal failure
-acute renal failure
-post-obstructive diuresis
-diabetes mellitus
-hypercalcemia
-canine pyometra
-hypokalemia
-hypoadrenocorticism
-liver failure
-central diabetes insipidus
-hyperadrenocorticism
-psychogenic polydipsia
Chronic renal failure
-major mechanisms contributing to polyuria
Too few functional nephrons
-solute diuresis
-no tubular response to ADH
Acute renal failure
-major mechanisms contributing to polyuria
-no tubular response to ADH
Post Obstructive Diuresis
-major mechanisms contributing to polyuria
-solute diuresis
-no tubular response to ADH
Diabetes mellitus
-major mechanisms contributing to polyuria
-solute diuresis
-possible decreased medullary tonicity
Hypercalcemia
-major mechanisms contributing to polyuria
-Calcium interferes with tubular response to ADH
Canine Pyometra
-major mechanisms contributing to polyuria
-no tubular response to ADH
Hypokalemia
-major mechanisms contributing to polyuria
-no tubular response to ADH
Hypoadrenocorticism
-major mechanisms contributing to polyuria
-dec. medullary tonicity
-dec. release of ADH
Liver failure
-major mechanisms contributing to polyuria
-dec. medullary tonicity
-NH4 interference with ADH
Central Diabetes Insipidus
-major mechanisms contributing to polyuria
-dec. release of ADH
Hyperadrenocorticism
-major mechanisms contributing to polyuria
-cortisol causes a dec. in ADH release
Psychogenic polydipsia
-major mechanisms contributing to polyuria
-dec. plasma osmolality causes a dec. in ADH release
Isosthenuria
-definition
-urine osmolality = plasma osmolality
Isosthenuria
-USGref range
-1.007 - 1.013
Normal plasma concentration
-300 mmol/kg
Hyposthenuria
-USGref value
- <1.007
Mechanisms of polyuria where solute diuresis contributes to the problem
-why
-chronic renal failure (too much solute for the remaining functional nephrons)
-post-obstructive diuresis (solute accumulates during obstruction and then overwhelms the nephrons after)
-diabetes mellitus (glucose in the tubular fluid reduces the osmotic gradient)
Mechanism of polyuria where dec. medullary tonicity contributes to the problem
-why
-chronic renal failure (damaged medullary tissue; poor blood flow; dec. sodium and Chloride transport in the ascending limb
-Diabetes mellitus (medullary washout)
-hyperadrenocorticism (persistent hyponatremia and hypochloremia leading to dec. Na and Cl transport)
-liver failure (dec. urea synthesis)
Mechanisms of polyuria where dec. tubular response to ADH contributes to the problem
-why
-chronic renal failure; acute renal failure; post obstructive diuresis (damage to renal tubular cells)
-hypercalcemia ( free Calcium interferes with ADH activity)
-pyometra (endotoxins interfering with ADH activity)
-hypokalemia (tubules less responsive to ADH)
-liver failure (increase in NH4 that enters tubules causes less response to ADH)
Mechanisms of polyuria where dec. ADH contributes to the problem
-why
-hypoadrenocorticism (less Na and Cl leads to hypoosmolar plasma, causing less of an ADH stimulus)
-Central Diabetes Insipidus (dec. ADH secretion from pituitary problem)
-Hyperadrenocorticism (increased cortisol inhibits ADH)
-Psychogenic polydipsia (increased water consumption causes hperosmolar plasma and less of an ADH stimulus)
Normal concentrated USG
-cat
-dog
-horse and cattle
-cat: > 1.080
-dog: 1.060
-horse and cattle: 1.045
USG 1.014 - 1.030
-definition
-impaired ability to concentrate
Dehydrated animal with a USG 1.014 - 1.030 could have?
-developing renal failure
-diabetes mellitus --> glucosuria
-hypoadrenocorticism
-partial diabetes insipidus
Dehydrated animal with isosthenuric urine if azotemic, could have?
-renal insufficiency/failure
-hypoadrenocorticism
Dehydrated animal with hyposthenuric urine could have?
-diabetes insipidus
-hypoadrenocorticism
Oliguric animal with USG > 1.030 could be?
-trying to concentrate
Oliguric animal with USG 1.014 - 1.030 could be?
-acute renal failure (if azotemic)
Oliguric animal with USG 1.007 - 1.013 could be?
-oliguric renal failure
-oliguric acute renal failure
Glucosuric animal with USG > 1.020 could be?
-diabetes mellitus
Glucosuric animal with USG 1.007 - 1.020 could be?
-diabetes mellitus and medullary washout
Hyponatremia and Hypochloremia with USG > 1.020 could be?
-hypoadrenocorticism & trying to concentrate
Hyponatremia and Hypochloremia with USG 1.007 - 1.013 could be?
-hypoadrenocorticism
-possible chronic renal failure
Hyponatremia and Hypochloremia with USG < 1.007 could be?
-hypoadrenocorticism
-decreased medullary tonicity
-decreased plasma osmolality
Explain variation in amount of Creatinine in urine
-amount of creatinine released each day should be constant, so variation is due to amount of H2O secreted
Gold standard for measuring protein loss per day via kidneys
-collect all urine produced during 24 hrs
-measure volume and protein concentration
How can urinary excretion of protein be assessed?
-compare urine excretion of and creatinine on a random sample
What can an increased protein/creatinine ration be due to
-inc. filtered load
-inc. tubular absorption
-dec. tubular resorption