Introduction to Urinalysis Flashcards
Primary functions of the urinary system
- Regulating plasma concentrations of Na+, K+, Cl-, Ca2+, and other ions
- Regulating blood volume and blood pressure
- Contributing to the stabilization of the blood pH
- Conserving valuable nutrients
- Eliminating organic wastes
- Synthesizing calcitriol
- Assisting the liver in detoxifying the blood and deaminating amino acids
Which parts of the nephron are located w/in the cortex?
- Glomeruli (where filtration occurs)
- PCT
- DCT
Which parts of the nephron are located w/in the medulla?
Renal pyramid (loops of Henle inside this) and sinus (w/ minor calyces that merge to form the major calyx)
The medulla is ____ to the lumen
Hyperosmotic
Function of the glomerulus
Responsible for the production of the filtrate; located at the proximal end of the proximal tubule
Function of the proximal convoluted tubule
- Significantly reduces the volume of water in the filtrate by reabsorbing approximately 2/3
- Na+, Cl-, glucose, and amino acids are absorbed from filtrate
- Removes unfiltered proteins or drugs out of the blood
- Secretes H+
Function of the descending limb of the Loop of Henle
- Passively removes water out of the lumen
- Permeable to urea
- Impermeable to Na+ and Cl-
Function of the ascending limb of Loop of Henle
- Na+ and Cl- are actively moved out of the lumen
- Impermeable to water
- Permeable to urea
Function of the distal convoluted tubule
In the presence of aldosterone, Na+ is actively transported out of the lumen (followed by water)
Function of the collecting duct
Determines the final concentration of urine
JGA senses decreases in __________ ______ and releases renin which stimulates the production of angiotensin II which in turn stimulates the adrenal cortex to secrete aldosterone
Na+; blood volume
Aldosterone actively increases _____ ______ from the lumen of the distal convoluted tubule and collecting duct and thus ______ pulls water out of the lumen. _______ is secreted into the lumen.
Na+ absorption; passively; K+
_______ in the heart sense a drop in blood pressure, increase in plasma osmolality, and/or exposure to aldosterone
Baroreceptors
The ______ synthesizes ADH which is transported to the pituitary gland for storage before it is released into the bloodstream
Hypothalamus
ADH causes changes in the epithelium of the _____ ______ _____ and _____ ______ that enhance the passive flow of water out of the lumen
DCT and CD
Patient with decreased blood pressure will compensate by doing what?
Produce more aldosterone
Three primary pigments found in the urine
- Urochrome
- Urobilin
- Uroerythrin
This substance indirectly stimulates the production of aldosterone
Renin
This is the primary source of yellow coloration and is produced at a constant rate; primarily responsible for urine coloration
Urochrome
This is an orange-brown colored pigment formed by the oxidation of urobilinogen; commonly found in old urines
Urobilin
This is a pink pigment that attaches to urates in the urine and gives amorphous urates a pinkish hue
Uroerythrin
Yellow foam in urine is most commonly due to what?
Bilirubin
White foam in urine is most commonly due to what?
Protein
This is a drug used to reduce discomfort in UTIs, causing urine to be very orange and obscures chemical testing
Pyridium
What three things are reported on urine containing pyridium?
- Color
- Clarity
- Specific gravity (by refractometer)
What is the clarity of normal urine?
Clear
List some nonpathologic states of slight turbidity in clear urine
- Amorphous phosphates precipitate out in alkaline urine
- Amorphous urates, calcium oxalates, or uric acid precipitate out in acidic urine
- Carbonates
List some nonpathogenic states of cloudy specimens
- Squamous epis from improper collection
- Bacteria (improper storage allows them to grow)
- Sperm
- Talcum powder
- Vaginal creams
- Radiogrpahic contrast
- Fat or chyle (digested from lymph vessels)
List some pathologic states from cloudy urine
- Bacteria
- Yeast
- Fungi
- RBCs
- WSBCs
- Trichomonas
- Fecal contamination
Describe a clear urine
- No haziness
- Easy to read printed material
Describe a slightly cloudy urine
Printed material is readable
Describe a cloudy urine
Printed urine material may still be seen but it won’t be readable
A ratio between the density of urine and the density of distilled water at the same temperature; a measure of the kidney’s ability to maintain the body’s water and chemical balance through reabsorption
Specific gravity
Specific gravity measures the amount of ____ ____; depends on the ____ and ____ of dissolved particles
Dissolved solids; mass; number
What is the principle of the refractometer?
Refractive index → ratio of the velocity of light through air is compared to the velocity of light through a solution
How do you correct the specific gravity in a refractometer for glucose?
For every gram of glucose/dL, subtract 0.004
How do you correct the specific gravity in a refractometer for protein?
For every gram of protein/dL, subtract 0.003
How can the [glucose] and [protein] be determined?
By the reagent strip
Why does using centrifuged or uncentrifuged urine not affect the specific gravity when using a refractometer?
B/c we’re measuring dissolved substances
In measuring specific gravity by reagent strip, when urine pH is ≥7.0, add ____ to the strip reading if it’s being read manually
0.005
Is there interference from glucose, protein, or radiographic dyes when measuring specific gravity by reagent strip?
NO
What is the specific gravity of the filtrate as it leaves the glomerulus?
1.010
Three factors that affect the refractive index of a solution
- Wavelength
- Temperature
- Concentration
This term is used to describe urine w/ a specific gravity of 1.010
Isosthenuria
This term is used to describe urine w/ a specific gravity of < 1.010
Hyposthenuric
If urine is constantly < 1.010 (hyposthenuric) what does this represent?
The kidney’s inability to concentrate urine
- Diabetes insipidus
- Renal disease
This term is used to describe ruine w/ a specific gravity of > 1.010
Hpersthenuric
If urine is constantly > 1.010 (hypersthenuric) what does this represent?
- Adrenal insufficiency
- CHF
- Hepatic disease
- Dehydration
What is the physiological limit of specific gravity?
1.040
If urine has a specific gravity < 1.003, what does this represent?
Probably diluted w/ water
What factors influence hypersthenuric specimens?
- Renal function
- State of hydration
- Volume of urine excreted
Low fluid intake = ____ specific gravity
High
High fluid intake = ____ specific gravity
Low
What factors could cause a specific gravity to be > 1.035?
- Dehydration
- Diabetes mellitus
- CHF
- Radiographic contrast
If the specific gravity is > 1.035, what should you do?
Make a 1:2 dilution w/ distilled water and multiply all digits to the right of hte decimal by your dilution factor
This is the measure of the concentration of dissolved particles in a solution expressed in osmoles of solute particles/kg of solvent
Osmolality
Osmolality only measures dissolved particles, thus _____ and ______ are not measured
Lipids and protein
Reference ranges for
- Specific gravity
- Urine color
- Urine volume
- Specific gravity: 1.003-1.030
- Color: colorless to yellow
- Volume: 600-2000 mL/day
Measurement of ____ is the most accurate method to determine solute concentration
Osmolality