Lab 4 - Urinalysis & Urea Clearance Flashcards
How is normal blood pH maintained in the kidneys?
Selective reabsorption of bicarbonate and excretion of H+
What is the nephron?
Functional and anatomical unit of the kidney
Each nephron consists of two main parts including:
- Glomerulus - tightly woven highly permeable capillary bed at end of afferent arteriole
- Renal Tubule - Proximal end of renal tubule is Bowman’s Capsule & is location at which plasma and its contents enter renal tubules
A dark coloured urine is indicative of what?
High urine concentration
What would cause blood to be in the kidney?
- UTI and kidney stones make blood pinkish
- Skeletal or cardiac muscle damage can result in myoglobin protein being released into blood (reddish brown discolouration)
Beats, rhubarb can turn blood red
UTI leads to what?
More RBCs and WBCs appearing in urine and making it “murky”
What does the presence of a leukocyte indicative of?
UTI; high [leukocyte] in urine = leukocyturia
Leukocyte esterase is?
Enzyme that a urinalysis strip is testing the presence of to see if WBCs are in the urine
Can Nitrites be filtered at the glomerulus? What is the presence of them in the urine referred to as?
- Common mistake, only nitrate can be filtered at glomerulus while nitries in urine is abnormal
- Nitrituria = positive for nitrites in urine
Nitrites in urine indicate UTI because of bacterial species that use enzyme nitrate reductase
How is urobilinogen made?
Hb broken and non-iron portion converted to bilrubin which is then metabolized into urobilinogen
Once formed in intestinal tract what are the two fates of urobilinogen?
- Half remains in intestines where it is converted to stercobilinogen which is eventually excreted in the feces (giving brown colour to feces)
- Absorbed into blood and recirculated to liver where it is diverted into small intestine (Enterohepatic urbilinogen cycle)
Is it normal to see urobilinogen in the urine?
Yes as it’s water soluble but low [urobilinogen]
What is hemolytic anemia?
- Complication of sickle cell disease, where it causes excessive destruction of RBCs and their contents
- Hb broken down more faster ==> Bilirubin produced and more urobilinogen formed
- Urobilinogen reabsorbed and then when secreted will have abnormal increased amount
How are gallstones and urobilinogen connected?
Gallstones obstruct bile ducts so urobilinogen absence in the urine
High [protein] in the urine is called?
Proteinuria
What is the reason for not seeing protein in the urine?
Design of glomerulus; 3 distinct layers of glomerulus that substances need to pass in order to be filtered - Renal filtration barrier
Darker shades of green mean more protein in urine
What are the conditions that cause proteinuria? What is common amongst these conditions?
Diabetic nephropathy, lupus nephritis
* Urinary content of albumin is abnormally elevated (common amongst)
What does a high albumin in the urine result in?
Secretion of excess fluids from blood into the interstitial spaces leading to tissue edema
What is tubular proteinuria?
The reabsorption of proteins in the tubule is impaired and results in an abnormal increase in urinary protein loss.
With respect to urine what can pH values range from?
4.5-8.0
What non-pathological factors influence urine specimen pH?
- Veg diet have increased alkalinity while high protein diet increases acidity
- Right in the morning, urine is more acidic
How does UTI causing bacteria influence urine pH?
Convert urea to ammonia and other alkaline waste products.
UTI patients urine = alkaline = more growth of bacteria
What is hematuria? What is hemoglobinura?
If RBCs in urine are intact - hematuria
If RBCs in urine are ruptured - hemoglobinura
What colour does analysis turn when there is non-hemolyzed blood? What about in hemolyzed blood?
Non-hemolyzed blood is the RBCs intact - green colour
Hemolyzed blood (RBCs ruptured) - green spots
Purpose of specific gravity?
Solutions relative density; testing patient’s ability for kidneys to concentrate urine and conserve water
Values are from 1-1.03
What is urine SG dependant on?
Individuals level of hydration
* Dehydrated = kidneys conserve much water as possible to prevent water content from dropping in body
* Higher SG for dehydrated people
* Overhydrated = more water to be released in urine and this leads to lower SG
What are ketones and where are they formed?
- Known as incomplete breakdown of fat
- Found in liver in conditions where glucose availability is limited
- When glycogen and glucose levels are gone, body relies on fat for energy source so more production of ketones needed
When would ketones appear in urine?
When production of ketones exceeds body’s use of them making them excreted in urine - Ketonuria
Typically see low values and magenta colour indicates high ketones
What happens to the body when there is excess ketones?
Ketoacidosis, pH drops
What is hyperbilirubinemia?
Detecting high concentrations of bilirubin in urine (NORMALLY NONE) results in large amounts of metabolite being excreted in urine
In the example where gallstones prevent urobilinogen formed so the bilirubin in bile is secreted out into the kidneys and urine
How is glucose reabsorbed?
SGLT-2 co transporters (Na+ and Glucose)
Which transporter for glucose is more important? SGLT-1 or SGLT-2?
SGLT-2 is more important for reabsorbing glucose (98% of reabsorption)
What indicates high levels of glucose in urine?
When there is so much that the transport capacity is overwhelmed that glucose leaks into urine - Glucosuria
Most common cause of glucosuria is?
Diabetes mellitus in which blood glucose levels become elevated due to inadequate insulin availability
How is urea created and where?
Urea is created via protein catabolism in the liver, and the breakdown of proteins is called deamination (R group is removed) where you are left with just the amino group
What can amino groups turn into that is toxic and hard to remove from the kidneys?
Ammonia; converted into urea via urea cycle to be filtered out of the kidneys
What is clearance?
Volume of plasma from which a substance is completely removed by the kidneys
Simply: Measures kidney’s abillity to excrete a substance from the plasma (into the urine) that has entered the renal tubules
Glucose has 0 clearance for a healthy individual because we don’t want that in our urine, however PAH is partially filtered but mostly secreted giving it a high clearance rate
If a substance is filtered through the glomerulus does it mean it can’t be reabsorbed?
Not necessarily; a substance can still be reabsorbed into the circulation and absorbed substances can always be excreted into the renal tubule
Normal urea clearance values?
64-99ml/min
Urea partially reabsorbed to help in osmotic gradient and bringing other things in
