Lab 4 - Urinalysis & Urea Clearance

Question 1

How is normal blood pH maintained in the kidneys?

Answer 1

Selective reabsorption of bicarbonate and excretion of H+

Question 2

What is the nephron?

Answer 2

Functional and anatomical unit of the kidney

Question 3

Each nephron consists of two main parts including:

Answer 3

1. Glomerulus - tightly woven highly permeable capillary bed at end of afferent arteriole
2. Renal Tubule - Proximal end of renal tubule is Bowman’s Capsule & is location at which plasma and its contents enter renal tubules

Question 4

A dark coloured urine is indicative of what?

Answer 4

High urine concentration

Question 5

What would cause blood to be in the kidney?

Answer 5

• 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

Question 6

UTI leads to what?

Answer 6

More RBCs and WBCs appearing in urine and making it “murky”

Question 7

What does the presence of a leukocyte indicative of?

Answer 7

UTI; high [leukocyte] in urine = leukocyturia

Question 8

Leukocyte esterase is?

Answer 8

Enzyme that a urinalysis strip is testing the presence of to see if WBCs are in the urine

Question 9

Can Nitrites be filtered at the glomerulus? What is the presence of them in the urine referred to as?

Answer 9

• 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

Question 10

How is urobilinogen made?

Answer 10

Hb broken and non-iron portion converted to bilrubin which is then metabolized into urobilinogen

Question 11

Once formed in intestinal tract what are the two fates of urobilinogen?

Answer 11

1. Half remains in intestines where it is converted to stercobilinogen which is eventually excreted in the feces (giving brown colour to feces)
2. Absorbed into blood and recirculated to liver where it is diverted into small intestine (Enterohepatic urbilinogen cycle)

Question 12

Is it normal to see urobilinogen in the urine?

Answer 12

Yes as it’s water soluble but low [urobilinogen]

Question 13

What is hemolytic anemia?

Answer 13

• 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

Question 14

How are gallstones and urobilinogen connected?

Answer 14

Gallstones obstruct bile ducts so urobilinogen absence in the urine

Question 15

High [protein] in the urine is called?

Answer 15

Proteinuria

Question 16

What is the reason for not seeing protein in the urine?

Answer 16

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

Question 17

What are the conditions that cause proteinuria? What is common amongst these conditions?

Answer 17

Diabetic nephropathy, lupus nephritis
* Urinary content of albumin is abnormally elevated (common amongst)

Question 18

What does a high albumin in the urine result in?

Answer 18

Secretion of excess fluids from blood into the interstitial spaces leading to tissue edema

Question 19

What is tubular proteinuria?

Answer 19

The reabsorption of proteins in the tubule is impaired and results in an abnormal increase in urinary protein loss.

Question 20

With respect to urine what can pH values range from?

Answer 20

4.5-8.0

Question 21

What non-pathological factors influence urine specimen pH?

Answer 21

• Veg diet have increased alkalinity while high protein diet increases acidity
• Right in the morning, urine is more acidic

Question 22

How does UTI causing bacteria influence urine pH?

Answer 22

Convert urea to ammonia and other alkaline waste products.
UTI patients urine = alkaline = more growth of bacteria

Question 23

What is hematuria? What is hemoglobinura?

Answer 23

If RBCs in urine are intact - hematuria
If RBCs in urine are ruptured - hemoglobinura

Question 24

What colour does analysis turn when there is non-hemolyzed blood? What about in hemolyzed blood?

Answer 24

Non-hemolyzed blood is the RBCs intact - green colour
Hemolyzed blood (RBCs ruptured) - green spots

Question 25

Purpose of specific gravity?

Answer 25

Solutions relative density; testing patient’s ability for kidneys to concentrate urine and conserve water

Values are from 1-1.03

Question 26

What is urine SG dependant on?

Answer 26

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

Question 27

What are ketones and where are they formed?

Answer 27

• 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

Question 28

When would ketones appear in urine?

Answer 28

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

Question 29

What happens to the body when there is excess ketones?

Answer 29

Ketoacidosis, pH drops

Question 30

What is hyperbilirubinemia?

Answer 30

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

Question 31

How is glucose reabsorbed?

Answer 31

SGLT-2 co transporters (Na+ and Glucose)

Question 32

Which transporter for glucose is more important? SGLT-1 or SGLT-2?

Answer 32

SGLT-2 is more important for reabsorbing glucose (98% of reabsorption)

Question 33

What indicates high levels of glucose in urine?

Answer 33

When there is so much that the transport capacity is overwhelmed that glucose leaks into urine - Glucosuria

Question 34

Most common cause of glucosuria is?

Answer 34

Diabetes mellitus in which blood glucose levels become elevated due to inadequate insulin availability

Question 35

How is urea created and where?

Answer 35

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

Question 36

What can amino groups turn into that is toxic and hard to remove from the kidneys?

Answer 36

Ammonia; converted into urea via urea cycle to be filtered out of the kidneys

Question 37

What is clearance?

Answer 37

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

Question 38

If a substance is filtered through the glomerulus does it mean it can’t be reabsorbed?

Answer 38

Not necessarily; a substance can still be reabsorbed into the circulation and absorbed substances can always be excreted into the renal tubule

Question 39

Normal urea clearance values?

Answer 39

64-99ml/min

Urea partially reabsorbed to help in osmotic gradient and bringing other things in