Lecture 7 - Physical and chemical exmination of urine

A: Urea, which results from protein and amino acid breakdown.

A: The inability of the kidneys to change the specific gravity of plasma ultrafiltrate (1.010), often seen in chronic renal disease.

A: Color darkens due to oxidation or reduction of metabolites, and clarity decreases due to bacterial growth and precipitation.

A: Large amounts of albumin in the urine.

A: The presence of ketones, often seen in uncontrolled diabetes or starvation.

A: 275 to 900 mOsm/kg, depending on diet, fluid intake, and physical activity.

A: The strip releases protons proportional to ionic concentration, causing a color change on the pad.

A: A purple color, indicating the presence of bilirubin.

A: They convert "nitrATE to nitriITE, which can be detected on a reagent strip as a sign of infection (e.g., with E. coli).

A: It indicates that plasma glucose levels have exceeded the renal threshold (160-180 mg/dL).

A: The breakdown of fatty acids, often seen in diabetes or fasting, confirmed by the Acetotest

A: The presence of bilirubin due to liver disease or biliary obstruction.

A: To evaluate the kidney's ability to concentrate urine and to diagnose causes of polyuria.

A: A pathological process, such as a urinary tract infection (UTI), indicated by white blood cells releasing this enzyme.

A: The use of reagent strips, which change color based on the urine's chemical composition.

Urea & 1/2

nitrogenous breakdown product of protein metabolism

inorganic chloride, sodium and potassium

increases indicative of disease

body's state of hydration

600 to 1800 mL/day

As the amount of solutes the body needs to excrete increases, the amount of water required to excrete them also increases. This is because the body uses water to flush out the solutes.

inability of kidneys to change specific gravity of plasma ultrafiltrate (which is 1.010).

chronic renal disease; kidney isn't able to concentrate the urine so specific gravity of urine and plasma is the same at 1.010.

Nitrite positive (+)

Advantage: does not interfere with chemical tests
Disadvantage: precipitates amorphous phosphates and urates

24 hrs

Advantage: prevents bacterial growth and metabolism
Disadvantage: interferes with drug and hormone analyses

6.0; urine culture transport

Advantage: excellent sediment preservative
Disadvantage: Acts as a reducing agent, interfering with chemical tests for glucose, blood, leukocyte esterase and copper reduction

to preserve cells and casts

Advantages: is a good preservative for drug analyses
disadvantages: inhibits reagent strip tests for glucose, blood, and leukocytes

Yellow

concentrated urine

dilute urine

dehyration

blood or blueberries

injury/myoglobin (skeletal muscles, cardiac muscles) in urine

Blood or myoglobin
Bilirubin
Porphyrins
Melanin
Indican (tryptophan)
Homeogentistic acid
Ingested substances (medications, dyes, vitamins, pigmented foods)

Normal, excess protein, kidney problem

normal

normal, but in need of water soon

severly dehydrated, liver disease

eaten beets, blueberries rhubarb, blood in urine

excess water

healthy

dehydrated

dehydrated, liver/ bile duct condition, food dye

rare genetic disease, bacteria or medication, food dye

No

produces white foam that rapidly dissipates

indicates large amounts of albumin in urine

increased bilirubin

describes the cloudiness of urine caused by suspended particulate matter that scatters light.

clear

1. Contamination from skin or vaginal secretions, bacterial growth, or fecal material
2. Precipitation of dissolved solutes, x-ray contrast media.
3. Red blood cells (RBCs), white blood cells (WBCs), epithelial, clots, bacteria, casts pathogenic

powder, lotion, semen, epithelial cells

ACIDIC

ALKALINE/BASIC

the crystals could be acidic; like amorphous urate when the urine is pink

decreased salts aka amorphous phosphate

aromatic odor

bacterial conversion of urea to ammonia

ingestion of certain fods or drugs change odor.

1. ketones produce sweet or fruity smell
2. amino acid disorders often produce odd odors.

when someone has diabetes and body can't break down glucose so body starts to break down the fat, releasing ketones in the urine.
- also seen in fasting individuals

no BCKAD enzyme which is used to break down isoleucine, leucine, and valine.

to the amount of solutes present in volume of water excreted

95% water
5% solutes

vary with patient's diet, physical activity, and health.

The color of urine is a crude indicator of its concentration. Darker urine generally suggests higher concentration, while lighter urine indicates it’s more diluted.

An expression of concentration in terms of density refers to specific gravity, which compares the density of a substance (like urine) to the density of water. It reflects how concentrated or diluted a solution is.

"Mass of solutes present per volume of solution" refers to the concentration of a solution, where the amount of solute (solid particles like salts or waste) is measured relative to the total volume of the solution, such as in urine.

The ratio of urine density to the density of an equal volume of pure water under specific conditions is called specific gravity. It measures how concentrated the urine is compared to pure water.

Both the number of solute particles and their molecular size affect specific gravity because the more particles and larger molecules present in a solution, the higher its density will be, which increases the specific gravity value.

no

concentration of a solution expressed in terms of osmoles of solute particles per kilogram (kg) of water

mOsm most often used for convenience due to low osmolality of biological solutions

275 to 900 mOsm/kg

275 to 300 mOsm/kg

relatively constant!!!

1. evaluate renal concentrating ability of kidneys
2. monitor renal disease
3. monitor fluid and electrolyte balance
4. differentially diagnose cause of polyuria

by measuring a colligative property of solution such as freezing point depression or vapor pressure depression.

urine test strip; reagent strips

reagent strips; urine test strip

plastic strip with reagent-impregnated pads which are dipped in urine resulting in a visual color change.

Qualitative results based on color change.

ascorbic acid (vitamin C)

fluorescent lighting; avoid direct sunlight; urine specimen at room temperature
1. using uncentrifuged urine, mix specimen well.
2. Dip reagent strip briefly into urine wetting all reaction pads and start timing device.
3. Remove excess urine by drawing edge of strip against rim of container or by blotting strip edge on aborbent paper.
4. At the appropriate times, read results of each reaction pad using the color chart on the container.
5. Discard strip into biohazard waste.

to confirm results obtained by reagent strip testing.
&
alternative method for highly pigmented urine

Specific tests are used to confirm results obtained by reagent strip testing to ensure accuracy and provide a more precise measurement. This is important because strip testing can sometimes give false positives or negatives due to various factors, like improper usage or environmental conditions.

Some tests are more sensitive than reagent strip testing because they can detect smaller amounts of solutes or substances in urine that may be missed by strip tests. These tests provide more detailed and accurate results, especially in cases where early detection of abnormalities is crucial.

Acetotest

if the ictotest turns purple = positive
if the ictotest turns pink = negative

BLOOD hemolyzed
non-hemolyzed
Urobilinogen
Biliruben
Protein
Nitrite
Ketones
Ascorbic Acid
Glucose
pH
Specific gravity
Leukocytes

Only measures ionic solutes (sodium, potassium, chloride, ammonium [NH4+])

"indirect chemical method"

- reagent strip pad impregnated with reagents
- when strip immersed in urine, protons are released from reagent in proportion to ionic concentration changing the pad color.

4.5 to 8.0; slightly acidic but more alkaline after meals

stability of formed elements

fresh urine!

- based on a double indicator system
- uses bromothymol blue and methyl red
- produces color changes from orange (pH 5.0) to green (pH7.0) to blue (pH 9.0)

Acidic environment

red blood cells (RBCs) in urine

free hemoglobin in urine

detects hemoglobin, so detects myoglobin

-Pad has chromogen and peroxide
-Pseudoperoxidase "reduces" peroxide, and chromogen is "oxidized", causing color change.

>20/ uL

WBCs are susceptible to lysis, so may not be seen but will release enzyme leukocyte esterase

leukocyte esterase cleaves the ester in pad and results in color change.

as few as 10 WBCs/ uL

Infection/UTI

presence of nitrate-reducing bacteria in urine, but it must give it adequate time in bladder to be reduced

bacteria does not reduce to nitrate to nitrite.

low levels of albumin

no; anything that is <1 to 2 mg/dL; so senstivie albumin tests are used to detect low level albuminuria.

diabetic patients to screen for signs of early kidney damage.

NO!

"double sequential enzyme reaction" that is specific for glucose;
Glucose oxidase in pad oxidizes glucose to form hydrogen peroxide and gluconic acid resulting in a color change.

detects sugars (except sucrose) and other reducing substances such as ascorbic acid, cysteine, and some drugs (e.g. Galactosemia)

Benedict's copper reduction test

bc not all sugars are detected in urine strip. Glucose oxidase is detected in urine strip only!!

an inherited metabolic disorder that makes your body unable to process a sugar called galactose. lack of GALT enzyme; patients do not have enough glucose in the body.

breakdown products of fatty acids
Acetoacetate
Acetone
b-hydroxybutyrate

NO!

beige to purple; acetest

direct (conjugated) bilirubin <-water soluble

Liver

no, so bound to albumin in plasma and too large filter at the kidneys

causes urine to be dark yellow to brown

a product of biliruben that forms in the intestines

hemolytic anemia in addition to cirrhosis and hepatitis.

RBC after 120 days break down and are picked up by the liver. Macrophage in the liver degrade hemoglobin. Hemoglobin converted to methmoglobin and then reduce to biliverdin (green color); biliverdin to billruben (red-orange color); bilirubin to bilirubin diglucuronide (move to bile) -> cont.

stereobilin