RENAL PHYSIOLOGYURINE FORMATION

LABORATORY:

URINALYSIS

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The Urinary System

Organs of the urinary system:Kidneys Ureters Urinary bladder Urethra

Kidney function - removes waste products from the blood stream and excess water

Urinary bladder stores urine, and ureters, bladder and urethra make up the urinary tract

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The Urinary System

Kidneys

Right Ureter

Urinary bladder

Urethra

Prostate gland

Left Ureter

Liver

Aorta

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Formation of Urine Three processes

of urine formation:

glomerular filtration tubular reabsorption tubular secretion

The nephron: allows for

reabsorption of water and electrolytes

plays a vital role in maintaining normal fluid balance

Nephron

- functional unit of the kidney where urine is formed.

STAGES IN URINE FORMATION:1.Filtration2.Reabsorption3.Secretion

filtration

Reabsorption

Secretion

Reabsorption of water

Nephron

-blood pressure forces small molecules

from the glomerulus to the capsule

1. filtration

Filtrates:glucose, amino acids

uric acid, urea

2. Tubular Reabsorption

-return of filtrates from blood

at the proximal tubule through diffusion

and active transport

3. Tubular Secretion

-movement of molecules from blood

into the distal convoluted tubule

Molecules:drugs and toxins

Reabsorption of water

-return of H20 via osmosis along the

loop of Henle and collecting duct

EXCRETION

excretion of urine formed

PATHWAY OF URINE

Nephron

- functional unit of the kidney where urine is formed.

STAGES IN URINE FORMATION:1.Filtration2.Reabsorption3.Secretion

UrinalysisSpecific Objectives:

Physical Characteristics Normal pH Specific Gravity ranges Presence of abnormal substances

in the urine specimens

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Physical Composition and Chemical Properties Urine 95% water 5% waste products Other dissolved chemicals

Urea, uric acid, ammonia, calcium, creatine, sodium, chloride, potassium, sulfates, phosphates, bicarbonates, hydrogen ions, urochrome, urobilinogen

Urinalysis

• a physical and/or chemical examination of the urine.

• It consists of a battery of chemical and microscopic tests to screen for:• urinary tract infectionsurinary tract infections• renal diseaserenal disease, and • diseases of other organs that result diseases of other organs that result

in the appearance of abnormal in the appearance of abnormal metabolitesmetabolites (break-down products) in the urine. 

Urinalysis• can reveal diseases that have gone unnoticed

because they do not produce striking signs or symptoms. • Examples include diabetes mellitus,

various forms of glomerulonephritis, and chronic urinary tract infections. 

• In other urinary diseases with symptoms, a urinalysis can help to confirm of rule out some diseases.

SPECIMEN COLLECTION • A "clean-catch" urine sample is

performed by collecting the sample of urine in midstream.

• Men or boys should wipe clean the head of the penis.

• Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well.

• A small amount of urine should initially fall into the toilet bowl before it is collected (this clears the urethra of contaminants).

• Then, in a clean container (properly labeled with the name of the patient and date), catch about 1 to 2 ounces of urine and remove the container from the urine stream.

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Specimens Types Varies in method used and in

time frame in which to collect specimen

Types of specimens: Random First morning Clean catch midstream Timed 24 hour

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Specimens Types (cont.) Random – most common, taken anytime of

dayFirst morning – has a greater concentration

of substances, taken in morningClean catch midstream – genitalia is

cleaned, urine is tested for microorganisms or presence of infection

Timed – specific time of day, always discard first specimen before timing

24 hour – used for quantitative and qualitative analysis of substances

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UrinalysisEvaluation of urine to obtain information

about body health and disease

Three types of testing: Physical Chemical Microscopic

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Physical Examination of UrineVisual examination of physical

characteristicsColor and turbidityVolume OdorSpecific gravity

The refractometer or a reagent strip is used to measure specific gravity

Reagent Strips

Refractometer

MACROSCOPIC URINALYSIS

• Clearing of the specimen after addition of a small amount of acid indicates that precipitation of salts is the probable cause of turbidity.

• A red or red-brown (abnormal) color could be from a food dye, eating fresh beets, a drug, or the presence of either hemoglobin or myoglobin.

• If the sample contained many red blood cells, it would be cloudy as well as red.

MACROSCOPIC MACROSCOPIC

URINALYSISURINALYSIS • The first part of a urinalysis is direct

visual observation. Normal, fresh urine is pale to dark yellow or amber in color and clear.

• Normal urine volume is 750 to 750 to 2000 ml/24hr.2000 ml/24hr.

• Turbidity or cloudiness may be caused by excessive cellular material or protein in the urine or may develop from crystallization or precipitation of salts upon standing at room temperature or in the refrigerator.

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Normal Values of UrineNormal values of various

elements have been established

Average adult daily urine output is 1250 mL/24 hours

Intake and output should be approximately the same

Examples of appearances of urine

a red, cloudy appearance red but clear yellow, but cloudy

pH

• The glomerular filtrate of bloodglomerular filtrate of blood plasma is usually acidified by renal tubules and collecting ducts from a pH of 7.47.4 to about 66 in the final urine.

• However, depending on the acid-base status, urinary pH may range from as low as 4.54.5 to as high as 8.08.0. • The change to the acid side of 7.47.4 is

accomplished in the distal convoluted distal convoluted tubule and the collecting duct.tubule and the collecting duct.

Specific Gravity (sp. gr.)

• (which is directly proportional to urine osmolality which measures solute concentration) measures urine density, or the ability of the kidney to concentrate or dilute the urine over that of plasma.

• Specific gravity between 1.0021.002 and 1.0351.035 on a random sample should be considered normal if kidney function is normal. • Since the sp gr of the glomerular filtrate in

Bowman's space ranges from 1.007 to 1.0101.007 to 1.010, any measurement below this range indicates hydration and any measurement aboveabove it indicates relative dehydrationrelative dehydration.

Specific Specific gravity gravity

Specific Gravity (sp gr)

• If sp gr is not > 1.022 after a 12 hour period without food or water• renal concentrating ability is

impaired• In end-stage renal disease, sp gr

tends to become 1.007 to 1.010.• Any urine having a specific gravity over specific gravity over

1.0351.035 is • either contaminated, • contains very high levels of glucose

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Apply Your KnowledgeWhat is the specific gravity shown on this refractometer screen?

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Apply Your Knowledge -AnswerAnswer

The specific gravity shown here is 1.030

What is the specific gravity shown on this refractometer screen?

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Chemicals Found in Urine Ketone bodiesKetone bodies – may indicate that patient is following

a low carbohydrate diet or that patient has conditions such as starvation

pHpH – provides information about metabolic status, diet, medication or several conditions

Blood (hematuria)Blood (hematuria) – may indicate patient is menstruating, have urinary tract infection or trauma

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Chemicals Found in Urine (cont.)

Bilirubin or urobilinogenBilirubin or urobilinogen – first signs of liver disease

GlucoseGlucose – common in patients with diabetes

ProteinProtein – usually indicates renal disease

NitriteNitrite – suggests bacterial infection

Leukocytes Leukocytes – urinary or renal infection

PhenylketonesPhenylketones – indicates PKU

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Microscopic Examination of Urine Microscopic examination used to view elements not

visible without microscope Centrifuge spins urine to cause heavier substances to

settle to the bottom

• Casts

• Yeasts

• Parasites

• Cells

• Crystals

• Bacteria

Glucose test • Benedict’s testBenedict’s test

• Aqueous glucose is mixed with Benedict's reagent, a solution of copper sulfate, sodium hydroxide, and tartaric acid.

• The mixture is heated. • Carbohydrates which react with Benedict's

reagent to reduce the blue copper (II) ion to form a brick red precipitate of copper (I) oxide are classified as reducing sugars.

Results of Benedict's Test with Glucose, Sucrose, and Fructose

Glucose

• Less than 0.1% of glucose normally filtered by the glomerulus appears in urine (< 130 mg/24 hr).

• Glycosuria (excess sugar in urine)

generally means diabetes diabetes mellitus.mellitus.

Protein Protein

• Exton’s Test• There are several acids which can

be used to precipitate proteins - sulfosalicylic, trichloroacetic, nitric, and acetic acids.

• Sulfosalicylic acid (SSA)Sulfosalicylic acid (SSA) is the most frequently used acid test because it does not require the use of heat. • Exton’s reagent is 5%

sulfosalicylic acid in a solution of sodium sulfate.

To perform the SSA procedure mix equal parts of patient urine and the reagent. Rate the To perform the SSA procedure mix equal parts of patient urine and the reagent. Rate the

amount of turbidity according to the following scale:amount of turbidity according to the following scale:

Interpretation

• In rough terms, trace positive results (which represent a slightly hazy appearance in urine) are equivalent to 10 mg/100 ml or about 150 mg/24 hours (the upper limit of normal).

• 1+ corresponds to about 200-500 mg/24 hours

• a 2+ to 0.5-1.5 gm/24 hours• a 3+ to 2-5 gm/24 hours • a 4+ represents 7 gm/24 hours or

greater.

Interpretation• Normally, only small plasma proteins

filtered at the glomerulus are reabsorbed by the renal tubule.

• Normal total protein excretion Normal total protein excretion does not usually exceed does not usually exceed 150 150 mg/24mg/24 hours or 10 mg/100 ml in hours or 10 mg/100 ml in any single specimen. any single specimen.

• More than 150 mg/day is defined More than 150 mg/day is defined as proteinuria. as proteinuria.

• Proteinuria > 3.5 gm/24 hours is Proteinuria > 3.5 gm/24 hours is severe and known as nephrotic severe and known as nephrotic syndrome. syndrome.

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Apply Your KnowledgeA urine analysis has detected that a patient has protein in his urine. Why is this important?

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Apply Your Knowledge -AnswerAnswer

Protein in the urine usually indicates renal disease

A urine analysis has detected that a patient has protein in his urine. Why is this important?

Ketones Gunning’s Test

• Ketones (acetone, aceotacetic acid, beta-hydroxybutyric acid) resulting from either diabetic ketosis or some other form of calorie deprivation (starvation)

• Shows positive test for: acetaldehyde and methyl ketones

Ketones Gunning’s Test • Detection of COOH group is possible

through its transformation to an ester in reaction with alcohol.

• The esters have characteristic smell of flowers or fruits

• It should appear the yellow precipitate of yellow precipitate of iodoformiodoform with characteristic smell

• Ketones Normal:There are no ketones in your blood or urine.

• Abnormal:Ketones are present in your blood or urine.

. • Indications of a positive test:

The formation of a yellow precipitate or suspension of

iodoform is a positive test

a negative test (left) and a positive test (right)

Smith’s Test (Bile pigments)

emerald green at the point of contact between urine sample and alcoholic iodine mixture

Bilirubin – green

Bilicyanine – blue

Choletelin - yellow

• Smith’s Test should be conducted to determine whether bilirubin is present in the urine(i.e., bilirubinuria).

• Urobilinogen is formed by intestinal bacteria from the breakdown of conjugated bilirubin, and it is usually excreted in feces. 

• However a small amount may be reabsorbed and excreted in urine.

• A positive test response indicates normal enterohepatic circulation of biliary pigments. High concentrations of biliary pigments may occur in hemolytic crisis, or cases of hepatic or intestinal dysfunction.

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EXPERIMENT 27….

FIRST PHASE:

• Collect urine sample from a donor from each group

SECOND PHASE:

• Unknown sample will be tested

Record all results and analysis in your lab work sheet.

• Post lab group discussion upon submission of all reports will be conducted.