Urinalysis chp 3

What are two characteristics of urine that make it in integral part of patient examination?

1. Readily available and easy to collect

2. Contains information about the body’s major metabolic functions that can be obtained through inexpensive tests

What is urine?

An ultrafiltrate of plasma

Approximately how much plasma is filtered to make 1200 ml of urine?

170,000 ml

What factors can affects the concentration of solutes in urine?

• dietary intake

• physical activity

• body metabolism

• endocrine functions

What is the normal composition of urine?

95% water and 5% solutes

What is the primary organic substance in urine?

Urea (around half of total dissolved substances)

What is urea?

A metabolic waste product of the liver from the breakdown of protein and amino acids

What some other organic substances found in urine?

creatinine and uric acid

What is the major inorganic solid found in urine?

Chloride

What are some other inorganic solids found in urine?

• sodium

• potassium

• phosphate

• ammonium

• calcium

Why is it difficult to establish normal concentrations of inorganic compounds?

They are heavily influenced by dietary intake

What are formed elements?

• bacteria

• cells

• casts

• crystals

• mucus

What does an increased amount of formed elements in urine often indicate?

Disease

What does urine volume depend on?

The amount of water the kidneys excrete

What is the amount of water excreted usually determined by?

Level of hydration

What are some factors that influence urine volume?

• fluid intake

• fluid loss from nonrenal sources

• Variations in ADH

• need to excrete increased amounts of dissolved solids like glucose or salts

What is the normal daily urine output?

1200-1500 ml with a range of 600ml to 2000ml considered normal

What is oliguria?

A decrease in urine output (less than 1ml/kg/hr in infants, <0.5 in children and <400 in adults

What is anuria?

The cessation of urine flow.

May results from serious damage to the kidneys or a decrease in blood flow to the kidneys

What is nocturina?

An increase in nocturnal excretion of urine

When do kidneys excrete the more urine?

During the day ( two to three more times than at nights)

What is polyuria?

An increase in daily urine volume (>2.5 l/day in adults and 2.5-3 ml/kg/hr a day in children)

What is polyuria often associated with?

Diabetes mellitus and insipidus

What can also cause polyuria?

• diuretics

• caffeine

• alcohol

  All of which suppress the secretion of ADH

What causes diabetes mellitus?

A defect in the either the pancreatic production of insulin or the formation of urine

What happens to glucose levels in diabetes mellitus?

Body concentration increases

What cause polyuria in diabetes mellitus?

Glucose levels increase, kidneys do no reabsorb the excess and thus increased amounts of water are needed to remove the excess glucose

What happens to the specific gravity of urine in diabetes mellitus?

Increases due to increased glucose content, even if it appears to be dilute

What causes diabetes insipidus?

A decrease in the function or production of ADH

What cause polyuria in diabetes insipidus?

Without ADH, water is not reabsorbed from the plasma filtrate

What is happens to the specific gravity is diabetes insipidus?

Urine is truly dilute causing a low specific gravity

What kind of container must urine be kept in?

A clean, dry, leakproof container

Why should disposable containers be used?

They eliminate the chance of contamination due to improper washing

What should containers for routine urinalysis have?

A wide mouth for easy of collection and a wide plate bottom to prevent overturning

Why should urinalysis containers be clear?

For ease in determining color and clarity

What is the recommended capacity for a urine collection container?

50 ml

What must happen immediately after collection?

A label with the patient’s first and last name and identification number, date and collection time, and additional information needed such age and preservative used must be attached to the container not the lid

When can a specimen be rejected?

1. When in improperly labeled containers

2. When label and requisition forms do not match

3. When exteriors are contaminated

4. Insufficient quantity

5. Specimen is contaminated with feces or toilet paper

6. Transported improperly

7. Improperly persevered

8. Collected in nonsterile container

9. Wrong method of collection for testing

What timeframe must a specimen be tested in without steps taken to preserve it?

Within two hours

When samples are refrigerated what temperatures should they be kept at and how long are they good for?

2-8 degrees Celsius and up to 24 hours if it is to be cultured

What must be done before preforming reagent strip testing on a refrigerated sample?

Must be brought to room temperature

What can refrigeration cause in the urine sample?

The precipitation of amorphous urate and phosphate crystals

What makes the ideal preservative?

Bactericidal, inhibit urease and preserve formed elements while also not interfering with chemical tests

Does the ideal preservative exist?

No

What are the advantages of a random specimen?

Easy to collect, used for routine screening tests

What are the disadvantages of a random sample?

May show erroneous results to due the dietary intake and physical activity of patient before collection of sample

What is the ideal screening specimen type?

A first morning specimen

What is the first morning specimen used for?

• Pregnancy tests (helps prevent false negatives)

• routine screening

• evaluating orthostatic proteinuria

What makes the first morning specimen ideal?

It is a concentrated specimen and thereby assures the detection of chemical and formed elements that may not be present in a dilute sample.

What is a 24-hour/timed specimen used for?

Quantitative chemical tests

What changes does a 24-hour collection account for?

• Diurnal variations in solutes like catecholamine and electrolytes which are low in the early morning and high during the afternoon

• daily activity such as exercise, meals and body metabolism

When can a shorter collection time be used for a specimen?

When the concertation of the particular substance to be tested remains constant

How must the patient begin and end the collection period for a 24/timed specimen?

With an empty bladder. Concentration of a substance in a particular period must be calculated only with the urine volume produced during that time.

What must happen upon arrival in the lab to a 24 hour specimen?

Must be mixed thoroughly and the volume accurately measured and recorded. Specimens collected in two containers must be combined

How must all specimens kept during the collection process?

Refrigerated, on ice or with an addition of a chemical preservative

What are some common errors associated with a timed collection?

• loss of urine specimen

• inclusion of two first morning specimens

• inaccurate measurement of total urine volume

• inadequate urine preservation

• transcription error

What is a catheterized specimen?

A specimen taken by passing a catheter through the urethra and into the bladder.

What test is most commonly requested with a catheterized specimen?

Bacterial culture

What is a midstream clean catch specimen an alternative to?

A catheterized specimen

What are the advantages of a midstream catch?

• safer and less traumatic to patient than a catheterized specimen

• less contamination by bacteria and epithelial cells

• more representative of actual urine that a routinely voided specimen

What test are commonalty ordered with a midstream catch?

• bacterial culture

• routine screening

What is a suprapubic aspiration?

A urine sample collected via the external introduction of a needle through the abdomen and into the bladder

Why are the advantages of suprapubic aspiration used?

• proves a sample free of extraneous contamination as the bladder is sterile under normal conditions

What tests are suprapubic aspirations often used for?

• bladder bacterial culture

• cytology

What are three tests used to collection prostatitis specimens?

• three glass collection

• pre- and post massage test

• stamey-meares/four glass test

How is a three glass collection preformed?

Area cleaned, first urine passed is collected and the midstream portion is collected in a second container. Prostate is then massaged and remaining urine collected in a third container

What is the second specimen in the three glass collection used as?

A control, if positive for bacteria third specimen is considered invalid due to contamination with infected urine

What are the three glass and four glass collections used to test for?

Prostatic infection

How is the pre- and post massage test preformed?

First specimen is a clean catch specimen, second is collected after the prostate is massaged

What is a positive result in the pre- post massage test?

Significant bacteriuria in the post massage specimen of greater than ten times the pre massage specimen

What are the four specimens collected in the four glass collection?

• First 10 ml of urine, represents urethral specimen

• second, 10 ml of urine after voiding another 100-150 ml from first specimen, represents bladder specimen

• third, fluid collected during a prostatic massage

• fourth, collected after the prostatic massage

What is the chain of custody?

A process that provides documentation that the sample submitted to the lab is from the individual being screened. It is a standardize form that must document and accompany every step of the drug test from collector to courier to lab to medical review officer to employer

What must be checked within four minutes of collection of a drug test?

Temperature, must be between 32.5 to 37.7 degrees

What also may be checked during a drug screen?

• pH (greater then 9)

• specific gravity (less that 1.005)

What also is inspected after collection of a drug test?

• color for possible signs of contaminants

• required volume