Chapter 3 Intro to Urinalysis

what are the percentages of water and solutes in urine?

urine is 95% water and 5% solutes

3 major organic constituents of urine

• urea - breakdown of amino acids

• creatinine - waste from metabolism of creatine in muscles

• uric acid - nitrogenous waste from breakdown of purines (RNA & DNA)

3 major inorganic constituents of urine

• chloride (main)

• sodium

• potassium

how can you tell if a fluid is urine?

test for urea & creatinine

typical daily urine output

600-2000mLconsidered normal (1200-1500 mL)

oliguria

decrease in daily urine output (< 400 mL per day in adults)

anuria

no urine flow at all

nocturia

peeing more at night

polyuria

peeing more daily

4 essential characteristics of a container for a routine urinalysis

1. wide mouth and flat bottom

2. clear material

3. @ least 50 mL capacity

4. clean, dry, leak-proof

what is the correct procedure for labeling urine specimens?

label immediately after collection, place label on container not lid.

What are the requirements for a correct label on a urine specimen?

• patient name

• identification number (MRN or DOB)

• date of collection

• time of collection

list 4 reasons why a lab would reject a urine specimen

1. unlabeled/mislabeled specimens

2. labels & requisition forms do not match

3. specimens contaminated with feces or toilet paper

4. containers with contaminated exteriors

what are some changes that can occur in a urine specimen that’s been left at room temp. for > 2 hrs

• darker color cus of oxidation

• increased odor cus of bacteria breaking down urea to ammonia

• pH increases (alkaline)

• decrease glucose

• bilirubin decreases if exposed to light

what are some changes that can occur to RBCs in a urine specimen that’s been left at room temp. for > 2 hrs

crenated/swelling → apoptosis/disintegration

what are some changes that can occur to WBCs in a urine specimen that’s been left at room temp. for > 2 hrs

disintegration

what are some changes that can occur to bacteria in a urine specimen that’s been left at room temp. for > 2 hrs

multiply (can falsely decrease glucose)

what are some benefits/disadvantages to refrigeration of a urine sample?

+ : prevents interreference with chemical tests & prevents bacterial growth for 24 hours

- : precipitates amorphous phosphates and urates

what are some benefits/disadvantages to using acid to preserve a urine sample?

advantage: prevents bacterial growth & metabolism

disadvantage: interferes with analysis of drugs & hormones

what are some benefits/disadvantages to using formalin to preserve a urine sample?

adv: excellent sediment preservative

dis: can interfere with glucose, blood, leukocyte esterase, and copper reduction tests

what are some benefits/disadvantages to using sodium fluoride to preserve a urine sample?

adv: preserves drug analytes

dis: inhibits reagent strips for glucose, blood, and leukocytes

describe the process for a random urine collection

pee in a cup at any time in day

describe the process for a first morning urine collection

pee in a cup after you wake up

• good for pregnancy tests, routine testing, orthostatic protein

describe the process for a 24 hr urine collection

1. pee and discard 1st morning specimen

2. collect all other urines from patient in a provided container

3. collect 1st morning specimen the next day

4. entire collection submitted to lab

what is the purpose of a catheterized specimen

used to obtain a sterile specimen, may be used if patient cannot void

what is the purpose of a supra-pubic aspirate

most sterile way to obtain a urine specimen because a needle is directly inserted into the bladder. Used for cytology studies & bacterial cultures

what is the use for a 3-glass or 4-glass urine collection?

used to diagnose prostatic infection in males.

what is the procedure for a 3-glass or 4-glass urine collection?

1. pee

2. mid-stream catch

3. prostate massage (for 4 glass collect prostate secretion before next step)

4. pee again