Urinalysis Flashcards
How is urine formed?
by kidneys as ultrafiltrate of plasma
How much filtered plasma does the body convert into urine?
~170,000 mL of filtered plasma to ~1,200 mL urine
What is urine composed of?
95% H2O and 5% Solute
- organic substances: urea, creatinine, uric acid
- inorganic solids: sodium, chloride, potassium
- vitamins, hormones, medications
What is the normal daily urine output?
1200 - 1500 mL per day
What factors affect urine volume?
fluid intake, loss from nonrenal sources, antidiuretic secretion, necessity to excrete glucose/salts
oliguria
decrease in normal daily output (<400 mL/day) from dehydration, vomit, diarrhea, burns
anuria
cessation of urine flow from renal damage
polyuria
increase in daily volume (>2.5 L/day) from diabetes mellitus/insipidus, alcohol, diuretics
diabetes mellitus
- defect in pancreatic insulin production causes increased body glucose concentration
- kidney won’t reabsorb excess glucose; excess excretion of water to remove
- urine appears dilute with high specific gravity and glucose
diabetes insipidus
- decrease in production/function of antidiuretic hormone; water not reabsorbed from plasma
- urine appears dilute with a low specific gravity
How is urine collected and handled?
tested within in two hours of collection; well-mixed
What happens when urine is unpreserved?
- increased bacteria
- decreased glucose, ketone, bilirubin, urobilinogen, RBC/WBC
- reduced clarity from bacterial growth and amorphous precipitation
What temperature is urine preserved at?
2-8 C
What is the benefit of refrigerating urine?
- decreases bacterial growth
- increases specific gravity
- precipitates amorphous crystals
What chemical preservatives are used for urine?
boric acid, chlorohexidine
What is a random void used for?
screening test (diet/activity dependent)
What is a first morning void used for?
concentrated for pregnancy and proteinuria detection
What is a 24-hour timed void used for?
quantitative urine chemistries
What is a midstream clean catch used for?
best type for bacterial culture and urinalysis
What is the normal color of urine?
light yellow to amber (urochrome)
What does a dark yellow/amber/orange urine with foam indicate?
bilirubin or protein
What does a dark yellow/amber/orange urine without foam indicate?
high urobilinogen-urobilin
What does a red and cloudy urine indicate?
RBCs
What does a red and clear urine indicate?
hemoglobin or myoglobin
What does a red (port-wine) urine with negative blood test indicate?
porphobilinogen-porphyrin oxidation
What does a brown urine indicate?
RBC in acidic urine (hemoglobin > methemoglobin oxidation)
What does a brown/black urine indicate?
melanin (malignant melanoma), homogentistic acid (alkaptonuria)
What does a blue/green urine indicate?
Pseudomonas species UTI
What are some non-pathologic reasons for a change in urine color?
menstrual, diet, medications
What does the clarity of a normal urine look like?
clear with no visible particulates
What does the clarity of an abnormal urine look like?
hazy, cloudy, turbid, milky
What are the non-pathologic elements that can be found in a turbid urine?
squamous epithelial cells, mucus, amorphous urates, amorphous phosphates
What are the pathologic elements that can be found in a turbid urine?
- cellular: RBC, WBC, renal-transitional epithelial cells
- microorganisms: bacteria/yeast
- abnormal crystals
What is specific gravity assessing?
the kidney’s ability to reabsorb essential chemicals/water from glomerular filtrate
What is specific gravity?
the density of a solution compared with density of distilled water at equal temperatures/volumes
How does the strip reaction for specific gravity work?
- polyelectrolyte on strip release hydrogen ions in a proportion to number of ions in solution
- utilizes bromothymol blue indicator to measure pH change
- as specific gravity, indicator changes from blue to green-yellow