Urinalysis Flashcards
What accounts for high false positives with Urinalysis dip?
Proteinuria will cause over-estimation of kidney’s concentrating ability
What accounts for low false positives with Urinalysis dip?
Highly buffered alkaline urine tends to lower the S.
What structure of the kidney reabsorbs glucose?
The proximal renal tubule
What threshold must glucose reach to begin spilling over into the Urine causing glucosuria?
160 - 180 mg/dl
Why is glucose considered a threshold substance?
If plasma glucose content is above a certain threshold it can’t keep up and the excess (about 160 -180mg) so you reabsorb unless there is more in tubes than can reabsorb
what is a “normal” test glucose dip outcome?
“negative” negative glucose is less than .5 g/day
what are potential causes of glucosuria?
diabetes mellitus, Cushing’s syndrome due to inappropriate release of cortisol which increase glucose in plasma, drugs
What do you do if you find unexpected glucosuria on your dipstick?
order a blood test
What accounts for the high false negative with glucose testing?
(VIT C)
ketones, abscorbic acid, asprin
When are keytones produced?
keytones are produced when you cant use glucose and start breaking down fatty acids and releasing keytones
How are keytones formed?
From the metabolism of fatty acids
What is the outcome of increased keytones in the blood?
electrolyte imbalance, dehydration, acidosis and eventual coma
What is the outcome of a dip test for normal keytone level?
normal keytone level = negative for keytones
Why is the urine dip not representative of the full load of keytones being produced by the body?
The dipstick we use detects only acetoacetic acid. There are 3 types of keytones: beta-hydroxybuturic acid, aceroacetic acid, acetone
In DKA what is the prdominate keytone?
beta-hydroxybutyrate
What are the two most common causes of ketonuria?
- Diabetes Mellitus 2. Increase metabolic states: hyperthyroidism, fever, pregnancy
What accounts for high false negative with keytone testing?
Prolonged air exposure - keytones are highly volatile and will lose count to air
What is the “normal” finding for a blood UA dip?
normal = negative
What does the UA dip blood test detect?
Free hemoglobin (lysed RBCs), Hemoglobin (intact RBC), myoglobin (muscle protein)
Presence of free hemoglobin in urine is referred to as____
hemoglobinuria
Presence of intact RBCs in Urine is termed ______
Hematuria
The clinical significance of blood in the Urine must determine the source. what are some example sources?
menstrual, glomerular, kidney stones, MI, exercise
The presence of _____ could cause a False negative blood UA - e.i. you could miss blood if you have positive of these
nitrites
What (2) could account for a false positive blood UA?
- menstrual blood
2. myoglobinuria
what accounts for false negative outcomes blood UA?
ascorbic acid (vit c) and nitrites
When is urinary pH generally higher?
after meals
What is a normal urine pH range?
4.5 -8 (usually 6)
what is the role of the kidneys in maintaining acid-base balance?
The kidneys facilitate the re-absorption of sodium and excretion of H+
Why do we need to be aware of pH run over?
Buffers from the protein area of the strip (pH 3.0) spill over to the pH area of the strip and make the pH of the sample appear more acidic that it really is
If you suspect a UTI, why would the pH alkaline vs acidic help you eliminate the suspect list?
UTI + alkaline indicates pseudomonas
UTI + acidic indicated ecoli
what may be indicated by an alkaline urine pH?
Alkalosis: metabolic or respiratory, Diet; vegetarians; high citrus intake
what may be indicated by an acidic pH?
Acidosis: respiratory or metabolic, diabetes mellitus, UTI, diet high meat, high cran
What is a normal outcome for UA dip protein?
normal = negative
undetectable amounts excreted, normally
What organ function is the protin UA dip sensative for? why
Kidney function
slit pores in a normal glomerular membrane are too small to allow passage of high molecular weight proteins. they also have a negative charge that repels proteins
What are some functional causes of proteinuria?
severe muscle exertion, pregnancy
what are some renal causes of proteinuria?
glomerulonephritis, nephrotic syndrome
What are pre- and post- renal causes of proteinuria?
fever renal hypoxia (pre)
contamination with vaginal secretions (post)
What conditions may have transient proteinuria?
fever, stress, exercise, or congestive heart failure
what are potential sources of false positives with protein UA
vaginal secretions and pyridium (pain)
What is the UA dip for bilirubin indicating?
increased bilirubin: bilirubinuria possible causes include, gallstones, bile duct obstruction, hepatitis
what is a source of false positives in bilirubinuria
puridium indicans
what is a source of false negatives in bilirubinuria?
light (breaks down bilirubin), nitrites, ascorbic acid
