Renal function test and urinalysis Flashcards
Symptoms of urinary tract infections
– burning, frequency, urgency
– should undergo urinalysis
– macroscopic UA (dip-strip) is normal,
microscopic analysis is not necessary
➔ Signs and symptoms suggestive of
urologic disease or if UA is (+) for _____
protein, heme, leukocyte esterase, or nitrite
TIMING for urine specimens
- First-voided morning specimens
are helpful for qualitative protein testing in pts with possible proteinuria or for specific gravity assessment. - Freshly voided specimen obtained a few hours after the patient has eaten and examined
within 1 hour of voiding is most reliable
Urine may be refrigerated, however, this increases crystal
formation
T/F The urine specimen should be collected after a genital or rectal exam
F - it should be collected before
HOW DO YOU GET A URINE SPECIMEN from children?
- UA can be obtained from males and females by covering the cleansed urethral meatus
with a plastic “U” bag - If bacterial culture is needed catheterization or suprapubic needle aspiration is recommended
Factors of macroscopic urine examination
Color and appearance
Specific gravity
pH
Protein
Glucose
Hemoglobin
Nitrite (bacteria)
Leukocyte esterase
Culture and sensativity
Urine is often colored secondary to drugs:
– Phenazopyridine (pyridium) will turn urine orange
– Nitrofurantoin (macrobid) will turn urine brown
– Metronidazole will turn urine reddish brown
causes of discolored urine
- Drugs
– Beet ingestion
– Vegetable dyes
– Concentrated urine
– Muscle trauma
T/F Odor of urine is rarely clinically significant
T
SPECIFIC GRAVITY of Urine
- A measure of urine concentration
- Used to determine hydration status and renal
function. - The specific gravity of urine (normal
1.003-1.030)
What should you consider of the urine specific gravity is low?
– Chronic renal failure
– Diabetes insipidus
– Intracranial trauma evaluating for lack of
antidiuretic hormone (vasopressin)
What should you consider of the urine specific gravity is high?
– Dehydration
– Preeclampsia
– CHF
What should you consider of the urine pH is low?
– acidosis
– dehydration
– diabetic ketoacidosis
– diarrhea
– starvation
– Uric acid kidney stones develop in acidic urine
pH of the Urine
- A measure of free hydrogen ions (H+) concentration in the urine
- Normal range 4.6-8.0
- Diet can impact pH, ie high protein usually acidotic
What should you consider of the urine pH is high?
– gastric suctioning that takes away stomach acids
– kidney failure
– kidney tubular acidosis
– pyloric obstruction
– respiratory alkalosis
– urinary tract infection
– vomiting
PROTEIN in the urine
- A measure of urinary albumin, the main protein
found in urine. - Normal range: negative
- Concentrated urine will give false positive
- Prolonged fever and excessive physical exertion
will cause transient proteinuria
What should you consider if the urine is positive for protein?
– Glomerular damage
– Hypertension
– Preeclampsia
GLUCOSE in the urine
- Glucose is present in glomerular filtrate, is reabsorbed in the proximal tubule by active
transport (requires carrier protein and ATP.) - Normal range: negative
- Most patients with positive reading
have diabetes mellitus
Glucosuria seen with serum glucose
_____ mg/dL
> 180
HEMOGLOBIN in the urine
- A measure of free hemoglobin in urine
(product of lysed red blood cells). - Normal range: negative
- Microscopic analysis of urinary sediment for
RBCs used for confirmation.
What should you consider if the urine is positive for hemoglobin?
– UTI
– Renal calculi
– Renal trauma
– Glomerulonephritis
– Rhabdomyolysis (strenuous exercise)
– Hemoglobinuria Nephritis
– Bladder or kidney cancer
NITRITE (BACTERIA)
- A urine dipstick test used for evaluation of
UTI. - Enterobacteriaceae (E.coli, most common
UTI causing bacteria) converts nitrate to
nitrite which gives a positive test. - Result may be negative as not all bacteria
are capable of converting nitrate. - Normal range: negative (does not R/O UTI)
What should you consider if the urine tests positive for nitrite?
– UTI
– False positive - dyes
LEUKOCYTE ESTERASE
- Detects esterase released by the leukocytes in
the urine and indicates the presence of WBCs. - A positive indicates pyuria and warrants
subsequent microscopy. . - Normal range: negative
What should you consider if the urine is positive for leukocyte esterase?
– UTI
– Pyleonephritis
– Nephrolithiasis
– Interstitial nephritis
– Vaginal contamination (yeast infection, STI,
bacteria vaginosis)
HOW TO PREPARE A URINE SPECIMEN FOR MICROSCOPIC EXAM
- Centrifuge a 10-mL specimen at 2000 rpm for 5
minutes - Decant the supernatant
- Resuspend the sediment in the remaining 1 mL of urine by tapping the tube gently against
countertop - Place 1 drop of the mixture on a microscope slide, cover with a coverslip, and examine first under a low power (10x) lens then under a high-power (40x) lens.
- Significant elements (particularly bacteria) are
more easily seen if the slide is stained with
methylene blue
Microscopic examination factors of urine
SQUAMOUS EPITHELIAL CELLS
RED BLOOD CELLS
WHITE BLOOD CELLS
CASTS
RED BLOOD CELL CASTS
WHITE BLOOD CELL CASTS
GRANULAR CASTS
BACTERIA
YEAST
Trichomoniasis
CRYSTALS
SQUAMOUS EPITHELIAL CELLS significance in the urine
- Squamous epithelial cells from the
skin surface or from the outer urethra
can appear in urine. - Their significance is that they
represent contamination of the
specimen with skin flora
RED BLOOD CELLS significance in the urine
- RBCs may appear normally shaped,
swollen by dilute urine, or crenated
by concentrated urine.
0-2 RBCs/HPF Normal - Much smaller, more round, than
WBCs, and don’t have a nucleus. - Red cells may simulate yeast
Significance of WHITE BLOOD CELLS in the urine
- Normal Range 0 - 5/HPF
- > 5 WBC/HPF; specimen is probably
abnormal. - Leukocytes have lobed nuclei and
granular cytoplasm
Significance of CASTS in the urine
- Urinary casts are formed only in the
distal convoluted tubule (DCT) or the
collecting duct (distal nephron). - Hyaline casts are composed primarily of
a mucoprotein secreted by tubule cells.
● Hyaline casts can be seen even in
healthy patients.
Significance of RED BLOOD CELL CASTS in the urine
- Red blood cells may stick together and
form red blood cell casts. - Such casts are indicative of
glomerulonephritis, with leakage of RBC’s
from glomeruli, or severe tubular
damage
Significance of white blood cell casts in the urine
- White blood cell casts are typical for
acute pyelonephritis, but they may also
be present with glomerulonephritis. - Their presence indicates inflammation of
the kidney, such casts will not form
except in the kidney (Distal convoluted
tubule or collecting duct)
Significance of GRANULAR CASTS in the urine
- When cellular casts remain in the nephron for
some time before they are flushed into the
bladder urine, - Cells degenerate to become 1st coarsely granular
cast, - Later a finely granular cast
Significance of Waxy casts in the urine?
suggest very low urine
flow associated with severe,
longstanding kidney disease such
as renal failure.
● Due to urine stasis and their
formation in diseased, dilated ducts,
these casts are significantly larger
than hyaline casts
Significance of BACTERIA in the urine
- Bacteria are common in urine
specimens because of the abundant
normal microbial flora. - If bacteria found, interpret in view of
clinical symptoms. - Get a urine culture and sensitivity
More than 100,000/ml colonies of
one organism reflects significant
bacteriuria. ***
Significance of YEAST in the urine
- Yeast cells may be contaminants or
represent a true yeast infection. - They are often difficult to distinguish
from red cells and amorphous crystals
but are distinguished by their tendency
to bud. - Most often they are Candida, which may
colonize bladder, urethra, or vagina
Significance of Trichomoniasis in the urine?
- “Trich” STI very common
- Flagelatted parasite
- Incidental finding in microscopic
exam as most people are
asymptomatic - Foul smelling urine
- Vaginal itching pain with urination
- Frothy discharge
Significance of crystals in the urine
- Common crystals seen even in healthy
patients include calcium oxalate, triple
phosphate crystals and amorphous
phosphates. - Very uncommon crystals include:
- Cystine crystals in urine of neonates with
congenital cystinuria or severe liver
disease
_____ may be detected in the urine even in the early stages of kidney disease.
Albumin
How often should patients with T1D and T2D undergo urinalysis?
Type 1 diabetes: tested annually, starting 5 years after onset of disease.
Type 2 diabetes: tested annually starting at time of diagnosis
According to the National Institutes of Health (NIH), a normal 24 hour urine protein test result shows less than____of protein per day
80 milligrams
Renal function tests include:
Blood Urea Nitrogen
Serum Creatinine
Endogenous Creatinine Clearance
GFR
Serum Albumin
Anion Gap
Calcium
Chloride
Glucose
Phosphorus
Potassium
Sodium
Blood Urea Nitrogen
- Measurement of blood urea nitrogen (BUN). BUN is a waste
product of protein breakdown. Helpful in assessing kidney
function. - Normal range: 7-10 mg/dL
- Unlike creatinine, BUN is influenced by dietary protein intake, hydration status, and gastrointestinal bleeding.
What should you consider if BUN is low?
nephrotic syndrome, acromegaly, celiac sprue,
malnutrition, pregnancy
What should you consider if BUN is low?
GI bleed, renal disease, post renal azotemia,
prerenal azotemia.
Approximately _____ of renal function must be lost before a significant
rise in BUN level becomes evident
two-thirds
T/F BUN level is less specific for renal insufficiency than an elevated serum creatinine level.
T
Serum Creatinine
- Creatinine, the end product of the metabolism of creatine in skeletal muscle, is
normally excreted by the kidneys. - Because individual daily creatinine production is constant, the serum level is a direct reflection of renal function.
- Serum creatinine levels remain within the normal range (0.8–1.2 mg/dL in adults; 0.4–0.8 mg/dL in young children) until approximately 50% of renal function has been lost.
- Unlike most other excretory products, the serum creatinine level generally is not influenced by normal dietary intake or hydration status. It is however elevated with long term use of supplemental creatine products.
Because creatinine production is stable and creatinine is filtered through the glomerulus, its
renal clearance is essentially equal to the _____
glomerular filtration rate.
the most accurate and reliable
measure of renal function
endogenous creatinine clearance
GFR
- GFR - glomerular filtration rate is one of the best
test to measure the level of kidney function and
determine the stage of kidney disease. - To obtain a GFR a serum creatinine test should be
obtained. That number is then calculated in a
formula with additional information such as
– Age
– Ethnicity
– Gender
– Height
– Weight - Normal range 90-120 mL/min
When does GFR become too low?
- GFR below 60 mL/min for 3 or more months is a
sign of chronic kidney disease - GFR lower than 15 mL/min is a sign of kidney
failure and requires immediate medical attention
Serum Albumin
- Measure of albumin a plasma binding protein synthesized by the liver. Albumin helps
to maintain osmotic pressure in the vascular space and also reflects overall nutritional
status. Generally decreased levels after age 40; edema seen with levels <2.5; - Reference range: 3.4-5.4 g/dL
What should you consider if Serum albumin is low?
– acute infection
– CHF
– Malnutrition
– Nephropathy
What should you consider if Serum albumin is high?
– dehydration
– Blood loss
Anion Gap
Anion Gap (AG) is the difference between the measured cations and measured
anions in the blood. Na is the primary measured cation and Cl and HCO3 are the
primary measured anions. Used to classify metabolic acidosis.
What should you consider if the anion gap is low?
– Hypocalcemia
– Hypoalbuminemia
– Hyponatremia
What should you consider if the anion gap is high?
– Ketoacidosis
– Lactic Acidosis
– Renal failure
– Toxic ingestion
Calcium
- Element. Sum of ionized calcium plus protein bound calcium. Important in cellular transport
mechanisms. - Normal range: 8.5-10.2 mg/dL
What should you consider is the urine calcium is low?
– Hypoalbuminemia (most common cause)
– Hypoparathyroidism
– Renal failure
– Vitamin D deficiency
What should you consider if urine calcium is high?
– Hyperparathyroidism
– Familial hypocalciuria
– Hyperthyroidism
– Immobilization
– Malignancy
Chloride
- Extracellular electrolyte. Levels usually increase or decrease in concert with sodium.
- Normal range: 96-106 mg/L
What should you consider if urine calcium is low?
– Addison’s disease
– Burns
– CHF
– GI loss
– Metabolic alkalosis
– Renal disease
– Respiratory acidosis
What should you consider if urine calcium is high?
Diabetes insipidus
Hyperparathyroid,
prolonged diarrhea,
renal tubular acidosis,
Respiratory alkalosis,
Severe dehydration
Phosphorus
- An inorganic anion, important calcium homeostasis. Assess along with calcium
- Normal range: 2.4 -4.1 mg/dl
What should you consider if phosphorus is low?
– Hungry bone syndrome
– Hypercalcemia
– Hyperparathyroidism
– Malabsorption
– Renal disease
– Vitamin D deficiency
What should you consider if phosphorus is high?
– Acromegaly
– Hypoparathyroidism
– Renal failure
– Sickle cell anemia
Potassium
- Intracellular cation, functions as an electrolyte. Important at maintaining acid/base balance.
- Normal range: 3.5-5.2meq/L
What should you consider if potassium is low?
– Bartter syndrome
– Excessive sweating
– GI Loss
– Increased urine secretion
What should you consider if potassium is high?
– Acidosis
– Diabetes mellitus
– Excessive intake
– Hypoaldosteronism
– Renal failure
– Tissue necrosis
Sodium
- Cation found mainly in the extracellular fluid. Used in the evaluation of hydration states.
- Normal range: 135-145 mEq/L
What should you consider if sodium is low?
– Addison’s disease
– CHF
– GI loss
– Hyperglycemia
– Hypothyroidism
– Nephrotic syndrome
– Renal failure
– Renal tubular acidosis
What should you consider if sodium is high?
– Glucosuria
