Week 13: Chp 61: Renal and Urinary System Laboratory Studies Flashcards
Laboratory Studies Include what
- blood tests
- urine tests
What are the different blood tests?
- serum creatinine
- blood urea nitrogen (BUN)
- blood urea nitrogen/ creatinine ratio
- uric acid
- bicarbonate
- electrolytes
What are the different Urine Tests?
- bedside urine dipsticks
- urinalysis
- culture and sensitivity
- composite urine collection
- creatinine clearance
- urine cytology
Blood Tests: Serum Creatinine
creatinine is the end product of protein and muscle breakdown in the body
- normal range: 0.5-1.2 mg/dL
- creatinine is filtered by the kidneys and excreted into the urine
- no commonly occurring medical condition other than renal dysfunction causes an increase in serum creatinine, making it the most reliable indicator of kidney function, specifically reflecting glomerular function
- males have slightly larger levels because of their larger muscle mass
What is the most reliable indicator of kidney function, specifically reflecting glomerular function?
serum creatinine
-it is filtered by the kidneys and excreted into urine, no commonly occurring medical condition other than renal dysfunction causes an increase in serum creatinine
An increase in serum creatinine indicates?
impairment in the renal system and warrants immediate investigation and intervention
- increase does not occur until approximately 50% of the kidneys function is lost
- can be attributed to causes such as acute and/ or chronic kidney injury or disease, cancer, diabetic nephropathy, shock, congestive heart failure, and consumption of a high-protein diet
A decrease creatinine level can be attributed to?
the loss of muscle mass or certain medications. including some classifications of antibiotics (e.g. aminoglycosides and cephalosporins) and lithium carbonate
Blood Tests: Blood Urea Nitrogen (BUN)
- normal range: 8 to 21 mg/dL
- urea nitrogen is the by-product of protein metabolism that occurs in the liver
- the kidneys are responsible for filtering it from the blood
- serum BUN is a measure of the renal excretion of urea nitrogen
Increased BUN
can occur not only in cases of renal dysfunction, but also with liver disease, dehydration, infection, consumption of a high-protein diet, GI bleeding, steroid use, and trauma
- serum creatinine should also be assessed with increased BUN since it deals with protein
- an elevated BUN is not diagnostic of renal dysfunction but certainly indicates it as a possibility
Decreased BUN
can be indicative of severe liver damage, malnutrition, consumption of a low-protein diet, or fluid volume excess
Blood Tests: Blood Urea Nitrogen/ Creatinine Ratio
can be utilized to assess if the cause of elevated BUN is renal or nonrenal in nature
-normal ratio of BUN to creatinine: 10:1 to 20:1
>in cases of hypovolemia or hypotension, the serum BUN rises more quickly than the serum creatinine level; this results in an increased ratio of BUN to creatinine
A decreased BUN/creatinine ratio can occur
in instance of fluid volume excess
What does it mean when both BUN and creatinine levels are increased and the ratio remains normal?
renal dysfunction is likely
Blood Tests: Uric Acid
- normal range: 3.5-8 mg/dL
- is a by-product of purine metabolism
- excess uric acid is then excreted into the urine
- uric acid values are dependent upon kidney function, the rate of purine metabolism, and dietary intake of foods containing purines
Purines
compounds that naturally occur in the cells of the body and are also taken into the body in dietary sources (e.g. organ meats, anchovies, sardines, shellfish, asparagus, beans, mushrooms, spinach)
hyperuricemia
excess uric acid in the body
- values greater than 12 mg/dL are critical and warrant immediate attention
- it can result in the development of gout (inflammatory arthritis that is caused by uric acid crystals in the joints and in severe cases can cause renal damage)
Increased uric acid can occur as a result of?
renal failure, multiple myeloma, malnutrition, leukemia, lymphoma, metastatic cancers, and alcoholism
-some medications such as acetaminophen (Tylenol), furosemide (Lasix), and aspirin when used long term
Decreased uric acid can occur as a result of?
burns, pregnancy, folic acid anemia, and Wilson’s disease
-medications such as allopurinol (Zyloprim), Rasburicase (Elitek), azathioprine (Imuran). and warfarin (Coumadin) are known to decrease uric acid levels
Blood Tests: Bicarbonate
normal range: 22 to 26 mEq/L
- component of arterial blood gas results
- bicarbonate ions (HCO3) are alkaline and serve as buffers in the bloodstream to maintain pH in the normal range of 7.35 to 7.45.
- the kidneys regulate the concentration of HCO3 in the blood by altering the rate of excretion and production of the ions on the basis of serum pH
Increase in Bicarbonate
because the ions are alkaline, an increase in the amount of bicarbonate ions increases the serum pH, resulting in metabolic alkalosis
-can occur as a result of severe vomiting or gastric suctioning, excess loss of potassium, or excess administration of bicarbonate
Decrease in Bicarbonate
lowers the serum pH, resulting in metabolic acidosis
- can occur in renal failure as the kidneys lose their ability to produce HCO3 to buffer the blood
- also occur as a result of diabetic ketoacidosis, severe diarrhea, malnutrition, and burns
Blood Tests: Electrolytes
Sodium (Na+), Potassium (K+), Phosphorus (PO4), and Calcium
Electrolytes: Sodium (Na+)
135-145 mEq/L
- primary cation in the ECF
- exhibits water-retaining effects
- in the late stages of renal failure, a patient sodium balance can be altered as fluids accumulate in the body because of the kidneys decreasing ability to filter and excrete properly
Electrolytes: Potassium (K+)
- 5-5 mEq/L
- one of the first electrolyte values to reflect an alteration in kidney function
- as kidney function declines, potassium values increase (hyperkalemia); can lead to cardiac dysrythmias
Electrolytes: Phosphorus (PO4)
- 5-4.5 mEq/L
- primary anion in the ICF
- exists as phosphate and is found along with calcium in the bones and teeth; phosphorus and calcium are inversely related
- kidneys are responsible for secreting phosphorous; as kidney function decreases, the phosphorus levels increase (hyperphosphatemia)
Electrolytes: Calcium
- 2-10.2 mg/dL
- main mineral in teeth and bones
- in declining kidney function, calcium levels decrease (hypocalcemia) as phosphate levels increase (hyperphosphatemia)
- hypocalcemia also occurs as the kidney function declines because the kidneys are unable to produce quantities of vitamin D sufficient for calcium to be absorbed from the GI tract
Urine Tests: Bedside urine dipstick
urine can be tested at bedside to assess urine specific gravity, the pH, and the presence of protein, glucose, bilirubin, blood, and ketones
- this method can provide the healthcare team with current information that may be needed to direct immediate treatment decisions for a patient
- available dipsticks include a color-coded chart corresponding to a grading scale to be used when interpreting results
- fresh sample should be used
- dipsticks should be stored in a dry, sealed container
Urine Test: Urinalysis
provides an overall examination of urine to provide baseline data or to monitor specific characteristics of urine
- most precise results are obtained by collecting urine from the first void of the day
- sample should be sent within 1 hour of collection; if cannot it should be refrigerated
What happens if the urinalysis is not analyzed within 1 hour?
RBCs hemolyze, bacteria multiply, casts disintegrate, and pH becomes increasingly alkaline
Urinalysis include data on multiple characteristics which are?
- color, turbidity, and odor
- specific gravity
- osmolality
- pH
- protein
- glucose
- ketones
- bilirubin
- RBCs
- WBCs
- Casts
- Bacteria
Urinalysis: Color, turbidity, and odor
urine should appear yellow in color because of the pigment urochrome; the range of the yellow color varies depending on hydration status
- urine should appear clear, without turbidity (cloudiness)
- normal urine smells faintly like ammonia but should not smell foul
Urinalysis: Color
normal finding: pale yellow
-abnormal: clear or pale indicates dilute urine related to excess fluid intake; dark amber indicates concentrated urine related to dehydration and presence of bilirubin; red/brown indicates blood, myoglobin, or bilirubin in urine; other colors may occur as a result of foods or medications
Urinalysis: Turbidity
normal findings: clear
-abnormal: cloudy indicates the presence of bacteria, pus related to infection, or sediment
Urinalysis: Odor
normal: faint odor of ammonia
- abnormal: foul indicates the presence of bacteria related to infection, dehydration, or the effects of some foods and medications
Urinalysis: Specific gravity
Normal: 1.005-1.030
-a measure of the concentration of solutes contained in the urine; reflects the ability of the kidneys to concentrate and dilute the urine effectively
-abnormal:
>increase indicates diabetes mellitus, dehydration or fever;
>decrease indicates renal insufficiency, diabetes insipidus, or diuretic use
Urinalysis: Osmolality
Normal: 250-900 mOsm/kg (24-hr collection)
-provides further information regarding the concentration of solutes in the urine
-more precise than specific gravity
-abnormal:
>increase indicates diabetes mellitus, dehydration, or fever
>decrease indicates renal insufficiency, diabetes insipidus, or diuretic use
Urinalysis: pH
neutral: 7.0
acidic: less than 7.0
alkaline: greater than 7.0
Normal findings: 4.5-8
-abnormal: altered indicates changes in renal function, infection, or certain medications and can also be related to the freshness of the sample
Urinalysis: Protein
Normal: 2-8 mg/dL
-not typically contained in the urine because they are large and are not permitted to cross intact glomerular membranes
-presence of protein in the urine is proteinuria; transient conditions such as infection and inflammation increase the permeability of the glomerular membrane, allowing some protein molecules to enter the urine
-abnormal:
>increase indicates stress, strenuous exercise, fever, septicemia, lead, mercury, or high-protein diet; persistently increased indicates acute or chronic renal disease
Proteinuria
presence of protein in the urine
- transient conditions such as infection and inflammation increase the permeability of the glomerular membrane, allowing some protein molecules to enter the urine
- when proteinuria is identified, urinalysis should be obtained after resolution of the infection or inflammation to ensure that the urine is then negative for proteins
Urinalysis: Glucose
Normal: Negative
- does not appear in the urine until the renal threshold has been reached at serum glucose levels of 200 mg/dL
- abnormal: presence indicates undiagnosed or uncontrolled diabetes mellitus or decreased renal threshold for glucose
Urinalysis: Ketones
Normal: Negative
- the partial metabolism of fatty acids in the body produces ketones
- normally no ketones in urine
- in situations where fat is burned as energy in place of glucose, as in diabetes, ketones are produced and present in the urine
- abnormal: presence indicates diabetic ketoacidosis, high-protein diet, or anorexia nervosa
Urinalysis: Bilirubin
Normal: Negative
- formed during the breakdown of hemoglobin and is not present in urine
- bilirubinuria (bilirubin in the urine) causes the urine to appear dark amber to brown in color
- abnormal: presence indicates hepatic biliary obstruction or liver disease
Urinalysis: RBCs
Normal: 0-4/ (hpf)
-not normally in the urine and are indicative of bleeding within the renal and/or urinary system
>slight increase is normal with presence of an indwelling urinary catheter or during menstruation
>significant increase indicates bleeding disorders, cystitis, tumor, calculi, or trauma
Urinalysis: WBCs
Normal: 0-5/ hpf
-small numbers can be present in urine samples because of perineal contamination during voiding
>increase indicates presence of inflammation, urinary infection, or fever
Urinalysis: Casts
Normal: Few or none
- molds formed around the outside of particles such as RBCs, WBCs, proteins, or bacteria
- not present in the absence of these particles
- described by the particle they surround (e.g. RBC cast, WBC cast)
- Abnormal: increased indicates presence of bacteria, kidney disease, or urinary calculi
Urinalysis: Bacteria
Normal: less than 1,000 colonies/mL
- urine can easily be contaminated during collection, so the presence of bacteria in a urinalysis does not definitely confirm a UTI; a urine culture should be obtained as well
- abnormal: an increase indicates possibility of a UTI or contamination during sample collection
Culture and Sensitivity
- helps in planning treatment for UTIs
- urine should be collected in the clean-catch technique and placed in a sterile specimen container
- takes 48 to 72 hours to isolate any bacteria present
- bacteria commonly isolated: Escherichia coli, enterococci, Klebsiella, and streptococci
Culture and Sensitivity: Culturing urine
useful to identify the number and type(s) of bacteria present
Culture and Sensitivity: Sensitivity testing
involves combining bacteria isolated in the urine with various classes of antibiotic medications to determine which are most effective at stopping the multiplication of the bacteria
Patient Education: Collecting a clean catch sample
required for urine cultures to ensure that any bacteria found in the urine are not there as a result of contamination
1. Wash hands
2. remove cap from sterile specimen container, ensuring not to touch the inside of the lid or container
3. Males: use enclosed towelette(s) to wipe the head of the penis
Females: spread the labia with one hand and use the other hand to wipe from front to back with the enclosed towelette(s)
4. begin urinating a small amount into the toilet; without stopping the flow of urine, place the cup into the stream of urine and collect enough urine to fill the cup. finish urinating into the toilet
5. securely attach the cap onto the sterile container, ensuring not to touch the inside of the lid or container
Composite Urine Collection
involves collecting all urine voided for a defined period of time ranging between 2 and 24 hours
- such specimens can be used to measure the quantity of specific components of the urine including electrolytes, minerals, creatinine, protein, and glucose
- collection begins by discarding the first voided urine of the time period; all other urine should be saved, and sample should be refrigerated or kept on ice for the duration of the collection
Creatinine Clearance
Normal: 88-137 mL/min
-type of composite urine collection
-reliable indicator of glomerular filtration rate (GFR)
-creatinine clearance measures the amount of creatinine excreted from the body during a defined time period; typically for 24 hours but a shorter time can be ordered
-a blood sample testing for creatinine is required and can be obtained at any point during the collection period
>the urine and blood samples are compared, and creatinine clearance is calculated using one of several mathematical formulas
-sometimes used for ensuring adequate dosing of medications
-decreased occurs as a result of renal impairment and muscle wasting
Urine Cytology
used to identify any abnormal cells present in the urine
-abnormal cells often present in urine with bladder cancer
-examination of urine is used as a diagnostic tool and a treatment marker for patients with bladder cancer
>a urine sample other than the first void of the day should be collected and sent to the lab for microscopic analysis within 1 hour of collection
