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