(12) Nonprotein Nitrogen Compounds Flashcards
What nonprotein nitrogen compound has the highest concentration in plasma?
Urea
Urea is formed in the:
liver
Urea is the major excretory product of what?
Protein metabolism.
The measurement of urea is used to evaluate what?
Renal function, hydration status, nitrogen balance, and verifying adequacy of dialysis.
What analytical method is most used for urea testing?
Enzymatic methods.
What enzyme is used to catalyze hydrolysis of urea in the sample?
Urease.
What product is produced following the urease hydrolysis reaction?
Ammonium ion.
What is the reference method used in urea measurement?
Isotope dilution mass spectrometry (IDMS)
In urea testing, if plasma is collected, what anticoagulants must be avoided?
Sodium citrate and sodium fluoride (citrate & fluoride inhibit urease).
Adult plasma/serum urea reference range:
6 - 20 mg/dL
2.1 - 7.1 mmol/L
Adult 24h urine urea reference range:
12 - 20 g/d
0.43 - 0.71 mol urea/d
Define azotemia.
An elevated concentration of urea in the blood.
Very high plasma urea concentration accompanied by renal failure is called:
Uremia or the uremic syndrome
Increased plasma urea is classified into what three main categories?
Prerenal, renal, and postrenal.
Prerenal azotemia is a result of:
reduced renal blood flow.
What causative factors would lead to prerenal azotemia?
Congestive heart failure, shock, hemorrhage, dehydration.
What could causes elevated urea concentrations?
A high-protein diet or increased protein catabolism (e.g., fever, major illness, corticosteroid therapy, GI hemorrhage).
Renal causes of elevated urea include:
Acute and chronic renal failure, glomerular nephritis, tubular necrosis, other intrinsic renal diseases.
Postrenal azotemia can be due to:
obstruction of urine flow anywhere in the urinary tract by renal calculi, tumors of the bladder or prostate, or infection.
What are the major causes of decreased plasma urea concentration?
Low protein intake and severe liver disease.
What is the reference range for urea nitrogen/creatinine ratio?
10:1 to 20:1
Elevated plasma urea, normal creatinine is classified as what condition?
Prerenal condition.
A high urea, elevated creatinine is classified as what condition?
Decreased urea production (e.g., low protein intake, acute tubular necrosis, severe liver disease).
