Kidney Function Tests Flashcards
The earliest manifestation of the abnormal function of the glomeruli is the appereance of ____ in the urine.
albumin
Hemoglobin mol wt 67 000, albuwmin mol wt 69 000
Hb normal in urine, albumin not!
At what blood pressure does GFR decrease?
GFR is decreased when BP is below 80 mm Hg.
The renal blood flow is about___ mL of plasma or ___ mL of blood per minute.
700 mL plasma
1200 mL blood
per minute
What are threshold substances?
Compounds whose excretion in urine are dependent on blood level are known as threshold substances.
List physical characteristics of urine (2)
- volume (average is 1.5L/day; increases with water intake, diuretic therapy, DM, chronic renal disease)
- specific gravity
List chemical characteristics of urine (8)
- reaction to litmus / pH
- proteins
- blood
- glycosuria
- ketone bodies
- bile salts
- bile pigments
- urobillinogen
List components of the nonprotein nitrogen fraction (6)
urea, aa, uric acid, creatinine, creatine, ammonia
Regarding NPN, what is the most specific and sensitive index of renal function?
Creatinine estimation
What is creatinine?
Creatinine is the waste product formed in muscle froma a high energy storage compound, creatine phosphate ( phosphocreatine).
Definition of clearance
Clearance is defined as the volume of blood or plasma completely cleared of a substance per unit time.
It is expressed as milliliter of plasma per minute (not as g or mg).
Creatinine is dependent on ___ (1) , and not affected by ___, ___, ___ (3)
Creatinine is dependent on total muscle mass of the body, and not affected by diet, age or exercise
Normal range of creatinine in serum:
adult male
female
children
Normal range of creatinine in serum:
adult male: 0.7-1.4 mg/dl
female: 0.6-1.3 mg/dl
children: 0.4-1.2 mg/dl
What are markers of the glomerular filtration rate (2)
- serum creatinine concentration
- creatinine clearance
methods for detection of creatinine (4)
- enzymatic methods
- chemical methods: the Jaffe reaction
- isotope dilution mass spectrometry (IDMS)
- high-performance liquid chromotography (HPLC)
creatine clearance formula and expected values for men and women
U/S * V
men 120+- 25ml
women 112+-20 mL/min
Creatinine clearance Cockcroft and Gault formula is only recommended in following conditions: (3)
- patients with early / minor renal disease
- assessment of possible kidney donors
- detection of renal toxicity of some nephrotoxic drugs
Cockcroft-Gault Formula for estimation of GFR limitations, it should not be used if (4)
- serum creatinine is changing rapidly
- the diet is unusual, e.g. strict vegetarian
- low muscle mass, e.g. muscle wasting
- obesity
A raised serum creatinine is a good indicators of ____ (1)
impared renal function
Does normal serum creatinine indicate normal renal function?
Not neccessarily. Serum Cr might not be elevated until GFR has fallen by as much as 50%
What is an azotemic state?
An increase in plasma urea concentnration characterizes the uremic (Azotemic) state.
What increases plasma urea concentration? (6)
- (1) a high-protein diet,
- (2) increased protein catabolism,
- (3) reabsorption of blood proteins after gastrointestinal
hemorrhage, - (4) treatment with cortisol or its synthetic analogues,
- (5) dehydration,
- (6) decreased perfusion of the kidneys (e.g., heart failure
- In this cases creatinine might be normal
decreased concentration of urea is caused by… (3)
- late stage of pregnancy
- starvation
- low protein diet
Why is serum urea inferior to serum creatinine as a kidney function test?
- high protein diet increases urea formation
- any condition that increases protein catabolism (e.g. Cushing sy, DM, starvation, thyrotoxicosis) leads to an increased urea formation
Why is serum urea inferior to serum creatinine as a kidney function test?
- high protein diet increases urea formation
- any condition that increases protein catabolism (e.g. Cushing sy, DM, starvation, thyrotoxicosis) leads to an increased urea formation
Normal range of serum urea concentration:
15-45 mg/dl
Normal range of BUN
7-18 mg/dl (2.5-6.4mmol/L)
Normal range of uric acid
male, female, children
male: 3.5-7.5 mg/dl female: 2.5-6.5 mg/dl children: 2.0-5.5 mg/dl
Factors that increase uric acid (3)
1.Gout disease
2.Renal disease
3.After increased breakdown
of nucleic acid and
nucleoprotein ( leukemia,
polycythemia, toxemia of
pregnancy, and after
irradiation of x-ray sensitive
carcinomas)
Factors that decrease uric acid concentration? (3)
- After the administration of
ACTH or cortisol – like
steroids
2.Certain drugs that decrease
the reabsorption of urate by
renal tubules ( aspirin,
probenecid, penicillamine) - by drugs (allopurinol) that
block a step in formation of
uric acid.
Sources of uric acid (3)
general: breakdown from nucleic acid
- ingestion
- destruction of tissue cells
- synthseized in the body from simple compounds
