Kidney Function Tests

Question 1

The earliest manifestation of the abnormal function of the glomeruli is the appereance of ____ in the urine.

Answer 1

albumin

Hemoglobin mol wt 67 000, albuwmin mol wt 69 000

Hb normal in urine, albumin not!

Question 2

At what blood pressure does GFR decrease?

Answer 2

GFR is decreased when BP is below 80 mm Hg.

Question 3

The renal blood flow is about___ mL of plasma or ___ mL of blood per minute.

Answer 3

700 mL plasma
1200 mL blood
per minute

Question 4

What are threshold substances?

Answer 4

Compounds whose excretion in urine are dependent on blood level are known as threshold substances.

Question 5

List physical characteristics of urine (2)

Answer 5

1. volume (average is 1.5L/day; increases with water intake, diuretic therapy, DM, chronic renal disease)
2. specific gravity

Question 6

List chemical characteristics of urine (8)

Answer 6

1. reaction to litmus / pH
2. proteins
3. blood
4. glycosuria
5. ketone bodies
6. bile salts
7. bile pigments
8. urobillinogen

Question 7

List components of the nonprotein nitrogen fraction (6)

Answer 7

urea, aa, uric acid, creatinine, creatine, ammonia

Question 8

Regarding NPN, what is the most specific and sensitive index of renal function?

Answer 8

Creatinine estimation

Question 9

What is creatinine?

Answer 9

Creatinine is the waste product formed in muscle froma a high energy storage compound, creatine phosphate ( phosphocreatine).

Question 10

Definition of clearance

Answer 10

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).

Question 11

Creatinine is dependent on ___ (1) , and not affected by ___, ___, ___ (3)

Answer 11

Creatinine is dependent on total muscle mass of the body, and not affected by diet, age or exercise

Question 12

Normal range of creatinine in serum:
adult male
female
children

Answer 12

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

Question 13

What are markers of the glomerular filtration rate (2)

Answer 13

1. serum creatinine concentration
2. creatinine clearance

Question 14

methods for detection of creatinine (4)

Answer 14

1. enzymatic methods
2. chemical methods: the Jaffe reaction
3. isotope dilution mass spectrometry (IDMS)
4. high-performance liquid chromotography (HPLC)

Question 15

creatine clearance formula and expected values for men and women

Answer 15

U/S * V

men 120+- 25ml
women 112+-20 mL/min

Question 16

Creatinine clearance Cockcroft and Gault formula is only recommended in following conditions: (3)

Answer 16

1. patients with early / minor renal disease
2. assessment of possible kidney donors
3. detection of renal toxicity of some nephrotoxic drugs

Question 17

Cockcroft-Gault Formula for estimation of GFR limitations, it should not be used if (4)

Answer 17

1. serum creatinine is changing rapidly
2. the diet is unusual, e.g. strict vegetarian
3. low muscle mass, e.g. muscle wasting
4. obesity

Question 18

A raised serum creatinine is a good indicators of ____ (1)

Answer 18

impared renal function

Question 19

Does normal serum creatinine indicate normal renal function?

Answer 19

Not neccessarily. Serum Cr might not be elevated until GFR has fallen by as much as 50%

Question 20

What is an azotemic state?

Answer 20

An increase in plasma urea concentnration characterizes the uremic (Azotemic) state.

Question 21

What increases plasma urea concentration? (6)

Answer 21

• (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

Question 22

decreased concentration of urea is caused by… (3)

Answer 22

1. late stage of pregnancy
2. starvation
3. low protein diet

Question 23

Why is serum urea inferior to serum creatinine as a kidney function test?

Answer 23

1. high protein diet increases urea formation
2. any condition that increases protein catabolism (e.g. Cushing sy, DM, starvation, thyrotoxicosis) leads to an increased urea formation

Question 24

Why is serum urea inferior to serum creatinine as a kidney function test?

Answer 24

1. high protein diet increases urea formation
2. any condition that increases protein catabolism (e.g. Cushing sy, DM, starvation, thyrotoxicosis) leads to an increased urea formation

Question 25

Normal range of serum urea concentration:

Answer 25

15-45 mg/dl

Question 26

Normal range of BUN

Answer 26

7-18 mg/dl (2.5-6.4mmol/L)

Question 27

Normal range of uric acid
male, female, children

Answer 27

male: 3.5-7.5 mg/dl female: 2.5-6.5 mg/dl children: 2.0-5.5 mg/dl

Question 28

Factors that increase uric acid (3)

Answer 28

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)

Question 29

Factors that decrease uric acid concentration? (3)

Answer 29

1. After the administration of
   ACTH or cortisol – like
   steroids
   2.Certain drugs that decrease
   the reabsorption of urate by
   renal tubules ( aspirin,
   probenecid, penicillamine)
2. by drugs (allopurinol) that
   block a step in formation of
   uric acid.

Question 30

Sources of uric acid (3)

Answer 30

general: breakdown from nucleic acid

1. ingestion
2. destruction of tissue cells
3. synthseized in the body from simple compounds