BUN Cr Ur Ac

Question 1

Normal BUN range for an adult

Answer 1

10-20 mg/dl

Question 2

Normal BUN range for a child

Answer 2

05-18 mg/dl

Question 3

Critical BUN value

Answer 3

> 100 mg/dL

Question 4

Indications for BUN testing

Answer 4

Kidney function
Liver function
hydration status

Question 5

BUN test explanation

Answer 5

Measures amount of urea nitrogen in blood
Protein –> amino acids
Amino acids catabolized in liver
End product –>ammonia –>urea
Urea transported in blood to kidneys for excretion

Question 6

Pt with elevated BUN levels have

Answer 6

Azotemia

Question 7

What does azotemia indicate?

Answer 7

Renal disease or livers disease

Question 8

Renal Parenchymal Disease Definition

Answer 8

1. Results from damage to filtering structures of kidney
2. Nephrotoxicity or inflammation damages delicate epithelial layers of nephron
3. Additionally, nephrotoxins damage renal cortex leading to ARF

Question 9

Causes of Renal parenchymal disease

Answer 9

Blood vessel disease: arthrosclerosis, decreased blood flow to the kidney
Blood clot in vessel in kidneys
Injury to renal tissue and cells
Glomerulonephritis
Acute interstitial nephritis
Acute tubular necrosis

Question 10

Prerenal Azotemia

Answer 10

1. Prerenal azotemia results from decreased blood flow to kidneys
2. Hypoperfusion leads to hypoxemia
3. Impaired blood flow results in:
   Decreased GFR
   Increased tubular reabsorption of Na & water
4. Results in electrolyte imbalances and metabolic acidosis

Question 11

Causes of Prerenal azotemia

Answer 11

Shock, dehydration, CHF

Question 12

Causes of Postrenal azotemia

Answer 12

1. Something blocks elimination of urine
2. Obstruction of urethra : BPH
3. Obstruction of one or btoh ureters: kidney stones, cancer of urinary tract
4. Obstruction at bladder level:
   Bladder stone
   Blood clot
   Neurologic disorders of bladder
   organs or structures

Question 13

How does liver disease affect BUN levels?

Answer 13

They are decreased

Question 14

How are BUN levels affected in concomitant liver and renal disease?

Answer 14

1. Normal BUN levels, but do not indicate normal renal excretory function
2. decreased formation of urea

Question 15

How does dehydration affect BUN levels?

Answer 15

Decreased volume –>decreased renal perfusion –>decreased renal excretion of urea

Question 16

How does CHF affect BUN levels?

Answer 16

Decreased CO –>decreased renal perfusion –>decreased renal excretion of urea

Question 17

causes of increased BUN levels

Answer 17

1. GI Bleed, Excessive Protein Ingestion (Atkin’s) & Starvation
   Increased catabolism of protein (and blood) –>increased urea formation
2. Sepsis: Decreased renal perfusion -> decreased renal excretion of urea
3. Renal Parenchymal Disease
   Inability to excrete urea
4. Ureteral Obstruction
   Stones or tumor
   Inability to excrete urea
5. Bladder outlet obstruction
   BPH
   Inability to excrete urea

Question 18

Normal Cr ranges

Answer 18

Adult 0.5-1.2 mg/dl
Children 0.3- 0.7 mg/dl
Infant 0.2 – 0.4 mg/dl

Critical Value >4 mg/dl

Question 19

Indications for Cr testing

Answer 19

Diagnose or monitor impaired renal function

Question 20

Cr test explanation

Answer 20

1. Measures amount of creatinine in blood
2. Catabolic product of creatine phosphate, High energy compound used in muscle contraction
3. Dependent on muscle mass
4. Excreted by kidneys
5. Creatinine level directly proportional to renal excretory function

Question 21

Causes of elevated Cr

Answer 21

Renal parenchymal disease: renal function is impaired
Prerenal disease: shock, dehydration, CHF,
Postrenal disease: obstruction
Rhabdomyolysis: injury of skeletal muscle, increased Cr

Question 22

True/False:

Cr levels rise before BUN levels

Answer 22

False. Serum creatinine rises much LATER than BUN

Elevated Cr indicates CHRONIC disease

Question 23

How are changes in Cr related to GFR changes?

Answer 23

Doubling of creatinine level suggests a 50% reduction in GFR: board question

Question 24

Cr Cl Test

Answer 24

1. Amount filtrate made in kidney depends on:
Amount of blood flow to kidney
Ability glomeruli to act as filter
2. Affected by
Age 
Muscle mass
High protein diet

Question 25

CrCl equation

Answer 25

CrCl = UV/P ``` U = urine cr mg/dl over 24 hours V = total urine vol over 24 hrs P = serum creatinine in mg/dl ```

Question 26

Increased CrCl

Answer 26

Exercise, pregnancy

Question 27

Decreased CrCl

Answer 27

impaired renal function, prerenal etiology

Question 28

Normal Uric acid range

Answer 28

Male 4.0-8.5 mg/dl Female 2.7-7.3 mg/dl Children 2.5-5.5 mg/dl Critical Value >12 mg/dl

Question 29

Indications for uric acid tests

Answer 29

Diagnose gout | Evaluate patients with recurrent kidney stones

Question 30

Uric acid test explanation

Answer 30

Waste product formed during recycling purine bases from RNA Formed in liver 75% excreted by kidney Level determined by rate of synthesis in liver and rate of excretion by kidney

Question 31

Clinical significance of Uric acid

Answer 31

``` Elevation of uric acid can be result of Overproduction Patients with congenital enzyme deficiency Patients with cancer Purine & DNA turnover is increased Idiopathic ```

Question 32

Causes of increased uric acid

Answer 32

1. Metastatic cancer, multiple myeloma, leukemia, cancer chemotherapy Rapid cell destruction  increased purines  increased UrAc 2. Rhabdomyolysis Muscle breakdown  increased muscle ATP  increased Ur Ac

Question 33

Causes of Decreased Uric acid

Answer 33

Gout Chronic Renal Disease Alcoholism: Accelerates breakdown ATP from liver  increased uric acid