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Wastes products of metabolism?

1. urea,
2. creatinine,
3. uric acid


Regulates the excretion of water and solutes such as?

How does it do this?

Regulates the excretion of water and solutes (sodium, potassium, and hydrogen)

largely by changes in tubular reabsorption or secretion.


Secretes hormones such as?

1. Renin,
2. prostaglandins,
3. bradykinin
4. Erythropoietin,
5. calcium,
6. phosphorus, and
7. (1,25-dihydroxyvitamin D3 or calcitriol)


The function of the kidneys?

1. Regulation of erythrocyte production
2. regulating mineral levels
3. Regulation of blood pressure
4. helping regulate the acid-base balance
5. elimination of metabolic toxins and water through the urine


Some have symptoms that are directly referable to the kidney such as? 2

Or external symtpoms such as? 3

1. gross hematuria
2. flank pain

1. edema,
2. hypertension,
3. signs of uremia


Many patients, however, are asymptomatic and are noted on routine examination to have an elevated or abnormal what? 2

serum creatinine concentration or an abnormal urinalysis


WHats azotemia? 2

Oliguria? 2

Anuria? 1

1. Elevated BUN and/or creatinine
2. The build up of abnormally large amounts of nitrogenous waste products in the blood

1. Urine output less than 400 mL/day
2. Urine output less than 20 cc/hr

1. Urine output less than 100 mL/day


What are the different kinds of azotemia?

1. Pre-renal failure (dehydration)

2. Intrinsic renal failure

3. Post-renal obstruction


Describe the following azotemias:

1. Pre-renal failure?

2. Intrinsic renal failure? 3

3. Post-renal obstruction? 2

1. Volume contraction, etc (dehydration)

-Arteriolar damage (acute hypertension)
-Glomerulonephritis etc

-Ureteral obstruction
-Bladder outlet obstruction


1. What does GFR equal?

2. Whats normal for men?
3. women?

4. How does it change with age?

5. What influences it? 4

6. How can it be measured? 3
(Whats the gold standard?)

1. Equal to the sum filtration rate of all the functioning nephrons

2. Normal for men = 130 mL/min/173 m2

3. Normal for women – 120 mL/min/173 m2

4. Decreased NORMALY with age

5. Influenced by
-body size
-Renal blood flow and hydrostatic pressures in glomerulus (BP)

6. Can be measured by:
-Creatinine clearance
-Urea clearance
-Inulin clearance- exogenous polysaccharide 100% filtered- gold standard for GFR


1. What is creatinine?

2. What is a normal creatine clearance? (men and women)

3. What is the downside to creatinine clearance testing?
4. Why does this happen? 2

1. Endogenous substance used to assess GFR

2. Normal values (up to age 40):
Men: 107-139 mL/min
Women: 87-107 mL/min

3. Overestimates true GFR by up to 40%
-Especially in persons with decreased renal function
-Reason: active tubular secretion of creatinine


Creatinine clearance procedure
What are the three steps?

1. Record patient’s height and weight
2. Collect 24-hour urine: measure total volume (TV) and urine creatinine (UCr) how much is being cleared
3. Collect blood specimen: measure serum creatinine (SCr) to see how much is endogenously produced


HOw can you calculate CrCl?

[UCr x TV(mL)/1440(min)]/SCr x 1.73/BSA

BSA(m2) = ([Ht (cm) x Wt (kg)]/3600)1/2


1. Estimated GFR/CCr calculateuion?

2. Whats the criticism?

3. What is this used for?

1. Estimated GFR/CCr (mL/min) =
[(140 - age) x wgt (kg)]/[72 x SCr]

Multiply results by 0.85 for women

2. Can overestimate the GFR

3. Measure serum creatinine and estimate GFR to assess renal function w/o urine


Standardizing the eGFR
MDRD Formula (Conventional calibration)
eGFR (mL/min/1.73m2) = ?

Normal should be?

eGFR (mL/min/1.73m2) =
186 x (Scr)-1.154 x (Age)-0.203

x (0.742 if female)

x (1.210 if African American)

MDRD = Modification of Diet in Renal Disease Study
(Scr) = serum creatinine value reported in mg/dL

Greater than 60


Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation

Why is this superior?

Creatinine measurements using external filtration markers (eg, iothalamate)
1. Provides a more accurate estimate of GFR among individuals with normal or only mildly reduced GFR
2. less bias,
3. improved precision, and
4. greater accuracy.
5. Better identification and early Tx of CKD
6. Prevent or delay renal failure
more accurate risk prediction for adverse outcomes compared with the MDRD study equation


Glomerular Filtration Rate (GFR)
In patients with kidney disease reduction in GFR:
1. What are the two kinds of problems it could be?

2. Level of GFR has prognostic indications but is NOT an exact correlate to what?

3. Stable GFR—does not necessarily imply what?

4. Some patients w/ renal disease may go unrecognized because why?

1. Either progression in underlying kidney disease or superimposed (often) reversible problem
2. the loss of nephron mass
3. stable disease
4. they have normal GFR


BUN (blood urea nitrogen)
comes from where?

Whats the normal range?

Usually measured with what to assess kidney function?

Urea nitrogen is what is formed when protein breaks down

Normal range: 6-20 mg/dL

Many drugs can effect the BUN
Usually measured with creatinine to monitor kidney function


What would increased theh BUN? 4

What would decrease it? 2

1. Renal Disease (failure)
2. Excessive protein breakdown (catabolism- tissue necrosis)
3. Very high protein diet
4. GI Bleeding
1. Liver disease
2. Starvation


1. Where does BUN come from?

2. The N takes up 3 H+ to form NH3+ which is what?

3. The ammonia (NH3+) is then processed through the what to become what?

1. When protein is used for energy the carbon is cleaved from the amino acid and leaves behind a Nitrogen.

2. ammonia.

3. the liver to become urea.


When the urea enters the blood stream it is called what?

Where is this excreted?

blood urea nitrogen

The blood urea nitrogen is then excreted by the kidney


BUN increases when protein is broken down and more ammonia forms: Examples are? 6 (most common)

1. Burns
2. Tetracycline
3. Steroids
4. Fever
5. Catabolic state
6. GI bleeding*****


BUN will decrease in liver failure. Why?

If the liver is unavailable to convert ammonia to urea then the BUN will decrease and the ammonia increases


BUN is filtered from the body through the kidneys. Decreased GFR (glomerular filtration rate) leads to increased BUN in 2 ways. What are they?

1. Decreased flow through the glomerulus
2. Slower transport time allows more BUN to be resorbed at the level of the PCT


What is creatinine:
1. HOw is it formed?
2. The more of what the higher the creatine?
(and vice versa)

1. Creatinine is formed from the normal breakdown of muscle
2. The more muscle mass the higher the creatinine
2. The lower the muscle mass the lower the creatinine (therefore normal reduction in creatinine as a person ages and loses muscle mass)


Lab Evaluation of Renal Function
1. What is creatine?
2. Whats the normal range? (mena nd women)

3. How much loss of renal function is needed to increase serum creatinine from 1.0 to 2,0 mg/dL?

4. Used in ratio with what to determine types if azotemia?

1. Waste product of protein breakdown excreted by kidneys
2. Normal range:
women 0.6-1.2 mg/dL

3. 50% loss of renal function is needed to increase serum creatinine from 1.0 to 2.0 mg/dL**

4. Used in ratio with BUN to determine types of azotemia


When is creatinine increased? 5

When is it decreased? 2

1. Increased:
2. Renal Failure
3. Diet: increased ingestion of meat
4. Meds: ACEIs, diuretics, NSAIDS, many others . . .
5. Muscle disease: muscular dystrophy, rhabdomyolysis

1. Pregnancy—normal occurrence
Range in pregnancy— 0.4 – 0.6 mg/dL


Creatinine is filtered through the kidneys:
1. Decreased GFR also leads to _________ creatinine
2. HOw is creatine handled differently than BUN by the kidney?

3. In the ____ creatinine is actively secreted from the body to be eliminated by the kidneys

3. This active secretion at the ____ can be blocked by drugs such as cimetidine and trimethoprim therefore _________ the serum creatinine


2. Instead of the creatinine being reabsorbed in the tubules like BUN with a decreased GFR the creatinine is just dumped out

3. DCT

4. DCT


Increased BUN and Creatinine

BUN? 4

Creatinine? 3

How is creatinine behave differently than BUN?

1. Decreased GFR
2. Less BUN presented at the glomerulus to be removed from the blood
3. Slower transport time through 4. PCT allows more reabsorption
Increased protein breakdown

1. Increased muscle breakdown
2. Blockage at the sites in the DCT that allow for active secretion
3. Decreased GFR as there is less creatinine presented at the glomerulus to be filtered out

not reabsorbed in the PCT like BUN


BUN creatinine ratio
1. Normal?
2. Elevated?
3. WHy is it elevated?

4. How do you calculate the ratio?

1. Normal is 10-20:1
2. Elevated is > 20:1
3. Increased ratio in a low flow (low blood pressure) state

4. Ratio = [BUN]/[serum creatinine]