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GI and Renal Exam 1 > 8 - Renal Physiology IV > Flashcards

8 - Renal Physiology IV Flashcards

1
Q

Which substance is excreted more than is filtered?

a. Sodium
b. Potassium
c. Chloride
d. Glucose

A

b. Potassium

Filtered = initially filtered into tubule
Secreted = actively pumped into tubule
Excreted = leaves body in the urine

The only one that is secreted is potassium

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2
Q

Re-absorption of glucose occurs in the:

a. Thin descending limb of the loop of Henle
b. Thick ascending limb of the loop of Henle
c. Distal tubule
d. Proximal tubule
e. Collecting duct

A

d. Proximal tubule

You want to reabsorb this quickly so you don’t lose it, don’t want to lose energy

Amino acids are also reabsorbed here

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3
Q

Define renal clearance

A

The renal clearance of a substance is the volume of plasma that is completely cleared of the substance by the kidney per unit of time

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4
Q

How do you measure renal clearance?

A

Renal clearance is measured in volume (of plasma). Volume of plasma totally cleared of the substance in a certain period of time. It is a theoretical concept since there is no single volume of plasma that is completely cleared of a substance

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5
Q

What is the function of clearance by the kidneys?

A

Clearance provides a useful way of quantifying the excretory function of the
kidneys. It can be used to quantify the rate at which blood flow through the
kidneys as well as basic function of the kidneys

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6
Q

Give an example of renal clearance

A

Example: if the plasma passing thought the kidneys contains 1 milligram of a substance in each milliliter of plasma.

If 1 milligram of this substance is also excreted into the urine each minute, then 1 ml/min of the plasma is “cleared” of the substance

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7
Q

What is the equation for renal clearance?

A

𝐶𝑥×𝑃𝑥=𝑉x 𝑈𝑥

𝐶𝑥=(𝑉 x 𝑈𝑥)/𝑃𝑥

𝐶𝑥= clearance of substance X
𝑃𝑥= plasma concentration of X
𝑉̇= urine flow rate
𝑈𝑥= urine concentration of X
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8
Q

What is the best overall index of kidney function?

A

GLOMERULAR FILTRATION RATE ***

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9
Q

How can you use clearance to estimate GFR (glomerular filtration rate)?

A

. If a substance is freely filtered and is not re-absorbed or secreted by the renal tubules, then the rate at which the substance is excreted in the urine (𝑉̇×𝑈𝑥) is equal to the filtration rate of the substance by the kidney (𝐺𝐹𝑅×𝑃𝑥)

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10
Q

What is the equation for GFR?

A

𝐺𝐹𝑅= (𝑉̇×𝑈𝑥)/𝑃𝑥

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11
Q

What substances fit these criteria?

A
  • Inulin, a polysaccharide molecule. It is not produced by our body and must be administrated intravenously to a patient to
    measure GFR
  • Creatinine, a by-product of muscle metabolism It is cleared from the body almost entirely by glomerular filtration
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12
Q

What is the approximate relationship between GFR and plasma creatinine concentration?

A

Decreasing GFR by 50
percent will increase
plasma creatinine to twice
normal if creatinine production by the body remains constant

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13
Q

How do you estimate the GFR from serum creatinine?

A

Using the Cockccroft & Gault Equation

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14
Q

What is the CG equation for males?

A

𝐶𝐶𝑟=((140−𝐴𝑔𝑒)×(𝐵𝑜𝑑𝑦 𝑊𝑒𝑖𝑔ℎ𝑡, 𝑘𝑔))/(72×𝑃𝑐𝑟, 𝑚𝑔⁄𝑑𝑙)

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15
Q

What is the CG equation for females?

A

𝐶𝐶𝑟=((140−𝐴𝑔𝑒)×(𝐵𝑜𝑑𝑦 𝑊𝑒𝑖𝑔ℎ𝑡, 𝑘𝑔))/(72×𝑃𝑐𝑟, 𝑚𝑔⁄𝑑𝑙) × 0.85

MULTIPLY BY 0.85***

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16
Q

What is another recommended equation you can use for estimating GFR?

A

Another recommended equations for estimating GFR from serum creatinine include the Modification of Diet in Renal Disease (MDRD) Study equation (can find online at NIH website)

17
Q

Which one should you use?

A

You can use either, but it will not change the diagnosis… Just sate which one you are using when you report it in the patient’s chart

18
Q

What is acute kidney injury (AKI) or acute renal failure (ARF)?

Same thing

A
  • A syndrome that results in a sudden decrease in kidney function or damage from few hours to few days
  • It is one of the most serious and common health problems in the US. It occurs in up to 1 in 5 patients in the hospital and twice as often in a critical care setting
  • It is defined as a rapid decline in glomerular filtration rate accompanied by accumulation of waste products in the blood and inability to keep the body balance of fluid and electrolytes
19
Q

What are the three different groups of etiologies of AKI?

A

Etiology of AKI has been categorized anatomically into:

  • Pre-renal
  • Renal (intrinsic, intra-renal)
  • Post-renal
20
Q

Describe pre-renal etiologies of AKI

A

It results from kidney hypoperfusion

21
Q

List the specific pre-renal etiologies of AKI

A

Intravascular volume depletion
- Hemorrhage, diarrhea, vomiting

Cardiac failure
- Myocardial infarction

Peripheral vasodilation (hypotension)
- Anaphylactic shock, sepsis

Renal hemodynamic abnormalities
- Thrombosis of renal artery

22
Q

Describe renal (intrinsic, intra-renal) etiologies of AKI

A

Renal etiologies are classified based on the site of injury in:

1. Vascular
2. Glomerular 
3. Tubular
4. Interstitial
23
Q

List the specific renal etiologies of AKI

A

Vessel and glomerular injury
- Vasculitis, glomerulonephritis

Tubular epithelial injury
- Ischemia, toxins (insecticides, poison)

Renal interstitial injury
- Pyelonephritis

24
Q

Describe post-renal etiologies of AKI

A

It occurs from urinary tract obstruction

25
Q

List the specific post-renal etiologies of AKI

A

Bilateral obstruction of ureters or renal pelvises
- Kidney stones

Uretic obstruction

Bladder/urethral obstruction

26
Q

So, what is the physiological effect of AKI?

A
  • Water and sodium overload due to decreased filtration rate (edema and hypertension)
  • Increase in plasma potassium concentration also due to decreased filtration rate (hyperkalemia)
  • Metabolic acidosis due to a decreased amount of urine
  • Anuria (in severe AKI)
27
Q

Describe chronic kidney disease (chronic renal failure)?

Same thing

A
  • It results in progressive and IRREVERSIBLE loss of large number of functioning nephrons
  • 26 million American adults have Chronic Kidney Disease
  • Clinical symptoms often do not occur until the number of functional nephron fall to at least 70 to 75 % below normal
  • It occurs because of disorders of blood vessels, glomeruli, tubules, renal interstitium and lower urinary tract
28
Q

What are all the different causes of chronic kidney disease (CKD)

A

Metabolic disorders

  • Diabetes mellitus***
  • Obesity***

Hypertension***

Immunologic disorders

  • Glomerulonephritis
  • Lupus erythematosus

Infection
- Pyelonephritis

Congenital Disorders
- Polycystic disease

29
Q

What is an important factor in the progression of chronic kidney disease?

A

AGE

30
Q

What is the disease that chronic kidney disease progresses to?

A

End-stage renal disease

31
Q

What are the stages of chronic kidney disease (CKD)?

A

Stage 1 = kidney damage with normal or increased GFR (>90)

Stage 2 = kidney damage with mild decrease in GFR (60-89)

Stage 3 = moderate decrease in GFR (30-59)

Stage 4 = severe decrease in GFR (15-29)

Stage 5 = kidney failure (

32
Q

How do you define kidney damage?

A

Kidney damage is defined as pathologic abnormalities or markers of damage, including abnormalities in blood and urine tests or imaging studies

33
Q

Describe glomerulonephritis

A
  • Glomerulonephritis can be acute or chronic
  • Acute glomerulonephritis can cause Acute Kidney Injury
  • Chronic glomerulonephritis can result in Chronic Kidney Disease and nephrotic syndrome
  • Patient can develop hematuria, proteinuria, azotemia (elevated blood nitrogen) and renal sodium and water retention
34
Q

Describe nephrotic syndrome

A
  • Increased glomerular permeability to large proteins such as albumin
  • GFR is decreased (many glomeruli may become nonfunctional)
  • Sodium and water retention
  • Edema and decrease in plasma volume
35
Q

Describe the relationship between hypertension and kidney disease

A
  • Hypertension can exacerbate injury to the kidney and abnormalities of kidney function can cause hypertension
  • Renal lesions that reduce the ability of the kidney to excrete
    sodium and water promote hypertension
    1 - Increased renal vascular resistance
    2 - Decreased glomerular capillary filtration fraction
    coefficient
    3 - Excessive tubular sodium re-absorption

GI and Renal Exam 1 (16 decks)

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