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Boards.CP.Chemistry > Renal Function > Flashcards

Renal Function Flashcards

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1
Q

Why does the BUN always slightly underestimate the GFR?

A

Urea is freely filtered and PARTIALLY REABSORBED by the nephron

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2
Q

What causes increased urea reabsorption?

A

Hypovolemia

-BUN underestimates GFR even more in hypovolemic states

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3
Q

What is Azotemia?

A

Increase in BUN

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4
Q

A High BUN and its toxic effects is called what?

A

Uremia

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5
Q

Why does creatinine slightly overestimate BUN?

A
  • Passes freely through the glomerulus
  • Small amount is secreted by the tubules
  • Quantity of tubular secretion increases with increasing serum creatinine concentration
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6
Q

What is a normal BUN/creatinine ratio?

A

10:1

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7
Q

What causes in increase in BUN/creatinine ratio?

A 
Renal hypoperfusion (hypovolemia, hypotension, etc.)
-Ratio may be >20:1

*Prerenal Azotemia

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8
Q

What is the BUN/creatinine ratio in intrarenal causes of renal failure?

A

Near Normal ratio (10:1)

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9
Q

What does the kidney do with Cystatin C?

A
  • Freely filtered by glomerulus

- Reabsorbed by the proximal tubule (completely)

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10
Q

Cystatin C vs. serum creatinine

A

Cystatin C is as a good for estimating GFR

-Less dependent on age, sex, or muscle mass

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11
Q

Cystatin C is a strong predictor of what?

A

Cardiovascular mortality in patients with chronic renal disease

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12
Q

What is a normal proteinuria?

A

does not exceed 150 mg/day

*mainly Tamm-Horsfall protein

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13
Q

Significant proteinuria is defined as what?

A

> 300 mg/day

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14
Q

How do you assess proteinuria?

A

24 hour urine collection

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15
Q

The urine dipstick result (1+ to 3+) is semiquantitative and most sensitive to what?

A

Albumin

*not sensitive enough to detect microalbuminuria

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16
Q

The presence of what proteins in urine suggest tubular dysfunction?

A
  • B2-microglobulin
  • Lysozyme

*These are freely filtered by the glomerulus and then completely reabsorbed by the normally functioning Proximal Convoluted Tubule (PCT)

17
Q

The current recommendation of the National Kidney foundation is annual testing for those at high risk for CKD, who qualifies for this?

A
  • Diabetes Mellitus
  • Hypertension
  • Family history of renal disease
18
Q

What is the recommended screening tests for high risk for CKD?

A
  • eGFR

- Microalbuminuria screen

19
Q

What is the microalbuminuria screen?

A

Urine albumin:Creatinie ratio

20
Q

Chronic Kidney disease is defined by what?

A
  • GFR <60 mL/min/1.73m^2 of body surface area

- Albuminuria for 3 or more consecutive months

21
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Causes

A
  • Prerenal - Hypoperfusion

- Intrarenal - Injury to nephron (glomeruli, tubules, vessels, or interstitium)

22
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-BUN:Creatinine ratio

A
  • Prerenal - >20:1

- Intrarenal - <20:1

23
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Urine specific gravitity

A
  • Prerenal - High (>1.020)

- Intrarenal - Low (<1.010)

24
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Urine Osmolarity

A
  • Prerenal - High (>500 mOsm/kg)

- Intrarenal - Low (300-500 mOsm/kg)

25
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-FE Na (fractional excretion of Sodium)

A
  • Prerenal - <1%

- Intrarenal - >1%

26
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-FE urea (fractional excretion of Urea)

A
  • Prerenal - <35%

- Intrarenal - >35%

27
Q

Acute Renal Failure - Postrenal:

  • Causes
  • BUN:Cr ratio
A

Bilateral obstruction of the renal collecting system

  • Bladder outlet obstruction (prostatism)
  • Ureteral obstruction (tumor, etc.)

BUN:Cr ratio often ELEVATED

28
Q

What is the most common cause of Intrarenal Acute Renal Failure?

A

Acute tubular necrosis (ATN)

29
Q

What are the most common causes of ATN

A
  • Ischemia

- Nephrotoxins

30
Q

In intrarenal ARF, urine may show “active” sediment:

-Glomerulonephritis

A
  • RBCs and RBC casts

- Granular casts

31
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Acute Tubular Necrosis

A

Granular casts

32
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Interstitial nephritis

A

Granular casts

33
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Pyelonephritis

A

WBC casts

34
Q

Acute Renal Failure - Prerenal vs. Intrarenal:

-Acute Allergic Interstitial nephritis

A

Eosinophils

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