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Nephrology > Mechanisms of Acute Renal Failure > Flashcards

Mechanisms of Acute Renal Failure Flashcards

1
Q

What are 3 characteristics of acute renal injury?

A
  1. Abrupt retention of urea/nitrogenous waste
  2. dysregulation of extracellular volume/electrolytes
  3. dysregulation of acid base balance
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2
Q

What are the Sx and lab guidelines for Acute kidney injury set by KDIGO?

A
  1. increase in serum creatinine ≥ 0.3 mg/dL in 48 hours
  2. increase in serum creatinine ≥ 1.5 times the baseline within the 7 days
  3. Urine volume less than 0.5 mL/kg/hours for 6 hours
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3
Q

What part of the nephron is in the:

  1. Cortex
  2. Medulla
A
  1. cortex - glomeruli

2. loop of henle, collecting tubule

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4
Q

How many nephrons are there in the kidney?

A

1,000,000

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5
Q

What are 3 causes of acute kidney injury? describe each of them.

A
  1. Prerenal: drop in BP, interruption of blood flow (hemolytic shock, GI bleeding, HF) = no structure changes to the kidney
  2. Intrarenal: direct kidney damage (inflammation, toxins, drugs, infection, reduced blood supply)
  3. Postrenal: obstruction of urine - back up leads to filtration failure
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6
Q

What 2 things account for almost 99% of all acute kidney injuries?

A
  1. Prerenal

2. Tubular cell injury

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7
Q

What are 2 causes of Tubular cell injury? give examples of each.

A
  1. Ischemia/Inflammation (sepsis, surgery, hypoperfusion)
  2. Toxins (Aminoglycosides, cis-platinum, NSAIDS, cyclosporin, RADIOCONTRAST)
    - NSAIDS, cyclosporin, radiocontrast - cause vasoconstriction (ischemia)
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8
Q

What is the blood pressure range that the kidney is able to regulate a stable GFR?

A

80-180

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9
Q

How is GFR regulated during Hypotension? (2 ways)

A

Prostaglandin E2 dilates the afferent arteriole

Angiotensin II contricts efferent arteriole

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10
Q

What drug inhibits the activity of prostaglandin on the afferent arteriole? What happens to the arteriole and what kind of patients should you not give it to?

A

NSAIDS (COX-2 inhibitors inhibit prostaglandin production)

-dont give to hypovolemic patients, afferent arterioles cant dilate

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11
Q

What drug inhibits the activity of angiotensin II on the efferent arteriole? what happens to the arteriole?

A

ACE inhibitors inhibit angiotensin II
ARBs
efferent arterioles dont constrict

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12
Q

What 3 features of blood supply of the kidney are very important to consider when dealing with Acute Renal Failure?

A
  1. the kidney is prone to hypoxia
  2. all renal artery branches are end branches w/o significant collateral supply
  3. kidneys receive 25% cardiac output
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13
Q

What part of the nephron (and 2 specific parts) are especially susceptible to ischemia?

A

outer medulla:

  1. PCT (S3 segment)
  2. TAL
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14
Q

What are two causes of Acute Tubular Necrosis (ATN)?

A
  1. Ischemia (outer medulla)

2. Toxins (endogenous/exogenous nephrotoxins)

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15
Q

Examples of endogenous and exogenous nephrotoxins?

A

endogenous: hemoglobin, myoglobin
exogenous: contrast agents, antibiotics

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16
Q

What are Sx of ATN?

A

MUDDY BROWN CASTS
Hx (meds, contrasts)
Abnormal volume status

17
Q

What do RBC casts in urine microscopy suggest?

A

Glomerulonephritis

18
Q

What do WBC casts in urine microscopy suggest?

A

Interstitial nephritis

19
Q

What do Bland, Hyaline casts suggest?

A

Prerenal azotemia

20
Q

How do you differentiate Prerenal azotemia and ATN? (BUN/Cr ratio, Urine sodium, Urine osmolality, Response to IV fluids)

A

Prerenal: >20:1 BUN/Cr ratio, <20 Urine sodium, >500 urine osmolality, <1% fractional sodium excretion, CREATININE IMPROVES in response to IV fluids

ATN: 10:1 BUN/Cr ratio, >40 Urine sodium, <400 Urine osmolality, Cr doesnt improve with IV fluids

21
Q

How do you manage Acute Kidney Injury?

A

Fix electrolyte abnormalities
Dialysis
Fix Volume depletion
stop Ace inhibs/ARB/NSAIDS

22
Q

What should you do with Uremic Pericarditis

A

HOLY SHIT DIALYSIS FO SHO

23
Q

How do you differentiate between AKI and Chronic Renal Failure?

A

acute: little urine output, recent onset of Sx(anasarca, discolored urine), increasing serum creatinine
chronic: stable Serum creatinine, ultrasonography (SMALL KIDNEYS), increased renal parenchyma echogenicity

Both (more common in chronic): anemia, hyperphosphatemia

Nephrology (13 decks)

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