Acute kidney injury

Question 1

a sudden decrease in kidney function, resulting in an inability to maintain acid-base, fluid and electrolyte balance and to excrete nitrogenous wastes

Answer 1

acute kidney injury (AKI) or acute renal failure

Question 2

A condition occuring in AKI where urea and other nitrogenous waste products are not excreted properly in urine and levels become elevated in the blood.

Answer 2

Uremia

Question 3

What are the 3 categories of AKI? Give one cause for each.

Answer 3

1) Pre-renal (hypovolemia leads to low kidney perfusion, HF, dehydration, diuresis, etc) Pre-renal is most common*
2) Intrinsic (kidney disease)
3) Post-renal (urinary obstruction like BPH)

Question 4

What happens to the kidney on an ACEI?

Answer 4

its efferent arteriole cannot constrict to maintain high pressure in the glomerulus thus decreasing GFR.

Question 5

When GFR decreases what happens to BUN and creatinine concentrations in blood?

Answer 5

They will both increase

Question 6

Does a decrease in GRF affect BUN and creatinine levels evenly? Why?

Answer 6

No! BUN is both filtered AND re-absorbed in the kidney. So a slower rate will 1) not filter as much BUN out of the blood and 2) gives the kidneys more time to reabsorb BUN back into the blood. So a slow GFR affects BUN much more significantly. (Creatinine is just excreted, no re-absorption)

Question 7

AKI result in a ___________to the GFR

Answer 7

decrease

Question 8

In a low flow state (ie low GFR) the kidney thinks there is hypovolemia. So besides having extra time to reabsorb BUN, what else is the kidney doing?

Answer 8

low volume triggers kidney to reabsorb Na and therefore H20. So low GFR often results in low Na and low H20 in urine….urine becomes concentrated (high osmolality = high specific gravity).

Question 9

What if there is an intrinsic problem with the kidney, for example a problem with the prox convoluted tubule. What would you expect to happen?

Answer 9

Reabsorption would not happen. So BUN would not be reabsorbed. Neither would Na (and H20). So BUN would only increase proportionately to creatinine and urine would have tons of Na and H20. Dilute urine = low concentration = low specific gravity

Question 10

What is the normal BUN:creat ratio?

Answer 10

15:1

Question 11

If you see a BUN:creat ratio of 20:1, where do you think your AKI is coming from?

Answer 11

Pre-renal.

Question 12

If you see a BUN creat ratio of 15:1 but the GFR is low, where is your AKI?

Answer 12

Intrinsic renal problem

Question 13

What is the specific gravity of plasma?

Answer 13

1.010

Question 14

What is the FENa?

Answer 14

Fractional Excretion of Na. It is equal to (urine sodium/plasma sodium) over (urine creat/plasma creat) Algebraically, if your urine sodium is high…we know the FENa will be high. Urine sodium is high when it cannot be reabsorbed…so it is a renal-renal problem. HIGH FENa = RENAL RENAL. (>2%)

Question 15

If you have low perfusion (pre-renal) problem for hours…what do you expect will happen?

Answer 15

Ischemia leads to tissue death of the kidney…aka acute tubular necrosis (ATN)

Question 16

What is another cause of ATN?

Answer 16

Nephrotoxins like aminoglycosides, cephalosporins, contrast dye, NSAIDS, ACEIs

Question 17

How could increased destruction of RBCs affect kidneys?

Answer 17

hemolysis from anemia, transfusion reaction, GI bleeds cause increase of RBC metabolism. RBC’s have proteins so this will lead to increased ammonia. IF the liver can convert to BUN you’ll have increased BUN

Question 18

In ATN, what’s commonly seen in the urine?

Answer 18

sediment, pigmented casts

Question 19

What is the goal in treating ATN?

Answer 19

Avoid buildup of excess fluid and waste. Restrict fluid intake, give diuretics, control potassium–Furosemide does both. Tubular cells will typically regenerate. Dialysis used if necessary

Question 20

An interstitial inflammatory response with edema and possible tubular cell damage is the typical pathologic finding

Answer 20

Interstitial Nephritis.
(So basically, the interstitium of kidneys becomes inflammed as an immune response. Causes are either drug related or AI disorder) FYI: prognosis is good

Question 21

What is a classic finding for Interstitial Nephritis?

Answer 21

Eosinophils present in immune responses

Question 22

How do you treat interstitial nephritis?

Answer 22

steroids

Question 23

Your patient has suddenly become hypertensive and edematous. You look at his urine and detect WBC’s, dysmorphic RBC’s and RBC casts. There is also some proteinuria. GFR is decreased. What do you suspect?

Answer 23

glomerulonephritis

Question 24

What causes glomerulonephritis?

Answer 24

Inflammation caused by either immune response (lupus, Berger’s) or infection (post strep, hepatitis)

Question 25

What is the treatment of glomerulonephritis?

Answer 25

steroids

Question 26

Post-renal kidney failure will likely result in the back-up of urine. It can back up in the urethra, bladder, ureters, and then the renal pelvis of kidneys. This is called__________________

Answer 26

hydronephrosis

Question 27

How would you diagnose hydronephrosis?

Answer 27

Hx, flank pain, suprapubic pain, UA, imaging (IVP, US, CT)

Question 28

How do you treat hydronephrosis?

Answer 28

remove obstruction! (Catheter, cholinergics to dilate ureters/urethra and promote micturation, surgery for structural problem, BPH meds, etc)

Question 29

What is considered “elevated proteinuria”?

Answer 29

> 150mg/day

Question 30

How much protein is excreted in the urine to make a dx of nephrotic syndrome?

Answer 30

> 3.5GRAMS/day

Question 31

What is the osmolality of normal urine?

Answer 31

250-300Osm

Question 32

When you have a pre-renal kidney failure, what will the osmolality be? intrinsic kidney failure?

Answer 32

> 500Osm–pre renal and Normal for intrinsic (250-300)

Question 33

On a UA dipstick, in reference to protein, what does trace, +1, +2, +3, +4 mean?

Answer 33

trace = 150mg/day (normal)
\+1 = up to 500mg/day
\+2 = up to 1.5mg/day
\+3 = up to 5mg/day
\+4 = >5mg/day

Question 34

on UA dipstick, what does +ketones indicate?

Answer 34

DKA, starvation

Question 35

What does +nitrites on UA indicate?

Answer 35

bacterial infection