Acute Kidney Injury (AKI)

Question 1

What is an acute kidney injury?

Answer 1

decrease in creatinine clearance that causes a sudden rise in BUN and Creatine

Question 2

What are the 3 types of Acute Kidney Injury?

Answer 2

Prerenal Azotemia (decreased perfusion)
Postrenal Azotemia (Obstruction)
Intrinsic renal disease (ischemia and toxins)

Question 3

What causes Prerenal Azotemia?

Answer 3

inadequate perfusion of the kidneys: any cause of hypoperfusion or hypovolemia will raise the Bun and Cr with the Bun raising more than Cr

Question 4

What are some of the common causes of Prerenal Azotemia?

Answer 4

Hypotension: sepsis, anaphylaxis, bleeding, dehydration
Hypovolemia: diuretics, burns, pancreatitis
Renal artery stenosis
Relative Hypovolemia: CHF, constrictive pericarditis, tamponade
Hypoalbuminemia
Cirrhosis
NSAIDS: constricting the afferent arteriole

Question 5

What causes Postrenal Azotemia?

Answer 5

Obstruction that blocks filtration at the glomerulus

Question 6

What are common causes of Postrenal Azotemia?

Answer 6

Prostate hypertrophy or cancer
Stone in Ureter
Cervical Cancer
Neurogenic (atonic) bladder
Retroperitoneal Fibrosis: hx of bleomycin or radiation therapy

Question 7

What is the major force that favors filtration?

Answer 7

Hydrostatic Pressure in the glomerular capillary

Question 8

What happens if Hydrostatic pressure in bowman space rises?

Answer 8

Fluid cannot filter through

Question 9

What causes Intrinsic Renal disease?

Answer 9

Acute tubular Necrosis (ATN) from toxins or ischemia of the kidney

Question 10

What are some of the common causes of Intrinsic Renal Disease?

Answer 10

Acute (allergic) interstitial Nephritis: penicillin
Rhabdomyolysis and Hemoglobinuria
Contrast, aminoglycosides, cisplatin, amphterisin, cyclosporine, NSAIDs
Crystals: hyperuricemia, hypercalcemia, hyperoxaluria
Proteins: Bence-Jones from Myeloma
Poststreptococcal infection

Question 11

What are some of the common presenting symptoms of AKI?

Answer 11

Nausea/vomiting
Fatigue/malaise
Weakness
SOB and edema from fluid overload

Question 12

What can severe AKI present with?

Answer 12

Confusion or seizures
arrhythmia from hyperkalemia and acidosis
Sharp, pleuritic chest pain from pericarditis

Question 13

What is the best diagnostic test for AKI?

Answer 13

Bun and Cr

Question 14

What is the best initial imaging test for AKI?

Answer 14

Renal Sonogram

Question 15

What is the Bun:Cr ratio in Prerenal Azotemia?

Answer 15

> 20:1

Question 16

What are common clues in the patient’s Hx for Prerenal Azotemia?

Answer 16

Hypoperfusion or hypotension

Question 17

What is the Bun:Cr ratio in postrenal Azotemia?

Answer 17

> 20:1

Question 18

What are common clues in the patient Hx for Postrenal Azotemia?

Answer 18

Distended bladder or massive release of urine with catheter

B/L Hydronephrosis on US

Question 19

When the cause of AKI is not clear what are the next best diagnostic steps?

Answer 19

Urinalysis
Urine Sodium
Fractional Excretion of Sodium or Urea
Urine Osmolality

Question 20

What is stimulated by a decrease in BP?

Answer 20

Aldosterone

Question 21

What is the action of Aldosterone?

Answer 21

Increase Sodium resorption leading to decreased urine sodium

Question 22

What hormone levels should increase when intravascular volume is low?

Answer 22

ADH: kidneys will absorb more water to fill the vasculature and increase renal perfusion producing more concentrated urine (Increased urine osmolality)

Question 23

What is the Urine Na level in Prerenal Azotemia?

Answer 23

<20

Question 24

What is the FENa in prerenal azotemia?

Answer 24

<1%

Question 25

What is the Urine Osmolality in Prerenal Azotemia?

Answer 25

>500

Question 26

What is the BUN:Cr ratio in Acute Tubular Necrosis?

Answer 26

<20:1

Question 27

What is the urine Na in acute tubular necrosis?

Answer 27

>20

Question 28

What is the FENa in Acute tubular necrosis?

Answer 28

>1%

Question 29

What is the urine osmolality in acute tubular necrosis?

Answer 29

<300

Question 30

Why is the Urine Osmolality low in acute tubular necrosis?

Answer 30

the tubule cells are damaged and cannot concentrate the urine

Question 31

What is Acute Tubular Necrosis?

Answer 31

Injury to the kidneys from ischemia and/or toxins tubular cells to slough off into the urine

Question 32

What mechanism is lost in Acute Tubular Necrosis?

Answer 32

The mechanism for resorbing Na and Water are lost with the tubular cells

Question 33

What is the most proven benefit to prevent contrast-induced nephrotoxicity?

Answer 33

Saline Hydration

Question 34

What is the exception to normal lab values seen in Acute Tubular Necrosis?

Answer 34

Contrast-induced renal failure

Question 35

What lab value are expected in contrast-induced renal failure?

Answer 35

Low Urine Na, FENa<1% and a high specific gravity

Question 36

What are the lab values in contrast-induced renal failure different than what would be expected in Acute tubular necrosis?

Answer 36

Contrast causes spasm of the afferent arteriole leading to renal tubular dysfunction; leads to increase in Na and H20 Resorption -causes high specific gravity, low urine sodium

Question 37

What drug is associated with Hemolysis in patients with G6PD deficiency?

Answer 37

Rasburicase

Question 38

What should be given prior to chemotherapy to prevent renal failure from tumor lysis syndrome?

Answer 38

Allopurinol Hydration Rasburicase

Question 39

What are common causes of Rhabdomyolysis

Answer 39

Trauma, prolonged immobility, snake bites, seizures and crushing injuries

Question 40

What are additional, less common causes of Rhabomyolysis?

Answer 40

Cocaine: constricts vessels Hypokalemia: constricts vessels Hypophosphatemia: constricts vessels Statins Viral infections

Question 41

What is the best initial test for Rhabdomyolysis?

Answer 41

Urinalysis

Question 42

What is the most specific diagnostic test for Rhabdomyolysis?

Answer 42

Urine test for Myoglobin

Question 43

What lab values are associated with Rhabdomyolysis?

Answer 43

Creatine Phosphokinase (CPK) markedly elevated Myoglobin in urine Hyperkalemia due to release of K from damaged cells Hyperphosphatemia due to release from muscle Hypocalcemia: Ca binds damaged muscles

Question 44

How do you treat Rhabdomyolysis?

Answer 44

Saline Hydration

Question 45

How do you manage Acute Tubular Necrosis (ATN)?

Answer 45

Hydration and correct electrolytes

Question 46

When is Dialysis the answer for Acute Tubular Necrosis (ATN)?

Answer 46

Fluid Overload Encephalopathy Pericarditis Metabolic Acidosis Hyperkalemia

Question 47

What is Hepatorenal Syndrome?

Answer 47

Renal failure developing secondary to liver disease: kidneys are intrinsically normal

Question 48

What do lab values in Hepatorenal syndrome resemble?

Answer 48

Preranal Azotemia

Question 49

What lab values are seen in Hepatorenal Syndrome?

Answer 49

Low urine sodium <10-15 FENa<1% Elevated Bun:Cr >20:1

Question 50

How do you treat Hepatorenal Syndrome?

Answer 50

Midodrine Octreotide Albumin: benefit less clear

Question 51

What procedure is commonly associated with cholesterol emboli lodging in the kidney leading to AKI?

Answer 51

Cardiac Catheter procedures

Question 52

What are clinical features seen with Cholesterol Emboli?

Answer 52

Blue/Purplish skin lesions in fingers and toes Livedo Reticularis ocular lesions

Question 53

What should you test for with suspected Cholesterol Emboli?

Answer 53

Eosinophilia Low C' Eosiophiluria Elevated ESR

Question 54

What is the most accurate diagnostic test for a cholesterol emboli?

Answer 54

Biopsy of skin lesion showing cholesterol crystals

Question 55

What is Acute (Allergic) Interstitial Nephritis?

Answer 55

Form of acute renal failure that damages the tubules on an idiopathic basis Ab and Eosinophils attack the cells lining the tubes as a reaction to drugs, infection and autoimmune conditions

Question 56

What medications are most commonly associated with Acute (Allergic) Interstitial Nephritis?

Answer 56

Penicillins and Cephalosporins Sulfa Drugs Phenytoin Rifampin Quinolones Allopurinol PPIs

Question 57

How does Acute (Allergic) Interstitial Nephritis most commonly present?

Answer 57

Rising BUN and Cr (Acute renal failure) with Fever, Rash, Arthralgias, eosinophilia and eosinophiluria

Question 58

What is the most accurate test for Acute (Allergic) interstitial nephritis?

Answer 58

Kidney Biopsy

Question 59

What other diagnostic tests are used for Acute (Allergic) Interstitial Nephritis?

Answer 59

Elevated Bun and Cr: ratio <20:1 WBC and RBC in urine

Question 60

How do you treat Acute (allergic) Interstitial Nephritis?

Answer 60

Usually resolves spontaneously upon stoppage of drug If Cr continues to rise give glucocorticoids -Prednisone, Hydrocortisone, Methylprednisolone