Acute Kidney Injury (AKI) (Teitelbaum)

Question 1

Cockroft and Gault formula. For what is it used and what is the formula?

Answer 1

Another way to estimate GFR is to estimate the creatinine clearance using the Cockcroft and Gault formula:

Creatinine clearance = [(A) x (140 - age) x weight]/ (72 x SCr)

Where:
the creatinine clearance is in ml/min
A=l.0 if male, 0.85 if female
Age is in years
Weight is in kg
Serum creatinine is in mg/dL

Question 2

What is required for a 24 hr createnine clearance test? What equation is used to calculate it?

Answer 2

Patient urine for 24 hour period, blood draw to determine plasma levels of creatinine.

ClCr = (UCr) V/ PCr where

ClCR = Creatinine clearance in mL/min
UCR = Urine creatinine in mg/dL
V = urine flow rate -->24hr urine volume /1440 (minutes in a day) in mL/min
Pcr = plasma creatinine in mg/dL

**note that this is the same equation used to calculate GFR for a generic substance, here we just make it specific for creatinine

Question 3

x

Answer 3

x

Question 4

SNGFR is proportional to _____.

Answer 4

PGC

Question 5

Vasodilation of the afferent arteriole is largely maintained by:

Answer 5

PGE1 and PGI2

Question 6

Vasoconstriction of the efferent arteriole is largely maintained by:

Answer 6

ATII

Question 7

Decreased afferent resistance will __ the GFR. What causes this?

Answer 7

Increase. Nitric oxide, prostaglandins E2 and I2, high protein diet/amino acids

Question 8

Increased efferent resistance will ___ the GFR. What causes this?

Answer 8

Increase the GFR. Angiotensin-II.

Question 9

Decreased efferent resistance will ___ the GFR. What causes this?

Answer 9

Decrease. ACE inhibitors and ARBs.

Question 10

Increased afferent resistance will ___ the GFR. What causes this?

Answer 10

Decrease. NSAIDs, adenosine, norepinephrine, endothelin, thromboxane

Question 11

Na (plasma)

Answer 11

Na- 140 ± 3 mEq/L (Tells you about the relative amount of water in the ECF compared with Na. It tells you nothing about total body Na; best considered as an indirect but readily available assessment of plasma osmolality that is accurate under most (but not all) circumstances).

Question 12

K (plasma)

Answer 12

K- 4.5 ± 0.6 mEq/L (Tells you about plasma K; relatively poor indicator of total body K).

Question 13

Cl (plasma)

Answer 13

Cl- 104 ± 3 mEq/L (Generally considered a passive anion; used in the anion gap calculation as described below).

Question 14

CO2 (plasma)

Answer 14

Total CO2 (tCO2)- 27 ± 2 mEq/L (Total CO2 content of blood; about 3 mEq/L higher than the arterial HCO3- because of dissolved CO2. Used for calculation of anion gap).

Question 15

Glucose (plasma)

Answer 15

Glucose (Fasting)- 90 ± 30 mg/dL

Question 16

Creatinine (plasma)

Answer 16

Creatinine- 1.0 ± 0.3 mg/dL (Used to estimate renal function; reciprocal (1/cr)
directly proportional to CrCl and, indirectly, to GFR).

Question 17

BUN (plasma)

Answer 17

BUN- 12 ± 4 mg/dL

Question 18

Phosphorus (plasma)

Answer 18

Phosphorus- 4.0 ± 1.0 mg/dL

Question 19

Ca (plasma)

Answer 19

Calcium- 9.5 ± 1.0 mg/dL

Question 20

Cholesterol (plasma)

Answer 20

Cholesterol- 140-200 mg/dL

Question 21

Osmolality (plasma)

Answer 21

Around 285 ± 3 mosm/kg H2O (Direct measurement of plasma osmolality;
difficult to obtain in a short time from a clinical lab).

Question 22

Azotemia:

Answer 22

Buildup of nitrogenous wastes in the blood; i.e. Blood Urea Nitrogen (BUN) and serum creatinine are increased.

Question 23

Oliguria

Answer 23

Urine volume is

Question 24

Anuria

Answer 24

Urine volume is

Question 25

What is the FENa? What is the clinical significance of this number?

Answer 25

FENa is the ratio of clearance of Na to Creatinine. It can help distinguish prerenal azotemia from other causes of AKI. FENa 2% indicates other cause. (radiocontrast and rhabdomyolysis are cause FENa

Question 26

Postrenal obstruction would likely show what on a FENa? Why?

Answer 26

FENa>2%. Obstruction generally decreases tubular sodium resorption, so the levels in urine will rise. Also, an impairment of H2O resorption lowers urine creatinine concentrations.

Question 27

UA pattern for prerenal azotemia

Answer 27

Relatively high specific gravity, no heme pigment, normal sediment (i.e. any casts are waxy or finely granular).

Question 28

UA pattern for Glomerulonephritis

Answer 28

Variable tonicity, + heme pigment, sediment exam reveals RBC and RBC casts.

Question 29

UA pattern for AIN

Answer 29

Isotonic urine, +/- heme pigment, white blood cell casts,

eosinophils (with allergic interstitial nephritis)

Question 30

UA pattern for Vascular

Answer 30

Variable isotonicity, +/- hematuria

Question 31

UA pattern for ATN

Answer 31

Typically isotonic, variable heme pigment (+ if from hemolysis or rhabdomyolysis). Sediment exam will show pigmented coarsely granular casts and renal tubular epithelial cells (RTEs).

Question 32

UA pattern for Obstruction

Answer 32

Tonicity usually isotonic or hypotonic, usually heme is negative unless superimposed infection. Micro may be totally benign or show evidence of superimposed infection (e.g. RBCs & WBCs).

Question 33

What is the most common cause of a sudden drop in GFR in hospitalized patients?

Answer 33

Pre-renal azotemia

Question 34

What does it mean to have a low Effective Arterial Blood Volume (EABV)?

Answer 34

This applies in cases of pre-renal azotemia that occur in hyper (versus hypo) volemic states. Examples are Congestive heart failure and cirrhosis, where volume overload is a problem, but kidneys are still unperfused due to low CO.

Question 35

Please name as many causes of pre-renal azotemia as you can.

Answer 35

Due to decreased volume - GI losses, Hemorrhage, 3rd space losses, renal losses

Due to low CO - CHF, MI, valvular disease, tamponade

Due to systemic arterial vasodilation - cirrhosis, sepsis, medication, autonomic neuropathy

Question 36

Please name as many causes of post-renal azotemia as you can.

Answer 36

Obstruction of ureters:
–Extraureteral (e.g. carcinoma of the cervix,
endometriosis, retroperitoneal fibrosis, ureteral ligation) o Intraureteral (e.g. stones, blood clots, sloughed papilla).

–Bladder outlet obstruction (e.g. bladder carcinoma, urinary infection, neuropathy).

–Urethral obstruction (e.g. posterior urethral valves, prostatic hypertrophy or carcinoma).

Question 37

Please state the four categories of intrinsic glomerular disease and give some specific examples.

Answer 37

Vascular diseases: e.g. cholesterol emboli, renal vein thrombosis

Glomerular diseases: e.g. acute glomerulonephritis, hemolytic uremic
syndrome

Interstitial diseases: Acute interstitial nephritis (e.g. allergic interstitial nephritis (AIN)), infection, myeloma kidney.

Tubular diseases: Ischemic or nephrotoxic acute tubular necrosis (ATN).

Question 38

True/False: Hyaline casts are found in healthy individuals and are not associated with pathology. (What forms these casts)

Answer 38

True. Tamm-Horsfall proteins secreted by the tubular cells form these proteins.