FEN

Question 1

Correction of free water deficit

Answer 1

Administer 4mL/kg for every 1meq/L increase over 145

Administer 3mL/kg for Na >170

Question 2

Plasma osmolality

Answer 2

(2 x Na) + (glucose / 18) + (BUN / 2.8)

Question 3

Extrarenal ADH effect

Answer 3

Arterial vasoconstriction stimulating renal mesangial cell contraction, decrease renin secretion, and increase ACTH secretion

Question 4

Obstructive renal disorder can cause what with ADH

Answer 4

Nephrogenic DI because of the pressure which decreases aquaporin expression

Question 5

SIADH management

Answer 5

Free water restriction
If Na <120, replace with NaCl
Consider furosemide

Question 6

Diabetes insipidus management

Answer 6

Central - vasopressin/desmopressin

Nephrogenic - thiazides to increase urine concentrating ability

Question 7

Na content in hypergylcemic state

Answer 7

Na decreased by 1.6meq/L for each 100 increase in glucose (mg/dL)

Question 8

Hyponatremia bucket differential

Answer 8

Decreased weight - renal loss or extrarenal loss

Increased or normal weight

Question 9

Hyponatremic renal losses differential

Answer 9

Na losing nephropathy
Diuretics
Adrenal insufficiency

Question 10

Hyponatremic extrarenal losses

Answer 10

GI losses
Skin losses
Third spacing
Cystic fibrosis

Question 11

Increased weight hyponatremia

Answer 11

Nephrotic syndrome
CHF
SIADH
Acute or chronic renal failure
Excess water infusion
Cirrhosis

Question 12

Na deficit equation

Answer 12

deficit=(desired Na -current Na)x0.6xwt

The 0.6 is the percent body water which should be higher in preterm

Question 13

Hypokalemia differential buckets

Answer 13

Decreased stores: with hypertension or with normal BP

Normal K stores

Question 14

Decreased K stores hypokalemia and HTN

Answer 14

Renovascular disease, excess renin, excess mineralocorticoid, Cushing syndrome

Question 15

Decreased K stores normal BP

Answer 15

Renal: RTA, fanconi syndrome, bartter syndrome, antibiotics, diuretics, ampho B
Extrarenal: skin loss, GI loss, high carb diet, enemas, malnutrition

Question 16

NaHCO3 replacement equation

Answer 16

NaHCO3 replacement (mEq) = 0.3xHCO3 deficit xweight

Question 17

RTA workup

Answer 17

Serum electrolytes
Urine pH and electrolytes (calcium, citrate, potassium, oxalate)
RBUS
Urine blood partial pressure of CO2 (nl >20; type I RTA <20)
Tubular reabsorption of phosphate (TRP)

Question 18

Type I RTA

Answer 18

Distal
Cannot secrete H
Normal renal bicarbonate threshold 
Most primary causes are AD
Can have secondary causes
Urine pH >6.2

Question 19

Type II RTA

Answer 19

Proximal
Decreased or absent proximal tubular HCO3 reabsorption, reduced renal bicarbonate reabsorption threshold
Large urine losses of bicarbonate
Can have urine pH <5.3

Question 20

FENa calculation and percentages

Answer 20

FENa = (urine Na x plasma Cr) / (urine Cr x plasma Na)
<1% normal
1-2.5% prerenal
>3% intrinsic

But premature infants have difficulty holding on to Na so their FENa may be elevated even though they are intravascularly depleted. However also limited ability to excrete Na load secondary to lower GFR

Question 21

Tubular reabsorption of phosphorus (TRP) equation

Answer 21

TRP = 1 - [100 x (urine Ph x plasma Cr) / (urine Cr x plasma Ph)]

Question 22

Estimated GFR calculation

Answer 22

Estimated GFR = (0.45 x height (cm)) / (plasma cr (mg/dL))

Question 23

Creatinine clearance calculation

Answer 23

Creatinine clearance = (urine Cr x volume) / plasma cr

Question 24

Tubular dysfunction

Answer 24

Fanconi syndrome
Lowe syndrome (oculocerebrorenal syndrome)
Cystinosis

Question 25

Adverse effects of NaBicarb administration for metabolic acidosis

Answer 25

Increased PCO2
Decreased ionized calcium (because bicarb causes calcium to bind albumin)
Decreased K
Increased Na
Hypertonic so increased risk of IVH

Question 26

Renin secretion in response to

Answer 26

Decreased renal perfusion (hypotension, volume depletion), an increased sympathetic activity

Question 27

Effects of angiotensin II

Answer 27

Stimulates release of aldosterone, which acts on the kidney and increases sodium reabsorption, increases chloride, increases, potassium, secretion, increases hydrogen, secretion

Angiotensin II also increases sodium and water resorption, arteriolar, vasoconstriction, stimulates release of ADH, stimulates release of aldosterone, activates vitamin D via PTH, activates erythropoietin

Question 28

GFR calculation

Answer 28

0.45 x height (cm) / plasma creatinine (mg/dL)

Use 0.33 for preterm infants

Question 29

Creatinine clearance

Answer 29

(Urine creatinine x volume (ml/min)) / plasma creatinine

Question 30

Fanconi syndrome describe lab findings and management

Answer 30

Lab: decreased phosphate, decreased TRP, metabolic acidosis, hypokalemia, normal GFR
Management: supplement with sodium phosphate, sodium and potassium citrate, and Vit D

Question 31

Cystinosis pathogenesis, describe lab findings and management

Answer 31

Patho: defective carrier mediated transport of cystine leading to excess cystine in lysosomes of many cells
Lab: normal plasma cystine levels
Diagnosis by cornea slit lamp - crystals
Management: cysteamine, renal transplant

Question 32

Oculocerebrorenal syndrome patho, diagnosis, and management (lowes syndrome)

Answer 32

X linked
Enzyme deficiency disrupting the Golgi apparatus
Cataract, glaucoma, mental deficiency, hypotonia, tubular dysfunction
Increased amniotic fluid AFP
Management: symptom directed

Question 33

Disorders that cause nephrocalcinosis

Answer 33

Williams syndrome
Type 1 RTA
Neonatal primary hyperparathyroidism
Bartters syndrome