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Flashcards in Renal1 Deck (30):
1

What is azotemia?

high levels of nitrogen-containing compounds in the blood (e.g., urea, creatinine)

Azotemia is characterized in all cases by a decrease in the GFR, and increases in BUN and serum {creatinine]

2

What are the three classifications of azotemia?

(1) pre-renal

(2) primary

(3) post-renal

3

What is a normal BUN:Cr ratio?

15

4

What is the cause of prerenal azotemia?

decreased blood flow (hypoperfusion) to the kidneys

However, there is no inherent kidney disease

5

What are some common causes of prerenal azotemia? (6)

 (1) hemorrhage

(2) shock

(3) congestive heart failure

(4) volume depletion

(5) adrenal insufficiency

(6) narrowing of the renal artery

6

How does plasma [K+] affect aldosterone secretion?

Increases in plasma [K+] --> increased aldosterone secretion --> increased Na reabsportion and increased K secretion

7

What are three toxicities of ACE inhibitors?

angioedema

hyperkalemia

chronic cough

 

8

What is the equation to find the filtered load of substance that is not additionally secreted or reabsorbed?

FL = GFR * plasma [ ]

mg/mL = mL/min * mg/mL

9

Clinically, creatinine clearance is used to measure/approximate what?

GFR

(glomerular filtration rate)

10

A 75 yo woman with a hx of atherosclerosis has narrowing of the renal artery lumen bilaterally. Arterial pressure distal to the stenoses has dec. by 25 mmHg. Labs show creatinine clearance of 95mL/min. What will the the affect on the GFR, efferent arteriolar resistance and renin plasma activity.

GFR: constant

Efferent artieriolar resistance: up

Renin activity: up

atherosclerosis --> dec. glomerular hydrostatic pressure --> dec. NaCl delivery to macula densa --> inc. renin release --> activation of RAA axis --> inc. angiotenisin II --> constriction of efferent arteriole --> inc. glomerular hydrostatic pressure --> inc. GFR to normal

11

Why is creatinine a good approximation of GFR? Why does creatinine overestimate GFR a bit?

Creatinine is a good approximation of GFR because is it freely filtered across the golmerular capillaries, and secretion is minimal.

It slightly overestimates the GFR because it is also secreted by from the peritubular capillaries into the proximal tubule.

(About 10-15% of the unfiltered creatinine is secreted, increasing the filtered fraction to 1.1 - 1.15)

12

Approximately what percent of unfiltered creatinine is secreted into the proximal tubule by the peritubular capillaries?

10-15%.

This explains why creatinine overestimated GFR slightly

13

A 38 yo man is brought to the ED 30 min after being in a car collision. He appears anxious but is oriented to time, person and place. Phys exam shows contusions and a shallow laceration over the left shoulder; x-ray shows no abnormalities. Labs are below. Urine output is 145mL/hr; ADH is given and 2 hr later his urine output is the same. WHich of the following is most likely responsible for his diuresis?

a. high sodium

b. hyperthyroidism

c. hypoaldosteronism

d. type 2 DM

e. vita. D deficiency

Q image thumb

Type II diabete mellitus

DM --> hyperglycemia --> filtered load of glucose exceeds  glucose transport maximum --> glucose in the urine --> osmotic diuresis

14

A 38 yo man is brought to the ED 30 min after being in a car collision. He appears anxious but is oriented to time, person and place. Phys exam shows contusions and a shallow laceration over the left shoulder; x-ray shows no abnormalities. Labs are below. Urine output is 145mL/hr; ADH is given and 2 hr later his urine output is the same. Why does this patient have hypernatremia?

a. high sodium

b. hyperthyroidism

c. hypoaldosteronism

d. type 2 DM

e. vita. D deficiency

Q image thumb

Despite the addition of ADH, the patient is still becoming deydrated due to the osmotic loss of fluid due to the DM. The patient's body will therefore activate the RAAS system to preserve blood volume. This will lead to an inc. in aldosterone --> inc. sodium reabsorption in the cortical collection duct --> hypernatremia.

 

15

A 38 yo man is brought to the ED 30 min after being in a car collision. He appears anxious but is oriented to time, person and place. Phys exam shows contusions and a shallow laceration over the left shoulder; x-ray shows no abnormalities. Labs are below. Urine output is 145mL/hr; ADH is given and 2 hr later his urine output is the same. Why can we rule out  (c)?

a. high sodium

b. hyperthyroidism

c. hypoaldosteronism

d. type 2 DM

e. vita. D deficiency

Hypoaldosteronism will not cause hypernatremia. (This patient is hypernatremic)

If a patient has hypernatremia, they likely do not have an aldosterone deficiency.

16

A previously healthy, 38 yo woman is brought to the ED after being found unconscious and lying on the ground by her coworkers. She appears severely dehydrated. Her plasma ADH level is increased 5-fold above normal. Ih which portions of her kidney tubule is most of the water being reabsored?

The proximal convoluted tubule.

Approx 66% of water and salt is reabsorbed in the proximal convoluted tubule. It is the main site of water and salt reabsorption, even in the presence of elevated ADH levels.

17

Explain the changes in concentration for inulin. 

Q image thumb

In the kidney, inulin is freely filtered, and neither excreted, nor absorbed.

The increase in concentration from 1 to 3 reflects 2/3 of the volume in the proximal convoluted tubule being reabsorbed. The increase in concentration from 3 to 12 in the distal convoluted tubule reflects 3/4 of the remaining water in the tubule being reaborbed (in the thin descending limb). The increase from 12 to 120 reflects 9/10 of the remaining water being reabsorbed in the collecting duct

18

How would the concentration for each of the following compare to inulin at the end of the proximal convoluted tubule?

a. sodium

b. creatinine

c. glucose

Q image thumb

sodium: decreased (around 1, reabsorbed in the same porportion to water)

creatinine: increased (creatinine is secreted in the proximal tubule)

glucose: decreased (should be zero; glucose in a healthy patient is entirely reabsorbed)

19

What is the fractional excretion of sodium (FENa)?

It is the precentage of sodium filtered by the kidney that is excreted in the urine.

20

What is oliguria?

Low urine output

21

A 43 yo man with renal insufficiency comes to the physician for an exam. Labs show a relatively constant production of urea and creatinine, and glomerular filtration is 60L/day. Plasma sodium is within normal limits. Further labs will most likely show which of the following?

a. elevated creatinine excretion

b. elevated urea excretion

c. increased FENa

d. Increased plasma [K+]

e. Increased plasma [Na+]

This man's GFR is down (normal is 180L/day), but his serum [Na] is normal. This must mean that is FENa (fractional excretion of Na) must be increased to maintain the normal serum sodium.

 

22

Name structures a-e

Q image thumb

a. psoas muscle

b. ureter

c. aorta

d. vertebral body

e. descending colon

23

What is nephrotic syndrome?

glomerular disorders characterized by proteinuria (>3.5g.day)

24

What classic changes are seen in the blood in someone with nephrotic syndrome? (4)

1. hypoalbuminemia --> pitting edema

2. hypogammaglobulinemia --> inc. risk of infection

3. hypercoaguable state -- due to loss of antithrombin III

4. hyperlipidemia and hypercholesterolemia --> may result in fatty casts in the urine.

25

A 48 yo man is brought to the physician because of persistent edema. Further eval. shows nephrotic syndrome. Renal biopsy confirms membranous glomerulonephritis. Which of the following substances is most likely to be elevated in this patient's plasma? Which will be decreased? Which will stay the same?

a. albumin

b. ammonia

c. glucose

d. HDL

e. LDL

f. potassium

--LDL will be elevated

--albumin and HDL will be lowered

--ammonia, glucose, and potassium will be unchanged.

 

26

What are the four causes of renal papillary necrosis?

1. chronic analgesic use

2. diabetes mellitus

3. sickle cell trait or disease

4. severe acute pyelonephritis

27

What is renal papillary necrosis?

necrosis of the renal papillae

28

How does renal papillary necrosis typically present?

with gross hematuria and flank pain.

29

A photo of a kidney specimen obtained at autopsy from a 68 yo woman is shown, Histologically, the glomeruli and interstitium are normal, but the distal portion of the renal pyramids shows coagulative necrosis. Which of the following conditions is the most likely cause?

a. DM

b. gout

c. miliary TB

d. mural thrombosis in the heart

e. recent streptococcal infection

Diabetes mellitus

coagulative necrosis of the distal portion of the renal pyrimids refers to renal papillary necrosis. Diabetes is one of the four major causes of this disease.

30

A recent streptococcal infection is associted with what type of kidney disease?

post-streptococcal glomerulonephritis, which is a nephritic syndrome.

Nephritic syndromes are glomerular disorders that are characterized by glomerular inflammation and bleeding.