Week 1 Review Session

Question 1

I did a kidney biopsy last week. The needle inadvertently went through the cortex and into the medulla. Which artery was most likely to have been punctured in the process?

Answer 1

Arcuate artery

Arcuate artery is between the cortex and medulla

Question 2

An increase in flow/NaCl delivery at the macula densa leads to which one of the following?

Answer 2

Afferent arteriolar vasoconstriction
Because more NaCl delivery = more kidney wants to retain shit = decrease GFR
Upregulates renin and modulates afferent arteriole
Does not say shit about efferent arteriole

Question 3

Why doesn’t capillary hydrostatic pressure not vary by much?

Answer 3

Because of modulation by afferent and efferent arteriole

Question 4

Which one of the following is most likely to increase GFR?

Answer 4

Afferent arteriolar dilatation

Question 5

Which one of the following is an important features that makes a substance a good marker of GFR?

Answer 5

Neither secreted nor reabsorbed

Example: Inulin

Question 6

What is clearance?

Answer 6

The volume per unit time of plasma from which the solute was completely removed
No single ml is actually cleared of all that substance, but rather some smaller quantity is removed from each of the many ml that pass through the kidneys

Question 7

Question 5: What is serum creatinine determined by?

Answer 7

Muscle mass
GFR
Higher muscle mass = greater GFR

Question 8

Under steady state conditions, which one of the following is correct?

Answer 8

ICF osmolarity = ECF osmolarity
ECF volume is a function of ECF effective solute content
ICF volume is a function of ICF effective solute content

Question 9

How do you quickly estimate plasma osmolality?

Answer 9

2*Na + 10

Question 10

How do you quickly estimate plasma tonicity?

Answer 10

2*Na + 5

Question 11

On the first day of your surgery clerkship, the Attending tells you to make sure her patient gets some extra IV saline overnight since her serum Na is low and therefore she is volume contracted. You tell her which one of the following?

Answer 11

Answer: But, Dr. I seem to recall learning that the serum Na does NOT tell us about the intravascular volume. I better go examine the patient
Volume depletion must be found through physical exam

Question 12

What is a more effective volume expander?

Answer 12

Saline > water
That’s because water will distribute to ALL compartments (ICF and ECF)
Salt will only distribute to ECF

Question 13

What are the most significant features of proximal tubule?

Answer 13

Highest water permeability

But urine remains nearly isotonic to plasma along PT length

Question 14

Which one of the following increases PT Na reabsorption?

Answer 14

An increase in filtration fraction
-because you are delivering more fluid into the lumen
-also because you have higher oncotic pressure in blood, further reabsorbing shit in the PT
Angiotensin 2 = increases sodium reabsorption at proximal tubule, so ARB would decrease PT Na reabsorption

Question 15

The permeability to water increases most in response to AVP in which nephron segment?

Answer 15

Collecting duct

Question 16

You develop a technique to stick a long but very skinny pipette into a single nephron of a human. In one of your classmates, you find that whether water-deprived or water-loaded, the tubule fluid osmolarity is

Answer 16

The late distal convoluted tubule
Only place where it is hypotonic
Berns’ favorite question!

Question 17

What is the specific gravity?

Answer 17

1.010 = normal plasma specific gravity
-represents urine osmolality of 300 mosm/kg
1.020 = abnormal = too much
Means osmolality is now 600 mosm/kg in plasma

Question 18

Which one of these diuretics would be most useful in treating someone with hyponatremia?

Answer 18

Furosemide (loop diuretic)
Reduce ability to concentrate urine in order to help with hyponatremia
Other diuretics do NOT reduce ability to concentrate urine

Question 19

You calculate an electrolyte free water clearance in a patient with hyponatremia to be 100 ml/day. Which one of the following statements is correct?

Answer 19

Hyponatremia will worsen if he drinks more than 500 ml/day

Remember tonicity is different from volume and last two answer choices point to ways to correct volume