Renal1 Flashcards
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]
What are the three classifications of azotemia?
(1) pre-renal
(2) primary
(3) post-renal
What is a normal BUN:Cr ratio?
15
What is the cause of prerenal azotemia?
decreased blood flow (hypoperfusion) to the kidneys
However, there is no inherent kidney disease
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
How does plasma [K+] affect aldosterone secretion?
Increases in plasma [K+] –> increased aldosterone secretion –> increased Na reabsportion and increased K secretion
What are three toxicities of ACE inhibitors?
angioedema
hyperkalemia
chronic cough
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
Clinically, creatinine clearance is used to measure/approximate what?
GFR
(glomerular filtration rate)
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
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)
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
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
Type II diabete mellitus
DM –> hyperglycemia –> filtered load of glucose exceeds glucose transport maximum –> glucose in the urine –> osmotic diuresis
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
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.
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.
Explain the changes in concentration for inulin.
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
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
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)
Name structures a-e
a. psoas muscle
b. ureter
c. aorta
d. vertebral body
e. descending colon
