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GU > Lecture 1: Renal Function > Flashcards

Lecture 1: Renal Function Flashcards

1
Q

What is the excretion product of

  • Proteins
  • Nucleic Acids
  • Muscle Creatine
  • Hemoglobin
A
  • Proteins: Urea
  • Nucleic Acids: Uric acid (Purines)
  • Muscle Creatine: Creatinine
  • Hemoglobin: Urobilin
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2
Q

How do the kidneys regulate BP?

A

Decreases in renal BP lead to JG cells in the afferent to release renin.

Renin increases peripheral vasoconstriction.

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3
Q

What triggers the release of EPO from the kidneys?

A

Hypoxia.

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4
Q

Why do diseased kidneys not release EPO?

A

Hypoxia in the body is not reflected in the kidneys due to the reduced metabolism from diseased tissue. This reduces/inhibits EPO secretion.

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5
Q

Where are the kidneys located?

A
  • Retroperitoneal
  • Just below rib cage
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6
Q

What are the 3 major sections of the kidney?

A
  • Renal Cortex
  • Renal Medulla
  • Renal Pelvis
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7
Q

How does the renal cortex look like histologically?

A

Spaghetti and meatballs.
Random intertwining of tubules and blood vessels, along with renal corpuscles scattered around.

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8
Q

What does the renal medulla look like histologically?

A

Bundles of pencils.
Parallel arrangements of tubules and blood vessels.

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9
Q

What are the parts of a nephron?

A
  • Renal corpuscle: Glomerulus + capsule
  • Tubules
  • Collecting duct (merging of tubule)
  • End in the terminal papilla.
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10
Q

What are the differences between a juxtamedullary nephron vs a cortical nephron?

A
  • JM = longer, mainly for URINE concentration.
  • Cortical = shorter, only dips a little into medulla.

Cortical nephrons make up 85% of all nephrons.

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11
Q

What part of the nephron corresponds to the macula densa?

A

Thick ascending limb closest to the capsule.

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12
Q

What part of the loop of Henle does a cortical nephron lack?

A

No thin ascending limb.

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13
Q

What is a horseshoe kidney and the main concerns associated with it?

A
  • Fusion of kidneys due to failure to separate.
  • Results in abnormal blood flow and ureter coursing.
  • Also often lower in the ribcage, so it is more vulnerable to trauma.

Cannot move higher than the IME (Inferior mesenteric)

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14
Q

What is the most common complaint associated with a horseshoe kidney?

A

UTI in children.

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15
Q

What is the most common complication due to a horseshoe kidney?

A

Ureteropelvic junction obstruction

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16
Q

How is a horseshoe kidney diagnosed?

A
  • CT w/ IV pyelogram
  • UA/culture
  • Renal function labs
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17
Q

How is a horseshoe kidney treated?

A

Symptomatic management.

Surgery is not always ideal due to the scar tissue that will form.

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18
Q

How often is our plasma volume filtered daily?

A

60x, around 180L/d in a healthy male at 125 ml/min for GFR.

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19
Q

What is primarily reabsorbed in the proximal tubule?

A
  • 60% of NaCl and H2O
  • 90% of HCO3-
  • Glucose, AAs
  • Most of K, PO4, Ca, Mg, Urea, and uric acid
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20
Q

What is primarily reabsorbed in the loop of Henle?

A
  • Descending: H2O
  • Ascending: 25% of NaCl
  • Some Ca, most Mg.
21
Q

What is the primary function of the Loop of Henle?

A

Countercurrent mechanism to generate concentrated urine.

22
Q

Where do loop diuretics work on specifically?

A

Thick Ascending Limb

Na/K/2Cl pump location

23
Q

What are the primary functions of the distal tubule?

A
  • pH regulation via H+ and HCO3-
  • Calcium regulation
  • K secretion
24
Q

What are the important cells of the cortical collecting duct and their functions?

A
  • Principal cells: reabsorbing NaCl and H2O, K secretion.
  • Intercalated cells: mediate HCO3- and H+ secretion/reabsorption.

Site of action for K+ sparing diuretics (principal cells)

25
Q

What are the functions of the medullary collecting duct?

A
  • Urine modification
  • Reabsorption of NaCl, water, and urea
  • Secretion of ammonia (NH3), H+
  • Secretion/reabsorption of K+
26
Q

What are the primary etiologies of AKI?

A
  • Hypotension
  • Obstruction of urine flow
  • Substance use
27
Q

How do the kidneys compensate for injury/loss?

A

Kidneys cannot regenerate nephrons, so compensatory renal hypertrophy occurs.

Often occurs as hyperfiltration.

Essentially, sending more plasma through nephrons.

28
Q

What does ESRD result from?

A
  • Loss of 80% of renal mass
  • Destruction of a significant amount of nephrons, that cannot compensate enough.
29
Q

Why do we use ACEIs and ARBs for proteinuria even without HTN?

A

Proteinuria signals the kidney that something is wrong, and will result in inflammation if left untreated.

30
Q

How does GFR change for someone with kidney disease?

A

It can decrease, stay the same, or even increase.

31
Q

What is generally considered CKD?

A

GFR < 60 for 3mo.

32
Q

What are some of the substances used to estimate GFR?

A
  • BUN
  • Creatinine
  • Cystatin C (newer)

All freely filtered

33
Q

What is kidney function proportional to?

A

Kidney size, which is also proportional to body size.

Big people = big kidneys

34
Q

What general factors affect GFR?

A
  • Body Surface Area (BSA)
  • Age
  • Gender
  • Race
35
Q

How does higher muscle mass affect GFR?

A

Higher mass = higher serum creatinine = lower GFR

36
Q

How does having higher serum creatinine affect GFR?

A

Inversely proportional. Lower GFR with higher serum creatinine.

37
Q

How do antibiotics affect creatinine levels?

A

Inhibits renal secretion, which results in higher serum creatinine and lower GFR.

38
Q

How can liver disease mask kidney damage?

A

50% of creatinine is produced by the liver, so damage to the liver results in a lower serum creatinine and higher GFR.

39
Q

What are the measurements required for a CrCl calculation?

A
  • Serum creatinine
  • Urine creatinine
  • 24-hour urine collection

Measures the upper limit of GFR

40
Q

What is urea?

A

Liver by-product from protein digestion.
Freely filtered and reabsorbed heavily in dehydrated patients.

Functions like a sponge.

41
Q

What decreases BUN?

A
  • Liver disease
  • Malnutrition
  • SCD
  • SIADH
42
Q

What is the usual etiology of increased urea?

A

Dehydration

43
Q

When is BUN usually used as an indicator?

A

Severe CKD

44
Q

What is Cystatin C?

A

Protein made by all nucleated cells in the body and is freely filtered.

It is not as affected by muscle mass and metabolism.

45
Q

What generally decreases Cystatin C?

A
  • Female
  • Smaller body mass
46
Q

What is the main prohibitive factor in Cystatin C calculations for GFR?

A

Cost.

47
Q

What equation was first used for CrCl and why?

A

Cockcroft-Gault, which assume stable Cr.

Does not account for BSA.

48
Q

What is the successor equation to the MDRD Study equation and the Cockcroft-Gault?

A

CKD-EPI, mainly for normal-mildly reduced GFR with no racial adjustment.

Preferred equation in the US.

GU (14 decks)

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