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Renal Function - Exam 1 Flashcards

1
Q

What are the 8 major renal functions?

A
  1. excretion of metabolic waste and foreign substances
  2. regulates water and electrolyte balance
  3. regulates plasma osmolality
  4. regulates RBC production by managing erythropoietin secretion
  5. regulates BP and vascular resistance
  6. regulates acid/base balance
  7. regulates Vit D production and bone mineral balance
  8. gluconeogenesis (especially during periods of prolonged fasting)
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2
Q

What are the following substances in the body wastes products?

Proteins
Nucleic Acid
Muscle Creatine
Hemoglobin

A

Proteins -> Urea
Nucleic Acid -> Uric acid
Muscle Creatine -> Creatinine
Hemoglobin -> Urobilin

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3
Q

What causes renin to be released? What happens next? _______ also impacts BP

A

↓ renal BP causes juxtaglomerular cells in afferent arteriole to release renin

Renin → peripheral vasoconstriction → ↑ BP

Maintenance of extracellular fluid volume also impacts BP

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4
Q

What happens in a heathy kidney when it senses a lower oxygen level?

A

Low oxygen levels trigger erythropoietin production by interstitial cells, leading to increased RBC production

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5
Q

What is happening in a diseased kidney in terms of oxygen consumption?

A

Slower local oxygen consumption of diseased renal tissue means oxygen levels do not drop at the same rate as the rest of the body and erythropoietin production is blunted

aka damaged kidneys use less oxygen due to damaged tissue so the rest of the body is hypoxic when the damaged kidney thinks everything is fine and does NOT release enough erythropoietin

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6
Q

What form of Vit D is made in the kidneys? What 2 things does the kidneys excrete excess of ?

A

Active vitamin D (calcitriol) is made in the kidneys

Kidneys excrete excess phosphorus or calcium

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7
Q

When are the kidneys important to gluconeogensis?

A

Most occurs in the liver, but kidneys also contribute, especially in a prolonged fast

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8
Q

What cavity are the kidneys a part of? What is the curved (medial) side of the kidney called?

A

retroperitoneal

hilum

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9
Q

Organized in pyramid-like structures collectively known as the ______. Pyramids end in ____ that are serviced by ______.

A

renal medulla

papillae

minor calyces

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10
Q

Medulla is surrounded by the _____ which itself is covered by a thin fibrous connective tissue capsule

A

renal cortex

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11
Q

______ are the part of the renal anatomy that are composed of the fluid and cells that secrete ECM. Some cell secrete _____

A

Interstitium

some cells secrete EPO

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12
Q

Describe the organization of the renal cortex and medulla?

A

Cortex: tubules and blood vessels are randomly intertwined

medulla: tubules and blood vessels are arranged parallel

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13
Q

How many nephrons are in a normal kidney? Are cortical and juxtamedullary tubules the same?

A

approximately 225-900k per kidney (Prof Jensen said closer to the 900K side)

NO! Cortical and juxtamedullary nephrons have differing tubules

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14
Q

What is the renal corpuscle? What is the collecting duct made from? Where does the collecting duct terminate?

A

beginning of nephron: Glomerulus + glomerular capsule

made from merged tubules
Collecting ducts merge and terminate in the renal papilla

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15
Q

Compare and contrast a juxtamedullary and cortical nephron

A
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16
Q

What is the major role of the juxtamedullary nephron?

A

urine concentration

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17
Q

What is the renal corpuscle? What does it surround?

A

Hollow sphere (Bowman’s capsule) made of epithelial cells, surrounding glomerulus

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18
Q

What direction does the blood flow in the afferent arteriole? What is important to note about it? What direction does the blood flow in the efferent arteriole?

A

carries blood INTO the corpuscle

Contains specialized juxtaglomerular (granular) cells next to the macula densa
Produce, store, and release renin

Efferent: OUT OF

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19
Q

______ is the interconnected capillary loops. What is filtered here?

A

Glomerulus

plasma is filtered through the glomerulus

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20
Q

Fluids and substances to be excreted exit glomerulus capillaries and enter ______. ______ surround capillary loops of the glomerulus

A

Bowman’s space

Podocytes

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21
Q

What are 2 responsibilities of podocytes? Where are they found?

A

Remove material trapped in the wall of the capillaries
Contract capillaries if needed

surround capillary loops of the glomerulus

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22
Q

What kind of cells release renin?

A

Juxtaglomerular cells

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23
Q

Which part of the tubule is the majority in the cortex? and which descends into the medulla?

A

Proximal convoluted tubule - in cortex

Proximal straight tubule - descends into medulla

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24
Q

Where is the macula densa found?

A

in the thick ascending limb of the LOH

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25
_____ is the third segment and known as the distal convoluted tubule. What is this section responsible for?
distal tubule acid/base balance
26
_____ is the last segment and joins tubules from nephrons that eventually empty into a minor calyx
collecting duct
27
_____ is the MC form of renal fusion. What is the cause?
horsehoe kidney thought to occur during fetal organogenesis (week 5 or earlier)
28
_____ is the MC presenting complaint in kids with horseshoe kidney?
**UTI but will present with complaints of abdominal pain and bloating
29
What are some common complications associated with a horseshoe kidney? What is the MC?
**Ureteropelvic junction obstruction- MC Urinary obstruction / hydronephrosis Renal lithiasis (kidney stones) Urinary tract infections Vesicoureteral reflux (weird angle of attachment) ↑ incidence of renal tumors/cancer ↑ incidence of CKD
30
What is the best way to dx a horseshoe kidney? What is the tx?
Abdominopelvic Ultrasonography (US)- preferred Voiding cystourethrogram (VCUG) Urinalysis/Urine Culture Renal function labs medical and surgical management. Surgically splitting the kidney is NOT preferred due to complications of blood and urine supply/output
31
What is happening in the Bowman's capsule?
Glomerular filtrate - like plasma, but minus large plasma proteins (albumin, globulins, etc.) Substances present in filtrate at the same concentration as plasma = “freely filtered” Na, K, Cl, HCO3 glucose, urea, amino acids insulin, ADH
32
What is the normal GFR for a healthy adult male? How many times a day does a healthy kidney filter all of the plasma?
125 mL/min 60 times a day
33
What is the circle section called? What is being reabsorbed here? What is the major one?
Proximal tubule reabsorbs: ~60% of NaCl and H2O ~90% of filtered HCO3- Almost all **glucose**, amino acids Most K, PO4, Ca, Mg, urea, uric acid
34
What is produced in the proximal tubule? What is secreted in the proximal tubule? **What is the major one?
ammonia urate creatinine urea **ammonia** protein-bound drugs
35
What is the circled part called? What is its major role?
Loop of Henle Important role in concentration of urine through a process known as the countercurrent mechanism
36
Where do loop diuretics work?
thick ascending limb of the loop of Henle these are the most potent diuretics
37
Where in the LOH are water and NaCl reabsorbed? What 2 additional things are reabsorbed here?
Reabsorbs: H2O → descending ~25% NaCl → ascending Some calcium and most magnesium
38
Briefly describe the countercurrent mechanism
water leaves during the descending LOH and the urine inside the nephron becomes very salty thin ascending loop the NaCl leaves and the urine becomes less concentrated thick ascending loop the NaCl are actively transported out and the urine looses more salt concentration during the collecting duct water leaves again causing the urine to increase in saltiness and in the medullary collecting duct urea and water leave which results in a super concentrated urine
39
What is section 3 named? Is it permeable to water? What is happening?
Descending Loop of Henle Highly water-permeable Reabsorbs… ~15% H2O
40
What is the section 4 called? Is it permeable to water? What is happening?
Thin Ascending Loop of Henle Impermeable to water and ions except Na+ and Cl-, which are reabsorbed by diffusion
41
What is section 5 called? Is it permeable to water? What is happening?
Thick Ascending Loop of Henle Very low water permeability Reabsorbs… NaCl via Na+/K+/2 Cl- pump Target for loop diuretics Some Calcium and Magnesium May HCO3- reabsorption May see secretion of urea
42
What is this section called? What is happening?
Distal tubule
43
Where do thiazide diuretics work on?
distal tubule
44
What is the blue circle called? What is the yellow? red? What is the function of each?
blue: collecting duct yellow: cortical collecting duct red: medullary collecting duct
45
Need to know what gets reabsorbed, excreted, the name and if any drugs act on the area for every section of the nephron.
do it!!!!!
46
What are the 3 causes of ACUTE nephron injury?
hypotension (due to blood loss, septic shock, dehydration, HF) obstruction of urine flow substances
47
What are some causes of chronic nephron injury?
Diabetes Mellitus HTN Cardiorenal syndrome Autoimmune diseases Infection/Inflammation Polycystic disease Nephrotoxic Substances
48
T/F: Nephrons will regenerate after loss
FALSE!!! they will NOT regenerate
49
____ is one way the kidney adapts to nephron loss. Name 3 causes in which this is normally seen. Need to have ___ function
Compensatory renal hypertrophy (increases the size of each cell in nephron) hyperfiltration can occur in: Pts born with one kidney Loss or donation of a kidney Pregnancy 80% function is pt was previously healthy
50
______ results when there is a significant destruction in the amount of nephrons and the nephrons cannot compensate?
End Stage Renal Disease (ESRD)
51
What is the renal progression due to severe or persistent disease? What does the matrix become?
Persistent glomerular HTN → Damaged glomeruli → Cellular distress and proteinuria → Inflammatory immune response → Renal tissue responds to inflammation with fibroblasts → Fibroblasts lay matrix that disrupts capillaries and tubules → Matrix becomes an acellular scar
52
What does GFR represent? What is normal? What is early CKD? What is CKD?
Gives rough estimate of the # of functioning nephrons normal: 100-125 mL/min/1.73 m **early CKD: 60-99 mL/min/1.73 m2 for 3+ mo with kidney damage markers** chronic kidney disease (CKD): GFR < 60 mL/min/1.73 m2 for 3+ mo
53
Which is better, serial GFRs or isolated GFR?
serial GFR!! it is all relative
54
What are 3 substances that are helpful when looking at the GFR?
Blood Urea Nitrogen (BUN) Serum Creatinine (Cr) Cystatin C
55
What are some factors that affect GFR estimation?
body surface area (larger body size, higher GFR) age (GFR decreases with age) gender (males tend to be higher due to higher average muscle mass and creatinine generation) some GFR calculation consider race but some do NOT
56
Where is creatine found/manufactured?
50% manufactured by the liver 50% absorbed from food (meat)
57
How is creatine used for fuel?
Creatine is taken up by high-metabolism tissues (skeletal muscle, brain) Metabolized by creatine kinase into creatine phosphate, which can be used to fuel production of ATP
58
_____ is a waste by-product of the metabolism of creatine and is produced at a fairly steady rate
Creatinine
59
Higher muscle mass leads to ____ serum creatinine and _____ GFR
higher muscle mass leads to higher serum creatinine and lower GFR
60
How are creatinine and GFR related?
inversely related, when one is higher the other is lower
61
People who have had their legs amputated will have higher/lower creatinine?
lower creatinine due to lower muscle mass
62
What are some factors that influence serum creatinine and GFR?
muscle mass dietary intake medications liver dz stage of CKD
63
What medications specifically effect serum creatinine and GFR? What effect does it have?
cephalosporins, aminoglycosides, trimethoprim cimetidine increased serum creatinine and lower GFR
64
What effect does liver dz have on creatinine and GFR?
decreased liver production of creatine = lower creatinine and higher GFR
65
What effect does early CKD have on serum Cr and GFR? Late CKD?
Early CKD - creatinine secretion is enhanced, blunting the expected rise in serum Cr Late CKD - extrarenal creatinine elimination increases, blunting expected rise in Cr
66
What does estimating the creatinine clearance using a 24 hour urine sample tell you?
Estimates renal function at a HIGHER level than GFR, because creatinine is secreted by proximal tubule as well as filtered by the glomerulus “The upper limit of what the true GFR may be”
67
What are the pt education points when instructing a pt on the 24 hour creatinine clearance test?
68
What are the 4 limitations of a 24 hour urine CrCl?
69
______ is produced by the liver as a waste by-product of the digestion of protein. What does BUN stand for?
Urea Blood Urea Nitrogen
70
approximately _____ of urea is reabsorbed in the renal tubules. What happens when the pt is dehydrated vs overhydrated?
30-70% dehydrated: BUN will be elevated because reabsorption increases in volume depleted pts overhydrated: BUN will be low because reabsorption decreased in volume replete pts
71
What is the normal BUN:Cr ratio? What happens when a person is dehydrated?
Normal BUN:Cr ratio - 10:1 to 20:1 Volume depletion - ratio may increase (20:1 or higher)
72
What are some factors that increase BUN?
RAS stands for renal artery stenosis
73
What factors will decrease BUN?
74
How are BUN and GFR related? Is the rate of urea production constant? What percent is passively reabsorbed? What happens when a person is volume depleted?
BUN and GFR are inversely related NOT constant!! 40-50% of filtered urea is passively reabsorbed urea reabsorption is increased in volume depletion
75
Is BUN or serum Cr more useful for calculating GFR? When is BUN used the most?
BUN is less helpful that serum CR BUN is the MOST helpful in severe CKD pts
76
______ is a protein produced at a fairly steady rate by all nucleated cells in the body. Is it freely filtered? reabsorbed? metabolized?
Cystatin C Freely filtered by the glomerulus Does NOT get reabsorbed in the tubules does get metabolized
77
Which one, cystatin C or creatinine, is LESS affected by muscle mass and metabolism?
cystatin C is less directly affected by muscle mass and metabolism than creatinine Not as impacted by age, sex, gender, or race as creatinine aka cystatin C is more stable of a test and is less swayed by outside factors
78
What are some factors that increase cystatin C? decrease?
79
When GFR is increasing what 3 things are decreasing?
decrease in BUN, creatinine and cystatin C
80
When is cystatin C used the most? Why?
Mostly used when high risk for creatinine not being as accurate especially in: Elderly patients Body builders Acutely ill patients, especially those with acute changes in muscle mass aka: amputations, cancer pts MORE EXPENSIVE!
81
What is the Cockcrault-Gault Equation based on? **Is is considered accurate? What are the limitations?
Estimates CrCl based on serum Cr in a pt with stable Cr **Overestimates CrCl - generally considered low accuracy limitations: does not account for BSA and highly dependent on serum Cr
82
What is the MDRD Study Equation based on? Is it accurate? What is an important thing to note?
Estimates GFR adjusted for body surface area More accurate than Cockroft-Gault formula need to adjust result for black patients
83
______ is more accurate estimate of GFR than MDRD or Cockrault-Gault equation. **Do you need to adjust it for race?
CKD-EPI Study No longer adjusted for racial status in US
84
_____ is the preferred GFR equation in the US. Does it use race a factor?
CKD-EPI 2021 does NOT adjust for race
85

GU (13 decks)

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