Exam 1: Lectures 3 & 4 Flashcards
What are the three systems that are used to maintain acid-base balance in the body?
-Blood buffer systems (Hemoglobin, proteins, inorganic phosphates)
-Pulmonary system (exhaling CO2 acid)
-Renal system (increase or decrease reabsorption of bicarbonate, excretion of H ions, formation of ammonia)
In acidic blood conditions, H+ ions are secreted in exchange for _________ and __________.
sodium, bicarbonate ions
In acidotic conditions, ammonia diffuses into the tubular lumen and subsequently ________ ions are reabsorbed while ammonium ions are excreted
sodium
In alkalotic blood conditions, tubular secretion of what is minimized?
and what is secreted more?
H+, bicarbonate
ammonia then combines with hydrogen ions to form ammonium ions in the tubular lumen to help regulate the (H+) concentration of urine.
Hydrogen ions are produced as waste from metabolism and are generally __________.
secreted
Bicarbonate can also be secreted but is more often reabsorbed, (usually up to _____ %) to help maintain the proper blood pH.
100
True or False?
The kidney plays the major role in metabolic acidosis, metabolic alkalosis, and in the compensation of respiratory acidosis or alkalosis.
true
What cells produce Renin?
juxtaglomerular cells
What reacts with the precursor angiotensinogen in the blood to produce angiotensin I?
Renin
Where is angiotensin I converted to angiotensin II?
in the lungs
How does the renal system control blood pressure?
at the juxtaglomerular apparatus by constriction of afferent arterioles under the control of renin
an enzyme produced by the juxtaglomerular cells, is secreted and reacts with the precursor angiotensinogen in the blood to produce angiotensin I.
Renin
Angiotensin I passes through the lungs where the enzyme ____________ changes it to the active angiotensin II.
angiotensin converting enzyme (ACE)
What are ACE inhibitors used to treat?
high blood pressure
What effect does angiotensin II have?
-vasoconstrictor (corrects blood flow in the efferent arterioles)
-stimulates the release of aldosterone (to retain Na and excrete K+)
-triggers release of ADH (vasopressin)
What happens when blood pressure is high or potassium decreases?
-renin is inhibited
-angiotensin inhibited
-sodium is excreted
Angiotensin II corrects renal blood flow by _________ the afferent arteriole and __________ the efferent arteriole, by stimulating sodium reabsorption in the proximal convoluted tubule
dilating, constricting
If water conservation is not needed, ADH is not secreted and the duct remains ___________ to water. the result is dilute urine.
impermeable
If the body becomes dehydrated, what does ADH do at the distal tubule and collecting ducts?
increases water permeability
Water diffuses into surrounding fluids (reabsorbed) resulting in concentrated urine.
______ enhances countercurrent multiplication and urea cycling by increasing transport of Na+ in LH
ADH
The ascending loop is impervious to water but actively recovers _____ reducing filtrate osmolarity to ______ mOsmol/kg.
Na+, 50-100
The descending and ascending loop and vasa recta form a countercurrent multiplier system to increase ________concentration in the kidney medulla.
Na+
Nearly ____ percent of water is recovered before the forming urine reaches the DCT, which will recover another ____ percent.
90, 10
_______ and __________ are involved in the regulation of blood pressure
Renin, angiotensin
In the collecting ducts, ADH stimulates _________ channel insertion to increase water recovery and thereby regulate osmolarity of the blood. Aldosterone stimulates Na+recovery by the collecting duct.
aquaporin
What are the two ways filtration can be indirectly estimated?
-classic clearance tests using a surrogate
-eGFR using serum creatine
Why is eGFR used instead of clearance tests?
Clearance tests slightly overestimate GFR so eGFR is more commonly used.
For clearance tests, the surrogate has to be…
-endogenous preferred
-completely filterable from plasma
-not be secreted by the renal tubules
-not be reabsorbed by the renal tubules
Test that measures the rate at which the kidneys can remove a filterable substance from the blood
clearance tests
We measure glomerular filtration rate (GFR) by comparing creatinine level urine collected over 24 hours compared to that of…
blood
What are the reported units for GFR?
ml/min
How is the creatinine clearance test preformed?
-pt collects urine for 24 hours
-draw blood and test for creatinine levels
-obtain height and weight info
-use GFR formula
Kidney damage is associated with a GFR of less than ____.
60
How many stages of chronic kidney disease are there?
5 (5 being the worst)
Creatinine is produced as a result of ________ destruction.
muscle
Men clear creatinine at a rate of _______ mL/min and women clear at a rate of ______ mL/min
110 to 150 mL/min
100 to 130 mL/min
Normal reference range of plasma creatinine?
0.5 to1.5 mg/dL
GFD decreased with….
age
Many medications must be adjusted for when renal impairment that is below ____mL/min
50
What is the standard clearance formula?
corrected clearance formula?
C = U * V / P
C = [U * V / P] x [1.73m^2/body surface area)
U = urine concentration
P = plasma concentration
V = volume of urine excreted
Using the Dubois equation, how is body surface area calculated?
BSA (m2) = 0.007184 x Height(cm)^0.725x Weight(kg)^0.425
The best overall index of kidney function is?
GFR
Why is the Cockcroft-Gault (CG) formula not recommended for clinical use.
formula has not been expressed using standardized creatinine values and it will give inaccurate results
The National Kidney Foundation recommends using the __________ Equation (2021) to estimate GFR.
CKD-EPI Creatinine
What is the CKD-EPI Creatine Equation (2021)?
eGFRcr = 142 x min(Scr/κ, 1)α x max(Scr/κ, 1)-1.200 x 0.9938Age x 1.012 [if female]
Scr = standardized serum creatinine in mg/dL
κ = 0.7 (females) or 0.9 (males)
α = -0.241 (female) or -0.302 (male)
min(Scr/κ, 1) is the minimum of Scr/κ or 1.0
max(Scr/κ, 1) is the maximum of Scr/κ or 1.0
What are the limitations of GFR calculations?
-Overestimates GFR by about 10%
-Tubular secretion increases with high blood creatinine levels
-Gentamicin, cephalosporins, and cimetidine inhibit tubular secretion
-Bacteria break down creatinine if urine is stored at room temperature
-Diet heavy in meat during timed collection increases urine creatinine
-Accurate results depend on the accurate completing of a 24-hour collection
-It must be corrected for smaller/larger body surface area
What method does not require urine collection and is used for long term monitoring?
Cystatin C
-test uses anti-cystatin antibodies
Small protein produced by all nucleated cells; filtered by glomerulus
Cystatin C
Why is cystatin C used for assessing renal function?
Absorbed and catalyzed by the renal tubules and broken down; no cystatin C is secreted. Levels in the blood remain at a constant level. When GFR is decreased, cystatin c levels are increased in blood.
-Serum levels directly reflect GFR
What test is essential for monitoring renal disease progression?
Cystatin C
Cystatin C is used to determine….
drug dosages and evaluating uremia
Normal range for Cystatin C?
0.51 - 0.98 mg/L
Beta2 microglobulin test can be run on what type of samples?
urine and/or serum
Small protein that dissociates from human leukocyte antigens at a constant Reabsorbed completely in normally functioning kidney but shows up in urine when tubular reabsorption is impaired.
Beta2 microglobulin
sensitive indicator of a decrease in GFR
Beta2 microglobulin
What can the Beta2 microglobulin test determine?
Indicates kidney transplant rejection or people with impaired or distinguishes tubular damage from glomeruli dysfunction.
Beta2 microglobulin:
If high in urine but normal in serum:
If high in blood but low in urine:
tubular dysfunction
glomeruli dysfunction
____________ appears early in diabetic nephropathy and persons with high blood pressure.
Albuminuria
What causes the presence of albumin in urine?
increased glomerular permeability due to changes in glomerular filtration barrier
What should be done if there is early detection of microalbuminuria?
additional testing and aggressive intervention
A microalbumin to creatinine ratio of ____ mg/g is considered diagnostic of microalbuminuria.***
greater than 30
(albumin/creatine)
Why is the urine dipstick an insensitive marker for albuminuria?
will not be positive till it exceeds 300 to 500 mg/day.
using a specific assay for albumin is a more sensitive technique.
What is the normal rate of albumin excretion?
less than 30 mg/day
What albumin excretion levels is moderately increased albuminuria?
30-300 mg/day
How is ACR calculated?
ACR is calculated by dividing albumin concentration in milligrams by creatinine concentration in grams.
Have to use g/dL creatinine, not mg/dL
Why would a physician want to assess tubular function?
to test the ability to reabsorb substances and concentrate urine.
What is the SG of urine just after filtration?
1.010
Why would the specific gravity remain fixed at 1.010 regardless of water intake or hydration level?
Patients with loss of tubular function lose the ability to adjust the filtrate.
(the first a.m. specimen will be the same as the last p.m. specimen)
Tubular reabsorption tests are a good indicator of…
early renal disease
Measure renal concentrating ability
(Salts and water)
What are tubular reabsorption tests often termed?
concentration or fluid deprivation tests
What are two tests used to measure concentration?
-specific gravity
-osmolality
(non-specific, but good for screening)
normal range for specific gravity?
1.003 to 1.035
What is one of the first functions to be lost as result of tubular damage?
the concentrating ability of the kidney
