Download Renal26-PreExamReviewII

Renal Test Review
3/24/2003, 10 am
Dr. Mallet
Misti Guarnere
Proscribe: Kevin Stancoven
Page 1 of 5
TEST REVIEW
Dr. Rosales couldn’t make it to the review, so if you have any questions about anatomy, you can go up to
his office and ask him.
Dr. Mallet presented a lot of slides from the class notes power points. I am not going to include all the
slides in this scribe, if you want to look at them, they are on the internet in the course website. Each
number in the outline below is the heading of the slide that he was talking about during the review. I am
only including what he said during the review, not what is on each slide.
1.
Basic process of urine formation
a. Filtration, reabsorption, & secretion
b. Net effect of filtration – excretion
c. Rate of filtration = GFR * Plasma concentration
d. Rate of excretion = Urine concentration * urine volume
e. Filtration – excretion = net reabsorption or excretion
2. Calculation of clearance = UV/P
a. Unit is volume/time
3. Inulin clearance = GFR
a. Creatine clearance about equal to GFR
i. Monitor plasma [creatine] over time to assess renal function
4. Structure of glomerular filtration membrane
a. Know layers that filtered fluid must pass through
b. Anions are freely filterable, even though there is a negative charge at the membrane
i. Anions are very small and easily pass through the slit pores
5. UP determine by balance of 3 pressures:
a. Plasma hydrostatic pressure
b. Plasma colloid pressure
c. Bowman capsule hydrostatic pressure
6. Glomerular capillary
a. Net filtration along entire length of capillary
b. Due to very high hydrostatic pressure in glomerular capillary
c. Skeletal muscle starts off with filtration, and the end of the capillary has reabsorption
7. PGC is affected by systemic arterial pressure (PA), afferent arteriolar resistance (RA), efferent
arteriolar resistance (RE)
a. Control. By constriction of afferent & efferent arterioles
b. Constriction of efferent arterioles will raise capillary pressure & increase GFR
c. Constriction of afferent arterioles will decrease pressure & decrease GFR
8. Renal prostaglandins dampen effects of angiotensin II, sympathetics
a. Protect against ischemia when arterioles are constricted
b. Sympathetic stimulation & angiotensin-II both stimulate prostaglandin formation
i. Sympathetic stimulation & angiotensin-II both cause constriction of the
arterioles in the kidney, and prolonged constriction could lead to ischemia of the
nephron
c. Prostaglandins only dampen constriction, they don’t completely relieve it
9. Pathological proteinuria: mechanisms
a. Loss of charge/size barrier
b. PCT failure to reabsorb proteins
c. Protein overload (extreme muscle injury or myeloma)
i. Overload not detected by dipstick (no albumin in urine)
10. Changes in solute concentrations along proximal tubule
a. Understand the changes in solute concentrations as they move down the PCT
b. Inulin represents the relative amount of water reabsorbed
Renal Test Review
3/24/2003, 10 am
Dr. Mallet
Misti Guarnere
Proscribe: Kevin Stancoven
Page 2 of 5
Any solute’s concentration line that is about inulin’s line will have net secretion of the
solute (PAH)
d. If the line is between inulin and Na/K, then the solute is reabsorbed some, but not as fast
as water reabsorption
e. If the line falls below the Na/K line, then all (or almost all) of the solute is reabsorbed
(glucose, amino acids, bicarb)
Mechanism: tubular Na+ reabsorption
a. Depends on Na
b. Na/K pump moves Na into interstitium
c. Na in lumen moves in down the gradient
i. Na entry often linked to absorption/secretion of other solutes
1. Ex.: glucose, K, H, etc…
d. Water follow Na via osmosis (next slide)
PCT: Example: Glucose reabsorption
a. Glucose & amino acids absorption only occurs in the PCT
b. Na moving into the cell provides energy for glucose to move into the cell against its
gradient
c. Same process for amino acids, although different transport proteins are used
Glucose reabsorption is saturable
i. Threshold – plasma concentration of glucose when glucose begins to appear in
the urine
ii. Threshold can be altered by GFR
1. increased GFR will decrease threshold
2. decreased GFR will increase threshold
Secretion of organic anions and cations
a. 3 active transport
b. PAH secretion: -KG & PAH absorbed from blood & PAH is exchanged with another
anion from the lumen
i. PAH clearance = renal plasma flow
ii. PAH competes with other anions to be secreted, & can prolong the effects of
certain medications that are anions
Tubular handling of organic acids and bases is affected by pH of luminal fluid
a. Acids – neutral form is HA (protonated) & is lipid soluble
i. Acid in the tubular lumen favors reabsorption of organic acids, but traps organic
bases in the lumen
b. Bases – neutral form is B (deprotonated) & is lipid soluble
c. Secretion of H+ favors absorption of acids & secretion of bases
Transport in Thick Ascending Limb of Henle’s loop
a. Na, K, 2Cl cotransport establishes the osmotic gradient & acts as a countercurrent
multiplier
i. Cotransporter concentrates the interstitial solute concentration
ii. Cotransporter is often the target of loop diuretics
Cation transport in collecting duct
a. Na enters principal cell via Na channels & K/H secretion occurs at the same time
i. The more Na reabsorbed, the more K or H is secreted into the lumen
b. Diuretics working on the nephron above the collecting duct will increase the [Na] in the
lumen at the collecting duct, and this will cause an increase in the amount of K/H
secretion
i. Predisposes the patient to hypokalemia or alkalemia
Antidiuresis: High ADH
a. High ADH secreted causes high solute concentration
b. Water is reabsorbed from the collecting duct because of the high insterstial [solute]
c.
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Renal Test Review
3/24/2003, 10 am
Dr. Mallet
Misti Guarnere
Proscribe: Kevin Stancoven
Page 3 of 5
c.
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Water is removed from the descending loop of Henle and taken away by the vasa recta to
maintain high insterstial [solute]
d. Water in vasa recta leaks out as the vessel moves down into the inner medulla, and is
later reabsorbed as the vessels moves back up into the cortex
Urea is concentrated in inner medulla
a. Urea reabsorption is high, further contributing to the high insterstial [solute]
Lumen osmolality along nephron length
a. Look at graph and notice the differences in osmolality in the nephron in both diuresis &
anti-diuresis
Free water clearance
a. Clearance of pure water from the plasma (by kidneys)
b. If urine is more dilute than plasma, then water is cleared from the body
c. If urine is more concentrated than plasma, then water is retained by the kidneys
Fractional excretion
a. Know how to calculate
Filtration fraction (no slide)
a. % of renal plasma flow that is filtered
b. GFR/Renal flow
Renal Fraction (no slide)
a. % of cardiac output flowing through the kidneys
Sympathetics stimulate Na+ reabsorption, renin secretion
a. Sympathetic stimulation increases Na reabsorption & renin secretion
b. Direct effect – Na reabsorption in PCT
c. Indirect effect – Renin secretion (angiotensin-II)
Angiotensin-II stimulates:
a. Systemic arteriolar constriction
b. Renal arteriolar constriction: efferents > afferents
c. Proximal tubular Na+ reabsorption
d. Thirst
e. ADH secretion from posterior pituitary
f. Aldosterone secretion from adrenal cortex
Factors controlling aldosterone secretion
a. Increase [K], [ACTH], [angiotensin-II]
b. ANP will suppress aldosterone release
ANP increases Na excretion
a. Increases GFR – afferent arteriole will dilate & efferent arteriole will constrict
b. Inhibits Na reabsorption in medullary collecting duct
c. Suppresses renin & aldosterone secretion
d. Systemic vasodilator
Plasma ADH vs. osmolality, blood volume
a. ADH more sensitive to osmolality changes
i. Fine tunes water control
b. Changes in blood volume (baroreceptors) will stimulate much more ADH to be released
Integrated response to hemorrhage
a. Look at flow chart on slide
Increased water retention following hemorrhage
a. Look at flow chart on slide
Disorder of salt & water balance
a. Hyponatremia & hyponatremia
i. Pseudohyponatremia
ii. Osmolar gap
b. Hypovolemia & hypervolemia (signs & symptoms)
Renal Test Review
3/24/2003, 10 am
Dr. Mallet
Misti Guarnere
Proscribe: Kevin Stancoven
Page 4 of 5
33.
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i. Orthostatic hypotension & tachycardia
ii. CHF (edema)
c. Inappropriate ADH
d. Diabetes insipidous
i. Central & nephrogenic
K secretion in the collecting duct
a. Na diffuses into the cell, K diffuse into the lumen
b. Stimulated by aldosterone
Four factors affect K+ secretion in collecting duct
a. Extracellular K+ concentration
b. Na+ concentration in tubular lumen: Na+/ K+ ‘exchange’ across luminal membrane
c. Extracellular pH: K+ and H+ exchange across cell membranes
d. Aldosterone: Stimulates K+ secretion in collecting duct
Cation exchanges in principal cells
a. Lower arterial pH (increased [H]) will cause more H to move into cell from interstitium
(K will move out of cell into interstitium), which will decrease the [K] inside the
principal cell, which will cause less K to be secreted into the lumen
b. Summary: low pH will decrease K secretion into urine
c. Vice versa for high pH
Diuretics
a. Know:
i. Different classes
ii. Where they act
iii. What processes are inhibited
b. May predispose patient to hypokalemia
PTH & calcitriol (vit. D3)
a. Both increase [Ca] in the plasma
b. Both increase phosphate excretion in urine
c. Know mechanisms for increasing [Ca]
Innervation of urinary tract
a. Know what innervated different parts of urinary tract
Innervation of bladder & urethra
a. Know what is innervated by:
i. Sensory fibers
ii. Parasympathetic fibers
iii. Sympathetic fibers
iv. Somatic (motor) fibers
Abnormalities of micturition
a. Know 4 abnormalities & why they occur
3 lines of defense against pH changes
a. Buffers
b. Respiration
c. Kidney function
Bicarbonate system
a. Openly adjusted buffers system
b. Adjusted by lungs & kidneys
Acidification of urine begins in PCT
a. Look at diagram
Collecting ducts can secrete H or HCO3
a.  intercalated cells secrete H
b.  intercalated cells secret HCO3
Mechanism to reabsorb filtered HCO3-
Renal Test Review
3/24/2003, 10 am
Dr. Mallet
Misti Guarnere
Proscribe: Kevin Stancoven
Page 5 of 5
a. Understand mechanism
46. H secretion
a. H is secreted either as
i. Titratable acid (phosphate)
1. look at diagram of mechanism
ii. ammonium
1. look at diagram of mechanism
47. Factors controlling renal H+ secretion
a. Aldosterone – increases Na reabsorption & increases H secretion
b. Plasma [K] – decreased [K] in plasma will decrease H secretion
c. Plasma PCO2 – increases PCO2 will increase H secretion
d. Lumen [Na] – increased lumen [Na] will increase H secretion
48. Davenport diagram
a. Won’t be on test, but understand how to tell if acidosis (or alkalosis) is respiratory or
metabolic
b. Also be able to determine is any compensation is present
49. Anion gap
a. Diagnosis of metabolic acidosis
b. [Na] – [Cl] – [HCO3]
i. normal gap is between 5-12
c. Know what changes vomiting & diarrhea will have on anion gap & pH