Renal Physiology Flashcards
Distributed wherever water is found. Marker for TBW?
Titrated water
A large molecule that cannot cross cell membranes. Marker for ECF?
Mannitol
A dye that binds to serum albumin. Marker for plasma ?
Evans Blue
What’s the Clearance of Na?
Plasma Na: 140 mEq /L
Urine Na: 700mEq /L
Urine flow rate: 1ml/min
5ml/min
Urine Flow Rate = Urine Conc x Urine vol / Plasma Conc
Urine flow rate = 700 x 1ml/min / 140
Urine flow rate = 5mL/ min
Insulin is infused in a patient. Whats the GFR?
Plasma conc = 1mg/mL
Urine vol= 60ml
Inulin concentration = 120mg/mL
120mL/min
GFR= urine conc x urine vol / plasma conc
GFR= 120 x 60 per hr / 1 = 7200 /60mins
GFR= 120mL/ min
50/M untreated DM.
What’s the clearance rate?
GFR= 120mL/min
Plasma glucose= 400mg/dL
Urine glucose= 2,500mg/dL
Urine flow rate= 4mL/min
25mL/ min
Clearance Rate = UV/ P
Clearance Rate = 2,500 x 4 / 400
Clearance Rate= 25 mL/min
50/M untreated DM.
What’s the Filtration Fraction?
GFR= 120mL/min
Plasma glucose= 400mg/dL
Urine glucose= 2,500mg/dL
Urine flow rate= 4mL/min
Since PAH values are not given for this example , FF cannot be computed .
However , in this context , if we have to guess in the exam, FF is above its normal average value of 20%.
RPF & FF increases in DM , which leads to eventual increase in GFR
Excretion of morphine can be increased by acidifying or alkalinizing the urine?
Acidifying urine, morphine is weak base.
When there’s No reabsorption of the substance. What is the TF/P value?
TF/P =1.0
TF: Tubular Filtration is urine at any point along the nephron.
P: Plasma is systemic plasma. It is considered to be constant
Reabsorption of the substance has been exactly proportional to the reabsorption of water. What’s the TF/P Value?
TF/P= 1.0
Reabsorption of the substance has been greater than the reabsorption of water. What’s the TF/P value?
TF/P = <1.0
Mas lesser ang reabsorption ng water
Reabsorption of the substance has been less than the reabsorption of water. What’s the TF/P value?
TF/P >1.0
Mas Greater ang reabsorption ng water.
Secretion of the substance. What’s the TF/P value?
TF/P >1.0
Wala ge reabsorb, ge secrete
What happens to the filtered load of Na+ if GFR spontaneously increases?
Filtered load of Na also increases.
Without a change in reabsorption, this increase in GFR would lead to increased Na excretion. However, glomerulotubular balance functions such that Na reabsorption also will increase, ensuring that a constant fraction is reabsorbed.
Effect of hyperaldosteronism on K+ levels and NH3 synthesis?
Causes Hypokalemia , hypokalemia stimulates NH3 synthesis which produces increase H+ excretion
What’s the free water clearance?
Urine flow rate : 10ml/ min
Urine osmolarity: 100 mOsm/ L
Plasma osmolarity: 300 mOsm /L
+6.7 mL/ min
CH2O = V - Osmolar
Free Water Clearance = 10 - (100x10/ 300)
Free Water Clearance = 10 - 3.33
Free Water Clearance= +6.7 mL/min
Vomiting effect on H+ and HCO3 ?
Metabolic alkalosis
H is lost from the stomach
HCO3 remains behind in the blood and the
HCO3 increases
Factors that Increases K+ secretion in the DCT. (6)
- Metabolic alkalosis
- High K+ diet
- Hyperaldosteronism
- Thiazide diuretic
- Loop diuretic
- Luminal anions
Boy 1 drinks 2L distilled water.
Boy 2 drinks 2L of isotonic NaCl. Both of them weighs 70kg.
Boy 2 will have ___________ urine osmolarity?
a. Increased
b. Decreased
Increased / Higher urine osmolarity
Boy 1: after drinking a distilled water, will have an increase in ICF and ECF volumes, a decrease in plasma osmolarity @ suppression of ADH secretion , and will produce dilute urine with a high flow rate.
Boy 2 : after drinking the same vol of isotonic NaCl, will have an increase in ECF volume only and no change in plasma osmolarity . Because Boy 2 ADH will not be suppressed , he will have a higher urine osmolarity and a lower urine flow rate.
45 / M with severe diarrhea. What’s the ABG interpretation?
ABG
pH = 7.25
PCO2 = 24 mmHg
HCO3= 10mEq/L
Decreased venous K+
Normal anion gap
Metabolic acidosis
45 / M with severe diarrhea. What’s the cause of decreased K?
ABG
pH = 7.25
PCO2 = 24 mmHg
HCO3= 10mEq/L
Decreased venous K+
Normal anion gap
A result of increased circulating levels of Aldosterone.
-loss of ECF volume due to diarrhea stimulates the release of aldosterone ; thus K secretion will increase in the distal tubule.
Arterial PCO2 level that inhibits reabsorption of filtered HCO3?
Inhibited by a DECREASED in arterial PCO2
-Decrease in arterial PCO2 cause a decrease in the reabsorption of filtered HCO3 by diminishing the supply of H+ in the cell for secretion into the lumen.
If X is freely filtered , is there net secretion or reabsorption of X?
Plasma inulin = 1 mg /mL
Plasma X= 2mg/ mL
Urine Inulin= 150mg/mL
Urine X= 100mg/mL
Urine flow rate= 1mL/min
There is net reabsorption of X
GFR= 150x1 / 1 = 150
Cx= 100 x1 / 2 = 50
Clearance of X is less than the clearance of Inulin (GFR) net reabsorption of X must have occurred.
Total daily excretion of H+ should equal to what ? to maintain balance.
Fixed acid production plus fixed acid ingestion.
1 g mannitol was injected into a woman. Plasma mannitol concentration =0.08g/L and 20% of this was excreted in the urine. What is the ICF volume?
10L
1g-0.2g/ 0.08g/L= 10 L
Mannitol is a marker of ECF volume
ECF Volume = amount of mannitol / concentration of mannitol
58M/ given glucose tolerance test. What happens when the plasma glucose concentration is higher than occurs at transport maximum?
Excretion rate of glucose increases with increasing plasma glucose concentrations
58/M with oat cell carcinoma of the lung , excretes urine with an osmolarity of 1000mOsm /L. Free water clearance is?
Negative free water clearance
SIADH can occur in patients with oat cell lung cancer. Increased ADH causes increase in water reabsorption, thus negative free water clearance.
Increased in the reabsorption of isosmotic fluid in the proximal tubule can be due to a/an ________ of filtration fraction.
Increased filtration fraction
Increasing filtration fraction means that a larger portion of renal plasma flows filtered across the glomerular capillaries.
Substances that could be used to measure interstitial fluid volume?
Inulin estimates ECF and Radioactive Albumin estimates plasma volume
Plasma PAH concentrations below the transport maximum. What’s the concentration to renal vein?
Concentration to renal vein is close to zero.
At plasma concentrations that are lower than at the transport maximum PAH, PAR concentration in the renal vein is nearly zero because the sum of filtration plus secretion removes virtually all PAH from the renal plasma.
Effect of water deprivation on reabsorption rate in the collecting ducts ?
Higher rate of H2O reabsorption in the collecting ducts.
Person with water deprivation will have a higher plasma osmolarity and higher circulating levels of ADH.
Dilatation of afferent arteriole. Effect on RPF and GFR?
Increased both RPF and GFR
What’s the effect on Ca on Patient X’s ABG ?
pH : 7.52
PCO2: 20 mmHg
HCO3: 16 mEq/L
Has decreased ionized Ca in the blood
During alkalosis, H+ is released from albumin which frees up space for Ca to bind, thus bound Ca will increase, but ionized / free Ca will decrease.
Differentiate person with severe water deprivation for those with SIADH?
Plasma osmolarity
Both will have hyperosmotic urine, negative free water clearance, normal corticopapillary gradient, and high levels of ADH.
Plasma osmolarity is low in ADH due to dilution of high water reabsorption .
Diuretic that decreases renal Ca clearance?
Thiazides
Patient X arrives at the ER with low arterial pressure and reduced tissue turgor.
ABG results shows
pH : 7.69
HCO3: 57 mEq/L
PCO2: 48 mmHg
What happens to H+ and K+?
Exchange of intracellular H+ for extracellular K+
Patient has metabolic alkalosis with respiratory compensation. Low H+ in the blood will cause intracellular H+ to leave cells in exchange for extracellular K+
Plasma osmolarity = 300 mOsm/L
Urine osmolarity = 1200 mOsm/L
What’s the diagnosis?
Water deprivation
The person with water deprivation will have a higher plasma osmolarity and higher circulating levels of ADH.
These effects will increase the rate of H2O reabsorption in the collecting ducts and create a negative free-water clearance.
What’s the effective RBF?
Urine flow rate :1 mL/min
Plasma PAH : 1 mg/mL
Urine PAH: 600mg/mL
Hct: 45%
1091 mL/min
RPF is calculated from the clearance of PAH.
CPAH = UPAH x V / PPAH
CPAH= 600 x 1 / 1 = 600 mL/min
RBF = RPF / 1 - Hct
RBF = 1091
Substance with highest renal clearance?
PAH
Replacing all volume lost in sweat by drinking distilled water. Effect on plasma osmolarity?
Decreased plasma osmolarity
Net loss of NaCl without a net loss of water.
Causes hyperkalemia ? (6)
- Insulin deficiency
- Beta antagonist
- Acidosis
- Hyperosmolarity
- Exercise
- Cell lysis
Aldosterone level causing metabolic alkalosis.
Hyperaldosteronism
Parathyroid hormone stimulates what substance/ enzyme on the renal tubule for it to exert its general action ?
Adenylate cyclase
40/M , hypertensive , hypokalemic, ABG pH 7.5 , calculated HCO3= 32mEq/L. Normal serum cortisol and urinary VMA , increased aldosterone, decreased plasma renin activity. What the diagnosis?
Conn Syndrome
Hypertension, hypokalemia, metabolic alkalosis , elevated serum aldosterone , and decreased plasma renin activity are all consistent with ?
Primary Hyperaldosteronism eg. Conn Syndrome
Patient with partially compensated respiratory alkalosis after 1 month on a mechanical ventilator. Choose ABG result.
A. pH 7.65 , HCO3: 48, PCO2 45
B. pH 7.50 , HCO3: 15, PCO2 20
C. pH 7.40, HCO3: 24, PCO2 40
D. pH 7.32 , HCO3: 30, PCO2 60
E. pH 7.31 , HCO3: 16, PCO2 33
B. Respiratory Alkalosis
Decreased PCO2 and decreased H+ and HCO3- by mass action. The HCO3- is further decreased by renal compensation for chronic respiratory alkalosis ( decreased HCO3 reabsorption )
Patient with chronic renal failure and decreased urinary excretion of NH4.
Choose ABG result.
A. pH 7.65 , HCO3: 48, PCO2 45
B. pH 7.50 , HCO3: 15, PCO2 20
C. pH 7.40, HCO3: 24, PCO2 40
D. pH 7.32 , HCO3: 30, PCO2 60
E. pH 7.31 , HCO3: 16, PCO2 33
E. Metabolic acidosis
In patients who have chronic renal failure and ingest normal amounts of protein, fixed acids will be produced from the catabolism of protein. Because the failing kidney doesn’t produce enough NH4 + to excrete all of the fixed acid, m. acidosis occur.
Patient with untreated diabetes mellitus and increased urinary excretion of NH4.
Choose ABG result.
A. pH 7.65 , HCO3: 48, PCO2 45
B. pH 7.50 , HCO3: 15, PCO2 20
C. pH 7.40, HCO3: 24, PCO2 40
D. pH 7.32 , HCO3: 30, PCO2 60
E. pH 7.31 , HCO3: 16, PCO2 33
E. Metabolic Acidosis
Untreated diabetes mellitus results in the production of keto acids, which are fixed acids that cause metabolic acidosis. Urinary excretion of NH4+ is increased in this patient because an adaptive increase in renal NH3 synthesis has occurred in response to the metabolic acidosis.
Patient with a 5-day history of vomiting.
Choose ABG result.
A. pH 7.65 , HCO3: 48, PCO2 45
B. pH 7.50 , HCO3: 15, PCO2 20
C. pH 7.40, HCO3: 24, PCO2 40
D. pH 7.32 , HCO3: 30, PCO2 60
E. pH 7.31 , HCO3: 16, PCO2 33
A. Metabolic Alkalosis
The history of vomiting ( in the absence of any other information) indicates loss gastric H+
Amount of K+ in tubular fluid exceed the amount of filtered K+ in a person on a high K+ diet. In what site of the nephron?
Late distal tubule & Collecting ducts
K+ is secreted by the late distal tubule and collecting ducts. Because this secretion is affected by dietary K+ , a person who is on high K diet can secrete more K into the urine than was originally filtered.
Tubular fluid / Plasma (TF/ P) osmolarity is the lowest in a person who has been deprived of water. In what Nephron site?
DCT
A person who is deprived of water will have high circulating levels of ADH.
Tubular fluid inulin concentration is highest during antidiuresis. In what nephron site?
Collecting Tubule
Because inulin, once filtered, is neither reabsorbed nor secreted , its concentration in tubular fluid reflects the amount of water remaining in the tubule.
Tubular fluid glucose concentration is highest. In what nephron site?
Bowmans space
Glucose is extensively reabsorbed in the early proximal tubule. The glucose concentration in tubular fluid is highest in Bowman space before any reabsorption has occurred.
5/ boy swallows a bottle of aspirin. The treatment increases the excretion of salicylic acid. What was the change in urine pH? Why?
Alkalinization , which converts salicylic acid to it’s A-form.
The A form is charged and cannot back-diffuse from urine to blood , thus trapped in the urine and excreted.
50/F , untreated with Dm. What is the rate of glucose filtered, reabsorbed and excreted?
GFR : 120 ml/min
Plasma glucose conc: 400mg/dL
Urine glucose conc: 2500mg/dL
Urine flow rate: 4ml/min
Filtered : 480mg/ min
Reabsorbed: 380mg/min
Excreted: 100 mg/min
Explanation
Filtered Load= GFR x Plasma glucose conc
Filtered Load= 120 x 400 = 48000 (1dL = 100mL) = 480 mg/ min
Excretion Rate= V x urine glucose conc
Excretion Rate= 4 x 2500= 10000 (1dL = 100mL) = 100mg/ min
Reabsorption Rate= Filtered Load - Excretion Rate
ReabsorptionRate = 480 - 100 = 380mg/min
50/F , untreated with Dm. What is the rate of glucose secretion rate and clearance rate?
GFR : 120 ml/min
Plasma glucose conc: 400mg/dL
Urine glucose conc: 2500mg/dL
Urine flow rate: 4ml/min
Filtered : 480mg/ min
Reabsorbed: 380mg/min
Excreted: 100 mg/min
Secretion Rate : -380mg/min
Clearance Rate: 25mL/min
Calculation:
Secretion Rate = Excretion Rate - Filtered load
Secretion Rate = 100-480mg/ min = -380mg/ min
Clearance Rate = UV/ P
Clearance Rate = (2,500mg/dL ) (4mL/min) / 400mg/dL = 25mL/min
Whats the formula of filtration fraction?
Filtration Fraction = GFR / RPF
RPF = Clearance of PAH = U PAH V PAH / P PAH
Since PAH values are not given for this case, filtration fraction is probably near it’s average value of 20%.
Associated with NAGMA.
a. Decreased HCO3
b. Increased Cl
c. Increased Na
Increased Chloride
Renal threshold for glucose ?
Plasma glucose of 200mg/dL
One nephron is already saturated
Drugs that causes hypokalemia and acts at the DCT ?
Thiazide diuretics and not Spironolactone.
Causes renal vasodilation?
Bradykinin
Marker to Total Body Water (TBW) ? (3)
- Titrated Water
- D2O
- Antipyrine
Compensatory response to hemorrhage? (4)
- Increased Renin
- Increased Aldosterone
- Increased Epinephrine
- Increased Heart Rate etc..
Increases Bowmans capsule pressure?
Ureteral stone obstructing outflow
Clearance of inulin is equal to ?
GFR
Formula for Clearance?
C= UV / P
Site for reabsorption of Na, H2O, HCO3, and glucose?
Early Proximal Tubule
Diuretic that decreases K+ excretion?
K sparing diuretics like Spironolactone
Formula of Urine Anion Gap?
UAG= Na + K - Cl
Site for reabsorption of Na, H2O , HCO3 and glucose ?
Early Proximal Convoluted Tubule
Substance with highest renal clearance?
PAH
Autosomal recessive metabolic disorder of lysine , hydroxylysine, and tryptophan metabolism?
GA-I : Glutaric Aciduria Type - 1
Used to measure GFR?
Inulin & Creatinine
Normal urine volume of the bladder after urination of normal young adult? (Normal post-void residual urine)
<50ml
Clearance equal to GFR?
Inulin & Creatinine
DKA , What anti-hypertensive triggered the condition?
Thiazide diuretics
When is hypertensive patient given with hypertonic solution?
- ECF Volume increases
- BP increases
- ICF volume decreases
When does Urge to defecate vs Urge to urinate happens ?
When rectum is 25% filled
When urinary bladder is 25% filled
What mechanism is called when Renal afferent arterioles reflexively responds to stretch by contracting in order to maintain constant renal blood flow and subsequently, GFR.
Myogenic Mechanism
Formula for RBF?
RBF= (RPF) / (1-Hct)
A man lost in a desert would have?
Decreased ECF & ICF Volume
Increased ECF & ICF Osmolarity
What is the sympathetic supply of the kidney?
Beta-1
What are the functions of the macula densa?
Detect changes in BP and GFR through Na concentration in the DT lumen
What is the action of JG cells?
Secrete renin
Which vaccines are live? (9)
- BCG vaccine
- Measles vaccine
- MMR vaccine
- Varicella Vaccine
- Rotavirus Vaccine
- Influenza attenuated vaccine (intranasal)
- Typhoid fever (oral) vaccine
- Oral Polio Vaccine
- Japanese Encephalitis
Which vaccines are inactivated ? (11)
- Hepatitis B vaccine
- DPT vaccine
- H. Influenza B vaccine
- Pneumococcal vaccine
- Hepatitis A vaccine
- Meningococcal Vaccine
- Influenza trivalent vaccine
- Human papillomavirus vaccine
- Typhoid fever (IM)
- Rabies vaccine
- Inactivated Polio Vaccine (IPV)
What is reabsorbed in the PCT? (6)
Na, K, H2O, Glucose, AA, Phosphate
What is reabsorbed in the LH? (4)
Na, K, Cl, H2O
What is reabsorbed in CCT?
Na, K, H2O
Which part of the glomerulus prevents albumin from being filtered?
Basement Membrane
How many Renal Pyramid ( Malphigian Pyramids) are there in each kidney?
Usually 7 but maybe up to 18.
It consists of tubules that transport urine from the renal cortex to the renal papilla.
PAH Clearance underestimates true RPF by how many percent?
10% due to RPF Kidney regions that do not filter and secrete PAH.
Benign proteinuria ?
Orthostatic proteinuria
Anemia in chronic kidney disease?
Due to low EPO synthesis and secretion.
Reasons why percentage of solute (eg Na or Glucose), reabsorbed in the tubules will remain the same despite changes in GFR.
Glomerulotubular Balance
