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Regions of the kidney most vulnerable to ischemic injury
PCT and ascending loop
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Which kidney is used for transplants?
Left, because it has a longer renal vein
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Fracture of which rib can result in kidney laceration?
12
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60 40 20 rule
- 60% of total body weight is water
- 40% is ICF
- 20% is ECF
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What substance is used to measure extracellular volume?
Inulin or mannitol
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How is renal clearance calculated?
C=(urine concentration x urine flow rate)/plasma concentration
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What substance is used to calculate GFR?
Inulin--for inulin, GFR=Clearance, so GFR=UV/P
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What substance is used to calculate RPF?
PAH--filtered and secreted
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How is RBF calculated?
- Use inulin to calculate RPF (RPF=inulin clearance)
- RBF=RPF/(1-Hct)
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What is the filtration fraction?
GFR/RPF
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Effect of prostaglandins on glomerulus
- Dilate afferent arteriole
- Increase RBF
- Increase GFR
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Effect of angiotensin II on glomerulus
- Constrict efferent arteriole
- Decrease RBF
- Increase GFR
- FF goes up
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Calculation of excretion rate
ER=Urine volume x concentration of substance in urine (VU)
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BUN:Creatinine ratio in prerenal failure
Over 20
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BUN:Creatinine ratio in intrinsic renal failure
Under 20
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Where are most solutes reabsorbed?
Early PCT
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Where is ammonia generated and secreted?
Early PCT
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Where is the urine most dilute?
Early DCT
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Describe the interacalated cells of the DCT
- Luminal transporter reabsorbs Ca in exchange for protons, and secretes protons
- Basal channel allows for secretion of chloride, to balance loss of positive charges from secreted protons
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Where are the JGA and macula densa?
- JGA--afferent arteriole, secretes renin
- Macula densa--DCT, senses Na concentration
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Effects of ANP
Increases GFR and Na filtration in the glomerulus, with no compensatory Na reabsorption, resulting in Na and water loss
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Five things that cause hyperkalemia
- Low insulin
- Beta antagonists (inhibit Na/K ATPase)
- Acidosis (i.e. from exercise)
- Digitalis
- Cell lysis
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Three things that cause hypokalemia
- High insulin
- Beta agonists (e.g. albuterol for asthmatics)
- Alkalosis
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If bicarb increases 1 mEq/L, what happens to carbon dioxide
It increases .7 mmHg
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Causes of normal anion gap metabolic acidosis
- Diarrhea
- Hyperchloremia
- Renal tubular acidosis
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Causes of high anion gap metabolic acidosis
- Methanol
- Uremia
- DKA
- Paraldehyde or phenformin
- Iron or isoniazid
- Lactic acidosis
- Ethelene glycol poisoning
- Salicylates
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Type I renal tubular acidosis
- Defect in proton excretion in the DCT. Associated with hypokalemia and risk of Ca kidney stones
- (NB: only case of acidosis with hypokalemia)
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Type II renal tubular acidosis
- Defect in bicarb reabsorption from the PCT
- Associated with hypokalemia and hypophosphatemic rickets
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Type III renal tubular acidosis
Aldosterone deficiency leads to increased potassium and impaired ammonia excretion from the PCT. Urine pH falls, due to loss of buffering capacity. Plasma pH falls due to impaired proton secretion in the DCT and collecting ducts
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