Renal Flashcards
How is plasm volume measured?
Radiolabeling albumin
How is extracellular volume measured?
Inulin or mannitol
Patient with Addison’s disease experiences what kind of volume shift?
Hypoosmotic volume contraction
What cells synthesize renin? Where are they located?
Juxtaglomerular smooth muscle cells contained in the afferent arteriole
How are RBCs prevented from filtration in the glomerulus?
Fenestrated capillaries
What is the equation for renal clearance?
Clearance of substance X = (urine concentration of X * urine flow rate)/plasma concentration of X
If clearance of substance is less than GFR, what does this mean?
Net tubular reabsorption of substance
If clearance of a substance is greater than GFR, what does this mean?
Net tubular secretion of substance X
What is renal clearance?
Volume of plasm cleared of a substance per unit of time
Inulin can be used to measure what?
GFR or extracellular volume
How is effective renal plasma flow estimated?
Para-aminohippuric acid clearance
How is renal blood flow calculated?
Renal plasma flow / (1-Hct)
What affect does probenecid have on penicillin?
It increases the half life of penicillin by inhibiting penicillin secretion in the proximal tubule via blocking the PAH transporter
Penicillin is secreted in the kidney by what transporter? Where?
Para-aminohippuric acid transporter in proximal tubule
What is the equation for calculating filtration fraction?
GFR/RPF
What is a normal filtration fraction?
20%
How do you calculate the filtered load?
GFR x plasma concentration
How is renal plasma flow estimated?
Para-aminohippuric acid
With an increased filtration fraction, what happens to protein concentration in peritubular capillary blood? What affect does this have on the nephron?
Increased protein concentration in peritubular capillary blood; which leads to increased reabsorption of water in the proximal tubule
What affects does decreased filtration fraction have on peritubular capillaries and the nephron?
Decreased protein concentration in the peritubular capillaries and decreased reabsorption of water in the proximal tubule
In dehydration what happens to GFR, RPF, and FF?
Decrease in GFR, large decrease in RPF, and therefore increase in filtration fraction
What affects do prostaglandins have on afferent arteriole? NSAIDs?
Vasodilate; NSAIDs cause vasoconstriction, could result in decreased GFR and therefore ischemia to kidney
How is the excretion rate calculated?
Urine flow rate x urine concentration of substance
What is the reabsorption rate?
Filtered - excreted
What is secretion rate?
Excreted - filtered
What is the equation for FENa?
(Plasma creatinine x Urine Na) / (Urine creatinine x Plasma Na)
What is seen on light microscopy from a section of the proximal convoluted tubule?
Simple cuboidal epithelium with brush border
What is seen on light microscopy from a section of the distal convoluted tubule?
Simple cuboidal epithelium with NO brush border
What type of epithelium is seen in the thin descending loop of Henle?
Simple squamous
What region of the nephron does PTH act to increase calcium reabsorption?
DCT
Where does PTH act in the kidney? What does it do?
Proximal to increase phosphate excretion and DCT to increase calcium reabsorption
What is Winter’s formula?
Pco2 = 1.5 [HCO3-] + 8 +/- 2
What is winters formula used for?
In simple metabolic acidosis, it can be used to calculate predicted resp compensation
If measured Pco2 is greater than the predicted Pco2 from winters formula, what is going on?
Concomitant respiratory acidosis
If measured PCO2 is less than predicted PCO2, what is going on?
Concomitant respiratory alkalosis
What drugs/nephrotoxins can cause Fanconi syndrome?
Ifosfamide, cisplatin, tenofovir, expired tetracyclines, lead poisoning
Expired tetracyclines can cause what syndrome?
Fanconi syndrome?
What is fanconi syndrome?
Generalized defect in reabsorption in PCT; cannot reabsorb glucose, aa, HCO3, and PO4
Fanconi syndrome can result in what acid/base disorder?
Metabolic acidosis - proximal tubular acidosis
Barter syndrome is a defect in what transporter?
NKCC2
What part of the renal tubule is affected by Bartter syndrome?
Thick ascending limb
What is the inheritance pattern of Bartter syndrome?
Autosome recessive
How does bartter syndrome present?
Hypokalemia, metabolic alkalosis with hypercalciuria; similar to chronic loop diuretic use
What is the inheritance pattern of Gitelman syndrome?
AR
What transporter is affected by Gitelman syndrome?
NaCl channel in DCT
What labs are seen in Gitelman syndrome?
Hypocalciuria hypomagnesemia, hypokalemia, metabolic alkalosis
What is the inheritance pattern of Liddle syndrome?
AD
What transporter/channel is affected by Liddle syndrome?
ENaC channel
Liddle syndrome results in what types of labs?
Increased Na reabsorption - resulting in HTN; hypokalemia, metabolic alkalosis, decreased aldosterone
What enzyme is defective in syndrome of apparent mineralocorticoid excess?
11 beta hydroxysteroid dehydrogenase
What is the mechanism of the enzyme 11 beta hydroxysteroid dehydrogenase?
Converts cortisol (active) to cortisone (inactive)
How does syndrome of apparent mineralocorticoid present?
Hypertension, hyperkalemia, metabolic alkalosis; low serum aldosterone levels
What disorder can be acquired from glycyrrhetinic acid?
Syndrome of apparent mineralocorticoid excess
Where is ACE made?
Kidney and lungs
What affect does AGII have on the posterior pituitary?
Increases release of ADH
What is the mechanism by which ANP vasodilates?
Increases cGMP, relaxing the vascular smooth muscle
What affect does ANP have on renin and aldosterone?
Reduces secretion of both renin and aldosterone
What is nesiritide?
Recombinant BNP; used for treatment of heart failure
What affect does ANP and BNP have on sodium?
Increases its filtration without increasing reabsorption; net effect is loss of both Na and water
What increases the secretion of renin?
Low Na sensed by macula densa, low BP sensed by JG cells, and sympathetics acting on beta1 receptors
What does the macula densa do?
Senses NaCl; if low - it promotes the secretion of renin from the JG cells
Angiotensin II constricts what vasculature?
Efferent arteriole
Where in the kidney is dopamine secreted from?
PCT cells
What affect does dopamine have on the kidney?
Promotes natriuresis; low doses promotes vasodilation; high doses promotes vasoconstriction
What is fenoldopam?
Dopamine receptor agonist - used in hypertensive emergencies
How is Epo regulated in the kidney?
Low oxygen states, HIF1alpha is not hydroxylated, and therefore is not degraded, resulting in transcription of erythropoietin
Where in the kidney is 1,25-OH D3 formed?
PCT
What is the action of 1alpha-hydroxylase?
Converts 25-OH D3 to 1,25-OH D3
What is ANP, BNP’s effect on the afferent and efferent arteriole?
Constricts efferent arteriole while vasodilating the afferent arteriole, resulting in increased GFR
When is PTH secreted?
Decreased serum calcium, increased plasm PO4, or decreased plasm 1,25-OH D3
When is aldosterone secreted?
Decreased blood volume (in response to AGII) and increased serum K+
Patient with high serum digitalis presents to the ER. What will you see on EKG? Why?
Peaked T waves and wide QRS due to hyperkalemia
Patient used way too much of his beta-adrenergic agonist. What effect does this have on K+? What will you likely see on ECG?
Results in hypokalemia (shifts K into cells); U waves and flattened T wave on ECG
What affect does low serum calcium have on the ECG?
QT prolongation
What are signs and symptoms of low serum calcium?
Prolonged QT interval on ECG, tetany, Chvostek sign (twitching), spasm (Trousseau sign)
Patient presents with increased urine frequency, abdominal pain, back pain and anxiety. Additionally, patient states she think she passed a renal stone. What is the likely cause?
Hypercalcemia
What are signs and symptoms of high serum calcium?
Abdominal pain, bone pain, renal stones, increased urine frequency, anxiety/altered mental status
What is seen on ECG in low serum magnesium states?
Torsades de pointes
What additional lab findings do you see with low serum magnesium?
Low serum calcium, low serum potassium
What are the signs and symptoms of hypermagnesemia?
Low DTR, lethargy, bradycardia, hypotension, cardiac arrest, hypocalemia
What are the signs of increased PO4 in serum?
Renal stones, metastatic calcifications, hypocalcemia
What are the results of low serum PO4?
Bone loss, osteomalacia (adults) and rickets (children)
What is Conn syndrome?
Primary hyperaldosteronism
What affect does salicylates have on acid/base status?
Early - respiratory alkalosis; late - anion gap metabolic acidosis
What does HARDASS stand for in acid/base status?
Non-anion gap metabolic acidosis; hyperalimentation, addison disease, RTA, diarrhea, acetazolamide, spironolactone, saline infusion
What is type I RTA?
Distal renal tubular acidosis - defect in ability of alpha intercalated cells to secrete H+ and therefore no new HCO3 production, resulting in metabolic acidosis
How does renal tubular acidosis present?
Symptoms of volume depletion; normal anion gap (hyperchloremic) metabolic acidosis
What drugs cause distal renal tubular acidosis?
(Type I); amphotericin B and lithium
What is the urine pH in distal renal tubular acidosis?
> 5.5 (because distal tubule is unable to secrete fixed acid)
Other than drugs, what else can cause distal renal tubular acidosis?
Congenital - obstruction; autoimmune (Sjogrens), analgesic nephropathy, sickle cell anemia
What drugs cause proximal renal tubular acidosis?
(Type 2) - acetazolamide and aminoglycosides
What is proximal renal tubular acidosis?
Defect in PCT HCO3 reabsorption
What is the urine pH in proximal renal tubular acidosis?
<5.5
Distal renal tubular acidosis is associated what electrolyte imbalance?
Hypokalemia
Distal renal tubular acidosis results in increased risk for what?
Calcium phosphate kidney stones
Proximal renal tubular acidosis is associated with what electrolyte imbalance?
Hypokalemia
Proximal renal tubular acidosis increases risk for what?
Hypophosphatemic rickets
What is a distinguishing feature of type 4 RTA?
Hyperkalemia (both type I and type II have hypokalemia)
What is the cause of type 4 RTA?
Hyperkalemic states - hypoaldosteronism, aldosterone resistance, K+ sparing diuretics, ACE inhibitors and ARBs are examples
What drugs can cause type 4 RTA?
Spironolactone, ACEi, ARBs
What serotypes of S pyogenes cause PSGN?
M12, M4, M1
PSGN is what type of HSR?
Type III
Goodpasture syndrome results in rapidly progressive glomerulonephritis. What type of HSR is this?
Type II
