Renal Flashcards

1
Q

Generalized resorptive defect in PCT

A

Fanconi syndrome

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2
Q
hypokalemia
hypochloremia
metabolic alkalosis
normotension
elevated plasma renin level
A

Bartter syndrome

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3
Q

Bartter pathophys

A

mutation involving the Na+/K+/Cl- cotransporter (NKCC2) results in salt and water loss resulting in
activation of the renin-angiotensin-aldosterone system secondary to volume depletion

renal vasoconstriction due to angiotensin II and hypokalemia leads to an increase in prostaglandin E (PGE)

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4
Q

Bartter symptoms

A
failure to thrive
increased thirst
polyuria
polydipsia
vomiting
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5
Q
Hypophosphatemia
Aminoaciduria
Renal glucosuria
Tubular proteinuria
Proximal renal tubular acidosis
A

Fanconi syndrome

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6
Q

Autosomal recessive mutation involving the Na+Cl- cotransporter

A

Gitelman syndrome

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7
Q

Gitelman symptoms

A
Hypokalemia
Hypochloremia
Metabolic alkalosis
Hypomagnesemia
Hypocalciuria
Normotension
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8
Q

Hypercalciuria in Barttter. T/F?

Explain

A

True

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9
Q

Where do loop diuretics work?

A

Inhibit Na+-K+2CI- channel in the thick ascending limb of loop of Henle.
By preventing Na+ and K+ reabsorption into the renal mediilla, they abolish the hypertonicity of the medulla (so urine cannot be concentrated in the collecting ducts). This results in marked diuresis.
They also increase Ca2+ excretion because they reduce the lumen positive potential in the loop of Henle

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10
Q

Where do thiazide diuretics work

A

Inhibit Na+-Cl~ symporter, thereby blocking Na+ and Cl- reabsorption in the distal convoluted tubule. NaCl is excreted along with water into the urine. They also increase Ca2+ reabsorption.

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11
Q

Spironolactone vs triamterene and amiloride

A
Spironolactone: Competitive antagonist at the aldosterone receptor in
collecting tubule (indirectly inhibits Na+ reabsorption).
Triamterene and amiloride: Directly block Na+ channels in the collecting tubule.
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12
Q

At PCT, what follows sodium

A

At luminal border, sodium moves along gradient (simple diffusion)

At basolateral border, sodium moves against gradient (primary active transport using ATP) to be reabsorbed

Cl- (electroneutrality)
H20 (osmosis)
Glucose (Na+Glu co-transport) 
amino acids
ca2+ (Na+Ca2+ co-transport) 
HCO3-
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13
Q

At PCT, what goes against sodium

A

H+

through Na+H+ exchanger

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14
Q

What do you know about Liddle syndrome

A

Extremely rare
Age of onset: childhood
Etiology: autosomal dominant mutation in the SCNN1B and SCNN1G genes on chromosome 16p → structural alteration in the β and γ subunits of the epithelial sodium channel (ENaC) in the collecting duct

Pathophysiology: structural alteration in the ENaC → ENaCs cannot be degraded by ubiquitin proteasomes → increased number of ENaCs in the collecting duct → increased reuptake of water and sodium (pseudohyperaldosteronism) → hypertension with low renin production and hypokalemia

Clinical features
Hypertension

Diagnostics
Hypokalemia
Metabolic alkalosis
Decreased renin and aldosterone levels

Confirmatory test: genetic testing

Treatment: lifelong oral potassium substitution with potassium-sparing diuretics that directly block ENaCs in the collecting duct (e.g., amiloride, triamterene

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15
Q

Spironolactone effective with Liddle syndrome?

A

The potassium-sparing diuretic spironolactone (an aldosterone receptor antagonist) is not effective in Liddle syndrome because the increased sodium channel activity is not caused by aldosterone.

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16
Q

Amiloride MOA

A

same as triamterene

17
Q

Triamterene MOA

A

A potassium-sparing diuretic that acts by direct inhibition of the epithelial sodium channels in the distal convoluted tubule and the collecting duct leading to reduced Na+ reabsorption and reduced K+ secretion as well as increased diuresis.

18
Q

Gitelman syndrome

A

Prevalence: 1/40,000
Age of onset: ≥ 6 years; diagnosis is usually made in adolescence or adulthood

Etiology: autosomal recessive defect in the SLC12A3 gene on chromosome 16p → impaired function of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule → impaired Na+ and Cl- reabsorption → mild natriuresis → mild volume depletion → mild RAAS activation

Clinical features
Fatigue, muscle weakness
Muscle cramps and/or tetany
Mild polyuria
Chondrocalcinosis
In some cases, mild hypotension
Diagnostics
Metabolic alkalosis
Severe hypokalemia
Hypercalcemia 
Hypomagnesemia 

Confirmatory test: genetic testing
Treatment
Mainstay of therapy: lifelong oral potassium substitution with potassium-sparing diuretics (spironolactone, amiloride)

19
Q

Bartter syndrome

A

Definition: a group of rare genetic disorders (autosomal recessive) that affect chloride reabsorption in the ascending limb of the loop of Henle

Prevalence: 1/1,000,000

Pathophysiology: failure to reabsorb Cl- from the ascending loop of Henle →
Failure to reabsorb Na+ → natriuresis (salt and water loss) → volume depletion → activation of the renin-angiotensin-aldosterone system (RAAS) →
Renal vasoconstriction → rise in the levels of prostaglandin E in an attempt to counter renal vasoconstriction → growth inhibition
↑ Aldosterone levels → enhanced K+ and H+ excretion → hypokalemia and metabolic alkalosis
↓ Paracellular reabsorption of calcium → hypercalciuria → hypocalcemia, nephrocalcinosis, renal stones

Clinical features
Antenatal symptoms: polyhydramnios, preterm delivery
Severe polyuria and polydipsia → life-threatening volume depletion and hypotension
Muscle atrophy, weakness, cramps, carpopedal spasm
Failure to thrive, developmental delay
Dysmorphic facies , strabismus, and sensorineural deafness
Symptoms of renal colic may occur during as a result of calcium stones.

Diagnostics
Laboratory diagnostics
Hypokalemia and metabolic alkalosis
Hypercalciuria 
Hyperuricemia (∼ 50% of cases)
Response to thiazide and loop diuretics 
Normal response to thiazide diuretics 
Blunted response to loop diuretics 
Confirmatory test: genetic testing
Treatment
Mainstay of therapy: lifelong oral potassium substitution with potassium-sparing diuretics (spironolactone, amiloride) 
Spironolactone, an aldosterone antagonist, is preferred over amiloride, an epithelial sodium channel (ENaC) inhibitor.