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Renal - Rao > Proximal Tubular Dysfunctions and Disorders of Water Balance > Flashcards

Proximal Tubular Dysfunctions and Disorders of Water Balance Flashcards

1
Q

What are the 2 structural Divisions and 3 functional divisions of the Proximal Tubule?

A

Structural:
• First 2/3 - PCT
• Last 1/3 - Proximal Straight Tubule

Functional:
• S1 - initial short segement of PCT
• S2 - Remaining PCT and cortical parse Recta
• S3 - Medullary parse recta

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2
Q

In what two functional divisions does excretion happen in the Proximal Tubule?

A

S2 and S3

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3
Q

What are the 2 pathways of Reabsorptionin the Proximal Tubule?

A

Trans Cellular

Para Cellular

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4
Q

What is the Primary driver of all transport in the Proximal Tubule?

A

Na+/K+ ATPase - it moves sodium against its gradient which can then be used to move other substances back in

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5
Q

What are the 3 ways that Proximal Tubule Reabsorption is controlled?

A
  1. Glomerulotubular Reabsorption
  2. Arterial Resistance (Pressure Natriuresis)
  3. Hormonal
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6
Q

What is Glomerulotubular Balance?

A

Tubules have INTRINSIC ability to INCREASE tubular uptake in response to Increased tubular load (flow)

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7
Q

What is Pressure Natriuresis?

A

Increase in Peritubular Capillary Hydrostatic Pressure reduces the net absorption of Na+ and H2O

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8
Q

What Hormones act as regulators in the proximal tubule?

• what do they regulate?

A
  • Angiotensin II - NaCl reabsoption and H+ secretion

* Parathyroid Hormone and FGF23 regulates Pi excretion

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9
Q

Why is the proximal tubule extremely susceptible to ischemia?

A
  • HIGH ATP dependence - ATP is needed for the NKA which creates the gradient for everything that happens in the proximal tubule
  • Cells here are also very dependent on cytoskeletal structure to remain in tact because they need to maintain a close relationship to prevent free movement of solutes
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10
Q

What are 6 potential areas for defects in the Proximal Tubule?

A
  1. Defective Solute Influx
  2. Leakage Back into the lumen
  3. Decreased Solute flux into the blood
  4. Defective energy generation or transportation
  5. Increased backflux across tight junctions
  6. Defective Transporter Recycling
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11
Q

What are the two classifications to Proximal Tubule Dysfunction and their subsets?

A
  1. Classification Based on the mechanism of Dysfunction
    a. Generalized
    b. Isolated Solute Transport disorders
  2. Classification Based on the Mode of Inheritance
    a. Genetic
    b. Aquired
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12
Q

Differentiate the typical causes of Generalized and isolated solute transport disorders.

A

Generalized:
• caused by defect in NKA usually or a dysfunction in cellular organelles involved in protein recycling

Isolated:
• Defect in Specific Transport Protein

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13
Q

Hereditary Renal Glucosurea
• Inheritance
• Mutation
• Manifestation

A

Inheritance:
• Autosomal Recessive

Mutation:
• SGLT2 transporter

Manifestation:
• Mild to Severe increased amounts of glucose in pee

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14
Q

Differentiate the 3 types of Glucoseurea.

A

Type A:
• Lowered Threshold Value at which Glucose starts to appear in urine (normal = 200 - 220 mg/dL)

Type B:
• Same Threshold, BUT once the threshold is met it approaches the Tm much faster

Type O:
• no presence of channels, you’re always just peeing sugar

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15
Q

Cystinurea
• Inheritance
• Mutation
• Manifestation

A

Inheritance:
• Autosomal Recessive

Mutation:
• Loss of AA transporter for Cysteine, Arginine, Ornithine, and Lysine

Manifestation:
• Cystals in urine or Kidney stones

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16
Q

What 4 things protein mutations could cause messed up elimination of phosphate?
• aquired or genetic?

A

Genetic:
• X-linked hypophosphatemia - PHEX gene mutation

  • Autosomal Dominant Hypophosphatemic Rickets - FGF-23 gene mutation
  • Autosomal Recessive Hypophosphatemic Ricks - increased FGF-23 or mutation in Na/Pi IIc transporter

Aquired:
• Oncogenic Hypophosphatemic Oseomalacia - increased production of FGF-23 by some tumors

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17
Q

What is the function of FGF-23?

A

Suppresses the Na+/PO4 transporter in the Proximal tubule

18
Q

What is the most common defect in phosphate reabsorption?
• Inheritance
• Mutation
• manifestation

A

X-Linked Phosphatemic Rickets
Inheritance:
• X-linked dominant

Mutation:
• PHEX gene - works to down regulate FGF-23 expression. FGF-23 gets over expressed in this disease THERE IS NO Na+/PO4 mutation. FGF-23 levels just stay high and down regulate the transporter in the proximal tubules

Manisfestation:
Rickets in kids; Osteomalacia in adults

  • Urinary Phosphate wasting
  • Low Serum Phosphorus
  • Elevated Serum Alkaline Phosphatase
  • Low Ca2+ and Calitriol
19
Q

Hartnup Disease
• Mutation
• Manifestation

A

Mutation:
• SLCA19 mutated - this is a neutral amino acid transporter

Manifestation:
• FAILURE TO THRIVE, Nystagmus, Ataxia, Photosensitivity, Tremor

20
Q

REVIEW PAPER SLIP ON FANCONI SYNDROME

A

REVIEW PAPER SLIP ON FANCONI SYNDROME

21
Q

Fanconi Syndrome

• possible causes

A
  • Defective Binding of Na with transport proteins
  • Defective insertion of Carriers into the brush border membrane
  • Leaky Membrane Tight Junctions
  • NKA Impaired
  • Mitochondrial Energy Generation Defect
22
Q

Fanconi Syndrome

• Metabolic Abnormalities

A
  • Aminoaciduria (generalized)
  • Glucosuria (with normal serum glucose)
  • Hypophosphatemia (multifactorial: decresae phosphate reabsorption from defect in Na/Pi carrier, inhibition of Na/Pi carrier from decreased degradation of parathyroid hormone in PT, decrease in calcitriol synthesis)
  • Hyperchloremic metabolic acidosis (due to bicarbonate loss)
  • Hypokalemia (along with natriuresis due to bicarbonate loss)
  • Uricosuria
23
Q

Clincial Manifestations of Fanconi Syndrome .

A
  • Polyuria and polydipsia
  • Volume depletion
  • Cardiac arrhythmias
  • Proteinuria
  • Growth retardation
  • Rickets
  • Renal stones and nephrocalcinosis
  • Extra renal organ involvement depending on the underline cause
24
Q

Fanconi Syndrome
• Inherited Causes
• Most important

A 
****Cystinosis****
Hepatorenal tyrosinemia
Hereditary fructose intolerance
Galactosemia
Glycogen storage disease type I
Wilson disease
Oculocerebral renal (Lowe) syndrome
Dent’s disease
Mitochondrial disorders (Cytochrome c oxidase deficiency)
25
Q

What are there so many drugs that can cause Fanconi Syndrome?

A

Proximal Tubule is often the first thing to come into contact with drugs on their way out of the body

26
Q

Fanconi Syndrome

• Drugs that can cause

A

Cancer Drugs:
• Ifosfamide
• Cisplatin

Hep B protease Inhibitors
• Cidofovir
• Tenofovir

Others
• Outdated Tetracyclines
• Aminoglycosides
• Cisplatin
• Ranitidine
27
Q

Fanconi Syndrome
• Heavy Metals that can cause
• Toxins that can cause
• Dysproteinemias that can cause

A

Heavy Metals
• Lead
• Cadmium

Toxins
• Toluene, Paraquat, Aristolochic Acid

Dysproteinemias
• Multiple Myeloma
• Light chain deposition disease

**Note: Acute tubular necrosis can also cause this

28
Q

Who is Inherited Fanconi Most Commonly Seen in?

• Acquired?

A

Inherited:
• Typically seen in children and usually more severe

Aquired:
• Typically seen in Adults usually more mild

29
Q

What is the difference between effective and ineffective osmoles?
•give two examples of each

A

Effective:
• Na+ and K+; these do not easily permeate any membrane

Ineffective:
• Urea and Glucose; these can easily travel between body compartment

30
Q

How is plasma Osmolarity Calculated?

A

Posm = 2 x [Na]

31
Q

What is the formula for plasma Na?

•What are changes in Plasma sodium concentration indicative of?

A

Plasma Na = Total Body Exchangable Na and K / Total body H2O

Changes in Total Body Water = only thing that really matters because Na concentration is never really going to change

32
Q

How much of a change in plasma osmolarity does there need to be to trigger ADH secretion?
• what about change in blood volume?

A
  • Change in Posm as little as 1% Stimulates ADH secretion

* Greater than 7% decrease in blood volume stimulates ADH secretion

33
Q

ADH
• what does it act on?
• In what ways does it act?

A

ADH is released from the pituitary and acts on the COLLECTING DUCT

Acts in 2 ways:
1. Short-term: there is a Rapid and Reversible increase in AQP-2 that is sent to the luminal surface

  1. Long-term: AQP-2 GENE EXPRESSION is upregulated, takes LONGER THAN 24hrs
    • Not Readily Reversible
34
Q

How do you determine if water is in XS or deficit?

• Formulas for calculating the amount?

A

If in XS Excess:
• Low Pna - sodium is diluted
• XS = 0.6 TBwt. x (1 - [Na]obs/140)

If in Deficit:
• High Pna - sodium is concentrated
• Deficit = 0.6 TBwt. x ([Na]obs/140 -1)

35
Q

What is the most common type of electrolyte disorder?

A

Hyponatremic Disorders

36
Q

What are the 3 types of Hyponatremic disorders?

• what ion are they typically associated with?

A

Most often associated with Na

3 types:
• Hyperosmolar Hyponatremia
• Normal Osmolarity Hyponatremia
• Decreased Osmolarity Hyponatremia

37
Q

What is Hyperosmolar Hypnatremia?

• causes?

A
  • Presence of other osmotically active substances that cause water movement OUT of cells
  • Since sodium resides OUTside of cells this dilutes Na concentration

Causes:
• Glucose - in absence of insulin
• Mannitol
• Glycine

38
Q

What is Normal osmolality Hyponatremia (pseudohyponatremia)?
• causes?

A
  • Occurs due to limitation of some Na assays when Na is measured in the WHOLE PLASMA while solid phase of Plasma is Greatly increased
  • Hypertriglyceridemia or Paraproteinemia may cause this misreading
39
Q

What is Hypoosmolar Hyponatremia aka TRUE HYPONATREMIA?

• causes?

A
  • ALWAYS due to impaired Urinary Dilution Mechanisms

* Appropriate or Inappropriate increase in ADH is present in the majority of cases of true hyponatremia

40
Q

Causes of True Hyponatremia with Volume Depletion?

A

Hyponatremia with volume depletion:

  • renal losses (diuretics, aldosterone deficit)
  • gastrointestinal losses (diarrhea, vomiting, bleeding)
  • skin losses (excessive sweating while ingesting some free water)
  • third spacing (pancreatitis, bowel obstruction, burns)
41
Q

Causes of True Hyponatremia with normal Volume status?

A

Hyponatremia with normal volume status:

  • Syndrome of inappropriate ADH release (drugs, tumors, pain, any lung or brain diseases)
  • Glucocorticoid deficiency (loss of negative feedback stimulates corticotropin releasing hormone which in turn stimulates ADH)
  • Hypothyroidism (increase ADH possibly due to low cardiac output state and impaired urine dilution from decreased GFR)
42
Q

Causes of True Hyponatremia with Volume Overload?

A

Hyponatremia with volume overload (however, effective circulating volume is usually decreased):

- Congestive heart failure
- Acute and Chronic kidney failure
- Cirrhosis
- Nephrotic syndrome

Renal - Rao (13 decks)

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