Proximal and Distal Tubule Disorders

Question 1

How many sections are in the PT ?

Answer 1

Two, the first 2/3 is the PCT and the final 1/3 is the PST (parsa recta)

Question 2

How many segments are in the PCT ?

Answer 2

Three, S1 S2 and S3

Question 3

What are the functions of the PT ?

Answer 3

Reabsorption of Water and electrolytes
Secretion of organic compounds
Hormonal function in vitamin D synthesis

Question 4

How is insulin taken in by the PT ?

Answer 4

Pinocytosis

Question 5

Is H secreted in the PT ?

Answer 5

Yes, H+ is secreted by the Na-H exchanger

Question 6

Is the PT succeptable to ischemia ?

Answer 6

Yes because it has a high level of mitochondria activity it is very dependent on ATP for proper function

Question 7

What are the six basic defects in the PT ?

Answer 7

1. Defective Solute Influx
2. Leakage back into interstitum
   3 Decreased Solute flux into blood
3. Defective energy generation
4. Increased back-flux across tight junctions.
5. Defective transport recycling

Question 8

What is a generalized PT dysfunction ?

Answer 8

It is usually due to a defect in energy generation ( NaKATPase ) or dysfunctional cellular organelles affecting transport protein recycling

Question 9

What is an isolated PT dysfunction ?

Answer 9

Usually a defect in a specific transport protein

Question 10

What is renal glucosuria ?

Answer 10

An AR inherited trate affecting the SGLT-2 glucose transporter

Question 11

What is Cystinuria ?

Answer 11

An AT inherited trare caused by a mutation in brush border transporter responsible for reabsorption of cystine and AA ornithine, lysine, and arginine

Question 12

What will cystineuria cause ?

Answer 12

Cystine stones and cystine crystals in the urine

Question 13

What are the inherited defects in phosphate reabsorption ?

Answer 13

X-Linked hypophosphatemia (PHEX)
A- Dom Hypophosphatemic Rickets (FGF23)
A-Rec Hypophosphatemic rickets

Question 14

What is the acquired defect in phosphate transport ?

Answer 14

Oncogenic Hypophosphatemic Osteomalacia (FGF23)

Question 15

What is the most common phosphate wasting disorder ?

Answer 15

X Linked Hypophosphatemia

Question 16

What causes X-Linked Phosphatemia ?

Answer 16

A defect in PHEX –> Increased circulating factor FGF-23 that down regulates activity of phosphate transporter rather than transport protein itself

Question 17

What does X-L-P cause

Answer 17

Ricketts in children and osteomalicia in adults

Question 18

What causes Falconi Syndrome ?

Answer 18

Can be inherited but usually is acquired.
DEFECTIVE BINDING of Na with transport proteins, defective insertion of carriers into brush border membranes. Impaired mitochondrial energy generation and leaky tight junctions.

Question 19

Bartter, Gitelman, and Liddle syndromes are disorders of what ?

Answer 19

Na handling

Question 20

Nephrogenic diabetes insipidus is a disorder of what ?

Answer 20

Water handling

Question 21

Distal renal tubular acidosis is a disease of what ?

Answer 21

Ammoniagenesis and urinary acidification.

Question 22

What are the defects in neonatal Bartter Syndrome ?

Answer 22

Autosomal Recessive: Na-K-2Cl cotransporter and the luminal potassium channel (ROMK) in the thick ascending limb of the loop of hen lie.

Question 23

What is the problem in classical Barter syndrome ?

Answer 23

Autosomal Recessive : Mutations in the luminal chloride channel in the distal tubule

Question 24

Does the difference between the Bartter Syndromes depend on the transporter involved ?

Answer 24

No it is determined by the clinical symptoms

Question 25

What causes Gittlemans syndrome ?

Answer 25

It is an Autosomal Recessive disorder associated with mutation s in the thiazide- sensitive cotransporter o the luminal side of the distal convoluted tubule

Question 26

What are the symptoms of neonatal Bartter Syndrome ?

Answer 26

Polyhydramos, preterm delivery, fever and dehydration in infancy, failure to thrive, Hypercalcinuria, Hypercalcinosis.

Question 27

What are the symptoms of Classical Bartter Syndrome ?

Answer 27

Presents later in infancyand is characterized by a failure to thrive, Polydipsia, Dehydration and salt craving

Question 28

Since the presentations of both types of Bartter Syndrome sound alike how the hell do you tell them apart?

Answer 28

Classical patients do have Hypercalciuria but do NOT HAVE NEPHROCALCINOSIS

Question 29

What is Nephrogenic Diabetes Insipidus ?

Answer 29

It is characterized by an inability to concentrate the urine despite normal or elevated levels of the antidiuretic hormone Arginine Vasopressin. The final effect is a failure of the insertion of the Aquaporin 2 channel in the lumen of the CD of the nephron

Question 30

What are the causes of acidosis with an elevated anion gap ?

Answer 30

Inborn errors of metabolism such as organic acidemias, Ketoacidosis, lactic acidosis secondary to hypo perfusion.

Question 31

Is there a RTA type 3 ?

Answer 31

No, Not ever