Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chem Path > L27 Renal tubular acidosis > Flashcards

L27 Renal tubular acidosis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What is the definition renal tubular acidosis?

All belongs to normal anion-gap/ high anion-gap metabolic acidosis?

A

Definition:
- defect in the ability of renal tubule to respond to academia appropriately

NAGMA
possible aetiologies
1. can be due to loss of bicarbonate/bicarbonate precursors
e.g. diarrhoea, type 2 (proximal) renal tubular acidosis (RTA)..

  1. decreased renal acid excretion
    e. g. type 1 (distal) RTA, type 4 RTA (hypoaldosteronism)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Normal physiology at the proximal tubules?

a) lumen
b) blood

A

a) lumen
- H+ leaves nephrons to lumen via Na/H exchange channels (H+ leaves, Na+ in)
> H+ becomes H2CO3 and releases CO2 and H2O
- CO2 enters back to proximal tubule

b) blood
- Na+ and HCO3- into blood
- Na+/K+ ATP channels; 3Na to blood, 2K+ into nephrons

Type 2 RTA:
when HCO3- not co-absorbed with Na+ into blood > Na+ won’t be reabsorbed into cell from lumen in exchange with H+, H+ remains to be at cell?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Normal physiology at the cortical collecting tubules?

a) lumen
b) blood

A

a) lumen
- H+ ATPase out to lumen
- H+/K+ ATP channels: H+ out to lumen, K+ into renal cells

b) blood
- HCO3- into blood, Cl- to nephrons
- Na+/K+ ATP channels; 3Na to blood, 2K+ into nephrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Name the locations of defects of Type 1, Type 2 and Type 4 renal tubular acidosis respectively.

A

Type 1: distal tubules
Type 2: proximal tubules
Type 4: Adrenal/renal tubules (hyperkalemic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

State the pathophysiology of Type 1, Type 2 and Type 4 renal tubular acidosis respectively.

A

Type 1: impaired distal urine acidification

Type 2: reduced proximal HCO3- reabsorption at apical membrane

Type 4: Aldosterone deficiency/ tubular resistance to aldosterone > no Na+ absorbed > hyperkalemia, more H+ (?)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the causes to Type 1 renal tubular acidosis? (2)

A

Distal tubule

  1. Primary
    - persistent (sporadic/AD/with neurosensorial deafness in AR inherited disease)
    (genetic mutation in H+ ATPase PUMP of alpha intercalated cells)
  2. Secondary
    - Hypercalciuria (e.g. hyperparathyroidism)
  • Amyloidosis
  • Autoimmune (e.g. SLE, RA, Sjogren’s syndrome - damage distal and collecting tubules)
  • Drugs (e.g. amphotericin B - anti-fungal, lithium)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Causes of Type 2 renal tubular acidosis?

A
  1. Primary isolated defect
  2. Secondary
    - Fanconi syndrome**: generalised proximal tubular dysfunction (unable to absorb a lot of electrolytes)
  • drugs (e.g. aminoglycosides, tenofovir)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Causes of Type 4 renal tubular acidosis?

A
  1. Primary
    - transient
  2. Secondary
    i. hypoaldosteronism
    (hyporeninaemic: diabetic nephropathy
    hyperreninaemic: Addison’s disease)
    ii. pseudohypoadosteronism
    (genetics, chronic interstitial nephropathies)
    iii. drug induced hyper K
    (e.g. ACEI, beta-antagonist)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which of the following about Type 1 Renal tubular acidosis is incorrect?

A. Acidaemia is the most serious among all
B. Plasma HCO3- is <10 mmol/L
C. Urine pH is >5.5
D. It causes hyperkalemia
E. Urine anion gap is positive
F. Urine osmolal gap is <150 mOsm/kg
G. It increases risk for calcium phosphate kidney stones

A

D
it causes hypokaleimia

C: higher other other types, because H+ are not excreted

G: metabolic acidosis increases urine Ca2+ excretion, thus cause an increase in Ca2+ by bone turnover > increases this risk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which type(s) of RTA are associated with poor growth/ osteomalacia?

A

Type 1 and Type 2 RTA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

List the clinical features of type I RTA. (4)

A
  1. Osteomalacia: Hypercalceuria due to reduced H+ secretion
  2. Nephrocalcinosis, nephrolithiasis: due to hypercalciuria + alkaline urine
  3. Muscle weakness: hypoK
  4. Polyuria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the gold standard for Type I RTA?

A

NH4+ loading test

  • ~ acid load
  • normal: urine pH <5.5
  • Type I RTA: Urine pH >5.5 (impaired distal urine acidification)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the gold standard for Type 2 RTA?

A

HCO3- loading test

  • normal: unchanged urinary HCO3-
  • Type 2 RTA: Urine pH >7.5 with FEhco3- >15% (fractional excretion) [reduced proximal HCO3- reabsorption]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which of the following about Type 2 Renal tubular acidosis are incorrect?

A. Urine pH is <5.5 
B. Hypokalemia
C. Urine anion gap is negative
D. Urine osmolal gap >150 mOsm/kg
E. Alkali therapy can improve hypo K
A

A and E are incorrect
A:
Urine pH varies!
<5.5 when urine is acidified by normal distal alpha-intercalated cells
>5.5 if exceeds reabsorption threshold (in HCO3- loading test)

B: because HCO3- not reabsorbed, osmotic diuresis > RAAS > hypokalaemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Type IV RTA causes hypo/hyperkaelemia? Why?

A

Hyperkalemia

- no RAAS > Na+ reduced, K+ increases in blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which of the following about Type 4 Renal tubular acidosis are incorrect?

A. Urine pH is <5.5
B. reduced effect on H+/ATPase in alpha intercalated cells thus reduced H+ excretion, causing acidemia

C. Urine anion gap is negative
D. Urine osmolal gap >150 mOsm/kg
E. there is reduced ammonium excreted in urine

A

C and D are wrong

  • Urine anion gap is positive
  • Urine osmolal gap < 150 mOsm/kg

E: because bonded with H+?

17
Q

Management for patient with Type I RTA?

How does it help?

A

Alkaline therapy can improve hypoK

Effect of giving alkali therapy:

  • Increased NaHCO3 distal delivery raises urine pH and allows more H to be secreted
  • Expands ECV > ↓aldosterone and thus ↓Na reabsorption > Resolves hypokalemia
18
Q

Management for patient with Type 2 RTA?

A

Alkali therapy (e.g. NaHCO3) must prescribe with K supplements

(because baseline hyperaldosteronism + distal HCO3 load in Type II RTA will further increase K secretion)

19
Q

Management for patient with type 4 RTA?

A
  1. Withdraw K retaining drugs
  2. Restrict dietary K
  3. Diuretics
  4. Fludrocortisone (mineralocorticoid effect)
20
Q

What is Fanconi syndrome and what are its causes? (3)

A

Fanconi syndrome
- generalised proximal tubular dysfunction

(- a cause of type II RTA)

Causes

  1. Multiple myeloma
  2. Wilson’s disease
  3. Lead poisoning
21
Q

What can patients with Fanconi’s syndrome presented with? (6)

A

Presentations:

  • bicarbonaturia
  • glucosuria
  • phosphaturia
  • uricosuria
  • aminoaciduria
  • tubular proteinuria
22
Q

Investigations for RTA?

- state what is ruled out in each investigation. (5)

A
  1. Plasma K
    - Hyperkalemia - type 4
  2. Urine for glucose and amino acids
    - Fanconi’s syndrome - type 2
  3. Bicarbonate infusion test - FEhco3 > 15% in proximal RTA - type 2
  4. USG urinary tract
    - nephrocalcinosis in distal RTA - type I
  5. Urine pH, Urine osmolar gap, urine anion gap
23
Q

Algorithm

NAGMA > 1st investigation?

A

Plasma K

  • if hyper = type 4
  • if hypo = others
24
Q

Algorithm

If plasma K checked: hypokalaemia - check what?

A

Urinary pH
- Urinary pH >5.5 = type 1 RTA

  • <5.5
    = diarrhea/ type 2 RTA/ carbonic anhydrase inhibitors
25
Q

Why is urine ammonia useful in RTA investigations?

A
  • At distal tubules, H+ are secreted as NH4+ (as buffer)

- assessment of Urinary NH4+ is useful for investigation of NAGMA/hyperchloraemic metabolic acidosis

26
Q

What is urine anion gap? (equation)

A

Una + Uk - Ucl (normalL 20-90 mmol/L)

27
Q

Why UAG decreases in NAGMA RTA with intact acidification mechanism ?

A

UAG= Una + Uk - Ucl

In NAGMA with intact acidification mechanism (e.g. proximal RTA), Unh4 is accompanied by a parallel increase in Ucl.

Increased H+ secretion  Increased NH4 (urine buffering) and Cl- accompanies  Negative UAG

28
Q

When will UAG increase in RTA?

A

When acidification is impaired

e. g. NH4 loading test
- in distal RTA, type 4 RTA, CKD

29
Q

Which of the followings are limitations of using urinary anion gap to make a diagnosis?

A. False+ in unmeasured anions in urine, e.g. ketoacids, hippurate (as toluene toxicity)
B. Invalidated in volume depletion

A

Both

B: reduce distal Na delivery impairs distal acidification

30
Q

What is UOG (urine osmolar gap)? (calculation)**

A

Measured Uosm - Calculated Uosm (= 2x [Una + Uk]+ Uurea + Uglucose)

Why? (read if don’t understand the calculation)
Under most conditions, the urine osmolality is generated by Na+, K+, urea, glucose (if present), and ammonium salts. Thus, if the urine osmolality is actually measured and calculated using the measured concentrations of Na+, K+, urea, and glucose (if present), the difference should represent the concentration of ammonium salts.

31
Q

What is the normal Urine osmolar gap?

A

10-100mOsm/kg

32
Q

UOG <150 mOsm/kg in metabolic acidosis suggest?

A

low ammonium (Unh4) = distal RTA

(repeated:
Under most conditions, the urine osmolality is generated by Na+, K+, urea, glucose (if present), and ammonium salts. Thus, if the urine osmolality is actually measured and calculated using the measured concentrations of Na+, K+, urea, and glucose (if present), the difference should represent the concentration of ammonium salts.)

33
Q

Which of the following will affect urine osmolar gap?

A. increased of unmeasured anions in urine
B. urease-producing bacterial UTI
C. urinary osmotically active substance (e.g. ethanol, mannitol)

A

Measured Uosm - Calculated Uosm (= 2x [Una + Uk]+ Uurea + Uglucose)

B & C only

B: increase in NH4
A: anions are not in the equation?

Chem Path (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions