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USMLE Renal > Renal Tubular defects and acidosis > Flashcards

Renal Tubular defects and acidosis Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the Renal Tubular defects and where do they occur in the nephron?

A
  • Fanconi syndrome - PCT
  • Bartter syndrome - TAL of LoH
  • Gitelman syndrome - DCT
  • Liddle syndrome - Collecting ducts
  • Syndrome of Apparent Mineralocorticoid Excess (SAME) - Collecting ducts
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2
Q

What Renal Tubular Defects cause decreased reabsorption?

A
  • Fanconi syndrome
  • Bartter syndrome
  • Gitelman syndrome
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3
Q

What Renal Tubular defects cause increased absorption and hypertension?

A
  • Liddle syndrome

- Syndrome of Apparent Mineralocorticoid Excess (SAME)

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4
Q

What hormone is responsible for the reabsorption of calcium in the distal tubules?

A

PTH

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5
Q

What are distinguishing features between Bartter and Gitelman syndrome?

A

Both present with Met alkalosis and hypokalemia. Bartter is more severe

Bartter has hypercalciuria (decreased Ca2+ in serum)
- Whereas Gitelman has hypocalciuria (increased serum calcium)

  • Gitelman presents with hypomagnesemia
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6
Q

What renal tubular defect is autosomal dominant?

A

Liddle syndrome

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7
Q

What is Liddle syndrome treated with?

A

Amiloride

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8
Q

What is Fanconi Syndrome due to a defect in and what does this lead to?

A

PCT defect

  • Increased excretion of all substances reabsorbed by PCT: AA, glucose, HCO3-, PO43-
  • Metabolic acidosis (RTA type 2)
  • Hypophosphatemia (retardation, rickets, osteopenia)
  • Hypokalemia
  • Volume depletion also common
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9
Q

What can cause Fanconi syndrome?

A
  • Hereditary defects (Wilson disease, tyrosinemia, glycogen storage disease)
  • Ischemia
  • Multiple Myeloma
  • Nephrotosxins/drugs - Ifosfamide, cisplatin
  • Lead poisoning
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10
Q

What is the defect in Bartter syndrome?

A

In TAL of LoH

  • Effects Na+/K+/2Cl- cotransporter
  • Similar to loop diuretic use
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11
Q

What lab results does Bartter syndrome give?

A

Met alkalosis

  • Hypokalemia
  • Hypercalciuria (hypocalcemia)
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12
Q

What is Gitelman syndrome due to a defect in?

A

NaCl in DCT

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13
Q

What lab finding is consistent with every Renal tubular defect?

A

HYPOkalemia

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14
Q

What Renal Tubular Defect has Metabolic acidosis with hypotension and hypokalemia?

A

Fanconi Syndrome

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15
Q

What is Liddle syndrome due to?

A

gain of function mutation

  • Decreased Na+ channel degradation
  • Increased Na+ reabsorption in collecting tubules
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16
Q

How can you differentiate between Renal Tubular defects (such as Liddle and SAME) with a hyperaldosteronism?

A

Present nearly identically however RT defects have almost undetectable levels of aldosterone

17
Q

What is Liddle syndrome treated with?

A

Amiloride

18
Q

What enzyme is responsible for SAME?

A 
11Beta HSD (Hydroxysteroid dehydrogenase)
- Deficiency or blockage of activity
19
Q

What substance can cause SAME?

A

Glycyrrhetinic acid

  • Present in licorice
  • Blocks activity of 11B HSD
20
Q

What does 11B HSD do?

A
  • Cortisol acts on mineralocorticoid receptors

- 11B HSD converts cortisol to cortisone making it inactive thus decreasing mineralocorticoid receptor activity

21
Q

What are the different types of Renal Tubular Acidosis (RTA) and what part of the nephron is affected?

A
  • RTA type 2 - Proximal Tubule
  • RTA type 1 - Distal Tubule
  • RTA type 4 / Hyperkalemic tubular acidosis - Collecting Duct
22
Q

What is RTA type 2?

A

Defect in HCO3- reabsorption

  • Increased excretion of HCO3- in urine
  • Met acidosis

Urine may be acidified by alpha-intercalated cells in CD but not enough to overcome HCO3- excretion

23
Q

What can cause RTA type 2

A
  • Fanconi syndrome
  • Multiple Myeloma
  • Carbonic Anhydrase inhibitors
24
Q

What is the serum K+ level in each type of RTA?

A
  • Type 2/Proximal RTA - Decreased K+
  • Type 1/Distal RTA - Decreased K+
  • Type 4 / Hyperkalemic tubular acidosis - Increased K+
25
Q

What type of RTA is associated with renal stones?

A

RTA type 1 / distal

- Due to increased urine pH and increased bone turnover related to buffering

26
Q

What are causes of Distal/ type 1 RTA?

A
  • Amphotericin B toxicity
  • Analgesic nephropathy
  • Congenital anomalies (obstruction of urinary tract)
  • Autoimmune (SLE)
27
Q

What are causes of Hyperkalemic tubular acidosis (type 4)?

A
  • Decreased aldosterone production (e.g. diabetic hyporeninism, ACEi, ARB, NSAIDs, heparin, cyclosporin, adrenal insufficiency)
  • Aldosterone resistance (e.g. K+ sparing diuretics, nephropathy due to obstruction, TMP-SMX)

USMLE Renal (11 decks)

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