SU2M - Tubulointerstitial disease

Question 0

4 General causes of AIN?

Answer 0

1. Acute allergic rxn to medications –> MOST COMMON CAUSE
   - ex: penicillinc, cephalosporins, sulfa drugs, diuretics (furosemide, thiazide), anticoagulants, phenytoin, rifampin, allopurinol, or PPIs
2. Infection –> esp in children
   - ex: strep, legionella pneumoniae, etc.
3. Collagen vascular disease
   - ex: sarcoidosis
4. Autoimmune dz
   - ex: SLE, Sjogren’s syndrome, etc.

Question 1

Acute interstitial nephritis: general characteristics?

Answer 1

• inflammation that involves the interestitium
• interestitium = tissue that surrounds glomeruli and tubules
• causes 10-15% of the cases of Acute Kidney Injury (AKI)

Question 2

AIN: ssx (5)?

Answer 2

• Classical findings:
  1. Rash
  2. Fever
  3. Eosinophilia
• also may be present:
  4. Pyuria
  5. Hematuria

Question 3

AIN: dx?

Answer 3

1. Renal function tests –> increased BUN & Cr levels
2. Eosinophilia on urinalysis –> suggests dx given the proper hx and findings!
3. Mild proteinuria - may be present
4. Microscopic proteinuria - may be present
   * *impossible to tell the difference btwn ATN and AIN on clinical findings alone! The only definitive test for AIN is renal bx, but not done very often bc its invasive!

Question 4

AIN: tx?

Answer 4

• remove offending agent –> should reverse sx –> if not add steroids too
• tx infection if present

Question 5

Acute v. Chronic interstitial nephritis?

Answer 5

Acute:
-interstitial nephritis –> RAPID deterioration in renal fctn
-associated with interstitial eosinophils or lymphocytes
Chronic:
-interstitial nephritis –> more indolent
-associated with tubulointerstitial fibrosis and atrophy

Question 6

Analgesic nephropathy: what is it?

Answer 6

-form of toxic injury to the kidney due to excessive use of over-the-counter analgesics –> containing phenacetin, acetaminophen, NSAIDs, or aspirin

Question 7

Analgesic neohropathy: 2 ways it can manifest?

Answer 7

1. Interstitial nephritis

2. Renal papillary necrosis

Question 8

Analgesic nephropathy: what can it lead to?

Answer 8

-acute or chronic renal failure

Question 9

Renal papillary necrosis: what is it most commonly associated with (6)?

Answer 9

1. Analgesic nephropathy
2. Diabetic nephropathy
3. Sickle cell dz
4. Urinary tract obstruction
5. Chronic alcoholism
6. Renal transplant rejection

Question 10

Renal papillary necrosis: dx?

Answer 10

-observing changes in the papilla or medulla in an excretory urogram

Question 11

Renal papillary necrosis: tx?

Answer 11

-tx underlying cause and stop offending agent (ex. NSAIDs)

Question 12

Renal tubular acidosis: what is it? What is it characterized by?

Answer 12

• disorder of renal tubules that leads to a non-anion gap hyperchloremic metabolic acidosis
• glomerular function is normal
• decrease in H+ excreted in urine = acidemia + urine alkalosis

Question 13

Type 1 RTA: what is the defect?

Answer 13

• distal
• inability to secrete H+ at the distal tubule –> so, new bicarbonate cannot be generated
• can’t acidify urine –> metabolic acidosis
• urine pH CANNOT be lowered below 6, regardless of the severity of the acidosis

Question 14

4 Consequences of distal RTA? Cause?

Answer 14

1. Decrease in ECF
2. Hypokalemia
3. Renal stone/nephrocalcinosis –> due to increased Ca and phos excretion into alkaline urine
4. Ricketts/osteomalacia
   * *cause of all: increased excretion of ions (sodium, Ca, K, sulfate, phos)

Question 15

What type of acidosis does distal RTA cause?

Answer 15

-hypokalemic, hyperchloremic, non-anion gap acidosis

Question 16

Distal RTA: sx?

Answer 16

-secondary to nephrolithiasis

Question 17

Causes of Distal RTA

Answer 17

1. Congenital* –> kids
2. Multiple myleoma*
3. Nephrocalcinosis
4. Nephrotoxicity (ex. Amphotericin B toxicity*)
5. Autoimmune dz (ex. Lupus, Sjogren’s*)
6. Medullary sponge kidney
7. Analgesic nephropathy w

Question 18

Distal RTA: tx?

Answer 18

1. Correct acidosis with sodium bicarb –> helps prevent kidney stones (major goal of tx!)
2. Administer phosphate salts –> promotes excretion of titratable acid

Question 19

Type 2 RTA: defect?

Answer 19

• proximal
• defect: inability to rabsorb HCO3 at the proximal tubule –> causes increased excretion of bicarb in the urine –> metabolic acidosis
• pt also loses K & Na in urine

Question 20

Type of metabolic acidosis caused by type 2 RTA?

Answer 20

-hypokalemic, hyperchloremic non-anion gap acidosis (same as w/ type 1)

Question 21

Causes of type 2 RTA in adults and children?

Answer 21

Children:
1. Fanconi's syndrome*
Adults:
1. Cystinosis*
2. Wilson's dz
3. Lead toxicity 
4. Multiple myeloma* --> make sure to rule this out in any pt with proximal RTA, bc the excretion of monoclonal light chains can be a common feature!! 
5. Nephrotic syndrome
6. Amyloidosis

Question 22

Neohrolithiasis and nephrocalcinosis in type 1 v type 2 RTA?

Answer 22

-both occur ONLY in type 1!

Question 23

Type 2 RTA: tx?

Answer 23

1. Tx underlying cause
2. DONT give bicarb to correct acidosis, bc they will just urinate it out!
3. Sodium restriction –> will increase sodium reabsorption = also increases bicarb reabsorption in PT!

Question 24

Type 4 RTA: what can it be the result of? Who is it commonly seen in? What is happening with Na, H, and K?

Answer 24

- can result from any condition where there is hypoaldo or increased renal resistance to aldo - common in pts with interstitial renal dz and diabetic nephropathy - characteristics: 1. Decreased Na absorption 2. Decreased H+ secretion --> in DT 3. Decreased K+ secretion --> in DT

Question 25

What type of acidosis does type 4 RTA cause?

Answer 25

- non-anion gap metabolic acidosis - acidic urine - HYPERkalemia

Question 26

Hartnup syndrome: what is it?

Answer 26

- autosomal recessive inheritance of defective amino acid transporter - causes: Decreased interstitial and renal reabsorption of neutral AAs, such as tryptophan --> causes nicotinamide deficiency

Question 27

Hartnup syndrome: clinical features?

Answer 27

- similar to pellegra: 1. Dermatitis 2. Diarrhea 3. Ataxia 4. Psychiatric disturbances

Question 28

Fancomi's syndrome: what is it?

Answer 28

- hereditary or acquired proximal tubule dysfunction - defective transport of any if these: 1. Glucose 2. AAs 3. Sodium 4. Potassium 5. Phosphate 6. Uric acid 7. Bicarb

Question 29

What can Fanconi's syndrome be associated with?

Answer 29

1. Glucosuria 2. Phosphaturia --> leads to skeletal problems: rickets/impaired growth in kids, osteomalacia, osteoporosis, pathologic fractures in adults 3. Proteinuria 4. Polyuria 5. Dehydration 6. Type 2 RTA 7. Hypercalciuria 8. Hypokalemia

Question 30

Fanconi's syndrome: tx?

Answer 30

Supplement: 1. phosphate 2. Potassium 3. Alkali 4. Salt 5. Hydration!