Le 16 Nephrolithiasis

Question 1

What should you think if recurrent stones?

Answer 1

probably some sort of biochem abnormality

Question 2

What is the breakdown of prevalence of the 4 types of stones?

Answer 2

80% Calcium
15% Struvite
5% Uric acid
1% cystine

Question 3

What does presence of cystine stones tell you?

Answer 3

patient has cystinuria?

Question 4

What is cystinuria?

Answer 4

congenital enzyme deficiency impairing epithelial transport di-basic AA cystine, ornithine, lysine, arginine [COLA]

Question 5

Transport of what 4 AA is impaired in cystinuria?

Answer 5

• cysteine
• ornithine
• lysine
• arginine

[COLA]

Question 6

What is the inheritance of cystinuria?

Answer 6

autosomal recessive

Question 7

What is clinical manifestation of cystinuria?

Answer 7

precipitation of hexagonal cystine stones; present as kids

Question 8

How do you diagnose cystinuria?

Answer 8

positive Na-nitroprusside test

Question 9

What is treatment for cystine stones?

Answer 9

alkalinize urine and hydration

Question 10

What is the appearance/pH of cystine stones?

Answer 10

• radiopaque
• hexagonal
• precipitate at low pH

Question 11

What is the morphology of struvite stones?

Answer 11

• radiopaque
• coffin lid
• precipitate at low pH
• composed of ammonium magnesium phosphate

Question 12

What do struvite stones tell you?

Answer 12

indicate urinary tract infection with urease + bugs –> proteus mirabilis, staph, or klebsiella that hydrolyze urea to NH3 and alkalinize urine

Question 13

What type of stones can form staghorn calculi?

Answer 13

struvite stones

Question 14

What 3 bugs should you think if struvite stones?

Answer 14

• proteus mirabilis
• staph
• klebsiella

Question 15

What is treatment for struvite stone?

Answer 15

eradicate underlying infection and surgically remove stone

Question 16

What are 3 risk factors for uric acid stones?

Answer 16

• decreased urine volume
• arid climates
• acidic pH of urine

Question 17

Are uric acid stones visible on CT? XRay? ultrasound?

Answer 17

on CT and ultrasound but not xray

Question 18

What diseases are associated with uric acid stones?

Answer 18

• hyperuricemia [gout]

- diseases w/ increased cell turnover like leukemia

Question 19

What is morphology of uric acid stones? pH?

Answer 19

• acidic pH

- rhomboid or rosette appearance

Question 20

What is treatment for uric acid stones?

Answer 20

alkalinization of urine

correct hyperuricosuria by diet or meds [allopurinol]

Question 21

What are some mechs that cause Ca stones?

Answer 21

• hypercalciuria
• hyperuricosuria
• hyperoxaluria
• hypocitraturia

Question 22

What is most common kidney stone presentation?

Answer 22

Ca oxalate stone in pt with hypercalciuria and normocalcemia

Question 23

What are some things that can result in oxalate crystal formation?

Answer 23

• ethylene glycol [antifreeze]
• vit C abuse
• crohns disease

Question 24

What is hypercalciuria?

Answer 24

urinary excretion > 200 mg/day women > 250 mg/day men

Question 25

What is intestinal vs renal hypercalciuria?

Answer 25

intestinal: normocalcemia, normal fasting urinary Ca, decreased PTH
renal: normocalcemia, high fasting urinary Ca, increased PTH

Question 26

What causes hyperoxaluria?

Answer 26

excessive intake green leafy vegetables

Question 27

What are the two types of primary hyperoxaluria?

Answer 27

type 1: glycolic aciduria = decreases 2-oxoglutarate:glyoxylate carboxylase

type2: glyceric aciduria = deficiency glyceric dehydrogenase

Question 28

Why does low citrate excretion put you at risk for Ca stones?

Answer 28

citrate is a Ca chelator in urine

Question 29

What is morphology of Ca stones?

Answer 29

envelope or dumbell shape

Question 30

At what pH do Ca phosphate and oxalate stones precipitate?

Answer 30

Ca phosphate at high pH

Ca oxalate at low pH

Question 31

Are Ca stones radioopaque or lucent?

Answer 31

radiopaque

Question 32

Are Ca stones radiopaque or lucent?

Answer 32

radiopaque