Le 16 Nephrolithiasis Flashcards
What should you think if recurrent stones?
probably some sort of biochem abnormality
What is the breakdown of prevalence of the 4 types of stones?
80% Calcium
15% Struvite
5% Uric acid
1% cystine
What does presence of cystine stones tell you?
patient has cystinuria?
What is cystinuria?
congenital enzyme deficiency impairing epithelial transport di-basic AA cystine, ornithine, lysine, arginine [COLA]
Transport of what 4 AA is impaired in cystinuria?
- cysteine
- ornithine
- lysine
- arginine
[COLA]
What is the inheritance of cystinuria?
autosomal recessive
What is clinical manifestation of cystinuria?
precipitation of hexagonal cystine stones; present as kids
How do you diagnose cystinuria?
positive Na-nitroprusside test
What is treatment for cystine stones?
alkalinize urine and hydration
What is the appearance/pH of cystine stones?
- radiopaque
- hexagonal
- precipitate at low pH
What is the morphology of struvite stones?
- radiopaque
- coffin lid
- precipitate at low pH
- composed of ammonium magnesium phosphate
What do struvite stones tell you?
indicate urinary tract infection with urease + bugs –> proteus mirabilis, staph, or klebsiella that hydrolyze urea to NH3 and alkalinize urine
What type of stones can form staghorn calculi?
struvite stones
What 3 bugs should you think if struvite stones?
- proteus mirabilis
- staph
- klebsiella
What is treatment for struvite stone?
eradicate underlying infection and surgically remove stone
What are 3 risk factors for uric acid stones?
- decreased urine volume
- arid climates
- acidic pH of urine
Are uric acid stones visible on CT? XRay? ultrasound?
on CT and ultrasound but not xray
What diseases are associated with uric acid stones?
- hyperuricemia [gout]
- diseases w/ increased cell turnover like leukemia
What is morphology of uric acid stones? pH?
- acidic pH
- rhomboid or rosette appearance
What is treatment for uric acid stones?
alkalinization of urine
correct hyperuricosuria by diet or meds [allopurinol]
What are some mechs that cause Ca stones?
- hypercalciuria
- hyperuricosuria
- hyperoxaluria
- hypocitraturia
What is most common kidney stone presentation?
Ca oxalate stone in pt with hypercalciuria and normocalcemia
What are some things that can result in oxalate crystal formation?
- ethylene glycol [antifreeze]
- vit C abuse
- crohns disease
What is hypercalciuria?
urinary excretion > 200 mg/day women > 250 mg/day men
What is intestinal vs renal hypercalciuria?
intestinal: normocalcemia, normal fasting urinary Ca, decreased PTH
renal: normocalcemia, high fasting urinary Ca, increased PTH
What causes hyperoxaluria?
excessive intake green leafy vegetables
What are the two types of primary hyperoxaluria?
type 1: glycolic aciduria = decreases 2-oxoglutarate:glyoxylate carboxylase
type2: glyceric aciduria = deficiency glyceric dehydrogenase
Why does low citrate excretion put you at risk for Ca stones?
citrate is a Ca chelator in urine
What is morphology of Ca stones?
envelope or dumbell shape
At what pH do Ca phosphate and oxalate stones precipitate?
Ca phosphate at high pH
Ca oxalate at low pH
Are Ca stones radioopaque or lucent?
radiopaque
Are Ca stones radiopaque or lucent?
radiopaque
