Nephrolithiasis Flashcards
Gold standard Dx of kidney stones?
Non-contrast CT.
What is the utility of U/S and KUB in kidney stone dx?
1) U/S detects hydro, but not good for distal stones or early hydro. Can be used in pregnancy.
2) KUB - not sensitive enough, but can be used to track resolution.
What lab test is ordered for kidney stones?
U/A micro. Should show RBCs - if not, probably not a stone.
What are the four kinds of kidney stones?
Calcium (80%), Struvite (15%), uric acid (5%), cysteine (1%).
At what pH do calcium stones precipitate at?
Calcium phosphate: high pH.
Calcium Oxalate: low pH.
X ray findings of calcium stones?
Radioopaque
Shape of calcium stones?
envelope or dumbbell-shaped (calcium oxalate).
What can cause calcium oxalate stones?
ethylene gycol (antifreeze), vitamin C abuse, hypocitraturia, malabsorption (eg crohns, short bowel).
Most common lab findings in pt presenting with calcium oxalate stone?
Hypercalciuria, normocalcemia.
Treatment of calcium oxalate stones?
Hydradation, thiazides, citrate.
What are struvite stones?
Ammonium magnesium phosphate
At what pH do struvite stones precipitate?
high pH.
X ray findings of struvite stones?
radioopaque
Shape of struvite stones?
staghorn caliculi, coffin lids.
Common causes of struvite stones?
Infection w/ urease + bugs such as proteus mirabilis, staph saphrophyticus, klebsiella.
What does urease + bugs have to do with struvite stones?
Convert urea to ammonia, alkanizing the urine and making conditions for precipitation.
Treatment of struvite stones?
Treat udnerlying infection + surgical removal of stone.
At what pH do uric acid stones precipitate?
low pH.
X ray findings of uric acid stones?
radiolucent. Must use CT or ultrasound instead.
Shape of uric acid stones?
rhomboid or rosettes.
Risk factors for uric acid stones?
Hyperuricemia (gout), High cell turnover conditions like leukemia and tumor lysis syndrome.
Treatment of uric acid stones?
Alkalinization of urine (potassium bicarb)
Inhibition of uric acid formation (allopurinol)
Make excess uric acid into soluble metabolite (rasburicase).
At what pH do cysteine stones precipitate?
low pH.
X ray findings of cysteine stones?
radiolucent.
Shape of cysteine stones?
hexagonal or staghorn caliculi.
Etiology of cysteine stones?
Hereditary (AR) condition - cysteine channels in PCT lose function; cystinuria. Cysteine poorly soluble, stones form.
In what age group are cysteine stones most commonly seen?
children
What is the test for cysteine stones?
Sodium cyanide nitroprusside.
Treatment of cysteine stones?
alkalinization of urine.
What are the easy guidelines for management of a kidney stone?
3cm - Surgery.
What other meds can be used as medical expulsive therapy?
CCBs (amlodipine)
Alpha blockers like terazosyn/doxyzosyn.
If the stone is proximal, what will be surgical approach be?
Laparoscopic > > > open
If the stone is distal, what will the surgical approach be?
percutaneous ureteroscopy + anterograde removal.
If the patient is septic, what will the approach be?
Nephrostomy (proximal), stent (distal).
