Nephrolithiasis Flashcards
What percentage of men and what percentage of women will have a kidney stone by age 70?
12% of men
5% of women
80% of stones are made of what?
calcium
Of the calcium stones, are there more calcium oxalate or more calcium phosphate stones?
more oxalate
What are the three less common kinds of stones?
uric acid
struvite
cystine
What is the most helpful imaging study for KS? Others?
CT scan is the most common, but we use US for repeaters and KUB can be helpful on occasion
KUB are only really good for what kind of stone?
calcium stones - they’re the only ones that would be radiopque on xray (cystine maybe, but less likely)
How do you treat a kidney stone acutely?
pain meds, hydration, alpha blocker or ca channel blocker
What are the different means you can use to get a stone out?
ureteroscopy extracorporeal shock wave lithotropsy endoscopic lithotripsy pyelolithotomy percutaneous nephrolithotomy
What will calcium oxalate crystals look like?
both dumbbell-shaped and envelope-shaped
some also have a needle-shaped appearance
What are the risk factors for calcium stone formation?
- increased calcium excretion
- increased uric acid excretion
- reduced citrate excretion
- low urine volume
- increased oxalate excretion
What are three things that can cause idiopathic hypercalciuria contributing to kidney stone formation?
- absorptive hypercalciuria (autosomal dominant elevated active vitamin D levels)
- Fasting (resorptive) hypercalciuria - bone loss
- Renal hypercalciuria - renal leak with abnormal calcium reabsorption in the proximal tubule
What are some things that can cause low citrate contributing to Ca kidney stones?
- chornic diarrhea
- renal tubular acidosis
- ureteral diversion
- high protein diet
- topiramate
Basically anything that gives metabolic acidosis!!!
What are some ways you can get hyperoxaluria contributing to Ca kidney stones?
- high oxalate diet
- increased oxalate absorption from a low calcium diet , absorptive hypercalciuria, enteric hyperoxaluria
- overproduction of oxalate (primary hyperoxaluri
What are some medical conditions associated with caclium stone formation>
primary hyperparathyroidism - too much Ca resorption from bone
medullary sponge kidney (reflux of urine back into the renal papilla of the kidney)
distal renal tubular acidosis
What should you do in a metabolic workup of a calcium stone?
- measure plasma calcium
- measure parathyroid hormone
- measure electrolytes
- check serum uric acid
- 24 hr urine collection for volume, calcium, uric acid, citrate, osalate, creatinine, pH, sodium, and phosphorus
What’s the dietary treatment for clacium stones?
increase fluid
decrease salt intake (NaCl is a drive of calcium excretioninto urine)
decrease protine (less acid in the urine, so you don’t get the acid-induced drop of citrate concentration)
maintain calcium!!!! counterintuitive, but you need Ca to bind to oxalate and limit oxalate absorption from the gut
limit oxalate
What meds can you give to manage Ca kidney stones?
thiazide diuretics!!
potassium citrate or bicarbonate (alkalinize the urine to increase citrate excretion)
orthophosphate
Allopurinol/Febuxostat to reduce uric acid production
calcium carbonate to bind to oxalate and stop absorption
Uric stones make up only 5-10% of the stones in the US. Where are they much much more common?
40% of stones in hot, arid climates due to low urine volumes and acidic urine pH
Do uric stones precipitate at alkaline urine or acidic urine?
acidic urine
How can you diagnose a uric stone?
analyze the stone material once recovered
indirectly by demonstratin increased urine uric acid excretion
What’s the treatment for uric stones?
increase urine output with fluid intake
alkalinization of the urine
allopurinol/febuxostat
What are struvite stones made of?
magnesium ammonium phosphate
What do struvite stones look like?
coffin lids
Struvite stones precipitate at alkaline urine or acidic urine?
alkaline - decreases the solubility of phosphate
What causes the increased ammonium levels for the struvite stone formation?
infection with urease positive bacteria like klebsiella or proteus
the ureas breaks down the urea to the ammonium
How do you treat struvite stones?
antibiotics to kill the bacteria
acetohexemic acid - a urease inhibitor so you don’t get the ammonium formation even if the bacteria are there
ESWL or percutaneous nephrolothotomy required because you can’t pass a struvite stone
What do cysteine stones look like?
hexagonal - practically pathognomonic for cystinuria
Cystinuria is a genetic disorder passed along in what inheritance pattern?
autosomal recessive
What’s the disorder?
imparied cystine transport leading to decreased proximal tubular re-absorption and increased cystine excretion
How are the cystinuria subtypes characterizes?
by how much cystine is excreted by the parents, who are usually asympaotmati cheteroxygotes:
1/1: only small amounts
II/II: large amounts
III/III; intermediate amounts
combinations can occur
What will cystein stones looke like on imagine compared to the calcium stones?
fuzzy gray in appearance - less radio-opaque than calcium
How do you deal with cystine stones medically?
high fluid intake (over 3 L/d)
alkalinization of urine
restrict dietary Na (you want more proximal reabsorption of cysteine and it will follow Na)
Penicillamine tiopronin, and and captopril will complex with cystine and make it more soluble for easy excretion
Why are the cystine stones relatively resistant to ESWL? What can you do then?
They’re softer than other stones
you can do percutaneous nephrolithotomy
ultrasonic lithotropsy
renal transplant will cure disease actually
If someone has a first stone, medical treatment is only indicated when what?
then there’s evidence of active stone disease: formation of new stones, enlargement of old stones, passage of gravel, multiple stones at presentation
What is the risk of a symptomatic 2nd stone in 1 year? 5 years? 10 years? Which gender?
15% at 1 year
35-40% in 5 years
50% at 10 years
men more than women
What are the complications of ESWL
ift he pieces only break down to a little less than 3 cm, you still have risk of obstruction (need stenting)
reversibly damages blood vessels and tubules
new hypertension rpesumably due to renin release from focal areas of renal ischemia
measureable impairment in renal function presumably due to scar formation
residual caliculi after ESWL have high incidence of stone formation
