Kidney Stones B&B Flashcards
what are the 4 types of nephrolithiasis (kidney stones)?
what symptoms do kidney stones cause?
- calcium
- struvite
- urate
- cystine
—> flank pain that is colicky (waxes/wanes), hematuria
what is the most common type of kidney stone and what is it usually caused by?
calcium stones - usually calcium oxalate, can also be calcium phosphate
most often idiopathic hypercalciuria
how do calcium kidney stones appear on x-ray and CT?
radiopaque - bright white
what are the common etiologies of calcium kidney stones? (5)
- most common: idiopathic hypercalciuria
- hyperparathyroidism —> hypercalcemia
- Crohn’s disease or gastric bypass —> high oxalate levels (calcium oxalate)
- ethylene glycol (antifreeze) —> oxalate formation
- Vitamin C abuse —> oxalate generation
what type of kidney stones can be caused by Crohn’s disease?
note calcium is normally bound to oxalate
Crohn’s disease: fat malabsorption —> fat binds to calcium, leaving oxalate free to be absorbed —> high oxalate levels —> calcium stones (calcium oxalate)
*gastic bypass can cause calcium oxalate stones by the same mechanism (fat malabsorption)
hyperparathyroidism can cause what type of kidney stone formation?
hyperparathyroidism —> hypercalcemia —> calcium stones
ethylene glycol (antifreeze) and vitamin C are similar in that they can both cause what type of kidney stone?
both generate oxalate —> high levels of oxalate can form calcium oxalate stones
Pt is a 24yo F presenting with flank pain and hematuria. She says she’s been drinking less water lately because she feels bloated. Blood test shows normal calcium levels, but urinalysis shows increased calcium. What is likely going on?
calcium stone (nephrolithiasis)
dehydration is a risk factor for nephrolithiasis
x-ray/CT will show radiopaque stone (bright white)
what 2 medications can you give a patient with recurrent calcium kidney stones?
- thiazides: decrease calcium in urine*
- citrate (potassium citrate): binds calcium but remains dissolved —> lowers urinary calcium
*recall that by inhibiting Na+ reabsorption, Ca2+ and Mg2+ secretion decreases (it’s a charge thing)
what are struvite kidney stones made of and what are they caused by?
struvite stones: ammonium, magnesium, phosphate
consequence of urinary tract infection by urease positive bacteria: proteus mirabilis, staphylococcus, klebsiella, enterobacter, pseudomonas - hydrolyze urea to ammonia, which makes urine alkaline —> stone formation
what kind of kidney stones will be caused by proteus mirabilis, pseudomonas, or klebsiella?
urease positive bacteria hydrolyze urea to ammonia, causing urine to become alkaline and form struvite stones (ammonium, magnesium, phosphate)
strUvite caused by Uti
how do struvite kidney stones present and how are they treated?
strUvite stones: caused by Urease positive bacteria (Urinary tract infection)
form “staghorn calculi” - like a cast of the renal pelvis and calyces, requires surgery
appear radiopaque on x-ray and CT
Pt is a 45yo M presenting with symptoms of a UTI (dysuria, frequency), mild flank pain, and hematuria. Labs are positive for the presence of staphylococcus. Imaging shows a radiopaque cast of the renal pelvis and calyces. What is going on and how will you treat it?
strUvite stones: caused by Urease positive bacteria (proteus, staphylococcus, klebsiella)
form “staghorn calculi” - like a cast of the renal pelvis and calyces, requires surgery
how will uric acid kidney stones appear on x-ray?
trick question! uric acid stones are radiolucent - cannot be seen on x-ray, need to be imaged with CT scan
what is the treatment for uric acid kidney stones?
hydration, potassium bicarbonate (alkalization of urine)
rarely allopurinol - xanthine oxidase inhibitor, reduces uric acid production
medical therapy effective, does not require surgery
Pt is a 37yo M living in Africa with a PMH of myeloproliferative disease, presenting with flank pain and hematuria. An x-ray is done which comes back normal. What is likely going on? What is a test you can run to confirm this?
uric acid stones - radiolucent on x-ray, need a CT scan to visualize
risk factors include high uric acid levels (gout, leukemia, myeloproliferative disease), acidic urine (chronic diarrhea), and living in a hot/arid climate (lower urine volumes make acidification more likely)
can be treated with medicine (potassium bicarbonate), surgery NOT required
what kind of kidney stone can be caused by chronic diarrhea? how can the stone be treated?
chronic diarrhea causes acidification of urine —> uric acid stones
treat with hydration + potassium bicarbonate (surgery NOT needed)
in which patients are cystine kidney stones found? how do the present?
cystine stones: rare, seen in children with cystinuria (tubular defect, cannot absorb cystine)
—> staghorn calculi, but NO history of UTI (contrast with struvite stone)
in which patients is urolithiasis (renal calculi) most common
males between 20-30
what is the most important determinant in the propagation of renal stones?
increased urinary concentration of the stone constituents such that it exceeds their solubility (supersaturation)
this is exacerbated by low urine output and dehydration
describe how hyperuricosuric calcium nephrolithiasis develops
calcium oxalate stones can be associated with increased uric acid secretion with/without hypercalciuria
in this setting, calcium oxalate is “nucleated” by uric acid crystals in the collecting ducts
under what conditions do calcium phosphate kidney stones precipitate and what does their presence suggest?
precipitate at high urine pH (alkaline environment)
suggest underlying metabolic disorder - Type I (distal) RTA (alkaline urine pH), primary hyperparathyroidism (high concentrations of Ca2+/PO4 in urine), or medullary sponge kidney (urine stasis, UTIs, distal RTA)
what kind of kidney stone can be treated with lithostat (acetohydroxamic acid)?
lithostat: irreversible inhibitor of bacterial urease
can be used in treatment of struvite stones (caused by urease-positive bacteria) - but note struvite stones must also be surgically removed (form staghorn casts)
cystinuria vs cystinosis
cystinuria: genetic defect in cystine absorption from proximal tubule —> cystine stones
cystinosis: genetic mutation causing systemic cystine accumulation within lysosomes —> Fanconi syndrome, progressive renal failure
