Nephrolithiasis Flashcards
What is linked to risk of kidney stones?
White males at highest risk, black males lowest risk
Hot weather
Lunar cycle
Whats the relationship between kidney stones and CVD?
Positively related
31% increased risk of MI
What types of stones are there & what are the risk factors?
- *Calcium 70-80%**
- hypercalciuria
- hyperuricosuria
- low urine volume
- hyperoxaluria
- low urine citrate
- *Uric acid**
- low urine pH
- metabolic syndrome
- *Magnesium ammonium phosphate (struvite)**
- urine infection with urea splitting bacteria
- *Cystine**
- cystinuria (autosomal receissive of cystine, ornitine, arginine, lysine)
Meds: indinavir, bactrim, allopurinol
How can you get hypercalciuria?
Bone resportion: hyperparathyroidism, hyperthyroidism, cancer, renal tubular acidosis (low serum bicarb –> lower pH –> more bone resorption bc bone releases bicarb)
Vitamin D excess i.e. inflammatory conditions-sarcoidosis, lymphoma
Idiopathic hypercalciuria: gut- absorptive, bone- increased turnover; kidney- renal leak
What are the 2 types of calcium stones you can get? Risk factors?
Calcium oxalate: 70% of stones, “envelope” shaped crystals
- normally 10% dietary oxlate absorbed in colon; 90% bound by Calcium and passes via stool; here we have increased oxalate absorption or production of oxalate
Risk factors: hypercalciuria, hyperuricosuria, hypocitraturia, hyperoxaluria, low urine volume; malabsorption, obesity/gout, and genetic disorders can cause it
Calcium phosphate: 10-15% of stones: “coffin lid” appearance on micro
risk factors: hypercalciruia, alkaline urine pH, medullary sponge kidney
- exact same minearl composition as bones & teeth
Uric acid stones: risk factors, imaging?
Diamond shaped, radiolucent on plain films, detectible by RUS or CT
Risk factors: acidic urine, gout, hyperuricemia, metabolic syndrome, malignancies
Struvite stones
MgNH4PO4 + CaCO3 stones
“Staghorn” stones
Urease producing bacteria: proteus, haemophilus, klebsiella, ureaplasma urealyticum
Risk factors: UTI
Cystine stones
Autosomal recessive defects in tubular transporters of dibasic AA’s: cystine, ornithine, arginine, lysine
Cystine insoluble in acidic urine
UA/micro: hexagonal urine cystals
Imaging: CT or RUS
Can present as staghorn = huge crystal
How do stone inhibitors work?
Neg charged molecules that inhibit crystal nucleation & prevent crystal growth
Adsorb onto crystal surface & interfere with lattice formation
Examples: magnesium, citrate, and macromolecules too
What are the signs and symptoms of kidney stones?
Acute, colicky flank pain radiating to the groin
CVA tenderness
Hematuria in 90%
Silent ureteral obstruction
Unexplained persistent UTI
painless hematuria
Note that crystals are not sensitive or specific for kidney stones
Differential dx for flank pain?
Musculocskeletal pain
Herpes zoster
Diverticulitis
Duodenal ulcer
Cholecystitis
Pyelonephritis
Renal infarct
Renal hemorrhage
Gynecologic disorders
Ureteral obstruction from ureteral stricture
What are your options for radiolotical dx of stones?
KUB: kidneys, ureter, and bladder X-ray
Better than CT scan
Helps you localize stones, find out how big they are, and plan your treatment
Preferred method for foollow up of radio-opaque stones
Renal ultrasound: can image both radiolucent and radioopaque; low radiation exposure, high specificity and sensitivity; not so good for small stones
Helical non-contrast CT: study of choice, faster and more sensitive, doesn’t require contrast; can visualize uric acid stones by gray-scale methods; dx of urinary tract abnormailities that predispose to stones and rule out conditions that present as renal colic
Which stones are more likely to pass?
<6mm will probably pass on its own
>6mm probably require stone intervention
How do you manage first time stones?
Risk factor assessment: job, fam hist, diet (protein, purines, Na, fluid, Ca, oxalate), eds (triamterene, indinavir, sulfonamides, carbonic anyhdrase inhibitors)
Lab evaluation: creat, HCO3, Ca, phos, PTH, UA, urine culture
Referal to stone clinic: children, solitary kidney, struvite stones (large stones), abnormal renal function, RTA
How do you mange recurrent stones / high risk pt’s?
24h urine collection for Ca, oxalate, citrate, uric acid, pH, cystine
Urine culture if struvite/staghorn
