Kidney Stones Flashcards
dietary interventions to prevent calcium stone reoccurrence
reduce Na, reduce animal protein, increase Ca intake, increase daily fluid intake, increase citrate, increase fruits and vegetables.
How does increased Ca intake help decrease Ca oxalate stones?
decreases oxalate absorption in GI tract if there’s more Ca ingested and it prevents urinary excretion of oxalic acid.
How does fluid decrease Ca oxalate stones?
increased urinary flow and decreased solute conc
How does increasing citrate decrease Ca oxalate stone?
decreases urinary Ca (binds to urinary Ca to inhibit stone formation)
How does increased fruits and veggies decrease Ca oxalate stone?
Increased citrate excretion in kidney
Is supplementary Ca increase or decrease risk for Ca oxalate stone?
increases.
Ok to increase dietary Ca to help reduce but supplementary can increase risk for stones.
What does high sodium intake do to risk for Ca oxalate stones?
high Na intake decreases Proximal tubule Na reabsorption so increases urinary Ca levels and increased risk for stone development.
What does coffee, alcohol and tea do for your risk of Ca oxalate stones?
helps decrease risk due to diuretic effect.
when a kidney stone need to first rule out what?
urosepsis, acute renal failure, complete obstruction
if stone is >10 mm
urology consult
If stone is <10 mm
hydration, pain control alpha blockers (tamsulosin) and strain urine to categorize
If stone is <10 mm at what point do you consult urology?
uncontrolled pain, no stone passage in 4-6 weeks.
treatment of stones >10 mm
shock wave lithotripsy or ureteroscopy but with big stones >15 mm need endoscopic stone fragmentation.
When do we put in percutaneous nephrostomy tube?
if hydronephrosis or signs of rapidly progressive renal failure
what causes cysteine kidney stones?
rare and seen with cysteinuria a genetic defect classified by urinary cysteine (often >400 mg/day)
Have hexagonal cysteine cyrstals
are cystine stones seen on CT scan?
can see on CT scan but less radiopaque compared to calcium nephroliths.
what shape of kidney stone do cysteine kidney stones have?
hexagonal
how to treat cysteine stones?
increase fluid intake to 2L and restrict intake of protein and sodium and alkalizing urine to increase cysteine solubility with potassium bicarbonate or potassium citrate will help keep ph>7.
how to treat uric acid nephrolithiasis?
xanthine oxidase inhibitors like allopurinol.
how does citrate help decrease formation of calcium stone?
it binds to calcium and decreases calcium stone formation. Dietary sources of citrate are 4 oz of lemon juice and increase urinary citrate excretion.
how does increasing fruit and vegetable intake and decreasing animal protein help decrease calcium stone formation
fruits and veggies increase citrate excretion in kidney
decreasing animal protein helps to decrease acid load and urinary calcium excretion
simple lifestyle changes to help decrease calcium stones?
restrict sodium and animal protein
increase calcium intake, citrate and fluids, fruits and vegetables.
alkaline urine (ph>8) hematuria with right frank pain, dysuria and recurrent UTI hx
Suggestive of struvite stones.
what causes struvite stones?
urease producing bacteria (Proteus and Klebisella) They convert urea to ammonia which raises urine pH and cyrstallizes with magnesium and trivalent phosphorus to make struvite crystals.
what can happen once struvite crystals are present?
they can expand over weeks to months and develop into a staghorn calculus and fill entire renal collecting system and once there the stones can continue to seed infections and have UTI’s and lead to loss of kidney function.
can antibiotics treat staghorn calculi?
difficult to manage with antibodies as it doesn’t eliminate the nidus for infection because bacteria can grow within the stone matrix and it is not eradicated until entire stone and fragments are removed.
how to manage staghorn calculi?
abx for UTI, percutaneous nephrolithotomy with lithrotripsy as 1st line.
Open surgical stone removal is indicated in morbidly obese individuals in whom fluoroscopy is difficult.
do we ever do nephrectomy for pt with staghorn calculi?
only if the kidney itself is poorly functioning and non functioning.
urine alkalinization is helpful for people who have
uric acid stones or calcium oxalate stones and have low urine citrate excretion.
predisposing factors for renal/perinephric abscess
DM2, renal stones (staghorn calculi) neurogenic bladder obstructive malignancy Polycystic kidney disease recent UTI with bacteremia
clinical presentation of a renal/perinephric abscess
fever, flank pain and or abdominal pain dysuria and increased urinary frequency no improvement with UTI after 3-5 days can be asymptomatic and especially in pts who are elderly or diabetic.
how does a perinephric abscess occur
with direct extension of pyelonephritis but can also happen from hematological seeding.
who gets these perinephric abscesses?
pregnant or DM2 or anatomical UTI abnormalities.
Are there UTI like symptoms with perinephritic abscess ?
no generally absent
UA will show pyuria but also can be normal if infection is walled off by urinary system
how to diagnose perinephric abscess?
CT scan of abdomen (preferred or U/S)
treatment for perinephric abscess
drainage percutaneously
and antibiotics
insidious onset fever, lumboabdominal pain, malaise, and weight loss
see recent UTI and UA has pyuria
perinephric abscess.
who gets recurrent calcium oxalate stones?
people with malabsorption
Crohn’s and Bariatric surgery pts because malabsorption causes more intestinal fatty acid binding to calcium which increases colonic oxalate absorption and renal oxalate excretion
why does bariatric surgery cause recurrent calcium oxalate stones?
due to hypocitraturia and hyperoxaluria.
malabsorption causes more intestinal fatty acid binding to calcium which increases colonic oxalate absorption and renal oxalate excretion
Malabsorption also causes low urinary citrate for unclear reasons. Maybe there’s hypokalemia or chornic metabolic acidosis (from malabsorptive diarrhea) and so there’s increased citrate reabsorption in renal proximal tubule and so there’s less citrate in urine. Citrate is also protective of kidney stone formation.
Treatment of bariatric pt with reoccurrent oxalate stones
low oxalate diet and exogenous citrate supplementation.
what are risk factors for uric acid stones?
hyperuricosuria and low urine PH
uric acid stones incidence
are they seen on XR?
10-15% of all kidney stones
seen in low pH urine and hyperuricosuria.
uric acid stones are radiolucent on XR but can be seen on renal U/S and CT scan
treatment of uric acid stones is to have:
hydration,
alkalinization of urine
low purine diet.
To alkalinize urine, to 6-6.5 need to take potassium citrate as uric acid stones are highly soluble in alkaline urine.
which type of stone is potassium citrate helpful for treating?
uric acid stones and cysteine stones
It stone is highly soluble in alkaline urine and citrate is a stone inhibitor and reduces crystallization.
allopurinol can also be used in
uric acid stones if potassium citrate doesn’t help and there are recurrent symptoms.
calcium oxalate stones are caused by
hyperparathyroidism (hypercalciuria)
malabsorption (hyperoxaluria)
distal RTA (hypocitraturia)
see envelope shaped crystals in urinalysis
uric acid crystals are caused by
gout
myeloproliferative disorders
TLS
see rhomboid and radiolucent stones
struvite stones are caused by
recurrent UTIs
see staghorn crystals and coffin lid crystals
cysteine crystals are caused by
decreased reabsorption of cystine in kidney
autosomal recessive treate
see hexagonal green/yellow crystals and large branched calculi.
prevention of cysteine stone formation:
alkalinization of urine with potassium citrate or bicarbonate and chelating agents
need to have higher urine volume.
renal colic with severe acute flank pain that radiates to ipsilateral groin
see macroscopic hematuria and urinary frequency
kidney stone presentation
best imaging study for scan:
non contrast helical C scan for high sensitivity and specificity
renal U/S can also be used in pregnant pts but inadequate for mid to distal ureteric stones.
if someone is taking topiramate then what kind of stone do they get?
calcium phosphate due to elevated urine pH.
seen with distal (RTA 1) and hyperparathyroidism
topiramate is a carbonic anhydrase inhibitor.
