Nephrolithiasis Flashcards
dietary factors that lead to nephrolithiasis
low fluid intake, calcium, K
high oxalate, protein, Na, sugar drinks
Inhibitors of stone formation
magnesium, citrate, pyrophosphate, THprotein
inhibits caox crystal formation and growth binding with oxalate
Magnesium
retards the crystal growth of CaP and CaOx crystals by binding to the surface of basic CaP crystals
pyrophosphate
chelates calcium, reduced calcium binding calcium with Ox and P
Citrate
acts as both promoter and inhibitor of stone formation
THProtein
metabolic processes that induce ca stone formation
Increase urine ca > 4 mkd, 250-300 mg/day; Urine Uric acid > 800 mg/day, urine oxalate > 45 mg/d, Dec Ucitratee < 320 mg/day; alterations in urine ph
most common metabolic abnormality in ca stone formation
absorptive hypercalciuria
most common cause of resoprtive hypercalciuria
primary hyperparathyroidism
highest source of uric acid
de novo synthesis
clinical conditions with hypocitraturia
overproduction acidosis, underexcretion acidosis
K deficiency
excess dietary protein
autosomal recessive condition in childhood with CaOx stones and nephrocalcinosis, frequent stone recurrence
primary hyperoxaluria
inflammatory bowel disease, jejunoileal bypass, bariatric surgery for morbid obesity
enteric hyperoxaluria
predispose to hyperuricosuric ca oxalate lithiasis
highly acidic urine (pH < 5.5)
predispose to caphos lithiasis
alkaline urine (pH > 6.7)
most impt in uric acid stones
low urine pH
main cause of idiopathic uric acid urolithiasis
low urine pH
patients with gouty arthritis and kidney stones, UA > 10 md/d, urine ua > 1000 mg/day
hyperuricosuria
Increases saturation of all stone forming elements
low urine volume
Pathophysio of uric acid stones
Low urine pH, volume
Hyperuricosuria
genetic disease caused by inactivating mutations of the subunits of a dibasic aminoacid transporter in then proximal tubule
cystinuria
most common primary inherited aminoaciduria
cystinuria
family hx of cystinuria (> 400 mg/day vs 30 mg), staghorn calculi, hexagonal crystals on urinalysis
cystinuria
most prevalent component of kidney stones
calcium oxalate
most likely cause of nephrolithiasis in a patient with distal RTA
hypocitraturia
depressions near the papillary tips, yellow crystalline deposits in the ducts of bellini, some randall plaques
Calcium phosphate
1st kidney stone work up
medical hx, stone analysis, urine analysis
Recurrent kidney stone
full metabolic evaluation - serum panel, PTH, VitD if hyperCa, 24ag urine >= 2 samples Na Ca Oxalate Uric acid citrate
indicative of minimal fluid intake
urine volume less than 2.5L
pH with increase risk of uric acid precipitation, idiopathic uric acid stone, intestinal disease and diarrhea and intestinal bypass surgery
less than 5.5
Increase risk of caphos precipitation, dRTa, primary hyperparathyroidism, alkali, ca tx
pH > 6.7
pH that indicates urinary tract infection fom urease producing bacteria
> 7-7.5
Normal UCrea
F: 15-20 mk
M: 20-25 mk
reflects dietary Na and K intake
24H urine Na and K
Major cause of hypercalciuria
High Na intake
Normal Urine Na K Ca
Na 100 K 40-60 Ca < 250-300 mg
Low Mg increases risk of
calcium stones
UMg <30-120 mg
UOxalate > 100 mg/day
primary hyperoxaluria
Higher Uphos > 1100 mg
calcium phosphate formation
hyperuricosuria, Uuric acid > 600-800
CaOx stones Uph > 5.5
Uric acid stones UpH <5.5
marker of dietary acid intake
sulfate
high ammonium/sulfate ratio
GI alkali loss
Normal Urine NH4
30-40 meq
Petsistent high Uca on a restricted diet
intestinal hyperabsorption of Ca
Elevated fasting Ca/Crea (0.11 mg/100 ml or <2.7 umil/100 mg), high serum calcium, elevated pth
primary hyperparathyroidism
Elevated Ca/Crea, normal serum Ca, normal or suppressed PTH
resoprtive hypercalciuria
elevated Ca/Cr, normal Ca, elevated pth
Renal hypercalciuria
Elevated Ca/Cr (0.2 mg/mg or 0.56 mmol/mmol) 4h Ca/Crea after 1 g oral load
absorptive hypercalciuria
dumbless shaped crystals
calcium oxalate monohydrate
Envelope shaped crystals
calcium oxalate dihydrate
Flat shaped or wedge shaped prisms, often in rosettes
Calcium phosphate
Gold standard for kidney stone diagnosis
noncontrast ct
un enhanced ct scan
ct stonogram
time when surgical intervention is indicated
4 weeks
average days of stone passage
40 days
medical expulsive therapy
ccb, steroids, a-blockers
target fluid intake
Urine volume > 2.5L
cystinuria > 4L water intake
Dietary mgt
Na < 100 meq/day animal protein 50-60 g/day Ca 1000-1200 mg avoid > 1g Vit C Fruits/vegetables
Drug of choice hypercalciuria in caOx and Caphos stone formers
Thiazides 25 bid
Tx hypocitraturia in caox and caphos, uric acid stones, cystine stones
20-80 meqs 3-4 doses
uric acid: pH goal > 6, cysteine pH > 7,
Treatment Ca stone formers with hyperuricosuria
Allopurinol 100-300 mg/d
cystine stones
penicillamine
Struvite stones when other interventions have failed
acetohydroxamic acid 15 mkd
first line therapy for uric acid stone formers
Urine alkalinization
tx of choice struvite stones, impacted stone; largest stone free rate and less recurrenfe rate
percutaneous nephrolithotomy
hexagonal stones- tx
Cystine, tiopronin
coffin lid like
struvite
uric acid stones are
pleomorphic