Nephrolithiasis

Types of stones and risk factors (JAMA 200S:293.1107: Lancet 2006:367:333)

• Calcium (Ca oxalate Ca phosphate): 70-90% of kidney stones

Urine characteristics: T Ca. t oxalate, t urate.! pH. I citrate, i volume 2° hypercalciuria: 1° hyperparathyroidism, type 1 RTA, sarcoid 2° hyperoxaluria: Crohn's or other ileal disease with intact colon Diet: t animal protein, t sucrose, T Na. i K. I fluid. 1 fruits vegetables

• Uric acid: S-10% of kidney stones, radiolucent on plain film

Urine characteristics: t uric acid (eg, gout), I pH (eg. from chronic diarrhea)

• Magnesium ammonium phosphate ("struvite" or "triple phosphate")

Chronic UTI with urea-splitting organisms (eg. Proteus) f urine NH3 and pH

• Cystine: inherited defects of tubular amino acid reabsorption

Clinical manifestations

• Hematuria (absence does not exclude diagnosis), flank pain. N V. dysuria. frequency

• Ureteral obstruction (stones -5mm unlikely to pass spont.) -»ARF if solitary kidney

• UTI: f risk of infection proximal to stone; urinalysis of distal urine may be normal Workup

• Noncontrast helical CT scan

• Strain urine for stone to analyze; U A & UCx. electrolytes. BUN Cr. Ca. PO4. PTH.

uric acid

• 24-h urine ( 6 wks after acute setting) for Ca. PO<. uric acid, oxalate, citrate. Na. Cr Acute treatment (NEJM 2004:350.684)

• Analgesia (narcotics or NSAIDs). aggressive PO IV hydration, antibiotics if UTI

• Consider CCB or alpha blocker to promote ureteral relaxation (Lone« 2006:368:1171)

• Indications for immediate urologic evaluation and/'or hospitalization: obstruction

(especially solitary or transplant kidney), urosepsis, intractable pain or vomiting. ARF

• Urologic Rx: lithotripsy, cystoscopic stent, percutaneous nephrostomy, stone removal

Chronic treatment

• Calcium stones: 24-h urine identifies specific urinary risk factors to treat i Na and meat intake (NEjm 2002.346 77), thiazides: decrease urine Ca Depending on 24-h urine: K-citrate, dietary oxalate restriction, allopurinol High dietary Ca is likely beneficial, unclear role of Ca supplements

• Uric acid: urine alkalinization (K-citrate). allopurinol

• Magnesium ammonium phosphate: antibiotics to treat UTI. urologic intervention

• Cystine: urine alkalinization (K-citrate), D-penicillamine, tiopronin

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