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uric acid stone (urate nephropathy, gouty nephropathy)
Etiology:
predisposing factors
1) 25% of patients with gout have uric acid stones
2) urine pH is often very acidic
3) hyperuricosuria
4) dietary protein excess can predispose to uric acid stones
5) colectomy & ileostomy predispose to uric acid stones because of decreased intestinal ureolysis & increased loss of water & alkali
6) chronic diarrhea
7) metabolic syndrome
8) lymphoproliferative & hematologic disorders
- tumor lysis syndrome
Laboratory:
1) urinalysis: urine is often very acidic
2) serum uric acid & urine uric acid levels are often normal
3) urine pH < 6.0 is risk factor [2]
3) 24 hour urine urate
a) > 1 g/day is risk factor
b) target is 100-300 mg/day [2]
Radiology:
1) uric acid stones are radiolucent
2) visualized by ultrasound or computed tomography (CT)
Management:
1) increased intake of fluids
2) decreased protein intake
3) alkalinizing urine to pH of 6.5
a) helps prevent uric acid stone formation
b) dissolves existing stones
c) potassium citrate treatment of choice [2]
d) NaHCO3 or citrate (Bicitra)
4) allopurinol or hypouricemic agent
a) not as effective as urine alkalinization, but helpful in patients with hyperurisocuria
b) used as prophylaxis for tumor lysis syndrome
Related
hyperuricemia
hyperuricosuria
urate; uric acid
General
urinary calculus (stone, nephrolithiasis, urolithiasis)
nephropathy
References
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed)
Lippincott-Raven, Philadelphia, 1998, pg 615-16
- Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 19.
American College of Physicians, Philadelphia 1998, 2012, 2015, 2021
- Wiederkehr MR, Moe OW.
Uric Acid Nephrolithiasis: A Systemic Metabolic Disorder.
Clin Rev Bone Miner Metab. 2011 Dec;9(3-4):207-217.
PMID: 25045326 Free PMC Article