1. Methods Results (Cont.)
Abstract number: 11573
Methods
Results (Cont.)
We identified three sets of guidelines for the prophylaxis of uric acid stone formation. These guidelines are widely acknowledged and are commonly referred to by urologists worldwide. We appraised the levels of evidence given for guidance published and hand searched reference lists. We methodologically appraised cited studies and graded the evidence used to support the guidelines according to the system described by the Centre for Evidence Based Medicine, Oxford (2011).
No randomised controlled trial evidence investigating the prophylaxis of uric acid stones was identified from the references cited by any of the three guidelines.
Guidelines for preventing the recurrence of uric acid stones: where is the evidence?
Results
Conclusion
R Macleod, M Jordaan, SJ Symons, CS Biyani
Pinderfields Hospital, Wakefield, England
A complete lack of controlled trial evidence may preclude consensus between guidelines. The guidelines are based on evidence from case series at best. It has been suggested that the well-established role of allopurinol in the treatment of this condition has prevented randomised trials in recent years but it is clear that evidence based medicine is not being practiced in the treatment of these patients.
TREATMENT (level of evidence)
GUIDELINE
DIET
FLUID VOLUME
URINARY ALKALINISATION
ALLOPURINOL
OTHER
AUA
Limit intake of non-dairy animal protein (5)
No comment
Potassium citrate to increase
pH to 6 (5)
Second line if alkalinisation fails (5)
EAU
Limit intake of urate-rich food to ≤500mg/day (5)
‘General measures’ (5)
Alkaline citrates or sodium bicarbonate
pH (4)
For patients with hyperuricosuria (100mg/day) + hyperuricaemia (300mg/day) (5)
CARI
Re: purines – ‘curb overindulgence’
(5)
Promote ‘large urine volumes’ (5)
Increase urine pH (4)
Recommended ( mg) (4)
Mentions acetazolamide for nocturnal urine alkalinisation (not recommended) (5)
Background
Urolithiasis is a common disorder affecting 1 in 10 worldwide. Recurrence rates are reported as 35% at 10 years, rising to 70% at 20 years. It is estimated that urolithiasis costs around $2 billion each year in the United States of America. Comprising around 10% of all urinary tract calculi, uric acid stones are known to have high recurrence rates relative to other stone types. Prophylaxis of recurrence is therefore an important management strategy for these patients. We undertook a systematic review of the current guidelines to appraise the evidence behind them.
References & Contact Information
1. Pearle, M. S., Goldfarb, D. S., Assimos, D. G., Curhan, G., Denu-Ciocca, C. J., Matlaga, B. R., ... & White, J. R. (2014). Medical management of kidney stones: AUA guideline. The Journal of urology, 192(2),
2. Turk, C., Knoll, T., Petrik, A., Sarica, K., Skolarikos, A., Straub, M., & Seitz, C. (2015). EAU guidelines on urolithiasis
3. Becker, G. (2007). Uric acid stones. Nephrology, 12(s1), S21-S25.
The three guidelines identified were those of the American Urological Association (AUA), the European Association of Urology and the KHA-CARI (Kidney Health Austraila – Caring for Australasians with Renal Impairment) guidelines.
All guidelines advise limiting purine intake, urinary alkalinisation and the use of allopurinol but the specific advice lacks consensus (see table). The AUA guidelines provide general fluid advice for all stone formers, citing ‘Grade B’ evidence based on a randomised prospective study of idiopathic calcium nephrolitihiasis. No advice specific to uric acid stone formation is provided. Other guidelines give general advice. Level 4 evidence, where cited, refers to case series.
Aims
The aim of this review was to investigate the hypothesis that there is an extremely low quality evidence base underpinning the methods currently used in the prophylaxis of recurrent uric acid stone disease as reflected by the evidence used to construct seminal guidelines.