Method of alkalization and monitoring of urinary pH for prevention of recurrent uric acid urolithiasis: a systematic review

Uric acid (UA) urolithiasis comprises around 5-10% of all stones and can frequently recur. Due to the fact that UA stones form in acidic urine with a pH <5.5, these patients require special attention compared to other stone patients. The international guidelines suggest treatment and metaphylaxis by urinary alkalization. The objective of this review is to critically asses the available evidence concerning the method and efficacy of this treatment modality. A systematic review on the methods of metaphylactic therapy using oral alkalization of UA urolithiasis was conducted by two authors. Evidence was sought using a predefined search strategy in seven different databases. The provided evidence was critically evaluated using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane collaboration tool for assessing the risk of bias. Twelve manuscripts were included of which one was a randomised trial. They focussed on ways to alkalize urine and its effect on stone recurrence. Because of their methodology and heterogeneity, the evidence is presented in a narrative review. There were differences in medication used for alkalizing urine, ways of monitoring urine pH and evaluating its efficacy. The reported outcomes also differed between studies. There is currently a lack of clear evidence for the method of alkalization of urine and the method of pH measurement. Besides this, for an established treatment modality, there is lack of long term results for the alkalization therapy. In conclusion, urine alkalization is an established treatment modality for the metaphylaxis of UA urolithiasis despite the lack of evidence from high quality studies on the methods of alkalization and its treatment efficacy. The studies published on this topic are scarce and contain notable risks of bias which should be kept in mind when interpreting the stated results.