Which of the following is the most important factor in uric acid stone formation?
A. Low urinary pHAnswer A
The most important factor in uric acid stone formation is low urinary pH as most patients have normal urinary uric acid levels. Uric acid solubility is significantly reduced when urinary pH is <5.5. Other important factors include low urine volume and a hyperuricosuria. Low urinary volume can more commonly occur in patients with chronic diarrhoeal conditions, ileostomies, excessive sweating or poor oral intake. Hyperuricosuria occurs in addition to hyperuricaemia in patients with primary gout, myeloproliferative conditions and Lesch-Nyhan syndrome. Hyperuricosuria occurs in patients without raised serum urate levels due to some medications (thiazides or salicylates) and excessive intake of dietary meats.