uric acid stones
Last reviewed 01/2018
Uric acid stones are an uncommon cause of urolithiasis. They are associated with excretion of acid urine of pH less than 5.5 below which uric acid is insoluble.
The stones are moderately hard with a smooth surface, and tend to be yellow / brown in colour. Pure uric acid stones are radiotranslucent but the majority have sufficient calcium to render them radioopaque.
Less than half of cases are associated with hyperuricaemia e.g. gout, or following chemotherapy in diseases with a rapid cell turnover, such as leukaemia.
Patients with an ileostomy are at increased risk of forming urate stones because urinary acidity is reduced.