Are crystals seen during urine microscopy helpful in the diagnosis of stone disease?
Cystine crystals and struvite crystals are always abnormal and diagnostic of an underlying disorder.
Cystine crystals are only present in people with cystinuria, an uncommon genetic disorder in which cystine is not reabsorbed normally by the kidney. Struvite crystals only form in humans when there is urinary infection with bacteria that possess urease activity.
Uric acid and calcium crystals may be more frequent in the urine of stone formers, but they are not diagnostic of disease because they also may be found in healthy people.
One situation in which the finding of calcium or uric acid crystals may be helpful is in patients with renal colic without a documented stone, where transient bursts of crystalluria may be causing symptoms.
