What further evaluation is needed for an asymptomatic patient whose urinalysis reveals the presence of calcium oxalate crystals and/or protein?
—Nick Shah, MD, Dunnellon, Fla.
Calcium oxalate crystals, which are often seen in normal urinalysis, are more likely to form in acidic urine. In a patient with a history of nephrolithiasis, the presence of these crystals may indicate the need for further quantification of urinary calcium. Proteinuria merits closer attention. Transient proteinuria may occur in 4% of men and 7% of women on a single urinalysis (presumably due to physiologic stress, e.g., with fever). Persistence on serial specimens, however, merits a careful history, physical exam, closer examination of the urinary sediment to rule out a glomerular source, and a serum creatinine determination. If these are normal, some authors recommend renal ultrasound and/or IV pyelogram. If all of the above are normal and the amount of proteinuria is small, it may be acceptable to follow the protein level over time.
—Christopher Ruser, MD (109-24)