Hematuria that is not explained by an obvious underlying condition (eg, cystitis, ureteral stone) is fairly common. In many such patients, particularly young adult patients, the hematuria is transient and of no consequence . On the other hand, there is an appreciable risk of malignancy in older patients (eg, over age 35 years) with hematuria, even if transient [2-4]. However, even among older patients, a urologic cause for the hematuria can often not be identified (61 percent in a series of 1930 patients referred to a Hematuria Clinic) . (See 'Transient or persistent hematuria' below.)
The etiology and evaluation of hematuria in adults will be reviewed here. The approach in children is discussed separately. (See "Evaluation of microscopic hematuria in children" and "Evaluation of gross hematuria in children".)
DEFINITION OF HEMATURIA
Hematuria may be grossly visible (macroscopic hematuria) or detectable only on urine examination (called microscopic hematuria).
Gross hematuria — Gross hematuria is suspected because of the presence of red or brown urine. The color change does not necessarily reflect the degree of blood loss, since as little as 1 mL of blood per liter of urine can induce a visible color change. In addition, the intermittent excretion of red to brown urine can be seen in a variety of clinical conditions other than bleeding into the urinary tract. (See "Urinalysis in the diagnosis of kidney disease", section on 'Red to brown urine'.) Gross hematuria with passage of clots almost always indicates a lower urinary tract source.
The initial step in the evaluation of patients with red urine is centrifugation of the specimen to see if the red or brown color is in the urine sediment or the supernatant (algorithm 1).