Asymptomatic microhematuria, one of the most common urological findings, presents an important diagnostic challenge. Because it is so prevalent with rates ranging from 2% and more than 30%, depending on the population, health care providers must balance the need for a thorough and complete workup with the potential risks and costs associated with diagnostic studies.1-4 While asymptomatic microhematuria is most often benign in origin—from infection, urinary stones, or benign prostatic hyperplasia—microhematuria is frequently the earliest sign of a number of urologic malignancies, most prominently bladder cancer, upper tract urothelial carcinoma, and renal cell carcinoma.
Despite this fact, data regarding the necessary components of a microhematuria workup are limited. And, until recently, broad recommendations for the appropriate evaluation of microhematuria were limited to the 2001 Best Practice Statement from the American Urological Association (AUA).5,6 However, these guidelines are more clear with the recent release of the AUA Guidelines for the Diagnosis, Evaluation, and Follow-up of Asymptomatic Microhematuria in Adults.7 This article reviews the key components of the new recommendations for the workup of asymptomatic microhematuria.
THE NEW GUIDELINES
The new AUA guidelines provide a definition of microhematuria that is a departure from the prior Best Practice definition requiring red blood cells (RBCs) to be present on two of three specimens. Now, a single properly collected urine specimen with three or more RBCs present per high-powered field (and with no evidence of infection) is sufficient to warrant evaluation unless a clear benign cause of origin such as trauma is present. While this change may seem minor, it has practical implications, simplifying when patients should be referred from their primary care doctors and expediting the urologic workup. Importantly, a positive dipstick is still not sufficient to diagnose microhematuria, and microanalysis is necessary to confirm the presence of RBCs.
COMPONENTS OF A MICROHEMATURIA WORKUP
The workup of microhematuria involves several steps. Initially, the microscopic urine evaluation should determine whether urinary casts or dysmorphic RBCs are present, suggesting medical renal disease. Serum creatinine/BUN should be obtained to evaluate for the same. Even if medical renal disease is suspected, there is still a risk of urologic malignancy, and the AUA guideline recommends that a full urological evaluation be performed nonetheless. Additionally, while microhematuria occurs more frequently in patients who are anticoagulated, urological evaluation is still warranted in these individuals in the setting of asymptomatic microhematuria.