New findings from a large study may improve clinical management of patients with asymptomatic microscopic hematuria (AMH).

Although patients with gross hematuria should be fully investigated, there is controversy about management of patients with AMH. Recently updated AMH guidelines from the American Urological Association provide insufficient information for decision making due to a shortage of research, the study’s authors noted.

AMH is a potential early sign of urologic disorders, but how to define clinically significant AMH, which patients require complete urologic workup, and how they should be examined remain unclear, according to a team led by Chang Wook Jeong, MD, of Seoul National University Hospital. “Even when no disorder is detected at initial work-up, some patients with AMH are later diagnosed with a significant lesion,” they wrote in an online report in The International Journal of Urology. “However, AMH is often inadequately managed for lack of high-quality evidence.”

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For the study, the investigators analyzed data from healthy adults age 20 and older who voluntarily participated in the hospital’s health screening program from 2005 to 2010. Among the 57,000 Korean patients, 6.2% had AMH based on initial urinalysis; of these, 1,619 patients agreed to undergo a repeat urinalysis, and 911 again had AMH. The study defined AMH more strictly than existing guidelines: 5 or more red blood cells per field viewed under a microscope.

The investigators then identified 131 lesions as underlying disease. Urinary stones were the most common cause (69.5%), followed by benign renal masses, such as angiomyolipoma (10.7%). Just 6 lesions were malignant: 3 renal cell carcinomas and 3 bladder cancers. Male sex and diabetes were significant predictors for detection of underlying diseases of AMH, more likely benign conditions such as urinary stones.

According to the researchers, their findings  demonstrate that a positive dipstick test does not reliably predict AMH, indicating that urine microscopy is a better baseline tool. In addition, AMH risk does not differ for daily users of aspirin or other anticoagulants, in line with a previous study. Thus, clinicians may conduct further urological evaluation as usual. The study also showed that female sex, older age, chronic renal failure, and current smoking significantly increases AMH risk whereas male sex and diabetes mellitus decreased the risk.

The 2012 American Urological Association guidelines suggest that further urological evaluation is not required for benign causes of AMH, such as pyuria. However, in this study, the detection of abnormal urologic findings did not differ between patients with or without pyuria. Further examination should be carried out even in AMH patients with pyuria, according to the investigators.

Renal function should be carefully monitored because renal disease might cause clinical problems during evaluation of AMH; for example, side effects from contrast injection during radiologic evaluation.

The study found a lower number of urological malignancies than other published research possibly due to differences in age, sex, and ethnicity.



  1. Kang, M, et al. The International Journal of Urology, 2015; doi: 10.1111/iju.12697.