Summary

Definition

Urine sediment after centrifuge normally contains 2 to 3 RBCs per high power field (RBC/HPF) on microscopic examination. [1] [2] [3] There is consensus that ≥3 RBC/HPF in 2 of 3 urine specimens signals microscopic haematuria (MH). However, fewer RBCs from just 1 specimen should not exclude patients with risk for malignancy from a complete evaluation, because intermittent bleeding may occur. [1] [3] [4]

Significance

Although less commonly associated with malignancy than gross haematuria, MH may signal cancer. However, about half of cases of MH are idiopathic. [2] [3] [5] [6] [7] [8] [Asymptomatic microscopic hematuria in adults: summary of the AUA Best Practice Policy Recommendations]

History

The most important initial diagnostic step is a detailed history, with the aim of identifying risk factors for malignancy. History may also indicate less serious causes (e.g., recent exercise or sexual activity, UTI, and menstruation).

Cancer risk factors

The risk of urinary tract malignancy increases with age >40 years, tobacco use, previous radiation exposure, and certain occupational exposures (dyes, benzenes, aromatic amines) and medications such as phenacetin (available only in Japan), cyclophosphamide, and aristolochic acid in some herbal weight loss preparations). [7] If malignancy is suspected, based on a high-risk profile, then evaluation of the entire urinary tract, including upper tract imaging and cystoscopy for the lower tract, is required. [1] [7] [9] [10] [11] [12] [13] By contrast, the work-up of low-risk patients can be more focused towards the suspected cause without a complete urinary tract survey.

Classification scheme

Considering the source of bleeding by anatomical site offers an organised approach. The upper urinary tract includes the kidneys (glomerular or non-glomerular) and ureters, with remaining structures in the lower urinary tract. These dividing lines are useful to apply during the history and physical examination, as well as when ordering diagnostic tests, because no one diagnostic test evaluates the urinary tract completely.

Diagnostic testing

Diagnostic testing must first confirm the presence of MH. Secondly, testing may distinguish an upper tract glomerular source from other causes, allowing a more refined work-up, but upper and lower tract diagnostic tests (imaging and cystoscopy) remain necessary in all patients with risk factors for urinary tract malignancy. Using urinary tumour markers for diagnosing urinary tract cancer has not demonstrated adequate specificity for reliable diagnosis in research trials. However, the markers may play a role in assessing treatment efficacy and in identifying recurrences after treatment. [14] [15]

Screening

The most often identified cancer in patients with MH is bladder transitional cell carcinoma. [6] [9] [16] [17] [18] The US Preventive Services Task Force estimates a positive predictive value of 5% to 8% for MH indicating bladder cancer and recommends against routine screening. [8] [B Evidence] One case-control study including people with renal neoplasms found that patients with ≥4 RBC/HPF or ≥5 RBC/HPF in a single urine sample were twice as likely to have concomitant MH (odds ratio of 2.2 for ≥4 RBC/HPF and 2.0 for ≥5 RBC/HPF) as patients without malignancy. [19]