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Asymptomatic microscopic hematuria.

Asymptomatic microscopic hematuria--the presence of at least three to five red blood cells per high-power field on microscopy--has been estimated to occur in as much as 16% of the general population, although population-based studies vary widely.

Since it is asymptomatic, the condition is most often discovered on routine urinalysis.

Asymptomatic miscroscopic hematuria may be slightly more prevalent in women, because they are more likely to harbor a silent urinary tract infection.

The possible causes are wide ranging and include infection, cancer, urinary stones or crystals, kidney disorders, and drug-induced bleeding, as well as minor incidental causes that don't require treatment.

Although the incidence of significant urologic disease in patients with asymptomatic microscopic hematuria is low--probably only about 5%--the amount of blood in the urine doesn't correlate with the severity of any underlying disease.

Therefore, every patient who has microscopic hematuria should get a full work-up, with the hematuria considered to be serious until proven otherwise.

The finding of microscopic hematuria should prompt a complete history and physical that focus on the urinary tract and risk factors for urologic disease.

The majority of patients--about 93%--will have some identifiable cause for the disorder.

However, in about 7%, the cause will remain unknown.

Benign causes include menstruation, vigorous exercise, sexual activity, viral illness, trauma, infection, and use of aspirin and nonsteroidal anti-inflammatory agents.

Red blood cell morphology can give a hint about the source of the bleeding: dysmorphic cells and red cell casts point to glomerular (kidney) bleeding, while bleeding from the lower urinary tract is usually the source of normal red cells.

Evaluation varies according to risk factors.

Cigarette smoking, exposure to industrial chemicals, family history or personal history of urologic disease, and age of more than 40 years all are risk factors for significant underlying disease.

These patients should be considered for full urologic evaluation.

Some of the components of this evaluation may be deferred in low-risk patients.

All women should have an exam of the urethra and vulva to rule out local causes of bleeding.

For low-risk patients, order upper urinary tract imaging--either a renal ultrasound, spiral CT, or intravenous pyelogram--and urine cytology.

If there are any positive, atypical, or suspicious findings, refer the patient for cystoscopy. If the results of the initial testing are negative, or if a cystoscopy is negative, have the patient return in 3-6 months for repeat urinalysis and cytology.

A 24-hour stone risk profile, which measures the volume of urine and its concentration and chemical composition, may be revealing.

High values could indicate the possibility of crystals in the urine.

These would not be apparent on imaging studies, but could be enough to cause microscopic bleeding and are a risk factor for stone development.

Some women have dilated blood vessels in the bladder lining, and they may not show on cystoscopy.

Increasing fluid intake and decreasing highly acidic substances (alcohol, caffeine, chocolate, tomatoes, citrus fruits, and spicy foods) can be helpful in decreasing irritation.

Refer high-risk patients for complete evaluation: upper tract imaging, cytology, and cystoscopy.

If the results are positive, treat the disorder. If the results are negative, repeat the urinalysis and cytology in 3-6 months.

The American Urologic Association recommends follow-up testing for both low- and high-risk patients for 3 years. If negative for 3 years, no further evaluation is necessary.

Patients with persistent microscopic hematuria should be evaluated for primary renal disease.

Even if the results continue to be negative, such patients should have a urine cytology and ultrasound every other year, since persistent microscopic hematuria could mask the symptoms of a developing urologic cancer.

Sources: Kristene E. Whitmore, M.D., associate professor of urology at Drexel University, Philadelphia; American Urology Association best practice policy recommendations; American Academy of Family Physicians treatment guidelines.
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Article Details
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Author:Sullivan, Michele G.
Publication:OB GYN News
Article Type:Disease/Disorder overview
Geographic Code:1USA
Date:Jun 1, 2005
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