Introduction

Hematuria is a term for blood in the urine whether the blood is visible (gross hematuria) or invisible (microhematuria).  Normally there is no blood in the urine.  Blood in the urine may be a sign of a serious disease such a cancer.  Gross hematuria (visible blood) requires a thorough diagnostic evaluation.  There are no diagnostic standards for microhematuria (invisible blood).  Microhematuria on 2 or 3 consecutive urine tests is considered significant and requires diagnostic evaluation.

Causes of hematuria

Blood in the urine can come from anywhere in the urinary system.  Conditions such as kidney stones and urinary infection are common causes.  Cancer within the urinary system can cause hematuria and is often the first sign of the problem.  Prior urinary problems such as surgery, scarring and irradiation may cause hematuria.  Also, hematuria may be due to certain medications to thin the blood such as aspirin and warfarin.  Often there is no serious cause of hematuria. 

Risk factors for hematuria

Patients with a smoking history or occupational exposure to benzenes and certain dyes are at risk for urinary disease that may cause hematuria.  Hematuria occurs in patients with recurrent kidney stones, urinary infection, analgesic abuse and pelvic irradiation for malignancy.  Men with prostate conditions are at risk for hematuria.

Evaluation for hematuria

A qualified urologist will offer the most thorough evaluation for hematuria.  Testing would include verification that the urinary tract is the source of hematuria and not some other source such as menstrual bleeding.  Routine evaluation includes urine cultures to exclude infection and ultrasound or CT scanning to check the kidneys for masses, stones or obstruction.   Urinary cytology uses voided urine to check for malignant cells.  Cystoscopy (direct inspection of the bladder and urethra) is necessary to exclude any abnormality of the bladder and urethra.

What if there is no positive testing?

Often patients with hematuria have no serious urological condition.  Patients with significant risk factors (smoking history or kidney stones) will require close monitoring and retesting.  Occasional referral to a nephrologist (kidney specialist) is necessary to evaluate for disorders of the kidneys. 

Common Questions patients have concerning blood in the urine:

         Q – How much blood is considered abnormal?
        A – Urine normally has no blood.  Minimal testing with ultrasound and cytology would offer assurance that there is no serious condition.  Direct inspection (cystoscopy) may be necessary depending on risk factors.

         Q – If I see blood and it goes away, is that a good sign?
        A – Visible blood requires a thorough evaluation especially if there are certain risk factors such as a smoking history. 

         Q – If after testing there is no positive finding, what is causing the blood to appear in the urine?
        A – Often there can be a micro defect in the filtration function of the kidney that lets blood or hemoglobin into the urine to cause the urine test to show blood.  Most often this is not a serious disorder.

        Q – How often should I be checked for hematuria.
        A – Microhematuria with out risk factors does not have a best practice standard for follow up.  A qualified urologist would offer a plan of surveillance for microhematuria.

Asymptomatic Microscopic Hematuria In Adults:  Summary of the AUA Best Practice Recommendations.  AFP March 15, 2001.