Hematuria is the discovery of blood in the urine. It can either be quite obvious where blood is visible to the naked eye, or microscopic, where only a urinalysis picks up the findings (asymptomatic microscopic hematuria). Large amounts of blood can make the urine appear to have a smoky reddish-brown appearance, while microscopic hematuria may appear as completely normal. Often the timing of the blood in the urine can diagnose where it is coming from, if blood is noted at the start but then disappears, it’s more likely to be at the urethra (or additionally the prostate gland in a male). If noted uniformly from start to finish in the stream, it is more like the kidneys, bladder or ureter as a primary source.
Kidney stones, tumors in the urinary tract or of the prostate, trauma, inflammation of the kidney due to glomerulonephritis (with many and varying etiologies), and polycystic kidney disease are some of the many causes that have to be ruled out in the face of a finding of hematuria. More benign findings such as contamination from a menstrual period, a urinary tract infection, a bladder infection, or even a prostate infection can all account for blood in the urine. Most initial testing looks for benign disease unless there is a known etiology, a large amount of blood, or risk factors for malignancy. A referral to a specialist usually then depends on which way the decision tree is leaning.
Microscopic hematuria is usually found incidentally on a urinalysis as part of a physical exam or even an insurance examination with a routine blood and urine collection. If a dipstick test is positive for blood, and there are three or more red blood cells per microscopic high power field, assessment for urinary tract infection, assessment of benign causes such as menstruation, vigorous exercise, recent procedure to the urinary tract, or history of kidney stones is developed. When casts of cells as well as protein are also found, a referral to a kidney specialist (nephrologist) often follows for a more detailed systemic workup.
When there are risk factors for malignancy, assessment is first made as to whether it is low risk or there is a history of renal insufficiency or sensitivity to radiation or contrast dye. Ultrasound and non-contrast CT are often done to evaluate the urinary tract and a urologist is often involved at this point. When the malignancy risk is higher and there are no sensitivities to testing, a CT is done and the urologist gets involved earlier, as cystoscopy may be the next step.
Microscopic hematuria is a little harder to evaluate and pinpoint a cause for. While in patients with gross hematuria the malignancy rate can be close to 30% and full investigation is started right at the onset, closer to 5% of microscopic hematuria has a malignant cause, and when the individual involved has no pain and the urine looks clear to the naked eye, workups are often postponed or avoided. After screening, repeating the urines at prescribed time intervals, and treating obvious causes such as infection, still half the diagnoses for microscopic hematuria remain unknown. Continued follow-up, imaging, and cystoscopy are done when the hematuria continues after all benign or treatable conditions are ruled out. When urinalyses are done over years and the hematuria disappears, the cause is overwhelmingly benign. If the hematuria persists, a full repeat evaluation should be considered within three to five years of the initial evaluation.
The discovery of a hematuria should always be taken seriously. Many are as simple as treating an infection, waiting for the end of the menstrual cycle, and making sure the sample is obtained clean-catch without contamination. A urinalysis should always be repeated to see that the hematuria has not persisted and has indeed been eradicated. When it persists, even though it may be a small amount and not visible to the naked eye, consultation with the doctor is a must to determine the next steps and to be sure that it is investigated and all possibilities of malignancy are ruled out.
Authored by Dr. Bob Goldstone, M.D.
The information contained on this page is not intended to provide medical advice, which should be obtained directly from your physician.