From the Guidelines
Trace blood in urine is not normal and should be evaluated by a healthcare provider. While small amounts of blood may occasionally appear in urine due to temporary causes like intense exercise, menstruation, or certain medications, persistent or unexplained blood in urine (hematuria) requires medical attention [ 1 ]. Potential causes range from urinary tract infections, kidney stones, and enlarged prostate to more serious conditions like kidney disease or cancer.
Key Considerations
- The American Urological Association defines microhematuria as three or more red blood cells per high power field on microscopic evaluation of urinary sediment [ 2 ].
- Patients with gross hematuria have a high association with malignancy, and all patients with gross hematuria should have a full urologic workup [ 1 ].
- Patients with microhematuria have a low risk of malignancy, but a cause is never found in most patients with asymptomatic microhematuria [ 1 ].
Evaluation and Next Steps
If you notice blood in your urine, even in trace amounts, schedule an appointment with your doctor. They will likely order urinalysis, imaging tests, or cystoscopy depending on your symptoms and medical history [ 1 ]. While waiting for your appointment, drink plenty of water to help flush your urinary system, but don't delay seeking medical care. Blood in urine occurs when red blood cells leak into urine from somewhere in the urinary tract, and identifying the source is essential for proper treatment.
Patient Risk Factors
Certain patient risk factors, such as age >35 years, smoking, and occupational exposure to chemicals, increase the likelihood of a urinary malignancy [ 1 ]. Patients without risk factors and with an identified benign cause of microhematuria are unlikely to gain any benefit from a complete imaging workup of microhematuria [ 1 ].
From the Research
Definition and Prevalence of Hematuria
- Hematuria is the presence of blood in the urine, which can be either grossly visible (macrohematuria) or only detectable under a microscope (microhematuria) 3.
- Microhematuria has a prevalence of 4-5% in routine clinical practice and is often asymptomatic 3.
Causes of Hematuria
- Hematuria can be caused by underlying diseases of the kidneys or the urogenital tract 3.
- Common causes of hematuria include urinary tract infection, benign prostatic hyperplasia, and urinary calculi 4.
- More serious conditions such as bladder cancer can also cause hematuria 5.
Evaluation and Management of Hematuria
- A thorough history and physical examination, measurement of inflammatory parameters and renal function tests, and ultrasonography of the kidneys and bladder are part of the basic diagnostic evaluation for hematuria 3.
- Patients with risk factors such as smoking, advanced age, and male sex may require augmented, risk-adapted diagnostic evaluation 3.
- The risk of malignancy with gross hematuria is greater than 10%, and prompt urologic referral is recommended 4.
Diagnostic Criteria for Microhematuria
- Microhematuria is said to be present when urine microscopy reveals three or more erythrocytes per high-power field 3.
- The presence of microhematuria may indicate an underlying disease requiring treatment, and further evaluation is necessary to rule out potential causes 3, 4.