Blood in the urine, known medically as hematuria, is the presence of red blood cells, indicating bleeding somewhere along the urinary tract (kidneys, ureters, bladder, or urethra). While the bleeding itself is often intermittent and may stop, the underlying condition rarely resolves on its own. Because hematuria can be the first sign of a serious disease, medical evaluation is required even if the visible blood disappears quickly.
Understanding Visible vs. Non-Visible Hematuria
Hematuria is classified into two main types based on visibility. Visible, or gross, hematuria is the presence of enough blood to turn the urine pink, red, or dark brown. This noticeable color change often prompts a faster search for medical attention.
The second type is non-visible, or microscopic, hematuria, where the urine appears normal, but red blood cells are detected during a laboratory test like a urinalysis. Microscopic hematuria is much more common, and the visibility of the blood does not necessarily correlate with the severity of the underlying cause.
Both types of bleeding can be intermittent, meaning the blood may appear in one sample and be absent in the next. For example, a small kidney stone might cause a temporary scratch and bleed, which then stops, but the stone itself remains.
Causes That May Resolve Without Intervention
Some causes of hematuria are temporary and may appear to resolve without specific medical intervention. Strenuous exercise, particularly long-distance running, is a known cause of transient hematuria, often resolving within 24 to 48 hours of rest. Minor trauma to the urinary tract, such as a direct blow during contact sports, can also cause temporary bleeding that subsides once the injury heals.
Furthermore, certain foods and medications can cause a false positive, or “pseudohaematuria,” by changing the urine color to red or pink (e.g., beets, rhubarb, specific dyes). These non-blood color changes resolve naturally as the substances are cleared from the body.
Urinary tract infections (UTIs) are a common cause of hematuria. While the bleeding may diminish, the underlying bacterial infection requires antibiotic treatment to truly resolve and prevent progression to a kidney infection.
Serious Underlying Conditions Requiring Immediate Investigation
The cessation of bleeding should never be interpreted as the resolution of a serious underlying condition. Kidney stones are a frequent cause of hematuria. As a stone moves or irritates the urinary tract lining, it causes bleeding, but the stone itself remains until it is passed or medically removed.
Chronic kidney diseases, such as Polycystic Kidney Disease (PKD) and glomerulonephritis, involve damage and inflammation to the kidney’s filtering units. This damage leads to microscopic blood in the urine, which may be persistent or intermittent, but the underlying disease is chronic and requires ongoing medical management.
The most concerning cause is cancer of the kidney, bladder, or prostate, which can manifest as painless, intermittent hematuria. The bleeding often stops and starts, but the tumor continues to grow regardless of the pattern, making prompt investigation mandatory, especially for individuals over 40 or those with risk factors like smoking.
When Medical Evaluation is Essential
A medical evaluation is always necessary following any episode of hematuria, even if the color returns to normal. The initial diagnostic process begins with a urinalysis to confirm red blood cells and check for signs of infection or kidney damage, such as protein in the urine. If hematuria is confirmed, further testing is guided by the patient’s risk factors and symptoms.
Diagnostic imaging, such as a kidney and bladder ultrasound or a CT urogram, is often performed to visualize the upper urinary tract for stones or masses. For high-risk individuals or those with visible blood, a cystoscopy may be necessary to examine the bladder lining directly for tumors.
Certain “red flag” symptoms should prompt emergency medical attention, regardless of whether the bleeding has stopped. These include the inability to urinate, passing large blood clots, or experiencing severe flank or abdominal pain.