Red blood cells (erythrocytes) carry oxygen throughout the body. While essential in the bloodstream, their presence in urine, a fluid normally free of these cells, is an unexpected finding. The urinary system filters waste from blood without allowing blood cells to pass. Therefore, finding red blood cells in urine indicates a deviation from typical bodily function that warrants medical attention.
Detecting Red Blood Cells in Urine
The presence of red blood cells in urine is medically known as hematuria, which appears in two forms. Gross hematuria is visible blood in the urine, making it appear pink, red, or tea-colored. Microscopic hematuria involves red blood cells not visible to the naked eye, identified only through laboratory analysis. This is defined by three or more red blood cells per high-power microscopic field in a urine sample.
Healthcare providers detect red blood cells in urine primarily through urinalysis. This often begins with a dipstick test, where a chemical strip reacts to hemoglobin by changing color. While dipstick tests are sensitive, they can yield false-positive results and do not differentiate between intact red blood cells, hemoglobin, or myoglobin. A positive dipstick result requires confirmation through a microscopic examination of urine sediment, allowing direct visualization and counting of red blood cells.
Underlying Factors
The presence of red blood cells in urine is a sign, not a diagnosis, pointing to a variety of underlying factors, from common, benign issues to more serious conditions. Urinary tract infections (UTIs) are a frequent cause, as bacteria can infect the lining of the urinary tract, leading to inflammation and irritation that causes red blood cells to leak. This irritation can affect any part of the urinary system, including the bladder, kidneys, or prostate.
Kidney stones, which are hard mineral deposits that form within the kidneys, can also lead to hematuria. These stones can irritate or damage the delicate lining of the urinary tract as they pass, causing bleeding. The size and location of the stone can influence the extent of irritation and the amount of blood present in the urine.
Certain kidney conditions directly impact the organ’s filtering capabilities, allowing red blood cells to enter the urine. Glomerulonephritis, for instance, involves inflammation of the glomeruli, the tiny filtering units within the kidneys, which can lead to blood and protein leakage. Polycystic kidney disease, characterized by the growth of numerous fluid-filled cysts, can also result in hematuria due to bleeding or associated infections.
In men, issues with the prostate gland can be a source of red blood cells in urine. An enlarged prostate, a common condition as men age, can put pressure on the urethra and cause bleeding. Similarly, inflammation or infection of the prostate, known as prostatitis, can also lead to the presence of blood in the urine.
Strenuous physical activity, particularly endurance sports like long-distance running, can temporarily cause red blood cells to appear in urine. This phenomenon, sometimes called “exercise-induced hematuria,” is often benign and resolves on its own within 24 to 72 hours.
Certain medications can also contribute to the presence of red blood cells in urine. Blood thinners, such as anticoagulants (e.g., warfarin) and anti-platelet drugs (e.g., aspirin), are designed to prevent blood clots but can increase the risk of bleeding throughout the body, including the urinary tract. Visible blood in urine is more common in individuals taking these medications.
Importance of Medical Evaluation
Regardless of whether blood in urine is visible or microscopic, its presence warrants a thorough medical evaluation to identify the underlying cause. While some causes are temporary and benign, others indicate more serious health concerns requiring prompt intervention. Self-diagnosis or delaying professional assessment is not advisable, as early detection often leads to more effective management.
A healthcare provider will begin with a comprehensive medical history and physical examination. Further diagnostic tests are necessary to determine the exact cause. These may include additional urine tests, such as a urine culture to check for infection, or specialized blood tests to assess kidney function. Imaging studies, such as an ultrasound or computed tomography (CT) scan of the kidneys and urinary tract, can provide detailed views to identify abnormalities like stones or growths. In some cases, a cystoscopy may be performed, involving the insertion of a thin tube with a camera into the urethra and bladder to directly visualize the urinary tract lining.