Red blood cells (RBCs) carry oxygen throughout the body. While primarily in the bloodstream, their presence in urine can signal various underlying health conditions. A minimal number might be normal, but an elevated count often indicates an issue requiring medical evaluation.
Understanding Red Blood Cells in Urine
The urinary system, including the kidneys, ureters, bladder, and urethra, filters waste from blood while retaining blood cells. Normally, the kidney’s filtration barrier prevents red blood cells from passing into urine. Therefore, a “normal” urine sample contains very few, if any, red blood cells.
Microscopic analysis of urine sediment determines the red blood cell count. A normal range is 0 to 3 red blood cells per high-power field (RBCs/HPF) when viewed under a microscope. More than 3 RBCs/HPF is defined as microscopic hematuria, meaning blood is present but not visible. Gross hematuria refers to visibly apparent blood in the urine, often appearing pink, red, or cola-colored.
Common Causes of Elevated Red Blood Cells in Urine
Several factors can lead to an increased presence of red blood cells in urine, ranging from benign conditions to more serious diseases. Urinary tract infections (UTIs) are a frequent cause, where bacteria infect parts of the urinary system, leading to inflammation and irritation that can cause bleeding.
Kidney stones, hard deposits of minerals and salts, can also cause red blood cells to appear in urine as they pass through the urinary tract, potentially causing irritation or obstruction. Various kidney diseases, such as glomerulonephritis, involve inflammation of the kidney’s filtering units and can result in blood leaking into the urine. Certain cancers of the bladder, kidneys, or prostate can manifest with hematuria, sometimes even before other symptoms appear. In men, an enlarged prostate can also lead to blood in the urine due to pressure on the urethra. Strenuous exercise can temporarily cause blood in the urine, a condition known as exercise-induced hematuria.
How Red Blood Cells in Urine are Detected
The detection of red blood cells in urine typically involves a urinalysis, a common diagnostic test. This process often begins with a dipstick test, which uses a chemically treated strip that changes color in the presence of blood components, indicating a positive result. While dipstick tests are sensitive, they cannot quantify the exact number of red blood cells or differentiate between intact cells and hemoglobin.
Following a positive dipstick result, or if blood in the urine is suspected, a microscopic examination of urine sediment is performed. A urine sample is centrifuged, and the concentrated sediment is then examined under a microscope. This allows healthcare professionals to directly visualize and count the number of red blood cells per high-power field, providing a more precise measurement.
When to Seek Medical Attention
Seek medical attention if you notice blood in your urine, even if it appears only once or is not accompanied by pain. Visible blood (gross hematuria) always warrants prompt evaluation. Similarly, if a routine urine test reveals microscopic hematuria, further investigation is often necessary.
Consult a doctor if hematuria is accompanied by other symptoms such as pain during urination, frequent urination, fever, flank pain, or unexplained weight loss. These additional symptoms can provide important clues about the underlying cause and guide diagnostic steps.