Blood in the urine, known as hematuria, is a common reason for a clinical workup. When a laboratory report specifies the presence of “non-hemolyzed blood,” it provides a significant clue about the source of the bleeding. This finding directs the medical investigation toward the structures of the urinary tract itself, helping to narrow the range of potential causes.
Understanding Hematuria and Non-Hemolyzed Cells
The term “non-hemolyzed blood” indicates that the red blood cells (RBCs) found in the urine are physically intact when observed under a microscope. These cells have not ruptured, and the hemoglobin remains inside the cell structure. This is often referred to as true hematuria.
This finding is distinct from “hemolyzed blood,” where the RBCs have broken apart, releasing free hemoglobin into the urine. Hemolyzed blood can result from systemic blood disorders, certain medications, or cell damage that occurred before the blood reached the kidney. The presence of intact, non-hemolyzed cells suggests the blood originated from a source along the urinary system—the kidneys, ureters, bladder, or urethra.
When RBCs pass through the kidney’s filtering units, the glomeruli, they typically become distorted, or dysmorphic, due to physical stress. The presence of non-dysmorphic, intact RBCs points toward a lower urinary tract source, such as the bladder or urethra, where the cells do not undergo this filtering stress. Microscopic hematuria is defined by confirming three or more RBCs per high-power field (RBC/HPF) on a microscopic examination of the urine sediment.
Primary Sources and Causes of Intact Red Blood Cells in Urine
One of the most common causes of non-hemolyzed blood is a urinary tract infection (UTI), where inflammation of the bladder or urethra causes irritation and minor bleeding. Once the infection is treated, the hematuria typically resolves.
Structural issues like kidney stones (nephrolithiasis) or bladder stones are frequent causes. These hard mineral deposits scrape against the lining of the urinary tract, causing irritation and bleeding. In older men, an enlarged prostate (Benign Prostatic Hyperplasia, or BPH) can also cause blood due to increased pressure and congestion in surrounding blood vessels.
Less concerning, temporary causes include strenuous exercise, such as long-distance running, or temporary dehydration. These benign causes often lead to transient hematuria.
The most serious potential causes involve malignancies, specifically cancers of the bladder or kidney. Bladder cancer is the most common cancer associated with hematuria, and the bleeding is often painless, which can delay diagnosis. While cancer is only found in a small percentage of patients (between 2% and 5%), it is the main reason a thorough workup is performed.
The Standard Diagnostic Workup
The investigation into non-hemolyzed blood in urine begins with confirming the finding and assessing the patient’s overall risk. Initial testing involves a complete urinalysis, including a dipstick test to detect blood, followed by microscopic examination to confirm the number and integrity of the RBCs. If a transient cause like a UTI is identified, the hematuria should be re-evaluated after treatment to ensure resolution.
For patients whose hematuria persists or who have risk factors, the next step involves imaging the upper urinary tract. A computed tomography (CT) urogram is frequently used because it provides detailed images of the kidneys, ureters, and bladder, allowing providers to detect stones, masses, or structural abnormalities.
Ultrasound is another option, offering a less invasive initial view, particularly of the kidneys and bladder.
To examine the lower urinary tract, a procedure called cystoscopy may be performed. During this procedure, a thin, flexible tube with a camera is inserted into the bladder through the urethra. This allows the physician to visually inspect the lining of the bladder for any tumors or other lesions. Cystoscopy is generally recommended for patients at intermediate or high risk for urinary tract cancer, helping to directly visualize the source of the bleeding.
When This Finding Signals a Serious Issue
The finding of non-hemolyzed blood becomes concerning when specific risk factors are present, prompting a complete diagnostic evaluation. Age is a significant factor, with patients over 50 years old having an increased risk of malignancy. A history of smoking, either current or past, is also a powerful independent predictor for bladder cancer.
Other concerning factors include a history of gross hematuria, which is visible blood in the urine, even if it has since resolved. Occupational exposure to certain chemicals or dyes, as well as a history of chronic irritative voiding symptoms, also raise the suspicion level.