A routine urine test for blood, known as hematuria, sometimes returns a result of “trace lysed blood.” This finding indicates an extremely small, microscopic amount of blood is present, too little to change the urine’s color. The terminology used on laboratory reports often requires careful interpretation to understand the potential underlying causes. Finding the source of this microscopic bleeding requires systematic evaluation, as causes range from harmless, temporary events to more significant conditions in the urinary system.
Understanding Trace Lysed Blood
The term “trace” signifies a minimal quantity, meaning the blood is only detected by chemical testing rather than being visible. “Lysed” refers to red blood cells (RBCs) having ruptured, releasing their internal contents, primarily hemoglobin. Consequently, a microscopic examination of the urine sediment will not show intact RBCs, but the chemical dipstick test will still detect the hemoglobin’s presence.
The lysis of red blood cells can occur for several reasons. Sometimes, lysis happens outside the body due to the urine sample being highly diluted, having a high pH (alkaline), or being stored too long before testing. When lysis occurs within the body, it often suggests the blood originated higher up in the urinary tract, such as the kidneys, or that a systemic issue caused the cell breakdown.
Transient and Non-Urinary Causes
Many instances of trace lysed blood are temporary or result from factors outside the primary urinary organs. One common non-disease cause is intense physical activity, particularly long-distance running, which can induce temporary hematuria. This exercise-induced blood is thought to be caused by physical trauma to the bladder or temporary changes in blood flow to the kidneys.
Contamination from external sources is another frequent reason for this finding, especially in women. Menstrual bleeding or recent sexual activity can introduce blood into the sample, leading to a positive result. Certain medications, such as blood thinners (anticoagulants) or non-steroidal anti-inflammatory drugs (NSAIDs), can also increase the likelihood of minor bleeding. Dehydration can also irritate the lining of the urinary tract, contributing to a transient finding of trace blood.
Pathological Conditions of the Urinary System
Infections and Obstructions
When trace lysed blood is persistent or cannot be attributed to external factors, it may indicate a condition within the urinary tract. Infections are among the most frequent causes, as a urinary tract infection (UTI) causes inflammation of the bladder (cystitis) or kidneys (pyelonephritis). This inflammation irritates the lining of the urinary tract, leading to bleeding.
The passage of kidney stones or bladder stones can also cause this finding, as the hard mineral deposits scrape against the lining of the ureters or bladder. Even small stones can cause mechanical irritation sufficient to release blood cells. In older men, an enlarged prostate gland, known as benign prostatic hyperplasia (BPH), is a common source of microscopic bleeding due to the stretching of blood vessels around the urethra.
Kidney Disorders and Malignancy
Conditions affecting the filtering units of the kidney, called the glomeruli, can also result in lysed blood. Glomerulonephritis involves inflammation of these filters, allowing red blood cells and their components to leak into the urine. Inherited disorders, such as polycystic kidney disease (PCD), which causes fluid-filled cysts in the kidneys, can also lead to bleeding. Persistent microscopic hematuria warrants investigation to exclude conditions like kidney or bladder cancer, especially in individuals with risk factors like a history of smoking or those over the age of 35.
Medical Diagnosis and Evaluation
The presence of trace lysed blood necessitates a comprehensive medical evaluation to confirm the finding and determine its origin. The initial step involves confirming the result with a microscopic urinalysis, which looks for intact red blood cells or other abnormal components. The absence of intact cells alongside a positive dipstick confirms the lysed nature of the finding.
If an infection is suspected, a urine culture is performed to identify bacteria and guide antibiotic treatment. If hematuria persists after treating an infection, or if no infection is found, further investigation is required. This often includes blood tests to assess kidney function and imaging studies to visualize the urinary tract.
Common imaging tools include ultrasound, CT scans, or MR urography to look for stones, tumors, or structural abnormalities. For the lower urinary tract, a procedure called cystoscopy may be performed, where a small camera is inserted into the bladder to directly examine the lining for sources of bleeding. The goal of this diagnostic process is to differentiate between benign, transient causes and conditions requiring specific medical intervention.