Hematuria is the medical term for blood in the urine, a symptom that can be visibly alarming or completely unnoticeable. When visible to the naked eye, it is called gross hematuria; the urine may appear pink, red, or cola-colored, though only a small amount of blood is needed for this change. If the blood amount is too small to be seen, it is referred to as microscopic hematuria, detectable only through laboratory testing. Blood clots in the urine signify a greater volume of bleeding and can cause painful passage or a blockage, requiring immediate medical attention.
Infections and Inflammatory Conditions
Infections are frequent causes of blood in the urine, primarily by irritating the lining of the urinary system. A common Urinary Tract Infection (UTI) occurs when bacteria enter the urethra and multiply, typically leading to cystitis in the bladder. The infection causes inflammation of the bladder wall, which leads to the shedding of red blood cells into the urine.
A more serious infection, pyelonephritis, involves bacteria traveling from the bladder up to the kidneys. This kidney infection causes inflammation within the renal structures, resulting in hematuria often accompanied by fever and flank pain. Bleeding results from the immune response damaging the mucosal surface. Hematuria typically resolves once the underlying infection is successfully treated with antibiotics.
Mechanical Causes: Stones, Obstruction, and Injury
Physical forces, such as the movement of solid masses or external trauma, can also cause bleeding within the urinary tract. Kidney stones (renal calculi) are hardened masses of minerals and salts that form inside the kidney and can migrate down the ureter. As these jagged stones pass, they scrape the interior lining of the urinary tract, causing tissue damage and bleeding. This irritation can produce gross hematuria and often leads to the formation of blood clots.
In older males, a non-cancerous enlargement of the prostate gland, known as Benign Prostatic Hyperplasia (BPH), is a common mechanical cause of bleeding. The prostate gland, which surrounds the urethra, can become quite vascular with age. Its increased size places pressure on the urethra and bladder neck, and the resulting stretch on the blood vessels can cause them to rupture, leading to recurrent hematuria. External trauma, such as a severe blow to the lower back or abdomen, can injure the kidneys or bladder directly. The force of impact can cause deep tissue tears or contusions, resulting in significant bleeding into the urine.
Structural Diseases of the Urinary Tract and Kidneys
The most serious, though less common, causes of hematuria involve structural diseases, including malignancies of the urinary organs. Bladder cancer is a notable cause of painless gross hematuria, meaning visible blood appears without accompanying discomfort. This symptom should never be ignored. Kidney cancer (renal cell carcinoma) and cancers of the ureter can also cause bleeding as the tumors grow and erode the surrounding blood vessels.
In prostate cancer, bleeding is generally considered a less common, later-stage symptom than with bladder or kidney malignancies. Bleeding from these cancers results from the tumor invading and damaging blood vessels. Beyond cancer, intrinsic diseases of the kidney’s filtering units, known as Glomerulonephritis, can lead to hematuria. This condition involves inflammation that damages the glomeruli, the microscopic filters responsible for cleaning the blood. Damage to these filters allows red blood cells to leak out, usually resulting in microscopic hematuria accompanied by an excess of protein in the urine.
When to Seek Medical Attention
Any instance of visible blood (gross hematuria) must prompt an immediate medical evaluation, even if the bleeding stops quickly or is painless. This symptom requires investigation to rule out a serious underlying condition within the urinary tract. The presence of blood clots is particularly concerning, as they can lead to a painful inability to urinate if they completely block the bladder outflow.
A physician typically begins the evaluation with a urinalysis to confirm the presence of blood and check for signs of infection or kidney disease. Diagnostic imaging, such as a CT scan or renal ultrasound, is used to visualize the kidneys, ureters, and bladder, looking for stones, tumors, or structural abnormalities. For patients over 40 or those with risk factors like a history of smoking, a cystoscopy may be performed. This procedure involves inserting a thin, lighted tube into the bladder to directly inspect the lining for suspicious lesions.