Guide To The Causes Of Blood In Urine (Hematuria)

August 7, 2023

Hematuria is the presence of red blood cells in an individual's urine and can be categorized in two different ways. Microscopic hematuria is the term used to describe blood cells in the urine that cannot be seen with the naked eye but can be seen through a microscope. Gross hematuria describes blood that can be seen in the urine with the naked eye. When an individual is affected by gross hematuria, their urine appears brown, red, or pink. It takes a nominal amount of blood to change the color of urine. Depending on its cause, other symptoms may or may not manifest in individuals affected by hematuria. Hematuria has many possible causes. Several diagnostic methods may be used to identify the underlying cause of hematuria, including a urinalysis, blood testing, CT scan, cystoscopy, kidney biopsy, and MRIs.

Urinary Tract Infection

An individual affected by a urinary tract infection may experience blood in their urine. The urinary tract consists of the kidneys; bladder; ureters, which are tubes that carry urine from the kidneys to the bladder; and urethra, the tube from the bladder to the outside of the body. Urinary tract infections are when any part of the urinary tract becomes infected by a harmful pathogen. Most urinary tract infections occur in an affected individual's bladder where urine is stored until it is ready to be emptied. Bacteria enter the body through the urethra and colonize in the bladder, and left untreated they can mobilize up the ureters and into the kidneys. Hematuria occurs when the infection causing pathogen damages the bladder walls, ureter walls, or tissues in the kidneys. The small vessels that supply these tissues become damaged as well, causing red blood cells to leak into the individual's urine stream. Most urinary tract infections begin with microscopic hematuria and will progress to gross hematuria without medical intervention.

Bladder Or Kidney Stones

An individual affected by bladder or kidney stones may have hematuria. Stones in the urinary tract typically begin inside of the kidney and then mobilize and enlarge in the ureters and bladder. The process of urinary tract stone formation may be referred to as renal lithiasis, urolithiasis, and nephrolithiasis. Stones that form in the urinary tract are not smooth and round but resemble deer antlers with sharp points and uneven edges. Smaller stones can be asymptomatic for several years, but a shift in position or changes in size can trigger symptoms. The irregular shape causes damage to the tissues of the kidneys, ureters, and bladder. The stone can penetrate the lining tissues of the urinary tract, rupturing and damaging the small vessels that supply them with blood and nutrients. Inflammation and irritation often result in the leakage of red blood cells into the urine. If a stone in the kidney or bladder obstructs the healthy flow of urine, it can back up into the kidneys and cause swelling and tissue damage. Once the stone passes or is removed, the backed-up urine can contain red blood cells that have leaked from damaged kidney tissues.

Kidney Infection

Kidney infection patients may notice blood in their urine. An infection of the kidneys is a type of urinary tract infection and may occur in one or both of an individual's kidneys. The kidneys are bean-shaped organs that sit just behind the rib cage in the middle of an individual's back. The kidneys contain thousands of tiny filters through which 150 quarts of blood flow through every day. Between one and two quarts of urine is produced through this process from the waste material and excess water the kidneys filter from the blood. However, this and other functions can become impaired when an infection-causing pathogen colonizes in the kidney. The infection causes damage in the tiny filters and other kidney tissues, resulting in symptoms like high fever, frequent and painful urination, nausea and vomiting, and pain in the back and side. Hematuria occurs because of the pathogenic and inflammatory damage that allows blood to leak from the vessels and small filters into the urine stream.


Glomerulonephritis is the inflammation of the tiny kidney filters called glomeruli. It has numerous causes, including viral infection, bacterial infection, lupus, Goodpasture's syndrome, IgA nephropathy, vasculitis, high blood pressure, glomerulosclerosis, and diabetes. Glomeruli are made out of numerous knots of tiny blood vessels that utilize homeostatic processes to extract excess fluid and waste substances from the blood. The more glomeruli that are affected by inflammation, the greater the amount of tissue damage and more of a decrease in kidney function. Glomerulonephritis can occur as an acute condition or as a chronic condition. Gross hematuria that turns the urine a dark red rust color is more likely to occur in individuals who are affected by acute glomerulonephritis, while microscopic hematuria is more likely to occur in chronic glomerulonephritis.

Enlarged Prostate

The prostate is a small male reproductive gland that sits right under the bladder. It is responsible for the production of a certain fluid added to sperm to produce semen. Men in their forties have a growth spurt of this gland that can cause it to become enlarged. Approximately ninety percent of men have an enlarged prostate by the time they are eighty-five years old. The urethra, a tube from the bladder to the outside of the body, runs directly through the prostate gland in a male. As the prostate becomes larger, it interferes with the healthy flow of urine out of the body. The increased pressure on the urethra causes the inability to empty the entire bladder of urine. Urine that cannot be emptied accumulates in the bladder, providing an ample breeding ground for pathogens to cause infection. Hematuria may occur as a result of frequent bladder infections. Chemicals and debris that accumulate in the bladder can promote the growth of stones in the lining of the bladder. Damage from stones and torn veins on the inner prostate surface are also prostate-related causes of hematuria.

Kidney Injury

An individual affected by an acute kidney injury may experience blood in the urine as a symptom of their medical disorder. An acute kidney injury describes when an individual incurs damage to their kidneys or experiences kidney failure that happens suddenly over a few hours to a few days. An acute kidney injury is caused by a variety of factors, including loss of fluid, loss of blood, hypotension, heart failure, heart attack, overuse of nonsteroidal anti-inflammatory drugs, severe allergic reactions, injuries, burns, and major surgery. Urinary tract blockage, multiple myeloma, sepsis, vasculitis, interstitial nephritis, scleroderma, and glomerulonephritis are also known to cause an acute kidney injury. Symptoms such as decreased urine output, leg swelling, ankle swelling, eye swelling, fatigue, nausea, confusion, chest pain, chest pressure, seizures, shortness of breath, and the presence of blood in the urine are indicative of an acute kidney injury.

Sickle Cell Anemia

A sickle cell anemia patient may experience blood in their urine as a symptom of their hematological abnormalities. Sickle cell anemia is an inherited form of anemia that causes red blood cells to take on sticky and rigid characteristics. These abnormal red blood cells are referred to as sickle cells and do not perform their job properly. This mechanism causes the patient to have too few healthy, functioning red blood cells in their body (anemia). The sickle cells in an affected individual's blood flow through blood circulation and eventually enter the kidneys. The abnormal red blood cells can accumulate in the small vessels of the kidneys and cause an obstruction in the normal flow of blood. When blood is unable to circulate through the kidneys due to the presence of blockages, cells begin to die in the tiny filters in the organ. Blood leaks into the urine because the cells in the kidney filters that make up the blood vessels become damaged from a lack of blood flow.

Certain Medications

An individual who takes certain medications may blood in the urine as an adverse side effect of the drug they are taking. This form of hematuria is often referred to as drug-induced hematuria. Certain medications are capable of causing both gross hematuria and microscopic hematuria. The most common medications used in the population that is known to produce blood in the urine are called anticoagulants and antiplatelets. These medications stop the body from forming excessive and inappropriate blood clots. Medications used to treat heart conditions and problems with the circulatory system like statins and antihypertensive drugs have also caused hematuria. Antibiotics that are derivatives of penicillin and antiretrovirals have been known to provoke hematuria in patients who take them for extended periods. Other medications that can cause blood in the urine include analgesics, anticonvulsants, and chemotherapy drugs.


Certain types of cancer may have blood in the urine as a symptom. The most common type of cancer known to cause hematuria is bladder cancer. The bladder is a muscular structure in the lower pelvis and it is responsible for holding urine until it is ready to be expelled from the body. Urine is produced by the kidneys and moves through tubes referred to as ureters before it reaches the bladder to be stored. The bladder is made of several muscles that expand and contract with the varying volumes of urine produced by the kidneys. When cancerous cells form in the bladder, the inner lining of the bladder wall becomes damaged. Tiny blood vessels that supply the bladder lining with blood become damaged or destroyed, allowing blood to leak into the urine.

Polycystic Kidney Disease

Hematuria may develop due to polycystic kidney disease, a disorder where numerous fluid-filled sacs or cysts develop in the kidneys. These cysts take up space, crowding out and damaging the healthy cells that make up the kidney tissues. Polycystic kidney disease makes it difficult for an affected individual's kidneys to do their job and filter waste from the blood that flows through them. The kidneys in an affected individual may become enlarged and can fail as a complication of polycystic kidney disease. The fluid-filled cysts in the kidneys can cause the small vessels in the glomeruli to rupture or become damaged. This malfunction allows blood to leak into the urine being produced. Blood remains in the urine as it flows through the ureters to the bladder and exits the body.

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