Causes of Blood Clots in Urine With or Without Pain
Clots can be small and wormlike
Medically reviewed by Matthew Wosnitzer, MD
Though blood clots in urine can be distressing, it's not uncommon for blood to occur there. Blood in urine, also known as hematuria, can affect as many as 30% of adults at some point in their lives due to trauma, vigorous exercise, urinary tract infections (UTIs), medications, enlarged prostate, endometriosis, kidney disease, and, in rare cases, cancer.
In many cases, the bleeding will not be visible (microscopic hematuria). In others, the bleeding and clots can be seen with the naked eye (gross hematuria). When blood clots develop, they tend to look like stringy worms.
Blood clots in urine warrant an investigation by a healthcare provider. They may be caused by something relatively benign and treatable, but they may also be due to something serious.
This article looks at the causes of blood clots in urine, including those that occur with and without pain. It also describes what you should do if you have hematuria and when blood clots may indicate a medical emergency.
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How Do Blood Clots in Urine Look?
Gross hematuria occurs when your pee (urine) appears pink, red, or brown due to the presence of blood. Though this can be alarming, it only takes 1 milliliter of blood per liter (mL/L) of urine to cause a visible change in urine color.
Blood clots are a possible symptom of gross hematuria. A blot clot, also known as a thrombus, forms when platelets (a type of blood cell) and a protein in your blood called fibrin work together to stop bleeding by forming a clot.
If there is sufficient blood in your urine, a clot may form. The appearance of a clot can vary, but they often look like stringy wormlike or jellylike blobs that are red or brownish. At other times, they may look like red or darkish chunks or specks floating in normal-colored urine.
The color or shape of a clot cannot reveal if the cause is serious or not serious. Because of this, it is important to see a healthcare provider to have it checked out. Immediate action is needed when there are numerous clots, large clots, or deep red urine.
Sex and Gender Definitions
For the purpose of this article, "male" refers to people with penises, and "female" refers to people with vaginas, regardless of the gender or genders they identify with.
Related: What the Color of Your Urine Means
Causes of Blood Clots in Urine Without Pain
Gross hematuria may or may not cause pain. Conditions or situations in which blood clots can form without pain include:
Strenuous Exercise
Post-exertional hematuria (PEH) is caused when vigorous or prolonged exercise places undue stress on the urinary tract, which is made up of the kidneys, bladder, ureters, and urethra.
Studies suggest that PEH affects 1 in 8 long-distance runners, particularly those under age 30, causing visible blood in urine lasting anywhere from a few hours to three days.
Traumatic Injury
Gross hematuria can occur after an injury of the urethra (the tube through which urine exits the body) or the bladder. This may be due to devices like a urinary catheter or cystoscope inserted into the urethra or recent surgery on the urinary tract.
Vigorous sex can injure the urethra and cause hematuria and, in males, hematospermia (blood in semen).
When an Injury Is Serious
Blunt-force kidney trauma (such as by a blow, fall, or impact injury) can sometimes be serious. Seek immediate emergency care if a blow to the kidneys causes visible blood in urine. Studies suggest gross hematuria is often a sign of a major kidney injury.
Enlarged Prostate
Blood in urine is a common occurrence in people with an enlarged prostate, otherwise known as benign prostatic hyperplasia (BPH). BPH, common in males over age 60, can sometimes cause pain but is more often associated with difficulty peeing, frequent urination, and dribbling after urination.
With BPH, hematuria is caused by the enlargement of blood vessels in the prostate gland that can burst and bleed into the urethra. Tiny clots can sometimes develop in more advanced cases.
Medications
Certain medications can cause hematuria and possibly the formation of clots in urine. These include common drugs like:
Aminoglycoside antibiotics (a type of broad-spectrum antibiotic)
Anticonvulsants (anti-seizure medications)
Diuretics ("water pills")
Elavil (amitriptyline) (an antidepressant)
Related: Cause of Hematuria in Females
Causes of Blood Clots in Urine With Pain
Blood clots in urine can cause pain if they grow to a certain size and block the flow of urine to the ureters (vessels that connect the kidneys to the bladder) or the urethra.
Other conditions associated with gross hematuria are characteristically painful. In such cases, hematuria and blood clots may be secondary to the pain rather than the cause of the pain.
UTI
A urinary tract infection is a bacterial infection of the urinary system. Most involve the urethra or bladder (cystitis), in the lower part of the urinary tract. Females are affected more than males. An infection of the kidneys is called pyelonephritis.
Most UTIs are caused by the bacterium Escherichia coli (E. coli), which normally resides in the bowel. The risk of clots increases when a kidney or bladder infection is severe and accompanied by symptoms like pus in the urine, foul-smelling urine, and back or flank pain.
Kidney and Bladder Stones
Kidney and bladder stones (known as renal calculi and bladder calculi) are hardened deposits that develop when minerals in your urine start to crystallize.
The passing of a stone can sometimes occur without notice. However, larger stones can become stuck in a ureter or urethra and cause extreme pain, nausea, and vomiting. When the stone finally does pass, it can tear the walls of the urinary vessels and cause bleeding.
Stones that are stuck can also cause bleeding as the buildup of urine behind the blockage can cause small blood vessels to burst. When the stone is finally passed, there may be a rush of blood and large, visible clots.
Endometriosis
Endometriosis occurs when tissue similar to the lining of the uterus (womb) grows outside the uterus. It is a condition that affects more than 11% of females in the United States between the ages of 15 and 44.
Pain is the most common symptom of endometriosis. On rare occasions, endometriosis can also cause hematuria when uterine tissues start to invade and penetrate the bladder wall.
The condition, known as bladder endometriosis or vesicle endometriosis, causes hematuria when the uterine tissue is shed during menstruation. As with normal periods, this causes bleeding and blood clots that can be passed from the body in urine.
Polycystic Kidney Disease
Polycystic kidney disease (PKD) is an inherited disorder affecting people of all sexes that causes fluid-filled cysts to form in the kidneys. In addition to hematuria, symptoms of PKD include back or flank pain, a swollen belly, high blood pressure, and an increased risk of UTIs.
Around 50% of people with PKD will experience blood in the urine as a symptom. While most cases are relatively harmless, persistent bleeding may indicate kidney failure, particularly when accompanied by nausea, vomiting, decreased appetite, weakness, and breathlessness.
A person may pass multiple clots in their urine in cases like this.
Sickle Cell Disease
Sickle cell disease (SCD) is an inherited blood disorder most commonly seen in Black people that causes red blood cells to become deformed. This can lead to anemia and symptoms like periodic pain, swelling of the hands and feet, frequent infections, and vision problems.
Hematuria with SCD tends to be relatively benign and triggered by dehydration. But sometimes, SCD can cause recurrent gross hematuria with massive clotting. This is most often seen with a form called heterozygous SCD that can make blood more viscous (syrupy) and prone to clotting.
Renal Vein Thrombosis
Renal vein thrombosis (RVT) is a rare condition in which a clot forms in one or both renal veins that carry blood away from the kidneys. RVT is a serious condition usually resulting from an underlying kidney problem like nephrotic syndrome or kidney tumors.
RVT can cause severe damage to the kidneys, leading to significant bleeding and the formation of clots. Other symptoms include lower back or flank pain, nausea, vomiting, fever, and decreasing urine output as the condition worsens.
In severe cases, a blood clot can get carried from the kidneys to the lungs and cause a potentially life-threatening condition known as a pulmonary embolism.
Cancer
Several urological cancers (cancers of the urinary tract) can cause gross hematuria and the formation of clots. These include:
Renal cell carcinoma: The most common type of kidney cancer
Transitional cell carcinoma; The most common type of bladder cancer, also known as urothelial cell carcinoma
Squamous cell bladder carcinoma; An uncommon form of bladder cancer
Prostate adenocarcinoma. The most common type of prostate cancer
Hematuria may be the first sign of cancer and something that tends to occur when the disease is advanced. Over time, the bleeding can become more persistent, causing pain, rust-colored urine, and the formation of clots.
Related: Causes of Hematuria in Males
What Should You Do About Blood Clots in Your Urine?
Blood clots in urine should never be considered normal. It takes a significant amount of blood for clots to form, and there is no way to tell what the cause of a clot is until you are examined by a healthcare provider (such as a urologist).
To start the investigation, the healthcare provider will review your medical history and risk factors for hematuria (including older age, family history, recurrent UTIs, and smoking).
A physical exam of the lower abdomen, back, groin, and genitals may be performed. A digital rectal exam (DRE) may be used in males to check for an enlarged prostate.
Urine tests are central to diagnosis and can check for blood in urine, protein in urine (a sign of kidney disease), reduced kidney function, or excessive white blood cells or pus in urine (a sign of infection). Blood tests can also check for signs of infection, anemia, or prostate inflammation.
Based on the initial findings, other tests or procedures may be ordered, such as:
Ultrasound: A noninvasive imaging study that can detect kidney stones, venous obstruction, and other problems with the kidneys or bladder
Computed tomography (CT): An imaging study that composites multiple X-rays to create detailed, three-dimensional (3D) "slices" of structures such as the kidneys or bladder
Cystoscopy: A procedure in which a flexible, fiber-optic scope is fed through the urethra to examine the bladder
Ureteroscopy: A procedure similar to cystoscopy that goes past the bladder to look for an obstruction or other problems in the ureters
Renal or bladder biopsy: A procedure to obtain tissue samples for evaluation in the lab, particularly if cancer is suspected
Related: How Blood Clots Are Diagnosed
Complications of Untreated Blood Clots in Urine
Mild hematuria can sometimes be a relatively benign condition that will resolve on its own. But whenever hematuria is visible, is persistent, or is causing clots, it needs to be looked at.
Blood clots in urine can sometimes be a sign of an undiagnosed kidney disease like glomerulonephritis and lupus nephritis. If left untreated, conditions like these can lead to:
Acute tubular necrosis: Destruction of tiny ducts in the kidneys that filter the blood
Acute kidney injury (AKI): Also known as acute kidney failure or acute renal failure
Permanent kidney damage: Leading to the rapid progression of kidney disease and the early onset of end-stage renal disease
Gross hematuria is also associated with an increased risk of urological cancers (like bladder or kidney cancer) compared to microscopic hematuria. In fact, over 60% of people with urological cancers have visible blood in their urine.
For males over 60, persistent gross hematuria is predictive of urological cancer in 1 in 5 cases. This is particularly true in those who smoke, have chronic UTIs, have indwelling catheters, or have chronic trouble urinating.
Sign of Urological Cancer
See a healthcare provider immediately if you have signs and symptoms of a urological cancer, including:
Blood in the urine
Problems with urination
Lower back or flank pain
Overly frequent urination
Painful urination
Swelling of the ankles and legs
Sudden increases in blood pressure
Loss of appetite
Unexplained weight loss
Related: What Are Early Symptoms of Bladder Cancer?
At a Provider’s Office: What Happens Next?
The treatment of blood clots in urine varies by the underlying cause. Some conditions like post-exertional hematuria and minor traumatic injuries can resolve on their own with time and rest. Medication causes of hematuria may benefit from a dose adjustment or a change in treatment.
Other cases may clear when the underlying condition is treated or controlled. This may involve treatments or procedures like:
Antibiotics: Used to treat UTIs, including cystitis and pyelonephritis
Shock wave lithotripsy; A noninvasive method of breaking up kidney or bladder stones so they can pass easily
Hormonal contraceptives: Used to ease endometriosis symptoms
Transurethral resection of the prostate (TURP): A surgery used to resolve bleeding and other symptoms of BPH
Jynarque (tolvaptan): An oral drug that can slow cyst formation in people with PKD
Bone marrow transplant: Reserved for severe cases of sickle cell disease
Anticoagulants: Given intravenously (into a vein) to treat renal vein thrombosis in tandem with short-term dialysis
Surgical resection: Used to treat urological cancers, typically in combination with chemotherapy, immunotherapy, and/or targeted therapy
Cancer Treatment and Hematuria
Certain cancer treatments can cause blood in the urine. This includes pelvic radiation (radiation-induced hematuria) and chemotherapy drugs like Cytoxan (cyclophosphamide) and Ifex (ifosfamide).
Summary
Blood clots in urine can occur with gross hematuria (visible blood in urine). The appearance of clots may or may not be accompanied by pain. The clots can vary in their appearance, ranging from stringy, wormlike blobs to red or darkened little chunks in normal-colored urine.
Blood clots in urine develop in response to strenuous exercise, trauma, medications, or an enlarged prostate. Potentially serious causes include bladder or kidney infections, bladder or kidney stones, endometriosis, polycystic kidney disease, sickle cell anemia, renal vein thrombosis, and bladder, kidney, or prostate cancer.
The treatment varies by the underlying cause.
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