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Where Does the Bleeding in Urine Come From?


Hematuria is the medical term for blood in the urine. It is alarming when your urine is bloody, although 1 teaspoon or less blood is enough to give the urine a red or brown color.

Less commonly, blood clots may also be present. Hematuria also can be microscopic, only discovered on a routine urinalysis. Your physician should see you if you have visible blood in the urine or persistent microscopic hematuria.

Where does the bleeding come from?

Bleeding may originate in the urinary system: the kidneys, ureters, bladder, urethra, and prostate gland. The urine is usually red or pink when bleeding is from the lower urinary tract: ureter, bladder, and urethra; the presence of clots makes that more likely. Microscopic hematuria may originate from anywhere in the urinary system, although the additional presence of protein in the urine (proteinuria) increases the likelihood of kidney disease. The microscopic appearance of the blood cells is useful for discriminating kidneys from other sites in the urinary tract.

Causes of Hematuria

Your physician should evaluate unexplained visible (macroscopic) hematuria. Red or brown urine is not necessarily due to blood. Severe muscle trauma releases myoglobin which also gives the urine a reddish appearance. Several inherited metabolic conditions can cause similar discoloration as can some medications. This should be considered when blood is detected on the urinalysis dipstick but is not seen under the microscope or when the urine is red-brown and no blood is detected by either urine dipstick or microscopic examination.

The disorders and diseases that cause hematuria include some serious conditions. They can be roughly divided into several groups:

  • Infections anywhere in the urinary system are common causes of hematuria. Most often, these are bladder infections, although the kidneys and prostate gland may also be suspect.
  • Kidney and bladder stones frequently cause blood in the urine. Despite their reputation, they do not necessarily have typical symptoms.
  • Inherited diseases include polycystic kidney disease, sickle cell disease, and benign familial hematuria. As the name implies, the latter is a familial disease that does not cause progressive kidney injury.
  • Cancer of the bladder or kidney may cause no specific symptoms early on and is only discovered when there is macrohematuria or as an incidental finding in radiological studies. The risk of bladder cancer increases in smokers, and men are several times more likely to develop bladder cancer than women.
  • Immune/inflammatory diseases of the kidney, including those caused by auto-immune disorders. These may be acute or chronic, mild or severe, and transient or progressive. This can be kidney-specific or part of a more generalized disease.
  • Physical injury to the kidneys or bladder, most often due to trauma, such as an automobile accident, a serious fall, or a sports injury.
  • Intense physical activity is most often seen in long-distance runners.
  • Some medications

Evaluation of Hematuria

A diagnosis plan outlines the evaluation of hematuria to identify important kidney and urological diseases. They also can help to avoid unnecessary testing and procedures. Macrohematuria should almost always undergo both kidney and urological evaluations.

You should promptly inform your physician about an episode of visible hematuria with or without symptoms. A lot of diagnostic information can be gathered from history, family history, blood pressure, physical examination, a urinalysis (that includes microscopic examination), and, when indicated, a urine culture.

  • Among the most common causes of blood in the urine is an infection of the urinary system. Symptoms of bladder, urethral, or kidney (pyelonephritis) infections and positive reactions to leukocyte esterase or nitrites on the urinalysis dipstick should prompt a urine culture. If the hematuria resolves and the urinalysis becomes otherwise normal after adequate treatment of an infection, further evaluation is usually unnecessary.
  • A family history of hematuria or kidney or urological diseases is an important diagnostic factor. Many of these are familial or inherited. Also of possible significance are a personal history of smoking, trauma to the abdomen or flank, previous kidney disease, kidney stones, a weak stream or pain with urination, blood clots in the urine, and drugs or medications that can cause hematuria or discolor the urine.
  • The urinalysis dipstick is extremely sensitive to the presence of blood. A microscopic evaluation will confirm the presence of red blood cells (RBC) when there is a positive result.
  • Microscopic examination of RBCs can indicate whether the bleeding is more likely from the kidney. The presence of dysmorphic (misshapen) RBC and RBC casts (cylindrical clumps of RBC) are highly associated with kidney diseases. Normal-appearing RBC may also be associated with inflammatory or cystic kidney disorders but may occur with urological disorders or cancer of the kidneys or bladder.
  • The combination of microscopic hematuria and persistent protein in the urine (proteinuria) on urinalysis in the absence of a UTI is commonly seen in many kidney diseases.

Kidney hematuria

Once macrohematuria or persistent microhematuria is established, most patients will have a blood test (comprehensive metabolic panel or CMP) to estimate kidney function and detect related abnormalities. A complete blood count (CBC) can test for anemia, other RBC abnormalities, and the types and amounts of white blood cells or platelets circulating in the blood. This initial assessment helps to determine whether the source of the bleeding is more likely kidney or urological. When there are indicators of possible kidney disease, a further evaluation usually includes:

  1. Extended blood and urine testing that includes alternate means to estimate kidney function, indicators of inflammation, blood levels of certain proteins, tests for potentially harmful immunological disorders, and quantification of the amount of protein in the urine. These tests help to determine a path forward.
  2. Radiological imaging of the kidneys can provide additional information about likely diagnoses. With suspected kidney disease, a kidney ultrasound study is often done to determine whether the kidneys are small, enlarged, scarred, cystic, or have an obstruction to urine flow.
  3. When the exact cause of kidney hematuria remains unclear, a kidney biopsy may be recommended. This is usually an outpatient procedure, done through the skin in the back where the kidneys are located and using a needle that obtains a very small piece of kidney tissue. Generally, it is done with a local anesthetic. Determining the type of disease from the biopsy specimen often has substantial implications for the optimal type and duration of treatments and short and long-term expectations.

Hematuria from the lower urinary tract

Vigorous exercise, sexual intercourse, sexually-transmitted diseases, and self-instrumentation of the urethra may cause hematuria. After these have been ruled out, the hematuria can be evaluated in several ways, depending on clinical or laboratory findings.

  • Ultrasound study of the kidneys and bladder. Although ultrasound is not optimal for a detailed examination of the urinary tract, it can reveal the presence of foreign bodies in the bladder, obstruction of urine flow, kidney or bladder stones, and kidney or bladder malformations. Ultrasound is an unreliable screening test for tumors.
  • Advanced radiology imaging such as computerized tomography (CT scan) or magnetic resonance imaging (MRI) provides greater detail about possible anatomical abnormalities of the urinary system and is particularly useful for detecting kidney or bladder cancer. The MRI also can identify prostate cancer in the majority of cases.
  • A cystoscopy uses a long, thin, tube-shaped instrument with a light and camera at one end and a viewing eyepiece or computer screen at the other. It is inserted through the urethra, often with a topical anesthetic. Views of the urethra and bladder can identify cancerous areas and other abnormalities. The cystoscope can also obtain small amounts of suspicious-looking tissue for further evaluation.
  • Urine cytology also can be used as part of the evaluation for bladder cancers. This may be done using voided urine or after first instilling fluid into the bladder. The cells are then prepared for examination by microscopy.

Treatment

Individuals with an inherited disorder called benign familial hematuria usually need no treatment. For all other hematuria diagnoses, the treatment is directed at the cause.

Key take-aways

  • If you have unexplained blood in your urine, whether visible or microscopic, you should receive an initial evaluation and subsequent testing, if necessary, to determine its cause.
  • Causes of hematuria can be benign (of no clinical consequence) or be a sign of kidney or urological disease. Some of these can be serious.
  • Often, no diagnosis is found after a thorough evaluation of microscopic hematuria. Most of these individuals do well in the long term.
  • Bladder infections are the most common cause of hematuria.
  • A complete urinalysis can provide useful clues as to the type and origin of the hematuria.
  • When the cause of hematuria is unknown, you may have other diagnostic blood and urine tests and radiological procedures, including an ultrasound, CT scan, or MRI.
  • Making a diagnosis, if possible, is essential since many causes require specialized treatments, and ongoing injury may become permanent.

References

NIDDK/NIH. Hematuria (Blood in the urine)

Healthline Why is there Blood in My Urine?

MedicineNet What Medications Cause Blood in Urine?

NIDDK/NIH Kidney Biopsy

Mayo Clinic Urine Color

American Urological Association Microhematuria: AUA/SUFU Guideline (2020)

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