Hematuria or haematuria is defined as the occurrence of blood or red blood cells in the urine. The word hematuria is derived from Greek haima (αἷμα) "blood" and ouron (οὖρον) "urine". Hematuria can be visible to the naked eye (termed "gross hematuria") and may appear red or brown (sometimes referred to as tea-colored), or it can be microscopic (i.e. not visible to the eye but detected with a microscope or laboratory test). The origin of the blood that enters and mixes with the urine can arise from any anatomical site within the urinary system, including the kidney, ureter, urinary bladder, and urethra, and in men, the prostate. Common causes of hematuria include urinary tract infection (UTI), kidney stones, viral illness, trauma, bladder cancer, and exercise. The underlying causes of hematuria can be divided into glomerular and non-glomerular causes, referring to the involvement of the glomerulus of the kidney. Notably, not all red urine is hematuria. Other substances such as certain medications and foods (e.g. blackberries, beets, food dyes) can cause urine to appear red. Menstruation in women may also cause the appearance of hematuria and may result in a positive urine dipstick test for hematuria. Additionally, a urine dipstick test may be falsely positive for hematuria due to other substances in the urine such as myoglobin during rhabdomyolysis. A positive urine dipstick test should be confirmed with microscopy, where hematuria is defined by three of more red blood cells per high power field. When hematuria is detected, a thorough history and physical examination with appropriate further evaluation (e.g. laboratory testing) can help determine the underlying cause.
|Hematuria (Differential diagnosis)|
|Other names||Haematuria, erythrocyturia, blood in the urine|
|Visible hematuria that is tea-colored|
|Symptoms||Blood in the urine|
|Causes||Urinary tract infection, kidney stone, bladder cancer, kidney cancer|
Glomerular causes include:
Visible blood clots in the urine indicate a non-glomerular cause. Non-glomerular causes include:
Medications that may cause urine to appear red include:
Foods that may cause urine to appear red include:
A urine dipstick may be falsely positive for hematuria due to other substances in the urine. While the urine dipstick test is able to recognize heme in red blood cells, it also identifies free hemoglobin and myoglobin. Free hemoglobin may be found in the urine resulting from hemolysis, and myoglobin may be found in the urine resulting from rhabdomyolysis. Thus, a positive dipstick test does not necessarily indicate hematuria; rather, microscopy of the urine showing three of more red blood cells per high power field confirms hematuria.
In women, menstruation may cause the appearance of hematuria and may result in a urine dipstick test positive for hematuria. Menstruation can be ruled out as a cause of hematuria by inquiring about menstruation history and ensuring the urine specimen is collected without menstrual blood.
The evaluation of hematuria is dependent upon the visibility of the blood in the urine (i.e. visible/gross vs microscopic hematuria). Visible hematuria must be investigated, as it is due to a pathological cause. In those with visible hematuria, urological cancer (most frequently bladder or kidney cancer) is discovered in 20-25%. Hematuria alone without accompanying symptoms should be raise suspicion of malignancy of the urinary tract until proven otherwise.
The first step in evaluation of red or brown colored urine is to confirm true hematuria with urinalysis and urine microscopy, where hematuria is defined by three of more red blood cells per high power field. Although a urine dipstick test may be used, it can give false positive or false negative results. In gathering information, it is important to inquire about recent trauma, urologic procedures, menses, and culture-documented urinary tract infection. If any of these are present, it is appropriate to repeat a urinalysis with urine microscopy in 1 to 2 weeks or after treatment of the infection. If the results of the urinalysis and urine microscopy reveal a glomerular origin of hematuria (indicated by proteinuria or red blood cell casts), consultation of a nephrologist should be made. If the results of the urinalysis indicate a non-glomerular origin, a microbiological culture of the urine should be performed, if it has not been done already. If the culture is positive, treatment of the infection should follow and urinalysis and urine microscopy should be repeated once complete. If the culture is negative or if hematuria persists after treatment, CT urogram and cystoscopy should be performed. Of note, hemodynamic stability should be monitored and a complete blood count should be ordered to assess for anemia.
In summary, those with visible hematuria confirmed by urinalysis and urine microscopy and with no recent trauma, urologic procedures, menses, or urinary tract infection should undergo cystoscopy and CT urogram.
After detecting and confirming hematuria with urinalysis and urine microscopy, the first step in evaluation of microscopic hematuria is to rule out benign causes. Benign causes include urinary tract infection, viral illness, kidney stone, recent intense exercise, menses, recent trauma, or recent urological procedure. After benign causes have resolved or been treated, a repeat urinalysis and urine microscopy is warranted to ensure cessation of hematuria. If hematuria persists (even if there is a suspected cause), the next step is to stratify the risk of the person for urothelial cancer into low, intermediate, or high risk to determine next steps. To be in the low risk category, one must satisfy all of the following criteria: Has never smoked tobacco or smoked less than 10 pack-years; is a female less than 50 years old or a male less than 40 years old; has 3-10 red blood cells per high power field; has not had microscopic hematuria before; and has no other risk factors for urothelial cancer. To be in the intermediate risk category, one must satisfy any of the following criteria: Has smoked 10-30 pack-years; is a female 50–59 years old or a male aged 40–59 years old; has 11-25 red blood cells per high power field; or was previously a low-risk patient with persistent microscopic hematuria and has 3-25 red blood cells per high power field. To be in the high risk category, one must satisfy any of the following criteria: Has smoked more than 30 pack-years; is older than 60 years of age; or has above 25 red blood cells per high power field on any urinalysis. For the low risk category, the next step is to either repeat a urinalysis with urine microscopy in 6 months or perform a cystoscopy and renal ultrasound. For the intermediate risk category, the next step is to perform a cystoscopy and renal ultrasound. For the high risk category, the next step is to perform a cystoscopy and CT urogram. If an underlying cause for hematuria is discovered, it should be managed appropriately. However, if no underlying cause is discovered, the hematuria should be re-evaluated with urinalysis and urine microscopy within 12 months. Additionally, for all risk categories, if a nephrologic origin is suspected, consultation of a nephrologist should be made.
The pathophysiology of hematuria can often be explained by damage to the structures of the urinary system, including the kidney, ureter, urinary bladder, and urethra, and in men, the prostate. Common mechanisms include structural disruption to the glomerular basement membrane and mechanical or chemical erosion of the mucosal surfaces of the genitourinary tract.
Acute clot retention is one of three emergencies that can occur with hematuria. The other two are anemia and shock. Blood clots can prevent urine outflow through either ureter or the bladder. This is known as acute urinary retention.
Blood clots that remain in the bladder are digested by urinary urokinase producing fibrin fragments. These fibrin fragments are natural anticoagulants and promote ongoing bleeding from the urinary tract. Removing all blood clots prevents the formation of this natural anticoagulant. This in turns facilitates the cessation of bleeding from the urinary tract.
The acute management of obstructing clots is the placement of a large (22-24 French) urethral Foley catheter. Clots are evacuated with a Toomey syringe and saline irrigation. If this does not control the bleeding, management should escalate to continuous bladder irrigation (CBI) via a three-port urethral catheter. If both a large urethral Foley catheter and CBI fail, an urgent cystoscopy in the operating room will be necessary. Lastly, a transfusion and/or a correction of a coexisting coagulopathy may be necessary.
In the United States of America, microscopic hematuria has a prevalence of somewhere between 2% and 31%. Higher rates exist in individuals older than 60 years of age and those with a current or prior history of smoking. Only a fraction of individuals with microhematuria are diagnosed with a urologic cancer. When asymptomatic populations are screened with dipstick and/or microscopy medical testing about 2% to 3% of those with hematuria have a urologic malignancy. Routine screening is not recommended. Individuals with risk factors who undergo repeated testing have higher rates of urologic malignancies. These risks factors include age (>35 years), male gender, previous or current smoking, chemical exposure (e.g., benzenes or aromatic amines), and prior pelvic radiation therapy.
In pediatric populations, the prevalence is 0.5–2%. Risks factor include older age and female gender. About 5% of individuals with microscopic hematuria receive a cancer diagnosis. 40% of individuals with macroscopic hematuria (blood easily visible in the urine) receive a cancer diagnosis.
Common causes of hematuria in children are:
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