What Is It, Causes, and More
Author:Nikol Natalia Armata
Editors:Alyssa Haag,Ian Mannarino, MD, MBA,Kelsey LaFayette, DNP, RN
Illustrator:Jessica Reynolds, MS
Copyeditor:Sadia Zaman, MBBS, BSc
What is hematuria?
Hematuria refers to the presence of blood in the urine. It is defined by the identification of three or more red blood cells (RBCs) per high-power field (HPF), in a urinary sample. RBCs in the urine can either originate from the kidneys or anywhere else in the urinary tract, which is composed of the ureters, the bladder, the prostate (in those assigned male at birth), and the urethra.The term hematuria comes from the Greek words “hema-”, which refers to the blood, and “-uria”, which refers to the urine. Blood in the urine can either be visible to the naked eye (i.e., gross hematuria), or can be detected microscopically (i.e., microscopic hematuria). Asymptomatic or symptomatic hematuria may be associated with many different medical conditions and should be investigated when detected.
What causes hematuria?
Most commonly, observing blood in the urine indicates an infection in the bladder (i.e., cystitis), or the kidneys (i.e., pyelonephritis). Trauma of the urinary tract, ranging from kidney stones to accidents, like improper foley catheter insertion or a fall that bruises the kidney, can also cause hematuria. Hematuria is also often associated with nephritic syndrome, which can result from glomerulonephritis, an inflammatory condition that damages the part of the kidney that filters the blood (i.e., glomeruli). In addition, polycystic kidney disease, an inherited disorder in which cysts develop on the kidney, can also result in hematuria. Malignancies, such as renal cell carcinoma, bladder cancer, and prostate cancer, can also cause hematuria.
Certain systemic conditions may also result in hematuria, including Alport syndrome, a condition that affects the tiny vessels of the kidneys; Goodpasture syndrome, an autoimmune disorder affecting the lungs and kidneys; and lupus nephritis, which is characterized by inflammation of the kidney triggered by lupus. These conditions can lead to nephritic syndrome, which characteristically presents as hematuria. Individuals with bleeding diathesis, like those using blood thinners, or thrombocytopenic individuals, may also experience blood in their urine. Individuals with sickle cell disease, a genetic condition in which red blood cells are abnormally shaped, also frequently experience hematuria.
When the presence of blood in the urine is not related to the urinary system, it may be related to a variety of conditions, including an enlarged prostate (i.e., benign prostatic hyperplasia); endometriosis (i.e., ectopic endometrial tissue) in the ureter, urethra, kidneys, or bladder; vigorous exercise; menstruation; or even recent sexual activity. Lastly, some foods (e.g., beets) and medications (e.g., rifampin) can change the color of an individual’s urine which can be confused for hematuria.
How is hematuria diagnosed?
To diagnose hematuria a health care provider will usually begin by assessing an individual’s symptoms, past medical history, and current medications. Individuals with gross hematuria may have pink, red, or brown urine. In most cases, people with gross hematuria are asymptomatic or may present with mild symptoms, like pain during urination or urinary urgency. Hematuria that presents with blood clots in the urine can sometimes be accompanied with bladder pain or pain in the back. A physical exam should always be performed to assess for tenderness and pain of the lower abdomen, pelvic region, and flanks (i.e., costovertebral angle tenderness).
Additional testing is usually required to determine the underlying cause of the hematuria. Urinalysis is the initial and most helpful test to perform. The presence of three or more RBCs per HPF on urinalysis is characteristic of microscopic hematuria. Alternatively, a urine dipstick can be performed, however, it is not as diagnostic and has many false positive or false negative results. Urine appearance, pH, the presence of proteins, white blood cells (WBCs), nitrites, crystals, and casts can also aid in the diagnostic process. For example, a urine sample with significant WBCs and positive nitrites suggests a urinary tract infection (UTI) from a Gram-negative microorganism as the likely cause of hematuria. Similarly, the identification of excessive proteins with hematuria favors the diagnosis of glomerulonephritis. Supplementary urine microscopy can be performed to examine urine sediments for RBC morphology, and RBC casts. Microscopy is the single most significant test which can differentiate between glomerular and non-glomerular bleeds. Dysmorphic RBCs and RBC casts, when identified, are diagnostic of glomerular pathology.
Initial ultrasound imaging of the kidneys, ureters, and bladder may also be performed in individuals with hematuria in order to assist with diagnosing anatomical causes of hematuria, such as a kidney stone or another mass. It can also be used to detect renal cysts. Abdominopelvic CT scan, with or without contrast, is the preferred modality to detect renal stones and other morphological abnormalities of kidneys. An abdominal and pelvic MRI are other useful modalities if a CT scan is contraindicated or not helpful.
Cystoscopy may also be used in order to detect carcinomas and inflammation. It may also be used therapeutically by removing stones remaining in the bladder. Lastly, to diagnose a glomerular cause of hematuria, a kidney biopsy is usually required.
How is hematuria treated?
Treatment for hematuria depends on the underlying cause. In asymptomatic individuals, with sparse incidents of hematuria, negative imaging, stable renal functions, and absence of proteinuria, observation may be a sufficient therapeutic approach.
For symptomatic cases and those with clear underlying causes, specific treatments will be required to resolve the underlying condition. These treatments can include antibiotics, immunosuppressant therapies, symptom management, and in some cases, surgical intervention.
What are the most important facts to know about hematuria?
Hematuria refers to the presence of blood in the urine, and can be classified as either microscopic or macroscopic. Hematuria typically occurs as a result of pathologies in the urogenital system, such as UTIs, stones, trauma, and malignancies. However, systemic conditions, like Alport and Goodpasture syndrome, can also present with blood in the urine. Diagnosis is based on medical history and clinical presentation but further testing, such as urinalysis, urine microscopy, ultrasound of the bladder and kidneys, CT, and kidney biopsy can be performed to confirm the diagnosis. Treatment depends on the underlying cause.
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Renal and urinary tract masses: Pathology review
Resources for research and reference
O'Leary, M. P., Glassock, R. J., & Lam, A. Q. (2020, Dec 9). Patient education: Blood in the urine (hematuria) in adults (Beyond the Basics). In UpToDate. Retrieved November 5, 2021, from https://www.uptodate.com/contents/blood-in-the-urine-hematuria-in-adults-beyond-the-basics.
Saleem, M. O, & Hamawy, K. (2021, Aug 11). Hematuria. In StatPearls [Internet]. Retrieved November 1, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK534213/
U.S. Department of Health and Human Services. (2016, July). Hematuria (blood in the urine). In National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved November 1, 2021, from https://www.niddk.nih.gov/health-information/urologic-diseases/hematuria-blood-urine