Hematuria or haematuria is defined as the presence of blood or red blood cells in the urine.
- In terms of visibility, 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 but detected with a microscope or laboratory test).
- In terms of the anatomical origin, blood or red blood cells can enter and mix with urine at multiple anatomical sites within the urinary system, including the kidney, ureter, urinary bladder, and urethra, and in men, the prostate. Non-glomerular causes can be further subdivided into the upper urinary tract and lower urinary tract causes. Normally, red blood cells should never pass from the glomerular capillary into the renal tubule, and this is always a pathological process. Glomerular causes include:
- IgA nephropathy
- Nephrotic syndrome
Non-glomerular hematuria
Visible blood clots in the urine indicate a non-glomerular cause.
False positive urine dipstick
A urine dipstick may be falsely positive for hematuria due to other substances in the urine. 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. are:
- Fever
- Strenuous exercise
- Acute nephritis
- Congenital abnormalities:
- Non-vascular: ureteropelvic junction obstruction, posterior urethral valves, urethral prolapse, urethral diverticulum and multicystic dysplastic kidney
- Vascular: arteriovenous malformations, hereditary hemorrhagic telangiectasias, renal vein thrombosis in newborns.
- Urinary stones.
- Coagulation disorders.
- Mechanical trauma: masturbation, foreign body.
- Nephritic syndrome: IgA nephropathy, Post-streptococcal glomerulonephritis, Benign familial hematuria, Alport syndrome.
- Sickle cell trait or disease.
Evaluation
The evaluation of hematuria is dependent upon the visibility of the blood in the urine (i.e. visible/gross vs microscopic hematuria). It is important to obtain a detailed history from the patient (i.e. recreational, occupational, and medication exposures) as this information can be helpful in suggesting a cause of hematuria. The physical exam can also be helpful in identifying a cause of the hematuria as certain signs found on the physical exam can suggest specific causes of the hematuria. Benign causes include urinary tract infection, viral illness, kidney stone, recent intense exercise, menses, recent trauma, or recent urological procedure. 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. The other two are anemia and shock. Urosepsis is the result of a systemic inflammatory response to infection and can be identified by numerous signs and symptoms (e.g. fever, hypothermia, tachycardia, and leukocytosis). 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.