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The Significance of Red Blood Cells in Urinalysis

written by: A. Jitesh•edited by: Diana Cooper•updated: 1/13/2011

Red blood cells in urinalysis may be due to certain medications or problems such as urinary tract infections or blood clotting disorders. Urinalysis is an important primary detection test. If red blood cells are present, further investigation is needed.

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    Urinalysis is the testing of the urine sample of a patient to detect various diseases. Urine removes waste substances from the body. The detection of different substances in the urine helps in making a diagnosis. Some substances are present as normal constituents of the urine in a particular amount and the estimation of their altered values helps in detecting abnormalities in the body. Some substances are usually absent in urine and hence their presence in the urine is also suggestive of some abnormality in the body.

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    Red Blood Cells in Urinalysis

    The medical term for red blood cells in the urine is hematuria. The red blood cells may be present in small amounts and visible only through a microscope. The urine is normal in color and this is known as microscopic hematuria. If they are present in sufficient amounts, the urine may be pinkish, red or smoky brown in color and this is known as frank or gross hematuria.

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    Possible Causes

    Usually microscopic hematuria means damage to the kidneys and visible hematuria means damage to the ureters, bladder and urethra.

    1. Urinary tract infections - this is more common in women than men

    2. Kidney or urethral stones - a common cause of hematuria in persons younger than 40 years of age

    3. Cancers of the bladder, kidney or prostate - more common causes in persons older than 40 years of age

    4. Kidney disease

    5. Blood clotting disorders

    6. Benign prostatic hypertrophy

    7. Medications like rifampin, warfarin, quinine, aspirin and phenytoin

    8. Chronic diseases like diabetes, hypertension and sickle cell anemia

    9. Strenuous exercise like running due to repeated jarring of the bladder

    10. Viral infections

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    The urine sample is collected in a specimen cup and sent to the laboratory for urinalysis. Microscopically it is examined for the presence of blood.

    The dipstick method can be used to detect blood in the urine but it is a qualitative and not a quantitative test.

    In microscopic urinalysis, the urinary sediment is examined for the presence of red blood cells after centrifugation of urine. In this, a quantitative estimation of the red blood cells in the urine can be done. The number of red blood cells in the urine is the number of cells viewed per high power field under maximum magnification of the microscope.

    The presence of red blood cells in the urine should warrant a complete history and examination of the patient as well as other investigations like ultrasound of the kidneys, intravenous pyelography, CT scan, cystoscopy and urine culture.

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    The presence of red blood cells in the urinalysis warrants consultation with a medical practitioner and treatment of the cause. Proper follow up should be done until the condition completely resolves.

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    1. A Manual of laboratory and diagnostic tests by Frances Talaska Fischbach, Marshall Barnett Dunning, 2008.

    2. Urinalysis and body fluids by Susan King Strasinger, 1994.