Causes of WBCs and RBCs in Urine

Causes of WBCs and RBCs in Urine
Causes of WBCs and RBCs in Urine (Image: andriano_cz/iStock/GettyImages)

A urinalysis typically includes dipstick tests for red blood cells (RBCs) and white blood cells (WBCs). Microscopic examination of the urine is also used to detect and quantify these cells. Urine normally contains no RBCs and only a few WBCs, at most. Several conditions and diseases -- most involving the urinary and reproductive systems -- can cause RBCs and WBCs in the urine. These conditions and diseases range in seriousness from relatively minor infections to cancer.

Urinary Tract Infection

Urinary tract infections (UTIs) are a leading cause of finding both WBCs and RBCs in the urine. WBCs move into the urinary tract to fight the infection. The RBCs typically indicate inflammation of the lining of the urinary tract due to the infection. With a UTI, the presence of RBCs in the urine is often not obvious by looking at the fluid with the naked eye. However, the cells can be detected with dipstick testing and seen on microscopic examination. The infection might be limited to the bladder or involve the upper urinary tract, including the kidney.

Genital Infections

A variety of female and male genital infections -- including sexually transmitted diseases -- can cause RBCs and WBCs in the urine. The presence of the blood cells is often due to contamination from the genitals as the urine passes from the body. Examples of genital infections that might, though not invariably, lead to RBCs and WBCs in the urine include:

  • Genital herpes
  • Vaginal yeast infection
  • Trichomonas ("trich") vaginitis
  • Chlamydia or, less commonly, gonorrhea
  • Bacterial prostatitis (infection of the prostate)

Kidney Diseases

Urinary RBCs and WBCs sometimes indicate the presence of kidney disease. Acute interstitial nephritis is an example, and is leading cause of sudden kidney failure. This condition often develops in response to certain medications or infections. Glomerulonephritis is another kidney disease that sometimes causes red and white blood cells in the urine, and can lead to acute or chronic kidney failure. This condition often develops after an infection or in association with autoimmune diseases, such as systemic lupus erythematosus. Doctors use an array of tests to diagnose these kidney diseases.

A kidney stone is another possible culprit that often causes visible blood in the urine. The blood is typically due to scraping of the urinary tract structures as the stone(s) moves through them. As blood contains both RBCs and WBCs, both cells types are likely to be present in the urine. Polycystic kidney disease -- an inherited disorder that causes multiple cysts in the kidneys -- can also cause both RBCs and WBCs to appear in the urine.

Other Causes

Other diseases and conditions can also potentially cause urinary RBCs and WBCs. Examples include:

  • Kidney or bladder cancer
  • Interstitial cystitis (noninfectious inflammation of the bladder)
  • Recent use of a urinary catheter
  • Rejection of a transplanted kidney

Considerations, Warnings and Precautions

In a woman having a period, the presence of menstrual blood in the urine can lead to the temporary presence of RBCs and WBCs but is of no consequence. Additionally, some foods and medications might give the urine an unusual tint that could potentially be mistaken for blood, or possibly interfere with dipstick test results for RBCs and WBCs.

See your doctor without delay if you notice visible blood in your urine or experience signs or symptoms suggestive of a urinary tract or reproductive system infection or disease, including:

  • Urinary urgency, frequency or painful urination
  • Markedly increased or decrease daily urination
  • Fever or chills
  • Flank, abdominal or pelvic pain
  • Unusual vaginal or penile discharge, itchiness, sores or a rash
  • Swelling of the feet, hands or face

Reviewed and revised by: Tina M. St. John, M.D.

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