Epithelial cells in urine

The presence of epithelial cells in the urine is common in the urinary sediment analysis.

Epithelial cells are constantly added to the urine as they are shed from the lining of the urinary tract.

It is usually due to the shedding of old cells and consequently a small amount of these cells appears in the urine sample.

There are three different types of epithelial cells, named according to the area where they come from:

• Squamous epithelial cells: Usually come from the urethra in both males and females or the vagina in females. They are the most common epithelial cells present in the urine and they do not have much clinical significance. They are large, flat and with irregular shape. They have a large nucleus and abundant cytoplasm. A large number in the urine may signify contamination by vaginal discharge. Sometimes, the squamous epithelial cells are infected by the bacteria Gardnerella Vaginalis. Under the microscope, the bacteria covers most of the cell and it is usually due to a vaginal infection.
• Transitional epithelial cells: They usually come from the kidneys, the ureters, bladder and upper urethra in males. They are smaller than squamous cells and have spherical or polyhedral. Their presence in small numbers in the urine is not considered abnormal. If they are present in large amount could signify a possible neoplasm. They also appear to increase after urinary catheterization or other invasive urological procedures.
• Renal tubular epithelial cells: They come from the renal tubules in the kidneys. The size and shape of these cells are different depending on the area from which they originate. They are smaller than the other epithelial cells, and may have a shape from round to columnar. Their present in the urine is clinically significant because they are associated with renal disease (glomerulonephritis, viral infections, etc.). Their presence in the urine is always considered an abnormal result.

The test is performed when there is a positive result in urine for proteins, blood, nitrites or leukocyte esterase. It is also performed in a routine urinary sediment analysis.

The presence of small amounts of epithelial cells in the urine is frequent. It only has a clinical meaning if they appear in large number or they are renal tubular epithelial cells.

To perform this test is necessary to collect a urine sample in a in a specific container using a special kit. The sample must be collected using the clean catch midstream urine procedure. First, you should urinate a small amount into the toilet bowl. Then, urinate a few inches of urine into the container and finally finish urinating into the toilet bowl.

If this procedure is not done correctly and the first part of the urination is collected, it is possible to find many epithelial cells in the sample from the urethra or the urinary meatus.

To study the epithelial cells under the microscope, it is necessary to obtain the urinary sediment. For this matter, the urine sample should be placed at rest for some hours waiting for the different elements of the urine (white and red blood cells, epithelial cells, crystals, etc.) precipitate to the bottom. As this process is very slow, the urine is centrifuged for about 5 minutes at 1500 or 2000 revolutions per second to obtain a sample of the sediment in less time.

The test result depends on the type of epithelial cells found in the urine sample:

• Squamous epithelial cells: It is considered abnormal when the number of cells significantly high. In that case it that may be due to:
  • Vaginal contamination
  • Urethritis
  • Vaginitis
• Transitional epithelial cells: It is considered abnormal when the number of cells significantly high. In that case it that may be due to:
  • Renal lithiasis
  • Urinary tract infection
• Renal tubular epithelial cells: If these cells appear in the urinary sediment is always considered an abnormal result. It may be a sign of kidney damage (renal tubules necrosis) and may be caused by:
  • Poisoning from heavy metals
  • Viral infection (Hepatitis B)
  • Pyelonephritis
  • Salicylate poisoning
  • Kidney transplant rejection
  • Acute tubular necrosis
  • Cytomegalovirus Induced Interstitial Nephritis
  • Glomerulonephritis