Urine samples can sometimes contain leukocytes. A leukocyte is a white blood cell, vital to the defenses of the immune system against disease. They do not usually occur in the urine in significant numbers.

Having leukocytes in the urine may be a symptom of an infection. A urinary tract infection (UTI) is often responsible for increasing leukocyte levels in the urine

An estimated 150 million UTIs occur worldwide every year.

This article will explain what an excess of white blood cells in the urine means, as well as how to treat a UTI.

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Leukocytes can sometimes show in urine tests.

An unusually high number of leukocytes in the urine indicates inflammation or infection along the urinary tract, often in the bladder or kidney.

These will show in a urine test. Women during pregnancy receive testing for urinary infections during their first prenatal visit, and they might need testing at other times during their pregnancy. Other people may require testing based on their health, symptoms, or a history of recurrent infections.

The doctor may carry out a dipstick test, in which a chemical strip detects an enzyme called leukocyte esterase that points to the presence of white blood cells, typically related to an infection. The dipstick test also highlights nitrites, which are a waste product from the breakdown of certain bacteria.

The presence of nitrites in the urine is highly specific to certain bacterial infections. Nitrites do not occur with all types of bacteria.

An absence of leukocyte esterase in the urine means that the urine is not likely to contain white blood cells, so it is not likely to be carrying infectious agents.

The doctor or laboratory technician may also perform a urine culture. This involves growing bacteria from the urine to identify the cause of the infection.

Leukocytes in the urine without nitrite

If the test for leukocyte esterase is positive but finds no nitrite, an infection may still be present.

The test is particular to certain bacterial enzymes, which means it can pick up specific bacterial infections with more certainty. However, it is not highly sensitive, which means that the test does not pick up all bacterial infections. E. coli bacteria are most commonly associated with nitrites in the urine.

Having leukocytes in the urine without nitrites can also lead to a false-positive result that points to a bacterial infection when there is none. The pathologist or technician will carry out further testing to confirm the presence of an infection.

This is particularly true when there are other causes of inflammation in the urinary tract. The genital canal can sometimes pass leukocytes into the urine during the process of giving a sample.

To avoid a false-positive result, people should clean the area around the urethral opening before giving the sample, using cleansing wipes and holding their labia or foreskin aside.

Take a sample halfway through urinating. The initial stream of urine may be contaminated by skin bacteria, so taking a sample this way also reduces the risk of a misleading outcome.

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White blood cells are a key part of the immune system.

Leukocytes are white blood cells. They are heavily involved in immune responses that protect people from infection.

There are several types of white blood cell. The two main leukocytes are phagocytes and lymphocytes.

Phagocytes are produced in the bone marrow. Their job is to engulf foreign particles, such as bacteria or parasites. This means surrounding, absorbing, and destroying a particle.

Lymphocytes are the white blood cells that recognize foreign particles based on previous encounters. They contribute to "adaptive" immunity, the sophisticated ability of the immune system to remember and produce tailored and effective responses to an infection.

Lymphocytes produce antibodies. These bind to foreign particles and allow the immune system to remember them later on, should the same infection occur.

There are other types of leukocyte. Cytotoxic white blood cells, for example, can kill other cells.

During pregnancy

A doctor will often carry out urinalysis during pregnancy to check for leukocytes. This is the same test that confirms a bladder or kidney infection.

This checks for certain pregnancy-related conditions too. One of these is preeclampsia, or high blood pressure during pregnancy. Protein in the urine and a raised blood pressure reading can indicate preeclampsia.

UTIs are common during pregnancy, and doctors will often find leukocytes in the urine that suggest the presence of an infection. However, some women who are pregnant have a bacterial infection in the urine without symptoms.

This is known as asymptomatic bacteriuria.

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A UTI is often the cause of leukocytes in the urine.

A UTI can affect the upper and lower urinary tracts, the kidneys, the bladder, urethra, and prostate.

Lower urinary tract infections may also have these specific names:

  • cystitis, or bladder infection
  • urethritis, an infection of the urethra, which is the tube carrying urine away from the bladder to the outside of the body
  • prostatitis, involving the prostate

Both upper and lower UTIs can lead to leukocytes in the urine.

Symptoms vary and often overlap, but they might include:

  • urinating more often, and a frequent sensation of needing to urinate
  • burning or painful urination passing of only small amounts of urine
  • difficulty urinating or pain when passing urine
  • discharge or cloudy urine
  • blood in the urine
  • low abdominal pain or pressure

Symptoms of more serious infections can include:

  • a fever and chills
  • flank or lower back pain
  • nausea
  • vomiting
  • feeling significantly ill

It is important to seek medical attention right away if any of these symptoms occur.

Most UTIs cause manageable infections that an individual can treat with antibiotics. The doctor may prescribe a range of different antibiotics, although they will only prescribe certain antibiotics to women during pregnancy.

More severe or serious infections with complications, such as abscesses, kidney involvement, or any infections that occur during pregnancy, may need more intensive treatment, including hospitalization.

The doctor may need to change the course of antibiotic drugs once the bacteria are identified. Certain bacteria can only be treated with specific antibiotics.

Some women have frequent UTIs. Preventative measures may include:

  • drinking more fluid
  • emptying the bladder without delay
  • urinating straight after sex
  • taking protective measures regarding sex, such as avoiding spermicides and diaphragms
  • using unscented, mild soaps for cleansing the genital area
  • wearing breathable, natural fabrics, such as 100 percent cotton

While UTIs can be irritating and are sensitive in nature, they are often preventable and usually treatable.