Leukocytes in urine refer to the presence of white blood cells in a urine sample, which can be a sign of inflammation or infection in the urinary tract. Although small amounts may be normal, high levels usually suggest a problem that requires further investigation.
Leukocytes, or white blood cells, are part of the immune system and help protect the body by detecting and destroying harmful microorganisms like bacteria, viruses, fungi, and parasites. They are produced in the bone marrow and circulate throughout the bloodstream and tissues.
The urinary tract is normally sterile, but leukocytes can appear in the urine when there is irritation, injury, or infection along the urinary tract. Their presence may indicate conditions like a urinary tract infection, kidney disease, or other health issues affecting the urinary system.
Normal ranges and what is considered high?
Leukocyte levels in urine can vary depending on the type of test used:
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Microscopy: Normally, fewer than 5 white blood cells (WBCs) are seen per high-power field (HPF). Counts above 10 WBCs/HPF usually suggest pyuria, which may be linked to infection or inflammation.
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Dipstick test: A negative result means no leukocyte esterase is detected. Positive results are reported as trace, 1+, 2+, or 3+, which reflect increasing amounts of leukocytes.
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Automated systems: Methods like flow cytometry are often more consistent than manual microscopy and may give a more reliable count.
Results should always be interpreted together with symptoms and other lab findings. Knowing which method was used makes it easier to understand whether leukocyte levels are within a normal range or if they may point to a health problem.
What does it mean to have leukocytes in the urine?
Leukocytes in the urine are called pyuria, which means there are more white blood cells than normal in the urine. This can be a sign of inflammation or infection in the urinary tract.
It’s normal to have up to 5 white blood cells per field under the microscope, or up to 10,000 per milliliter of urine. Slightly higher levels can sometimes be seen in women and may still be normal.
If the number of leukocytes is higher than expected (especially if there are other changes in the urine, like blood, a bad smell, or visible particles), or if there are symptoms like pain when urinating or lower belly pain, the doctor may order more tests to find out what’s causing it.
What causes leukocytes in the urine?
Leukocytes in the urine can be caused by:
1. UTI
A urinary tract infection (or UTI) is the most commonly occurring reason for increased levels of leukocytes in the urine. High levels indicate that the immune system is trying to fight off a fungal, bacterial or parasitic infection by fungus.
With infection, other characteristics will also be noted in the urine, such as the presence of epithelial cells and the microorganism responsible for the infection. Learn more about UTI symptoms and check-out our online symptoms quiz to assess your risk.
What to do: If infection is suspected, the doctor will likely order a urine culture test, which is a urine test that attempts to isolate and identify a possible microorganism that is causing the infection. Depending on the microorganism, the doctor will then recommend indicated treatment.
If a bacterial infection is confirmed, for example, and the patient is symptomatic (e.g. pain and burning with urination, discharge, etc.), the doctor may prescribe antibiotics. Read more about the UTI treatment options your doctor may consider.
If a fungal infection is confirmed, the doctor will likely prescribe antifungal medication, such as fluconazole or miconazole. The medication chosen depends on the type of fungus identified. If parasites are the cause of the infection, (e.g. Trichomonas sp, which is the most common type of parasitic infection), the doctor will likely treat with metronidazole or tinidazole.a f
2. Urine sample contamination
Contamination of a urine sample can occur when bacteria or leukocytes from other areas of the body (e.g. like the genital skin or genital discharge) get into a urine sample.
It may lead to a false lab result, which reports leukocytes in the urine that are unrelated to infection or inflammation.
What to do: Patients that are asymptomatic will likely be asked to repeat the urine sample. To prevent a contaminated urine sample, you should collect a urine sample mid-stream into a sterile container.
3. STI
Sexually-transmitted infections (STIs) like chlamydia or gonorrhea can spread through unprotected sex and cause harmful bacteria to enter the genital or urinary tract. These infections can lead to inflammation of the urethra and activate the immune system, increasing leukocyte migration to the urine.
STIs can lead to additional symptoms, like pain or burning with urination, abnormal discharge, itching, and pelvic or testicular pain.
What to do: If you notice new genital or urinary symptoms after unprotected sex, you are advised to see your doctor for a urine or swab test. If positive, the doctor will initiate treatment, which may involve the use of antibiotics. You should avoid sex until treatment is completed.
Your sexual partner/s should also be instructed to get tested and treated.
4. Urinary tract obstruction
A blockage anywhere long the urinary tract that restricts normal urinary flow can lead to a build-up of urine. This build-up can lead to pressure, irritation and possible and infection, which activates the immune system to send white blood cells to the area.
This finding is related to conditions like an enlarged prostate, stones, or tumors. An obstruction can present with symptoms like decreased or painful urination, abdominal pain, plank pain, blood in the urine, nausea or fever.
What to do: If you are unable to urinate or note a weak stream that does not resolve, you should seek medical attention. The doctor will order imaging to locate where the blockage is, which will help to guide treatment. To relieve the discomfort of a full bladder, the doctor may perform a catheterization to drain the urine. Infections causing the blockage will likely require treatment with medication.
5. Kidney problems
Kidney dysfunction, as is seen with nephritis or kidney stones, can also cause elevated levels of leukocytes in the urine. Kidney problems can also leads to crystals in the urine or, sometimes, red blood cells.
Both nephritis and kidney stones may also present with some characteristic symptoms such as back pain, difficulty peeing and decrease in the quantity of urine.
What to do: If you suspect you have kidney stones or nephritis, it’s important to see your doctor or a urologist. They will likely order an ultrasound and urine testing in order to identify the the reason for the increase in leukocytes and start the appropriate treatment. Complete our online kidney symptoms quiz to determine your risk for kidney disease.
6. Systemic lupus erythematosus
Systemic lupus erythematosus is an auto-immune disease, which means it’s a condition where the immune cells attack the body, causing joint, skin, eye and kidney inflammation. In the presence of this disease, urine testing will often show high levels of leukocytes. This combined with CBC blood testing can help with diagnosis.
Learn more about the symptoms of lupus and what can cause it.
What to do: Correcting leukocyte levels in the urine is typically done under medical supervision. Usually, the doctor will prescribe medication according to the symptoms presented by the patient, such as anti-inflammatory medication, corticosteroids, or immunosuppressive drugs. In short, by managing symptoms related to lupus, it is possible to decrease urine leukocyte levels.
7. Use of medication
Some types of medication, such as antibiotics, aspirin, corticosteroids, and diuretics can cause elevated leukocyte levels in the urine.
What to do: If you are taking any type of medication that may be causing an increase of leukocytes in the urine, it’s important to bring your concern to your prescribing doctor.
8. Holding urine
Holding urine for long periods of time can promote the growth and development of microorganisms, resulting in a urinary tract infection and causing leukocytes to appear in the urine.
In addition, if you hold urine for too long, your bladder will begin to weaken overtime and eventually will be unable to empty completely. This causes urine to pool inside the bladder, causing microorganisms to grow.
What to do: If you suspect this might be the cause, it’s important that you relieve yourself as soon as you feel the urge to pee. This will prevent the accumulation of urine and microorganisms in the bladder.
To prevent infections from reoccurring, it is recommended that you drink at least 2 liters (about 8 cups) of water per day.
9. Cancer
Although it is not as frequently occurring, bladder, prostate or kidney cancer can weaken the immune system and lead to elevated leukocyte levels in the urine. In addition, leukocytes can appear as a side effect of cancer treatment.
What to do: The presence of leukocytes in the urine is common finding in urinary tract or genital cancers. If you have cancer and your levels happen to be elevated, your doctor will likely keep checking urine leukocytes levels as a way of tracking disease progression as well as your body’s response to treatment. Read more about the cancer blood tests your doctor may order to rule out this disease.
What test methods detect leukocytes?
Leukocytes in the urine are typically detected through several types of urinalysis methods.
Urine dipstick test
This test uses a chemical strip with a reagent pad that reacts to leukocyte esterase, an enzyme released by neutrophils. A color change on the strip indicates a positive result and suggests the presence of leukocytes. It is a fast and cost-effective screening tool for pyuria.
A positive dipstick does not confirm infection, but rather indicates that further testing, like microscopy or culture, is warranted.
Urine microscopy
Microscopic analysis involves spinning a urine sample and examining the sediment under a microscope. The number of leukocytes is counted per high-power field (HPF). A normal result is typically 0–5 WBCs/HPF. Values higher than this suggest pyuria.
Urine culture
Urine culture is used to confirm bacterial infection. A positive culture (typically >100,000 CFU/mL of one type of bacteria) with leukocytes supports a diagnosis of urinary tract infection (UTI). Multiple bacterial species may suggest contamination.