UNDERSTANDING LEUKOCYTES IN SEMEN: WHAT THEY ARE, WHY THEY MATTER, AND HOW THEY'RE TREATED

When couples are trying to conceive and face difficulties, a semen analysis is often one of the first tests ordered. Most people focus on sperm count, motility, and morphology—but there’s another component in the semen report that often raises questions: leukocytes, also known as white blood cells (WBCs).

If you’ve seen the term “round cells” or “leukocytes” in your or your patient’s semen analysis report, you may be wondering: What does it mean? Is it a problem? Should it be treated? This blog will walk you through everything you need to know about leukocytes in semen—why they matter, how they are tested, and what they mean for fertility.

What Are Leukocytes in Semen?

Leukocytes, or white blood cells, are part of the body’s immune system. In small numbers, they are naturally present in semen and help defend the reproductive tract from infection. However, an elevated number of leukocytes can indicate inflammation, infection, or other problems that may impact sperm health and fertility.

According to the World Health Organization (WHO), a concentration greater than 1 million leukocytes per milliliter of semen (≥1 × 10⁶ WBC/mL) is considered abnormal, a condition referred to as leukocytospermia or pyospermia.

What Are Round Cells in Semen?

When a semen sample is analyzed under a microscope, the technician may see cells that are not sperm—these are grouped together as round cells. There are two major types of round cells:

1. Leukocytes (White Blood Cells)

2. Immature Germ Cells (Spermatogenic Cells)

Both appear round and lack tails, making them difficult to distinguish under a basic microscope. However, it's crucial to differentiate between these two, because their presence suggests very different things.

• Leukocytes may indicate infection or inflammation.

• Immature germ cells may suggest a disruption in spermatogenesis (sperm development).

Why Is It Important to Differentiate Between Leukocytes and Immature Germ Cells?

Differentiating between leukocytes and immature germ cells is important for diagnosis and treatment. Here's why:

Failing to make this distinction can lead to unnecessary treatment (e.g., antibiotics for a patient without an infection) or missed diagnoses (e.g., testicular failure).

How Are Leukocytes and Germ Cells Distinguished?

1. Peroxidase (Endtz) Staining

This is the most common and specific test used to identify leukocytes in semen. White blood cells—especially neutrophils, the predominant type in semen—contain an enzyme called myeloperoxidase. When the sample is treated with a staining solution, only the leukocytes turn a dark brown or black color.

• Positive stain = leukocytes

• Negative stain = likely immature germ cells or other round cells

Reference: WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th edition (2021)

2. Esterase Testing

Like peroxidase staining, esterase-based tests detect enzymatic activity within leukocytes. Some labs use leukocyte esterase test strips, similar to those used in urinalysis.

However, these strips are less specific than direct peroxidase staining and may produce false positives from other cell types or debris. They should not be used alone for diagnosis.

3. Immunocytochemistry (Advanced)

For research or high-complexity clinical labs, immunocytochemical staining using antibodies to CD45 (a marker of WBCs) can be used to confirm the presence of leukocytes. This is more specific but not commonly performed in routine semen analysis.

What About Dipstick Testing for Leukocytes?

Some labs or at-home kits use urinalysis dipsticks to detect leukocytes. These test strips turn color in the presence of leukocyte esterase. However:

• They are not validated for semen.

• They lack specificity.

• They do not distinguish between cell types.

In other words, dipstick testing may be quick, but it’s not reliable. For clinical decision-making, staining methods such as peroxidase (Endtz) testing are preferred.

Can You Tell How Testing Was Performed from the Semen Report?

Yes—and this is an important question to ask.

Look for These Clues on the Report:

1. Explicit WBC Count:

   • If the lab states “WBCs: X million/mL” or “Leukocytes per high power field,” they likely performed a peroxidase stain.

   • If it only says “round cells,” the lab may not have distinguished between types.

2. Mention of Staining Method:

   • Reports should mention “Endtz stain,” “peroxidase test,” or “WBC-specific stain.”

3. Qualitative measurement of > 1 million/ml or < 1 million/ml
   1. a leukocyte esterase test strip was used. The test is less accurate and has many false positives

4. Microscopic Images or Videos:

   • Some high-quality andrology labs provide stained cell images or even videos documenting the findings.

   • This increases diagnostic confidence and helps guide treatment.

What Does an Elevated Number of Leukocytes in Semen Mean?

An elevated leukocyte count—leukocytospermia—can have several implications:

1. Infection

• Bacterial prostatitis or epididymitis is a common cause.

• Sexually transmitted infections (e.g., Chlamydia, Gonorrhea) may also be responsible.

2. Inflammation Without Infection

• Some men have increased leukocytes without evidence of infection.

• This may be due to oxidative stress, prior infection, or autoimmune conditions.

3. Obstructive Conditions

• Blockage of the seminal tract may cause backpressure and inflammation, leading to leukocytospermia.

How Do Leukocytes Affect Fertility?

Leukocytes can affect fertility in several ways:

1. Oxidative Stress

Leukocytes produce reactive oxygen species (ROS). In excess, these can damage sperm membranes and DNA, reducing motility and increasing DNA fragmentation.

Studies show that high ROS levels correlate with:

• Poor sperm motility

• Increased sperm DNA fragmentation

• Reduced fertilization rates in IVF

Reference: Agarwal et al., Fertility and Sterility, 2014; WHO Manual, 6th ed., 2021

2. Cytokine Release

Leukocytes release inflammatory cytokines that can damage surrounding sperm and impair sperm-oocyte interaction.

3. Impact on ART Outcomes

Elevated leukocyte counts have been associated with lower success rates in intrauterine insemination (IUI) and IVF, particularly when sperm motility is already borderline.

When Should You Order Additional Testing?

When leukocytospermia is detected, the following workup is often recommended:

1. Semen Culture

To rule out infection, especially in the presence of symptoms (pain, burning, swelling), a semen culture should be performed. Be sure the sample is collected under sterile conditions.

2. Urine Culture

Sometimes bacteria in semen come from the urinary tract. A post-ejaculate urine culture may help distinguish the source.

3. STI Testing

In sexually active men or those with risk factors, test for:

• Chlamydia trachomatis

• Neisseria gonorrhoeae

• Ureaplasma and Mycoplasma

4. Reactive Oxygen Species (ROS) Testing

Advanced labs may test for ROS levels to assess the degree of oxidative stress.

When Should Leukocytospermia Be Treated?

Not all elevated leukocyte counts require treatment.

Treat When:

• There is symptomatic infection (e.g., fever, pain, urethral discharge).

• Semen culture identifies pathogenic organisms.

• Leukocytospermia is persistent and accompanied by poor sperm motility or high DNA fragmentation.

• You are preparing for assisted reproductive techniques (ART) and want to optimize semen quality.

Consider Watchful Waiting When:

• Leukocytospermia is mild and no organisms are identified.

• Sperm parameters are otherwise normal.

• The patient is asymptomatic.

How Is Leukocytospermia Treated?

Treatment depends on the underlying cause.

1. Antibiotics

If infection is suspected or confirmed:

• Empirical treatment with antibiotics like doxycycline or fluoroquinolones is common.

• Therapy typically lasts 2–3 weeks, and a repeat semen analysis is done afterward.

Reference: AUA Guidelines on Male Infertility; WHO Manual, 6th ed.

2. Anti-inflammatory Medications

In cases of sterile inflammation or prostatitis, NSAIDs or medications like alpha-blockers may reduce inflammation and improve sperm quality.

3. Antioxidant Therapy

High leukocytes often correlate with oxidative stress. Supplements that may help include:

• Vitamin C and E

• Zinc

• Coenzyme Q10

• N-acetylcysteine

4. Lifestyle Modifications

Encourage:

• Smoking cessation

• Weight loss if obese

• Reduced alcohol intake

• Avoidance of hot tubs or prolonged heat exposure

Summary: What You Need to Know About Leukocytes in Semen

Final Thoughts

An elevated number of leukocytes in semen doesn’t always mean there’s an infection—but it always warrants further investigation. Accurate testing, including differentiation between WBCs and immature germ cells, is essential to guide proper management.

If you or your patient receives a report indicating “round cells” or “leukocytospermia,” ask the lab:

• Did they use a peroxidase stain?

• Are images or documentation available?

• Was a semen culture performed?

Understanding the presence and impact of leukocytes is an important part of male fertility evaluation—and one that shouldn't be overlooked.

References

1. World Health Organization. WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th ed., 2021.

2. Agarwal A, Mulgund A, Hamada A, Chyatte MR. "A unique view on male infertility around the globe." Reproductive Biology and Endocrinology. 2015.

3. AUA Guidelines on Male Infertility. American Urological Association. 2020.

4. Henkel R. "The impact of oxidants on sperm function." Andrologia. 2011.

5. Comhaire F, Mahmoud A, Depuydt C, Zalata A. "Semen analysis and sperm function testing." Clinics in Laboratory Medicine. 2000.

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