Other Semen Analysis Parameters

Ejaculate Volume

The role of the semen is to efficiently transport sperm to the cervix while protecting them from the harsh, acidic environment of the vagina. A standard semen analysis almost always includes an assessment of ejaculate volume, color, and time for liquefaction. Some labs will also routinely check pH and sometimes semen fructose. These semen parameters will make more sense if you know the relative contributions of the testicles, seminal vesicles, and prostate to the ejaculate fluid.

1) Testicles: 0.1 cc. The testicles supply the sperm and a small amount of fluid (about 5–10 percent of the total ejaculate volume). Because this is such a small percentage of total volume, men who have had a vasectomy, in which the flow of fluid from the testicles is blocked, do not notice any difference in ejaculate volume.

2) Seminal vesicles: 1.5 cc, alkaline pH. The seminal vesicles supply the bulk of the fluid volume (about 65–70 percent). Seminal vesicle fluid causes the ejaculate to coagulate, and also provides fructose as an energy source for the sperm. Since the majority of fluid comes from the seminal vesicles, the overall pH of a normal ejaculate is alkaline.

3) Prostate: 0.5 cc, acidic pH. The prostate gland produces around 25–30 percent of seminal fluid. Prostatic fluid provides enzymes that cause the coagulated semen to liquefy, thereby releasing the sperm into the cervical mucus. Typically, the ejaculate liquefies completely within twenty to thirty minutes when evaluated in the lab.

4) Bulbourethral glands (Cowper’s glands): The bulbourethral glands are pea-sized glands, located at the base of the penis, that open into the urethra. With arousal, these glands produce a small amount of a clear, salty, viscous secretion called pre-ejaculate. The pre-ejaculate serves to lubricate the urethra and neutralize any acidic urine that may remain within the urethra from the last urination. Although the bulbourethral glands do not typically serve as a reservoir for sperm, their fluid can pick up sperm dwelling within the urethra from the last ejaculation and carry them out.

So, to summarize the relative contributions of these structures to the volume of semen that comes out at the time of ejaculation:

1) Testicles: 5 percent of total ejaculate volume

2) Seminal vesicles: 65–70 percent of total ejaculate volume

3) Prostate: 25–30 percent of total ejaculate volume

Normal Ejaculate Volume

The 6th edition of the WHO criteria defines a normal ejaculate volume as 1.4 cc or more.

If a man has a low ejaculate volume (<1.4cc) on his first semen analysis, it is sometimes due to reasons such as missing part of the specimen collection or feeling “inhibited” with the novel experience of trying to ejaculate into a cup.  On repeat testing, I recommend to these patients to try for 3-5 days of abstinence and come into the lab well hydrated. I will order post-ejaculate urinalysis testing on these men, but often the ejaculate volume is normal on repeat exam. 

I do not really worry about higher than normal ejaculate volumes, unless there is a concern about urine leaking out with ejaculation.  This is extremely rare and would likely only occur in men with significant neurologic issues.  Presumably the semen pH would be lower (see below) since urine is acidic.

Low ejaculate volumes can cause problems with fertility- for more detailed information on this, please see "Reversible Semen Analysis Factors" in the Sperm Boot Camp section of this website.

Semen pH and Semen Fructose

In normal circumstances, ejaculate is alkaline (with a pH of 7.5 or more), since the alkaline fluid produced by the seminal vesicles is the largest contributor to ejaculate volume. The seminal vesicles also produce fructose. So when the ejaculate has a basic pH and contains fructose, that indicates that fluid from the seminal vesicles is making it into the ejaculate. This is important because the fluid from the seminal vesicles causes sperm to coagulate, keeping them near the cervical opening and protecting them from the harsh vaginal environment.

When the semen is acidic (pH of less than 7.5) and/or there is no fructose in the ejaculate, this is generally indicative of a blockage at the level of the ejaculatory ducts (which can occur is isolation, as well as associated with other genital duct abnormalities such as congenital bilateral absence of the vas deferens).  For more information on this, please see "Reversible Semen Analysis Factors" in the Sperm Boot Camp section of this website (although some of the causes of obstruction are not technically "reversible" but can be bypassed in some circumstances).

Semen Color

This assessment is highly subjective and rarely clinically useful. One exception is with complete ejaculatory obstruction, where the semen is often entirely clear.

Semen Liquefaction and Semen Viscosity

Enzymes in the prostatic fluid cause the coagulated sperm to gradually liquefy, thereby facilitating release of the sperm into the cervical canal. The rate at which the semen liquefies is often measured as viscosity (a normal value is under 2) or liquefaction time (normal times range between 5 and 25 minutes, with an average around 20 minutes; abnormally long liquefaction times are generally defined as more than 30 minutes).

Abnormal semen liquifaction/viscosity is a rare cause of fertility issues.  For more detailed information on this topic, please see "Reversible Semen Analysis Factors" in the Sperm Boot Camp section of this website.

Pyospermia - White Blood Cells in the semen

All men have some white blood cells (WBCs) present within their semen, as they play a role in maintaining a good, healthy environment for sperm. However, elevated levels of WBCs can be a marker of inflammation and/or infection. When too many WBCs are seen in the sperm, it is called pyospermia.  Pyospermia leads to high amounts of free radicals, which can be quite damaging to sperm.

You may see WBCs reported on a semen analysis in one of two ways. When they are reported as numbers per cc, I consider “normal” to be 1 million/cc or under. When they are reported as number of WBCs seen under a tabletop microscope, I consider “normal” to be 10–15/hpf or less.

Round Cells vs. White Blood Cells

Unfortunately, on microscopic examination WBCs look very similar to immature sperm cells, and the two cannot be differentiated with the standard staining techniques that labs generally use to evaluate sperm morphology. The term “round cells” is sometimes used to denote cells that could be either WBCs or immature sperm cells. In the absence of clinical signs of infection (such as painful urination, blood in the ejaculate, urethral discharge), elevated numbers of round cells in the semen usually represent immature sperm cells about two-thirds of the time and WBCs about one-third of the time.  One factor to take into consideration with these predictive statistics, however, are that higher numbers of immature sperm cells are usually seen in men with lower sperm counts. [Patil PS. JCytol 2013]  So if a man has normal sperm counts and elevated round cells, there is a higher likelihood that these are actually white blood cells.

Special laboratory techniques are available that can differentiate WBCs from the immature sperm cells, but these techniques are usually only performed by fertility-specific labs. Most hospital labs (and some fertility-specific labs) do not perform this more advanced testing and only report the number of round cells that are present. This presents a potential problem when the number of round cells is elevated, since the clinician does not know if they represent potentially harmful WBCs or relatively harmless immature sperm cells.

If you encounter this type of problem, the best solution is to find another lab in the area that offers the specialized testing to differentiate WBCs from immature sperm cells.  Examples include peroxidase staining (also called an Endtz test), Wright staining, and immunohistochemical techniques. The second-best option is to treat with antibiotics and anti-inflammatory medications, knowing that there is a two-thirds chance that you are taking these medications for no reason (i.e., the round cells were actually just immature sperm cells)- the odds of this are lower in men with normal sperm counts as described above.  This is a less-good option since antibiotics can cause side effects such as increased the risk of diarrheal disease and selection for the growth of antibiotic-resistant bacteria within the body. Semen cultures are rarely helpful, since contamination of specimens by non-harmful bacteria present at the very end of the urethra is extremely common.

For more detailed information on pyospermia, please see "Reversible Semen Analysis Factors" in the Sperm Boot Camp section of this website.