Cowper’s glands are two small, pea-sized glands in the male reproductive system that produce the clear fluid released from the penis during sexual arousal, commonly called pre-ejaculate. Also known as the bulbourethral glands, they sit just below the prostate on either side of the urethra, tucked within the muscular tissue of the pelvic floor.
Location and Structure
Each Cowper’s gland is a small, round structure positioned behind and to the side of the membranous urethra, the narrow section of the urinary passage that runs through the pelvic floor. The glands are surrounded by a mix of muscle types: voluntary muscle on the outer sides and involuntary smooth muscle on the inner and upper surfaces. This muscular arrangement helps squeeze secretions out of the glands during arousal.
From each gland, a thin duct extends forward and drains into the bulbous urethra, the wider section closer to the base of the penis. Under normal conditions, the glands and their ducts are so small they don’t show up on imaging scans. They only become visible when something goes wrong, such as a cyst or inflammation.
What Cowper’s Glands Do
The primary job of Cowper’s glands is producing pre-ejaculate, an alkaline, mucus-like fluid released during sexual stimulation. This fluid serves several purposes at once, all aimed at improving the chances of successful reproduction.
First, it neutralizes leftover acidity in the urethra. Urine is acidic, and residual traces of it create an environment that damages sperm. The alkaline pre-ejaculate raises the pH inside the urethra so that sperm can pass through safely during ejaculation. The same buffering effect extends into the vaginal canal, which is also naturally acidic. By arriving ahead of semen, the fluid helps prepare a less hostile environment for sperm survival.
Second, the glycoproteins in pre-ejaculate act as a lubricant, coating the urethra and the tip of the penis. This reduces friction during intercourse and eases the passage of semen. Those same glycoproteins carry immune-related properties that may help protect reproductive tissues from certain pathogens. Components of the fluid also contribute to the process of semen coagulation, the initial thickening of semen after ejaculation that plays a role in keeping sperm near the cervix.
Pre-Ejaculate and Pregnancy Risk
A common question about Cowper’s gland secretions is whether they contain sperm. The answer: often, yes. A study published in Human Fertility found that 41% of men produced pre-ejaculatory samples containing sperm, and in nearly all of those cases a significant proportion of the sperm were motile, meaning capable of swimming toward an egg. In most of those men, sperm concentration in pre-ejaculate was similar to levels found in their ejaculate.
The sperm in pre-ejaculate likely comes from residual semen left in the urethra from a previous ejaculation, or from small amounts released before the main ejaculation. While the total sperm count in pre-ejaculate is generally lower than in a full ejaculation, it can still be enough to cause pregnancy. This is why the withdrawal method is considered unreliable as a sole form of contraception.
Pre-Ejaculate and STI Transmission
Pre-ejaculate can carry sexually transmitted infections. Research has found HIV-infected white blood cells in the pre-ejaculatory fluid of men living with HIV, and delayed condom use (putting a condom on only before ejaculation rather than before any genital contact) is a documented risk factor for HIV transmission. Herpes simplex virus (both HSV-1 and HSV-2) and the bacteria that cause gonorrhea have also been detected in urethral secretions. This means STIs can be transmitted even without ejaculation, through pre-ejaculate alone.
Conditions That Affect Cowper’s Glands
Problems with Cowper’s glands are uncommon, but they do occur. The most recognized condition is a syringocele, a cystic swelling of the gland’s duct. This happens when the duct becomes blocked, either from a congenital narrowing or from acquired causes like prolonged catheter use or infection. Many syringoceles cause no symptoms at all and are discovered incidentally during imaging for other issues. When they do cause problems, symptoms can include difficulty urinating, a weak stream, or in more severe cases, urinary tract infections affecting the bladder or kidneys.
Cowperitis, or inflammation of the glands, can result from bacterial infection spreading from the urethra. In adults, this can lead to a painful mass in the area between the scrotum and anus, and sometimes a persistent draining sinus if left untreated. MRI is typically used to evaluate the structural damage and guide treatment.
Rarely, stones can form within the glands or their ducts. These are usually visible on standard X-rays because they tend to be calcium-dense. Even more rarely, tumors can develop in Cowper’s glands. When a suspicious lesion is found, ultrasound through the perineum provides an initial look, while CT or MRI scans are needed for a more detailed assessment.
How They Develop
Cowper’s glands form during fetal development from the same embryonic tissue that gives rise to the prostate. Between roughly 8 and 18 weeks of gestation, hormones (specifically dihydrotestosterone) drive the differentiation of the urogenital sinus into several male reproductive structures, including the bulbourethral glands. In females, the equivalent structures are known as Bartholin’s glands, which serve a similar lubricating function.
Excessive Pre-Ejaculate
The volume of pre-ejaculate varies widely between individuals. Some men produce almost none, while others produce enough to soak through clothing during arousal, a condition sometimes called copious pre-ejaculation. While not dangerous, it can cause significant embarrassment and anxiety. The variation is largely due to differences in gland size and individual hormonal response to arousal, not to any underlying disease. For men who find it distressing, the issue is worth discussing with a urologist, as treatment options exist.