Aspermia is the lack of semen, not to be confused with azoospermia, which is the lack of the reproductive sperm cells in the semen. It is one of the causes of male infertility. Aspermia has two major causes: retrograde ejaculation and ejaculatory duct obstruction. Men with aspermia experience the sensation of ejaculation, but no semen exits the body.
Retrograde ejaculation is a condition in which the semen flows into the bladder instead of outside the body through the urethra. In normal ejaculation, the sphincter at the entrance to the bladder contracts, forcing the semen to be ejected away from the bladder and out of the urethra. Retrograde ejaculation is therefore caused by a malfunctioning bladder sphincter, caused by either weak muscles or defects in the nerves supplying the muscles.
Aspermia due to retrograde ejaculation can be caused by complications of surgery to treat prostate or testicular cancer, or by nerve damage caused by disease. Some associated conditions are diabetes, multiple sclerosis, and spinal cord injury. Retrograde ejaculation may also be caused by medications including tamsulosin, used to treat benign tumors of the prostate, antihypertensives used to treat high blood pressure, and antidepressants and antipsychotics used to treat mood disorders. Sometimes changing medications can reverse the condition. Retrograde ejaculation is not dangerous or life threatening, though it causes infertility and may also diminish sexual sensation.
Ejaculatory duct obstruction, the other possible cause of aspermia, may be due to congenital cysts in the ejaculatory ducts, or by inflammation brought about by inflammation or tuberculosis of the prostate. The sexually transmitted infection chlamydia is another possible cause. In addition to aspermia, ejaculatory duct obstruction can also cause pain in the pelvis, especially after ejaculation. Ejaculatory duct obstruction can also result in oligospermia, in which some semen is ejaculated, but less than a normal amount. This condition can be treated surgically through transurethral resection of the ejaculatory ducts (TURED) or through balloon catheterization of the urethra or rectum.
Men suffering from aspermia often have normal amounts of sperm cells and can father a child, though the sperm must be harvested and injected into the female. In retrograde ejaculation, the sperm may be harvested by running the patient's urine through a centrifuge to separate out the semen, while in men with ejaculatory duct obstruction, the sperm must be harvested directly from the testicles.