Post-vasectomy testing is carried out to check that a vasectomy has been successful. A vasectomy is a surgical procedure undertaken to render a man sterile (unable to father children). The procedure involves cutting the tubes (vas deferens) that carry sperm from the testicles, preventing it from mixing with semen, the fluid produced in the seminal vesicles and then ejaculated.

The success or failure of a vasectomy can be determined after the operation by testing the semen ejaculated by the patient to see whether it contains sperm. If the vasectomy has been successful, there will be no sperm in the semen. Testing for sperm after a vasectomy is called post-vasectomy semen analysis (PVSA).

  • The number and timing of tests traditionally, two PVSA tests have been recommended at between 12 and 16 weeks post-vasectomy and after at least 20 ejaculations. However, many practitioners recommend only one test, in some cases after a much shorter time, such as four weeks.
  • How to measure vasectomy success a vasectomy is considered to be a success if it leads to azoospermia (the absence of sperm in the semen). However, studies suggest that sperm can lose their ability to fertilise a female egg before azoospermia is reached. In these cases the sperm are non-motile or unable to move independently to the female egg and are therefore unlikely to cause pregnancy. Thus patients may be able to rely on vasectomy for contraception before PVSA testing confirms azoospermia.
  • Post-vasectomy testing occurs with only one azoospermic test at three months and after a minimum of 20 ejaculations (an earlier test cannot be recommended on the poor evidence available).
  • If the semen sample is azoospermic at three months (i.e. the test is negative), the patient can be considered sterile and no further follow-up is necessary.
  • If a sample contains sperm at the three month test (i.e. the test is positive), further tests are required.
  • If motile sperm are present, the vasectomy is probably a failure and another test one month later will confirm this (and a decision can be made about revasectomy).
  • If non-motile sperm are present, further tests should be performed monthly until either an azoospermic sample is provided or "special clearance" (due to persistent non-motile sperm) can be given. Special clearance could be given when the patient has provided two samples in a row containing < 100,000 sperm/ml (non-motile) at least seven months post-vasectomy.
  • Approximately 80% of patients would be cleared after one test and the remaining 20% can continue follow-up until cleared, as described above.
  • Vasectomy failures will be detected at the three month test, and hence histological testing of the vas deferens is not necessary (however, it may be useful in a training situation).