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J Urol. 2005 Jul;174(1):29-36.

How little is enough? The evidence for post-vasectomy testing.

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Australian Safety and Efficacy Register of New Interventional Procedures-Surgical, Royal Australasian College of Surgeons, Adelaide, South Australia, Australia.



Post-vasectomy semen analysis (PVSA) is the traditional method of confirming sterility after vasectomy. However, PVSA protocols vary in the end points accepted, and the number and timing of tests. In this systematic review we make evidence based recommendations on the appropriate PVSA protocol.


Databases (MEDLINE, Current Contents, Cochrane Library and EMBASE) were searched up to and including March 2003. Studies were included if they dealt with post-vasectomy testing and contained data on at least 1 of the time or number of ejaculations to azoospermia, pregnancy, repeat vasectomy and histological analysis of vas specimens.


A total of 56 studies were included in the review. Time to achieve azoospermia was variable, although the median incidence of patients with azoospermia was consistently more than 80% after 3 months and after 20 ejaculations. A small percent of patients (14,845 or 1.4%) demonstrated persistent nonmotile sperm, although some of them eventually achieved azoospermia. The reappearance of nonmotile sperm was reported in 7 studies, occurring up to 22 months after vasectomy.


The evidence supports a PVSA protocol with 1 test showing azoospermia after 3 months and 20 ejaculations. If the sample is positive, periodic testing can continue until azoospermia is achieved. Patients with persistent nonmotile sperm in low numbers could be given cautious assurance of success. No evidence was located to support histological testing of the excised vas deferens.

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