Recanalization after a vasectomy: Definition, probability and more

Spontaneous recanalization is where the vas deferens manages to “grow back” and reverse the vasectomy making a man fertile again. Because a vasectomy has recanalized, that doesn’t mean a full restoration of fertility. Any re-growth is likely to be a channel that is much smaller than the original vas deferens was, hence fertility is likely to be much reduced.

There are two categories – early and late recanalization. Early recanalization is most likely to happen in the first few weeks following a vasectomy before having been given the all-clear. Many of the statistics of failure will refer to this period. Statistics are typically 0% – 1% of vasectomies, and are usually referred to as “Technical failures.” Technical failure does not necessarily mean that the vas deferens has recanalized – it often means that the semen analysis still shows live sperm after a set period – often 16 weeks. All men take varying lengths of time to clear, and it’s not unusual to take more than 16 weeks. Most men will clear eventually. It’s not possible to give percentages of recanalization, and late clearance as most studies cease monitoring men after a set length of time. Hence the expression “Technical failure” – all men who haven’t cleared at the end of the set time of the study for whatever reason.

Late recanalization is where the all-clear has been given, and the vasectomy spontaneously reverses itself at a later date. Early and late recanalization should not be confused – nor should the statistics.

The reason doctors want you to go back for semen analysis after a vasectomy is to make sure that a technical failure hasn’t happened. The bottom line is that you aren’t clear until it has been proven by semen analysis, and it’s the patient’s responsibility to supply samples as indicated by the doctor.

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From this point on, this page will discuss the late recanalization of vasectomy – early failures should be picked up by semen analysis as above.

How often does it happen?

All birth control methods have a risk of failure, but vasectomy is the most reliable of all the methods available. According to the Faculty of Sexual & Reproductive Healthcare (FSRH) Clinical Guidance, the failure rate of vasectomy should be quoted as approximately 1 in 2000 (0.05%) after clearance has been given.1 Therefore, the chances of a vasectomy spontaneously reversing itself are very rare. Harvard Medical School reports that recanalization occurs in approximately 1 in 4000 (0.025%) vasectomies.2

It should be appreciated that as late recanalization is a very rare phenomenon, the research into its exact causes remains limited by the small number of subjects being available at the time any particular study is being undertaken. Very often, the published literature is in the form of individual case histories, as opposed to larger studies.

How is it physically possible for the vas deferens to re-connect?

There are two recognized mechanisms for late recanalization to happen. The first is initiated by the formation of sperm granuloma, and the second is micro-recanalization through scar tissue. In addition, there are other factors such as length of vas deferens excised, the technique used, and the experience of the surgeon.

Sperm Granuloma

After a vasectomy, sperm often leak from the vasectomy site or from a rupture in the epididymis. Sperm have solid antigenic qualities – the immune system views sperm as foreign agents and attacks them. Sperm leakage provokes an inflammatory reaction. The body forms pockets to trap the sperm in scar tissue and inflammatory cells. Firm balls of tissue (sperm granulomas) about one-half inch in diameter then form in about 60% of vasectomy patients.2 Studies into recanalization look for possible causes. In the case of granuloma, most studies report a strong correlation – one study reports the presence of granulomas as “A constant.”3

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What happens is that a nodule in the vas deferens arising from a granuloma progresses to a benign, malignant growth known as Vasitis Nodosum. This growth can join up with the distal vas allowing sperm to flow. Studies report that vasitis nodosa is more common than sometimes thought,45 and although it’s growth can cause recanalization, it’s a rare occurrence.4

Scar Tissue

If there is a lot of scar tissue after vasectomy, a process called Microrecanalization can happen, allowing sperm to wriggle their way through new and very small channels in the scar tissue. The reason that this happens is one of the body’s many self-healing mechanisms. “Microrecanalization provides protection of the testis and maintenance of spermatogenesis in man after vasectomy.”6

The formation of microchannels is believed to be associated with poor technique during the vasectomy procedure. Examples include inadequate closure of the vas at the initial vasectomy procedure, vas injury in which lumen opening was exposed, or tying of the cut vas decreasing local blood circulation which results in open and exposed vas lumen.7

There are a few studies that have looked at scar tissue samples taken from men after vasectomy. One study found microchannels in “smooth muscle, connective tissue, and scar tissue”.6 Another found, “a series of spontaneously recanalized ductus deferens and those of the contralateral ductus deferens displaying many tortuous epithelial tubules growing from the mucosal epithelium of distal stumps intruding into the fibrous scar tissue of the proximal stumps.” 8

Is there any way of avoiding it?

There are surgical techniques that have been proven to minimize the risk of recanalization. Firstly, a technique called fascial interposition added to the standard procedure is now accepted as the most reliable method of performing vasectomy. In the traditional approach, a short piece of the vas deferens is cut and removed, and the remaining two ends are tied. Fascial interposition involves pulling the sheath covering the vas deferens over one severed end, then sewing it shut to create a natural tissue barrier. The American Academy of Family Physicians (AAFP) site has some photographs and an explanation.

Some of the early studies report that using fascial interposition, recanalization is reduced to zero.910 However, these studies are quite small. A Chinese study of 7 techniques involving 2713 men found that vasectomy plus interposition is the most reliable vas occlusion technique.11 A review of previous studies published in 2004 concluded that “Five comparative studies, including one high quality randomized clinical trial, provided good evidence that fascial interposition increases the occlusive effectiveness of ligation and excision.”12

Secondly, there is strong evidence that using cautery to seal the ends increases reliability. Combining fascial interposition with cautery provides the highest level of occlusive effectiveness.12

Thirdly, the length of the vas segment removed may have a bearing on how reliable vasectomy is. It should be pointed out that using fascial interposition and cautery remain critical steps. One study found that “Physicians with a high rate of success removed a significantly longer section of vas than physicians exhibiting higher failure rates. At least 15 mm of vas should be excised to maximize the success of the procedure. Excised vas segments less than 15 mm had up to a 25-fold greater incidence of failure.”13 Another study recommends removal of 3-5 cm.14

References and futher reading has a strict sourcing policy. We rely on evidence-based medicine, peer-reviewed studies, reputable clinical journals, and medical associations. Learn more about how we ensure our content is accurate and up-to-date by reading our editorial policy.
  1. FSRH Clinical Effectiveness Unit. Male and Female Sterilisation. Faculty of Sexual & Reproductive Healthcare (FSRH). September 2014. ISSN: 1755-103X
  2. Vasectomy and Vasovasostomy (Reversal Surgery). Well-Connected reports. Harvard Medical School. September 2001.
  3. Cánovas I, Tramoyeres G, Sánchez B, et al. [Spontaneous recanalization of the vas deferent after vasectomy: report of 2 new cases. Bibliographic review]. Arch Esp Urol. 2004;57(7):743-745.
  4. Llarena I, Vesga M, Marín L, Pertusa P. [Vasitis nodosa]. Arch Esp Urol. 1997;50(5):534-536.
  5. Kiser G, Fuchs E, Kessler S. The significance of vasitis nodosa. J Urol. 1986;136(1):42-44. doi:10.1016/s0022-5347(17)44719-7
  6. Freund M, Weidmann J, Goldstein M, Marmar J, Santulli R, Oliveira N. Microrecanalization after vasectomy in man. J Androl. 1989;10(2):120-132. doi:10.1002/j.1939-4640.1989.tb00073.x
  7. Wei C. [Multiple tiny channels, a type of reanastomosis after vasectomy: a pathological study of 38 cases]. Shengzhi Yu Biyun. 1987;7(1):61-62.
  8. Hayashi H, Cedenho A, Sadi A. The mechanism of spontaneous recanalization of human vasectomized ductus deferens. Fertil Steril. 1983;40(2):269-270. doi:10.1016/s0015-0282(16)47251-1
  9. Esho J, Cass A. Recanalization rate following methods of vasectomy using interposition of fascial sheath of vas deferens. J Urol. 1978;120(2):178-179. doi:10.1016/s0022-5347(17)57094-9
  10. Late failure of vasectomy. Lancet. 1985;1(8432):794-795.
  11. Li S, Xu B, Hou Y, Li C, Pan Q, Cheng D. Relationship between vas occlusion techniques and recanalization. Adv Contracept Deliv Syst. 1994;10(3-4):153-159.
  12. Labrecque M, Dufresne C, Barone M, St-Hilaire K. Vasectomy surgical techniques: a systematic review. BMC Med. 2004;2:21. doi:10.1186/1741-7015-2-21
  13. Kaplan K, Huether C. A clinical study of vasectomy failure and recanalization. J Urol. 1975;113(1):71-74. doi:10.1016/s0022-5347(17)59412-4
  14. Mellin H, Bauer H, Rattenhuber U. [Failure following fertility vasectomy]. Med Welt. 1980;31(47):1723-1724.
  15. Sherlock D, Holl-Allen R. Delayed spontaneous recanalization of the vas deferens. Br J Surg. 1984;71(7):532-533. doi:10.1002/bjs.1800710720

Medically reviewed by

Dr. Aaron Wiegmann, MD

Review date

May 22, 2021

Authored by content team

Last updated

May 22, 2021