出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/10 12:30:58」(JST)
Vasectomy reversal is a term used for surgical procedures that reconnect the male reproductive tract after interruption by a vasectomy. Two procedures are possible at the time of vasectomy reversal: vasovasostomy (vas deferens to vas deferens connection) and vasoepididymostomy (epididymis to vas deferens connection). Although vasectomy is considered a permanent form of contraception, advances in microsurgery have improved the success of vasectomy reversal procedures. The procedures remain technically demanding and expensive, and may not restore the pre-vasectomy condition.
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Technical advances in vasectomy reversal mirror those in microsurgery over the past 100 years. As a discipline, microsurgery was first performed by Carl Nylen in Sweden for middle ear surgery in 1910,[1] but grew most rapidly as a discipline in the 20th century stimulated by its success in microvascular reconstruction of war-injured soldiers. The first microsurgical vasectomy reversal was performed by Earl Owen in 1971.[2]
Vasectomy is a common method of contraception worldwide, with an estimated 40-60 million individuals having the procedure and 5-10% of couples choosing it as a birth control method.[3] In the USA, about 5% of men later go on to have a vasectomy reversal afterwards.[4] However the number of men inquiring about vasectomy reversals is significantly higher, with many "put off" by the high costs of the procedure and pregnancy success rates (as opposed to "patency rates") only being around 55%.[5]
While there are a number of reasons that men seek a vasectomy reversal, some of these include wanting a family with a new partner following a relationship breakdown / divorce, their original wife/partner dying and subsequently going on re-partner and to want children, the unexpected death of a child (or children - such as by car accident), or a long-standing couple changing their mind some time later often by situations such as improved finances or existing children approaching the age of school or leaving home.[6] Patients often comment that they never anticipated such situations as a relationship breakdown or death (of their partner or child) may affect their situation. A small number of vasectomy reversals are also performed in attempts to relieve post-vasectomy pain syndrome.
In the UK, 16% of all men under 70 have had a vasectomy, and with remarriages account for 40% of all marriages, there are a significant proportion of men finding themselves in a new relationship and regretting their decision to have a vasectomy.[6] Combined with longer life histories, the rate of divorce and remarriage is thought to be driving the increase in vasectomy reversals and inquiries for vasectomy reversals in recent times.[6]
Sperm are produced in the male sex gland or testicle. From there they travel through tubes (efferent tubules), exit the testes and enter a “storage site” or epididymis. The epididymis is a single, 18-foot-long (5.5 m), tightly coiled, small tube, within which sperm mature to the point where they can move, swim and fertilize eggs. Testicular sperm are not able to fertilize eggs naturally (but can if they are injected directly into the egg in the laboratory), as the ability to fertilize eggs is developed slowly over several months of storage in the epididymis. From the epididymis, a 14-inch, 3 mm-thick muscular tube called the vas deferens carries the sperm to the urethra near the base of the penis. The urethra then carries the sperm through the penis during ejaculation. A vasectomy interrupts sperm flow within the vas deferens. After a vasectomy, the testes still make sperm, but because the exit is blocked, the sperm die and eventually are reabsorbed by the body.
A problem in the delicate tubes of epididymis can develop over time after vasectomy.[7] The longer the time since the vasectomy, the greater the “back-pressure” behind the vasectomy. This “back-pressure” may cause a “blowout” in the delicate epididymal tubule, the weakest point in the system. The blowout may or may not cause symptoms, but will probably scar the epididymal tubule, thus blocking sperm flow at second point. To summarize, with time, a man with a vasectomy can develop a second obstruction deeper in the reproductive tract that can make the vasectomy more difficult to reverse. Having the skill to detect and fix this problem during vasectomy reversal is the essence of a skilled surgeon. If the surgeon simply reconnects the two freshened ends of the vas deferens without examining for a second, deeper obstruction, then the procedure can fail, as sperm-containing fluids are still unable to flow to the place of the connection. In this case, the vas deferens must be connected to the epididymis in front of the second blockage, to bypass both blockages and allow the sperm to reenter the urethra in the ejaculate. Since the epididymal tubule is much smaller (0.3 mm diameter) than the vas deferens (3 mm diameter, 10-fold larger), epididymal surgery is far more complicated and precise than the simple vas deferens-to-vas deferens connection.
A general or regional anesthetic is most commonly used, as this offers the least interruption by patient movement for microsurgery. Local anesthesia, with or without sedation, can also be used. The procedure is generally done on a “come and go” basis. The actual operating time can range from 1–4 hours, depending on the anatomical complexity, skill of the surgeon and the kind of procedure performed.
After anesthesia and scrubbing the scrotum with soap and water, the vas deferens is exposed through a small, 1–2 cm incision in the upper scrotum on each side. The vas deferens is cut sharply in half, both above and below the vasectomy site. A special bipolar microcautery is used to judiciously control any bleeding. One end of the vas deferens, termed the abdominal end, is inspected and flushed with salt solution to ensure that it is not blocked as it courses from the scrotum to the prostate (a “saline vasogram”). If a blockage is suspect above the vasectomy site, then this must be dealt with as well, if sperm is to return to the ejaculate after surgery. The testicle end of the vas deferens is then compressed and inspected for fluid. This fluid is examined with a microscope for color, consistency and for sperm. This information is used to decide whether or not a secondary epididymal obstruction is present (see Table below).
| Grade | Vasal Fluid Findings | Procedure Suggested |
|---|---|---|
| 1 | Normal appearing sperm with motility | Vasovasostomy |
| 2 | Mostly normal appearing, nonmotile | Vasovasostomy |
| 3 | Mostly sperm heads without tails, nonmotile | Vasovasostomy |
| 4 | Only sperm heads | Vasovasostomy |
| 5 | No sperm, creamy fluid | Vasoepididymostomy |
| 6 | No fluid | Vasoepididymostomy |
| 7 | Clear fluid, no sperm | It depends |
If sperm are found at the testis end of the vas deferens, then it is assumed that a secondary epididymal obstruction has not occurred and a vas deferens-to-vas deferens reconnection (vasovasostomy) is planned. If sperm are not found, then an epididymis to vas deferens connection (vasoepididymostomy) is needed to restore sperm flow. Other, more subtle findings that can be observed in the fluid—including the presence of sperm fragments and clear, good quality fluid without any sperm—require surgical decision-making to successfully treat.
For a vasovasostomy, two microsurgical approaches are most commonly used. Neither has proven superior to the other.[8] What has been shown to be important, however, is that the surgeon use optical magnification to perform the vasectomy reversal. One approach is the modified 1-layer vasovasostomy and the other is a formal, 2-layer vasovasostomy.
A vasoepididymostomy involves a connection of the vas deferens to the epididymis. This is necessary when there is no sperm present in the vas deferens.
With vasectomy reversal surgery, there are two typical measures of success: patency rate, or return of some moving sperm to the ejaculate after vasectomy reversal, and pregnancy rates. In a recently published report[9] 95% of men with a vasovasostomy had motile sperm in the ejaculate within 1 year after vasectomy reversal. Interestingly, almost 80% of these men achieved sperm motility within 3 months of vasectomy reversal. The case for vasoepididymostomy is different. Fewer men will eventually achieve motile sperm counts and the time to achieve motile sperm counts is longer.
What has also been published is that:
Another issue to consider is the likelihood of vasoepididymostomy at the time of vasectomy reversal, as this technique is generally associated with lower patency and pregnancy rates than vasovasostomy. Web-based, computer models and calculations have been proposed and published that described the chance of needing an vasoepididymostomy at reversal surgery.[11]
The pregnancy rate is often seen as a more reliable way of measuring the success of a vasectomy reversal than the patency rates, as they measure the real-life success of whether the man succeeds in the aim of having a new child.
Pregnancy rates range widely in published series, with a large study in 1991 observing the best outcome of 76% pregnancy success rate with vasectomy reversals performed within 3 years or less of the original vasectomy, dropping to 53% for reversals 3–8 years out from the vasectomy, 44% for reversals 9–14 years out from the vasectomy, and 30% for reversals 15 or more years after the vasectomy.[7] BPAS cites the average pregnancy success rate of a vasectomy reversal is around 55% if performed within 10 years, and drops to 25% if performed over 10 years.[12] Higher success rates are found with reversal of vasovasostomy than those with a vasoepididymostomy, and factors such as antisperm antibodies and epididymal dysfunction are also implicated in success rates.[13]
Also relevant to pregnancy success rates is the female partner's own fertility and age.
The current measure of success in vasectomy reversal surgery is achievement of a pregnancy. There are several reasons why a vasectomy reversal may fail to achieve this:
In general, vasectomy reversal is a safe procedure and complication rates are low. There are small chances of infection or bleeding, the latter of which can result in a hematoma or blood clot in the scrotum that needs surgical drainage. If there is significant scar tissue encountered during the vasectomy reversal, fluid other than blood (seroma) can also accumulate in a small number of cases. Painful granulomas, caused by leaking sperm, can develop near the surgical site in some cases. Very rare complications include compartment syndrome or deep venous thrombosis from prolonged positioning, testis atrophy due to damaged blood supply, and reactions to anesthesia.
Assisted reproduction uses “test tube baby” technology (also called in vitro fertilization, IVF) for the female partner along with sperm retrieval techniques for the male partner to help build a family. This technology, including intracytoplasmic sperm injection (ICSI), has been available since 1992 and became available as an alternative to vasectomy reversal soon after. This alternative should be discussed with couples during a consultation for vasectomy reversal.
Published research attempts to identify the issues that matter most as couples decide between IVF-ICSI and vasectomy reversal, two very different approaches to family building. This research has generally taken the form of cost-effectiveness or cost-benefit analyses[19] and decision analyses[20] and Markov modeling.[4] Since it is difficult to perform randomized, blinded prospective trials on couples in this situation, analytic modeling can help uncover what variables affect outcomes the most. From this body of work, it has been observed that vasectomy reversal can be the most cost effective way to build a family if: (a) the female partner is reproductively healthy, and (b) the surgeon can achieve good vasectomy reversal outcomes. If the surgeon can achieve high “patency” rates (moving sperm in the ejaculate) after vasectomy reversal, then vasectomy reversal is competitive with IVF-ICSI.[20] In the special instance of couples with advanced maternal age (defined as a female partner > 38 years old), case series’ have reported that pregnancy rates with vasectomy reversal are competitive with IVF-ICSI.[21] When Markov modeling was applied to probe the issue of pregnancy rates after reversal surgery in more depth, the results revealed that female reproductive health is far more important than: (a) the age of the vasectomy, (b) the age of the man, or (c) the vasectomy reversal patency rate. Ultimately the decision to pursue a vasectomy reversal is a personal one for each couple.
Sometimes it is not clear to couples who want children whether they should do a vasectomy reversal or pursue assisted reproduction. There are several questions for couples to ask themselves.
Every patient who is considering vasectomy reversal should undergo a screening visit before the procedure to learn as much as possible about his current fertility potential. At this visit, the patient can decide whether he is a good candidate for vasectomy reversal and assess if it is right for him. Issues to be discussed at this visit include:
Immediately before the procedure, the following information is important for patients:
After le procedure, patients should perform the following tasks:
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| リンク元 | 「精管再開通」「精管復元術」 |
| 関連記事 | 「reversal」 |