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A sizable minority of
men receiving vasectomy by simple ligation and
excision—perhaps the most commonly performed male
sterilization technique in low-resource settings—may
still be at substantial risk for fertility six
months after the procedure. Of more than 200
participants in a prospective study in Mexico,1
17% had not achieved sperm clearance by 24 weeks,
according to semen analysis.
Although male
sterilization is a highly effective and permanent
form of contraception, men who have just undergone
the procedure must typically use a backup method
until semen analysis confirms the absence of sperm.
In low-resource areas, however, such testing is
often unavailable; thus, men are told to follow
current clinical guidelines—to use backup for 10-12
weeks, or until they have ejaculated 15-20 times.
To test the validity
of 12 weeks and 20 ejaculations as cutoff points,
researchers enrolled men seeking a vasectomy at
three public clinics in Mexico City in 1995-1996,
and followed them for up to 24 weeks after the
procedure. Six experienced surgeons (two per
clinic)—who had attended a workshop designed to
ensure use of a standardized technique—performed a
simple ligation and excision procedure.
The men returned to
the clinic every other week to provide a semen
sample, which was examined microscopically for sperm
concentration and motility according to World Health
Organization guidelines, and to report the number of
ejaculations since their most recent visit. Men were
considered to have achieved sperm clearance at their
first of two consecutive visits in which the semen
sample contained no sperm.
The analysis included
217 men, aged 21-58 years (mean, 32 years). By the
end of the study, 78% of men had achieved sperm
clearance and 17% had not; 5% had dropped out or had
been lost to follow-up. Of those whose semen samples
still contained sperm, fewer than one-third had
"persistent but low sperm concentrations," and were
presumed to have had a successful vasectomy with
delayed sperm clearance; the remainder were
considered to have had a failed vasectomy. In the
latter group, sperm concentrations at 22-24 weeks
were greater than three million sperm per mL of
semen, including active sperm; the average
concentration was greater than 39 million/mL,
indicating "a significant risk for pregnancy" for
the patients' fertile female partners.
Time to sperm
clearance varied widely. Sperm clearance was reached
at medians of 10 weeks and 32 ejaculations. At 12
weeks, 63% of patients produced sperm-free semen;
13% had at least three million sperm per mL, most of
them more than 20 million/mL. At the 20th
ejaculation, only 44% of men produced sperm-free
semen, whereas 21% had sperm concentrations
exceeding three million per mL.
Cumulative event
probabilities estimated by life-table analysis
showed that sperm clearance was achieved by 60 per
100 study participants at 12 weeks, and by 82 per
100 at 22 weeks. In addition, the Kaplan-Meier
cumulative event probability of achieving sperm
clearance was 28 per 100 men at the 20th
ejaculation.
According to
chi-square analysis, failure rates among individual
surgeons (range, 7-20%) did not differ
significantly. However, each surgeon performed only
29-45 vasectomies in the study, which may have
precluded the detection of meaningful differences.
The researchers
believe that the most likely cause of vasectomy
failure in the study was reattachment of the severed
vas ends soon after vasectomy, noting that men with
a failed vasectomy typically experienced a brief,
dramatic reduction in sperm concentration sometime
in the early postvasectomy period. Furthermore, they
suggest that the high number of such cases in the
study "was likely related to the occlusion method
used." However, they say that they are unaware of
any randomized, controlled trial to date that has
compared simple ligation and excision with other
techniques—for example, those in which the severed
ends of the vas deferens are sealed by applying
surgical clips, by burning (or cauterizing) the ends
or by covering one end with the tissue layer
surrounding the vas.
According to the
researchers, the study findings show that
"guidelines...based only on the time or number of
ejaculations after vasectomy cannot adequately
replace semen testing when ligation and excision are
used." For situations in which semen testing is not
an option, they note that a cutoff of 12 weeks is
probably more reliable than that of 20 ejaculations,
yet each "leaves a substantial number of men at risk
for continued fertility."
—C. Coren
1.
Barone MA et al., A prospective study of time and
number of ejaculations to azoospermia after
vasectomy by ligation and excision, Journal of
Urology, 2003, 170(3):892-896.
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