The vas deferens derives from the Wolffian (mesonephric) duct and shares a common
origin with the kidney (1). Intrinsic Wolffian duct defects may result in failure
of the vas deferens to develop, a condition that can occur in isolation or combined
with renal agenesis or malformations. A missing vas, that is, unilateral absence of
vas deferens, albeit relatively uncommon may be found by urologists performing vasectomies
or evaluating men with fertility problems (1, 2). It is, therefore, important that
urologists be aware of the practical implications when finding such a case scenario.
In this issue of the International Braz J Urol, Miller and colleagues give us useful
guidance by reporting the prevalence of congenital unilateral absence of vas deferens
in a cohort of 23,013 men presenting for vasectomy over a 20-year period in Quebec
City, Canada (3). Among the confirmed cases, namely, those with i. No prior genital
surgery or trauma and ii. A missing vas at the time of vasectomy, and iii. Confirmed
sterility by a post-vasectomy semen analysis (PVSA) after unilateral vasectomy, a
missing vas was found once in every 479 men subjected to vasectomy. In their study,
most vasectomies had been performed using a non-scalpel technique combining thermal
cautery and fascial interposition (4), which has shown to be as effective as ligation
and fascial interposition (5). To our knowledge, the paper by Miller et al. is the
largest series reported to date thus making it sound to assume that most urologists
performing vasectomies will find such a case in their career. Interestingly, the authors
identified a group of 34 men (0.15%) in whom a missing vas was suspected but could
not be confirmed, mostly due to the absence of a PVSA to confirm sterility or a history
of prior surgery or scrotal anomaly that might account for the missing vas.
The study of Miller and colleagues highlights three relevant aspects for practicing
urologists that need to be discussed further. First, the importance of physical examination
before the vasectomy and during fertility evaluation. Second, the role of post-vasectomy
semen analyses, and lastly, the importance of surgical planning in difficult vasectomy
cases.
Palpation of the vas deferens is essential and should be included as part of the routine
physical examination in all men seeking vasectomy or fertility (6). The finding of
a missing vas should prompt urologists to order an abdominal ultrasound study to detect
any renal anomalies (6). In healthy men seeking vasectomy, it might be argued that
ultrasound is unnecessary as the finding of a single kidney is not clinically relevant.
An objection is that although up to 80% of men with a congenital unilateral absence
of vas deferens (CUAVD) have ipsilateral renal agenesis, the kidney may be present
and other renal malformations such as ectopia, malrotation, fusion or polycystic disease
may occur (7). Despite not warranting further intervention, informing the affected
men that they have only one kidney or a renal anomaly is good medical practice as
it may prompt such men to take a better life-style, thus preventing the occurrence
of type 2 diabetes and hypertension that may impact their renal function later in
life (8). On the other hand, 1–2% of males investigated for infertility have congenital
absence of vas agenesis (1, 6, 9). Whereas the condition is often associated with
bilateral vas absence and azoospermia and most men with CUAVD are fertile, men with
a single vas may present with mild oligozoospermia as testicular sperm output is cut
in half (10). Furthermore, CUAVD may be associated with mutations in the cystic fibrosis
transmembrane conductance regulator (CFTR) gene (1). The most alarming fact is that
if both the male and female partners carry such mutations- a carrier frequency of
4% has been reported in Caucasian women- the newborn may present with congenital bilateral
absence of vas deferens (CBAVD) and therefore infertility due to obstructive azoospermia
or with the life-threatening autosomal disease named cystic fibrosis (1, 6, 11). Having
said that, proper counseling seems advisable to all men with CUAVD regardless of their
fertility status. In a man seeking vasectomy and therefore presumably fertile there
is a small possibility that his male offspring harbor CBAVD if his female partner
is a carrier of CFTR mutations. Identification of such condition earlier in life may
be important not only for diagnosing infertility in the offspring but also for counseling
about the chances of paternity and the risks associated with the use of assisted reproductive
technology (ART) (11, 12). And in those individuals with fertility problems, particularly
if candidates for ART, genetic screening of CFTR mutations is not a mere academic
exercise; it is deemed necessary to allow couples to make informed decisions about
their plan of parenthood (1, 12, 13).
A post-vasectomy semen analysis is recommended to all men subjected to vasectomy.
In recent guidelines issued conjointly by the British Andrology Society and the British
Association of Urological Surgeons, assessment of one semen specimen preferably examined
within 1 hour of the collection in a laboratory that uses proper methods- is enough
to confirm sterility if no sperm are seen (14). PVSA should take place a minimum of
12 weeks after vasectomy and after a minimum of 20 ejaculations (recommendation grade
B). The reason is the earlier the testing, the higher the chance of a false-positive
result. And data indicates that by 20 ejaculates, 80% of men show azoospermia or sperm
numbers below detectable levels (15). Men with fewer than 3 ejaculations per week
reach azoospermia approximately 5 weeks later than those with a higher ejaculation
frequency (16). This means that not only the interval between vasectomy and PVSA is
important but also the number of ejaculations. According to the aforementioned guidelines,
in the presence of residual sperm vasectomy success is confirmed if <100000/mL non-motile
sperm. However, this “special clearance” with non-motile spermatozoa is still under
discussion (17, 18), as proper laboratory methods are crucial to ensure accuracy of
results (19, 20). Interestingly, in the study of Miller et al., approximately 30%
of all men subjected to vasectomy failed to comply with the recommendation of providing
a specimen for analysis. The rate of non-compliance dropped to 20% among those in
whom a unilateral vasectomy had been performed -probably due to the perception of
the uncertainty of its success- but the figures were still high. Since surgeons are
ultimately responsible for counseling their patients about potential risks and complications,
including vasectomy failure and recanalization, it seems crucial to emphasize patients
the importance of the PVSA, both verbally and written.
Lastly, given the higher rate of misdiagnosis reported in men with prior scrotal surgeries
or testis abnormalities, it must be admitted, as suggested by Miller et al., that
men with a suspected absent vas ipsilateral to such abnormalities would be better
treated where a vasectomy can be combined with testis delivery. In our center, our
preference is to perform vasectomies on an outpatient basis under intravenous sedation
with propofol in association with spermatic cord block with Marcaine (21). If needed,
the testis can be delivered and the scrotal contents explored without jeopardizing
the effectiveness of the surgical intervention.
CONCLUSIONS
A missing vas (unilateral congenital absence of vas deferens) is found once in approximately
480 men subjected to vasectomy. Palpation of the vas deferens is essential and should
be included as part of the routine physical examination in all men seeking vasectomy
or fertility. The finding of a missing vas may be associated with renal agenesis /
abnormalities and or genetic mutations with potential risks for the offspring. Patients
should be offered proper counseling and further testing whenever indicated. A post-vasectomy
semen analysis is recommended to all men subjected to vasectomy. PVSA should take
place a minimum of 12 weeks after vasectomy and after a minimum of 20 ejaculations.
Evaluation of a single semen specimen is enough to confirm sterility if no sperm are
seen. Men with a history of prior surgery or scrotal abnormalities in whom a missing
vas is suspected may require scrotal exploration to avoid misdiagnosing the absent
vas.