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Congenital Bilateral Absence of the Vas Deferens (CBAVD)

Definitions of Vas Deferens Aplasia

Congenital bilateral aplasia of the vas deferens (CBAVD) is the bilateral absence of the vas deferens, often associated with malformations of the urinary tract or the seminal ducts (Tüttelmann et al., 2008).

Epidemiology

Unilateral absence of the vas deferens occurs in 0.6–1%. Bilateral absence of the vas deferens is rare and, in 3%, the underlying cause of obstructive azoospermia.

Etiology of Vas Deferens Aplasia

Mutations of the CFTR:

Genetic mutations of CFTR (cystic fibrosis transmembrane conductance regulator) result in the bilateral absence of seminal vesicles and/or vasa deferentes. The manifestation of cystic fibrosis is not obligatory, as CBAVD is considered to be a minimal manifestation of cystic fibrosis. Numerous different mutations have been described, detectable in at least 80% of men with CBAVD.

Association with unilateral renal agenesis:

Patients with CBAVD without CFTR mutations will have in up to 40% a unilateral renal agenesia. Unilateral renal agenesia results from a developmental disorder of the urogenital ridge, which affects the ureteric bud, the mesonephric duct (Wolff duct), and sometimes also the paramesonephric duct (Müller duct), depending on the time and extent. Concomitant malformations of the internal genital organs are common.

Signs and Symptoms

The vas cannot be palpated. Unilateral absence of the vas deferens does not cause any complaints. Men with CBAVD are infertile due toazoospermia.

Diagnosis

• Semen analysis: azoospermia and signs of obstruction (pH <7, low semen volume, low fructose)
• Normal hormone concentrations
• Transrectal ultrasound: absence of seminal vesicles possible.
• Mutation analysis of the CFTR gene is indicated if azoospermia is present and the vas cannot be palpated.

Treatment of CBAVD

Treatment is only necessary for reproduction, which is possible with intracytoplasmic sperm injection. The risk of cystic fibrosis (CF) is increased, and genetic diagnosis and counseling can assess the risk individually.

Genetic Counseling

Cystic fibrosis (mucoviscidosis) is an inherited autosomal recessive disease; the basic risk is 1:2500. A man with CBAVD has the CFTR mutation in both alleles and will in any case pass it on to his children. The partner has the risk of 4–5% for carrying one allele of a CFTR mutation. Without genetic screening of the partner, the child's risk for cystic fibrosis is approximately 1:100. If a genetic diagnosis of the partner excludes frequent CFTR mutations, the risk of the child for cystic fibrosis is still around 1:960 (Lewis-Jones et al., 2000) (Tuettelmann et al., 2008).

References

Lewis-Jones, D. I.; Gazvani, M. R. & Mountford, R. Cystic fibrosis in infertility: screening before assisted reproduction: opinion.
Hum Reprod, 2000, 15, 2415-2417.

Tüttelmann, F.; Gromoll, J. & Kliesch, S. [Genetics of male infertility].
Urologe A, 2008, 47, 1561-2, 1564-7

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