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Congenital Bilateral Absence of the Vas Deferens (CBAVD)
Definitions of Vas Deferens Aplasia
Absence of the vas deferens may occur unilateral or bilateral, it may be associated with absence of the seminal vesicles or with abnormalities of the urinary tract (Tüttelmann et al, 2008):
- Congenital unilateral absence of the vas deferens (CUAVD)
- Congenital bilateral absence of the vas deferens (CBAVD)
Unilateral absence of the vas deferens occurs in 0.6–1%. Bilateral absence of the vas deferens is rare and in 6% the underlying cause of obstructive azoospermia.
Etiology of Vas Deferens Aplasia
Mutations of the CFTR:
Mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) lead to a bilateral absence of the seminal vesicles and/or vasa deferentes. The (pulmonary) manifestation of cystic fibrosis is not obligatory. Numerous different mutations have been described, which can be detected in 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. The mechanism for this disorder is unclear.
Signs and Symptoms
The vas cannot be palpated. Unilateral absence of the vas deferens does not cause any complaints. Men with CBAVD suffer from azoospermia and infertility.
- Semen analysis: azoospermia and signs of obstruction (pH <7, low semen volume, low fruktose)
- 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, genetic diagnosis and counseling can assess the risk individually.
Cystic fibrosis (mucoviscidosis) is 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 general basic risk of 4$ndash;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 frequent CFTR mutations are excluded by genetic diagnosis of the partner, the risk of the child for cystic fibrosis is reduced to about 1:960 (Lewis-Jones et al, 2000) (Tuettelmann et al, 2008).
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- 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
Deutsche Version: CBAVD