What are the other Names for this Condition? (Also known as/Symptoms)

• Absent Vasa
• CAVD (Congenital Absence of Vas Deferens)
• Congenital Aplasia of Vas Deferens

What is Congenital Bilateral Absence of Vas Deferens? (Definition/Background Information)

• Congenital Bilateral Absence of Vas Deferens (CBAVD) is a condition where a male child is born without the vas deferens. The vas deferens are tubes that transport sperms out of the testes
• About 98% of males with a genetic condition, known as cystic fibrosis, are also known to have Congenital Bilateral Absence of Vas Deferens. Since the majority of cases are associated with cystic fibrosis, having a family history of cystic fibrosis is the single biggest known risk factor for developing CBAVD
• CBAVD is caused by mutations in the CFTR gene, which through a complex process, obstructs the development of the vas deferens, leading to their disintegration. In cases that are not associated with cystic fibrosis, the exact cause of Congenital Bilateral Absence of Vas Deferens is unknown
• A diagnosis of CBAVD may involve the assessment of symptoms, an examination of the scrotum under general anesthesia and ultrasound scan of both the scrotum and trans-rectal area
• In individuals with Congenital Bilateral Absence of Vas Deferens, the development of the testes and their function are reported to be normal, despite symptoms of infertility. Thus, the treatment for infertility may involve retrieval of the sperm for assisted reproductive procedures
• Congenital Bilateral Absence of Vas Deferens cannot be cured, since the vas deferens cannot be restored. Nonetheless, successful pregnancies are possible due to procedures that enable sperm retrieval for medically-assisted reproduction

Who gets Congenital Bilateral Absence of Vas Deferens? (Age and Sex Distribution)

• Congenital Bilateral Absence of Vas Deferens is a condition that is present at birth. It only affects the male babies
• The condition is reported to occur in 0.1% of all males (1 in 1000) and contributes to 1-2% of infertility incidences
• No racial and ethnic group predilection is noted

What are the Risk Factors for Congenital Bilateral Absence of Vas Deferens? (Predisposing Factors)

• The single major risk factor for developing Congenital Bilateral Absence of Vas Deferens is a family history of cystic fibrosis, a genetic disorder that severely affects the lungs and digestive system. About 98% of males with cystic fibrosis are also known to have CBAVD
• In a minority of CBAVD cases where there is no relationship to cystic fibrosis, the exact risk factors are unknown

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Congenital Bilateral Absence of Vas Deferens? (Etiology)

• In individuals with cystic fibrosis, Congenital Bilateral Absence of Vas Deferens is caused by mutations in the CFTR gene, which stands for cystic fibrosis transmembrane regulator gene
  • The CFTR regulates chloride ion channels through cell membranes, and consequently water transport. The water movement is necessary for maintaining the consistency of mucus, which protects the airways, organs of the digestive system, and the reproductive system
  • When the CFTR gene is mutated, water transport becomes affected, leaving the mucus thick and sticky. Since this is a genetic condition, the presence of thick mucus plugs/hinders the development of the vas deferens, leading to their deterioration in the fetus, thus causing CBAVD
  • The condition can occur in the background of cystic fibrosis. The association of CBAVD with cystic fibrosis is considered an “atypical” form of cystic fibrosis
  • The condition is inherited in an autosomal recessive pattern, in which both copies of the gene are defective causing the condition to be manifested
• In males with CBAVD without cystic fibrosis, the genetic cause is often unknown. Some CBAVD cases have been reported to be linked to structural defects of the urinary tract including unilateral renal agenesis (which is the absence of one kidney)

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children, born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected). 

What are the Signs and Symptoms of Congenital Bilateral Absence of Vas Deferens?

The signs and symptoms of Congenital Bilateral Absence of Vas Deferens may be associated with cystic fibrosis or be independent of the genetic disorder. The common signs and symptoms of CBAVD may include:

• In individuals with cystic fibrosis:
  • Infertility
  • Signs and symptoms of the respiratory system
  • Frequent sinus infections
  • Chronic issues with digestive system
  • Reduced secretion of enzymes by pancreas

Note: Not all individuals are known to have the classic symptoms of cystic fibrosis involving the digestive and respiratory system.

• In those without cystic fibrosis, but with urinary tract malformations such as unilateral renal agenesis:
  • Infertility
  • Blood in urine
  • Foamy urine
  • High protein in urine
  • High blood pressure

Note: Men with CBAVD and without cystic fibrosis may not exhibit symptoms of urinary tract malformation(s) until adulthood or even later.

How is Congenital Bilateral Absence of Vas Deferens Diagnosed?

An accurate diagnosis of Congenital Bilateral Absence of Vas Deferens may require information from the following:

• A physical examination
• An evaluation of family medical history including history of cystic fibrosis
• An assessment of the symptoms
• Examination of scrotum under general anesthesia
• Ultrasound imaging of the scrotum and trans-rectal region to confirm the absence of vas deferens
• Genetic testing of fetal cells to check for mutation(s) in CFTR gene
• In order to rule out other reasons of infertility, the following tests may be performed:
  • Testicular biopsy
  • Testes fine needle aspiration (FNA)
  • Testis sperm extraction (TESE)
  • Infertility tests on the partner

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Congenital Bilateral Absence of Vas Deferens?

The most common complication of Congenital Bilateral Absence of Vas Deferens is infertility.

• Individuals with CBAVD are generally known to have issues related to sperm production (testicular failure) as well
• Depression and emotional distress may be observed with infertility

How is Congenital Bilateral Absence of Vas Deferens Treated?

Congenital Bilateral Absence of Vas Deferens is an incurable disorder, which cannot be treated and restored. The treatment measures are directed towards addressing the issue of infertility and treating underlying cystic fibrosis.

• The treatment options for resultant infertility are tailored toward the retrieval of sperm with methods, such as microsurgical epididymal sperm aspiration (MESA), for assisted reproduction techniques (in-vitro fertilization procedures)
• Symptomatic treatment of cystic fibrosis is undertaken to address respiratory distress and digestive issues
• Treatment of urinary tract abnormalities (if any) may be necessary

How can Congenital Bilateral Absence of Vas Deferens be Prevented?

• Currently, there are no specific methods or guidelines to prevent Congenital Bilateral Absence of Vas Deferens, since it is a genetic condition
• Genetic testing of the expecting parents (and related family members), as well as prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks prior to planning for a child
• Active research is currently being performed in order to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Congenital Bilateral Absence of Vas Deferens
• Regular medical screening at periodic intervals with tests and physical examinations are strongly recommended

What is the Prognosis of Congenital Bilateral Absence of Vas Deferens? (Outcome/Resolutions)

• The prognosis of Congenital Bilateral Absence of Vas Deferens, in a majority of individuals, depends upon the severity of cystic fibrosis. Nevertheless, the restoration of vas deferens is not possible
• Although the condition may lead to infertility, the sexual drive or performance is not known to be compromised. CBAVD-associated infertility can be potentially addressed through procedures involving the retrieval of sperm, followed by in vitro fertilization (IVF) of the egg

Additional and Relevant Useful Information for Congenital Bilateral Absence of Vas Deferens:

The condition can either be unilateral or bilateral i.e., termed Congenital Unilateral Absence of Vas Deferens (CUAVD) or Congenital Bilateral Absence of Vas Deferens (CBAVD).