Congenital absence of the vas deferens
Encyclopedia
Congenital absence of the vas deferens (CAVD) is a condition in which the vasa deferentia
, male reproductive
organ
s, fail to form properly prior to birth
. It may either be unilateral (CUAVD) or bilateral (CBAVD).
testicles to the penis
. Therefore, men who are missing both vas deferens are typically able to create sperm but are unable to transport them appropriately. Their semen
does not contain sperm, a condition known as azoospermia
.
cystic fibrosis
and occurs because of a mutation in the CFTR gene
, while the smaller group (estimated between 10 and 40%) is associated with Unilateral Renal agenesis
(URA). The genetic basis of this second group is not well understood.
Mutation of the CFTR gene is found to result in obstructive azoospermia in postpubertal males with cystic fibrosis. Strikingly, CAVD is one of the most consistent features of cystic fibrosis as it affects 98-99% of individuals in this CF patient population. In contrast, acute or persistent respiratory symptoms present in only 51% of total CF patients.
In the subset of males with both CBAVD and URA, the CFTF mutation has been shown to occur at a rate only slightly higher than the overall population. Thus, McCallum, et al. have suggested another mutation may be responsible for this condition.
. However, as the risk of either cystic fibrosis or renal agenesis is likely to be higher in the children, genetic counseling is generally recommended.
Vas deferens
The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....
, male reproductive
Sex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
s, fail to form properly prior to birth
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
. It may either be unilateral (CUAVD) or bilateral (CBAVD).
Presentation
The vas deferens connect the sperm-producingSpermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
testicles to the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
. Therefore, men who are missing both vas deferens are typically able to create sperm but are unable to transport them appropriately. Their semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...
does not contain sperm, a condition known as azoospermia
Azoospermia
Azoospermia is the medical condition of a male not having any measurable level of sperm in his semen. It is associated with very low levels of fertility or even sterility, but many forms are amenable to medical treatment...
.
Causes
There are two main populations of CAVD; the larger group is associated withcystic fibrosis
Cystic fibrosis
Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...
and occurs because of a mutation in the CFTR gene
Cystic fibrosis transmembrane conductance regulator
Cystic fibrosis transmembrane conductance regulator is a protein that in humans is encoded by the CFTR gene.CFTR is a ABC transporter-class ion channel that transports chloride and thiocyanate ions across epithelial cell membranes...
, while the smaller group (estimated between 10 and 40%) is associated with Unilateral Renal agenesis
Renal agenesis
Renal agenesis is a unilateral or bilateral medical condition in which one or both fetal kidneys fail to develop leading to oligohydramnios, resulting in a 40-fold increase in perinatal mortality.It can be associated with RET or UPK3A.-Bilateral:...
(URA). The genetic basis of this second group is not well understood.
Mutation of the CFTR gene is found to result in obstructive azoospermia in postpubertal males with cystic fibrosis. Strikingly, CAVD is one of the most consistent features of cystic fibrosis as it affects 98-99% of individuals in this CF patient population. In contrast, acute or persistent respiratory symptoms present in only 51% of total CF patients.
In the subset of males with both CBAVD and URA, the CFTF mutation has been shown to occur at a rate only slightly higher than the overall population. Thus, McCallum, et al. have suggested another mutation may be responsible for this condition.
Treatment
Individuals with CAVD can reproduce with the assistance of modern technology in a procedure known as intracytoplasmic sperm injectionIntracytoplasmic sperm injection
Intracytoplasmic sperm injection is an in vitro fertilization procedure in which a single sperm is injected directly into an egg.-Indications:...
. However, as the risk of either cystic fibrosis or renal agenesis is likely to be higher in the children, genetic counseling is generally recommended.