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Blockage of sperm transport from the testis


               Blockage of sperm transport from the testis

Sperm from the testis must pass through the epididymis and vas deferens on their journey to the ejaculate. Blockage, or obstruction, of sperm transport from the testis can cause a zero sperm count, even though the testis continues to produce sperm. Obstruction in one (unilateral) or both (bilateral) sides may be due to either missing or blocked tubes (ducts). Obstruction may occur at any point from the epididymis up to the ejaculatory ducts in the prostatic urethra.

Obstructions can result from a variety of causes and include:

Congenital absence of the vas deferens

Infection

Vasectomy

Obstructions in region of prostate

Congenital absence of the vas deferens

Absence of the vas deferens prevents sperm from passing from the testis into the ejaculate. When men are born with this condition it is known as congenital absence of the vas deferens and these men are usually missing both their vas deferens and two thirds of their epididymis. In most cases, congenital absence of the vas deferens results from a genetic change or mutation to a gene called the ‘cystic fibrosis transmembrane regulator’ (CFTR). More complex changes (or mutations) of this CFTR gene have also been found to cause cystic fibrosis, a serious condition causing breathing and bowel problems from early infancy. Men with cystic fibrosis also have congenital absence of the vas deferens. However, infertile men with congenital absence of the vas deferens usually have no significant history of respiratory disease. Men with congenital absence of the vas deferens are now regarded as having an extremely mild form of the cystic fibrosis syndrome.

In men with congenital absence of the vas deferens, it is possible to collect sperm directly from the testis or from the small remaining part of the epididymis and achieve pregnancies using assisted reproductive technologies. Due to the genetic basis of this problem, genetic screening of the man and his partner for mutations in the CFTR gene is essential prior to starting treatment because if both partners have CFTR mutations, then there is a high risk of cystic fibrosis in their children born from assisted reproductive technologies.

Absence of the seminal vesicles usually occurs in association with congenital absence of the vas deferens. The prostate and seminal vesicles contribute approximately 90% of the quantity of the ejaculate, so absence of the seminal vesicles can cause a smaller amount of ejaculate (usually about 0.5 ml, normal men > 2 ml). The seminal vesicles also contribute to making the ejaculate alkaline, so when they are absent the acidity of the ejaculate is increased.

Infection

Infections of the reproductive tract may lead to blockage of sperm transport and preventing sperm from being ejaculated.

Sexually transmitted diseases such as gonorrhoea and chlamydia may result in damage and blockage of the epididymis, preventing sperm from passing from the testis to be ejaculated. Because the testis only contributes a small part of the quantity of the normal ejaculate, blockage at this level does not change the ejaculate volume.

Since the ejaculatory duct passes through the prostate gland, infections of the prostate can cause swelling and block off the ejaculatory duct preventing sperm from being ejaculated. Because the prostate and seminal vesicles contribute the majority of fluid to the ejaculate volume, blockage at this level will reduce the volume of ejaculate. Infections of the prostate and seminal vesicles can also cause inflammatory cells to pass into the ejaculate, which may damage the sperm.

Vasectomy

Vasectomy involves the cutting and removal of a section of the vas deferens, the tube which carries sperm from the testis to the urethra at the base of the bladder. Vasectomy is a safe and effective long-term contraceptive option however about 6% of Australian men who have had a now seek to have the operation reversed in order to father more children.

Evidence does not support long term changes in testosterone levels following vasectomy. However with the passage of time, damage to the sperm producing tubes of the testis may occur. In addition, scarring and blockages in the epididymal tubes can also occur. Sperm antibodies develop in 80% of men who have had a vasectomy. For these reasons, vasectomy reversal surgery is less successful if 10 years have elapsed since the original vasectomy.

Storage of sperm before vasectomy

Vasectomy is a safe and effective contraceptive option however all men should consider it irreversible. Unfortunately life is unpredictable. Young men, particularly those who have never had children, should be dissuaded from vasectomy and seek other methods of contraception. Another option is to consider long-term storage of sperm prior to the vasectomy. Sperm can be stored at very low temperatures while still maintaining a reasonable sperm quality. The knowledge that sperm has been stored for the future insemination of a spouse may be reassuring and a reasonable “insurance policy” for couples considering vasectomy.

Obstructions in region of prostate

Infections of the prostate can cause swelling and blockage of the ejaculatory duct as this duct passes through the prostate gland. Blockage in this region will prevent sperm from being ejaculated.

Occasionally, a man may have a congenital abnormality (a problem they have been born with) in which ‘cysts’ in the prostate gland have formed. By pressing on the ejaculatory ducts, these cysts can also cause blockage of sperm at this level.

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