Sperm cells mature within the testicular tissue. This process takes about 74 days. The sperm cells enter the epididymis via 12–20 efferent ducts (ductuli efferentes).
At the head of the epididymis, the efferent ductules merge into a single epididymal duct (ductus epididymis = tubulus). The epididymal duct is 6 m long and winds through the epididymis in numerous loops and twists.
At the tail of the epididymis, the epididymal duct opens into the vas deferens. Sperm cells can survive in the epididymis for up to 2 weeks and continue to mature there.
The vas deferens is 40–60 cm long. It initially runs in coils at the junction with the epididymis. It extends from the scrotum to the external inguinal ring and from there through the inguinal canal to the internal inguinal ring.
The vas deferens extends to the prostate, where it meets the seminal vesicles at the seminal hillock. This is where the sperm are produced, which enter the urethra during ejaculation.
Male Reproductive System @ bilderzwerg /AdobeStock
- Conditions associated with the absence of sperm in the ejaculate (azoospermia)
When a couple is unable to conceive, a semen analysis (spermiogram) is of central importance. If doctors find no sperm in the ejaculate, this is referred to as azoospermia (not to be confused with aspermia, which is the absence of ejaculation).
Azoospermia may be caused by a failure of sperm to mature within the testicles themselves (non-obstructive azoospermia).
Possible causes include:
- Damage to testicular tissue (e.g., following testicular inflammation)
- Genetic defects (e.g., Klinefelter syndrome)
If sperm production is possible, the cause of azoospermia is a blockage of the sperm ducts (obstructive azoospermia). Doctors can determine this through a testicular biopsy.
Normally, a single testicle with intact sperm maturation and patent spermatic ducts is sufficient for fertility.
- Obstruction in the region of the efferent ductules
This is a diagnosis of exclusion. An obstruction is present when a testicular biopsy shows normal sperm maturation (spermatogenesis) but no sperm are found in the epididymis.
- Epididymal agenesis (duct aplasia)
In rare cases, the epididymis fails to develop. This is often genetically linked to cystic fibrosis.
Cystic fibrosis is an inherited disease in which the secretion of all the body’s glands is impaired. Due to the production of thick mucus, patients are prone to chronic respiratory infections. The life expectancy of patients is significantly lower.
- Lower (distal) obstruction of the spermatic ducts caused by an utricular cyst
An utricular cyst is a cystic dilation of regressed (rudimentary) female genital structures (derivatives of the Müllerian ducts). This cystic dilation compresses the vas deferens at its junction with the urethra. The obstruction can be resolved by endoscopically opening the cyst.
- Inflammation-related scarring of the vas deferens
Inflammation in the area of the testicles, epididymis, and vas deferens can lead to scar-induced obstruction of the seminal ducts.
In the past, tuberculosis or sexually transmitted diseases were the cause of inflammation-related obstructions of the seminal ducts. Today, nonspecific inflammation of the epididymis is the most common cause.
- Postoperative blockages of the spermatic ducts
Any surgical procedure in the area of the spermatic cord carries the risk of injury to the vas deferens. This is particularly likely during surgery for undescended testicles or inguinal hernia repair.
In cases of unexplained azoospermia, doctors must therefore investigate any previous surgical procedures.
The most common cause of postoperative azoospermia today is elective vasectomy (sterilization) performed as a form of contraception.
If life circumstances change later and the couple wishes to have children again, microsurgical refertilization is possible.
- Microsurgical vasovasostomy
In this procedure, doctors surgically expose the vas deferens in the area where it was previously ligated. This is possible following an orchidopexy, inguinal hernia surgery in the inguinal canal, or a vasectomy at the base of the scrotum.
First, the doctor identifies the scar, dissects the vas deferens above and below the scar, and excises the scar tissue. He then checks the patency of the vas deferens.
To do this, they take 2 ml of saline solution and flush the vas deferens with it. They check for patency by applying pressure to the epididymis.
If the vas deferens is patent, fluid will flow out of the opened vas deferens. The doctor should be able to detect sperm cells or sperm fragments in this fluid.
If patency is confirmed, the ends of the vas deferens are reconnected using microsurgery. This can be performed using two different techniques:
- Single-layer vasovasostomy: Here, 3–5 microsurgical sutures are passed through the entire wall of the vas deferens. These sutures keep the lumen of the vas deferens open. The doctor then closes the spaces between the sutures with an additional 3–5 sutures.
Single-layer vasovasostomy
- Two-layer vasovasostomy: In this procedure, 6 sutures are placed as an inner suture row in the area of the endothelium. A second outer suture row with an additional 6 sutures seals the suture and ensures the tear resistance of the anastomosis.
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Two-layer vasovasostomy
The likelihood of success for a vasovasostomy is equally high for both surgical procedures.
Following a vasectomy, patients achieve a patency rate of 70–90%. The rate of successful pregnancies, at approximately 45–70%, is lower than the patency rate.
The time interval between vasectomy and refertilization is critical. If more than 15 years elapse between vasectomy and refertilization, the rate of successful pregnancies drops to approximately 30%.
In cases of obstruction in the epididymis, the vas deferens can be surgically anastomosed to the epididymal duct (tubulus). This procedure is technically challenging due to the small size of the epididymal duct (diameter 0.2 mm) and its thin wall (thickness 0.03 mm).
The patency rate ranges from 30 to 80%. The reported rates of successful pregnancies also vary between 10 and 55%.
The data show that intussusception of the tubule into the opened duct yields better results than side-to-end anastomosis.
However, scarring can cause even initially successful recanalizations to close again.
If microsurgical procedures are unsuccessful, or if the spermatic ducts are absent, doctors can surgically retrieve sperm cells provided sperm production is intact. The presence of spermatogenesis must be confirmed by a testicular biopsy.
- MESA (Microsurgical Epididymal Sperm Aspiration)
In cases of obstruction in the epididymal region with a blocked epididymal duct, doctors use a surgical microscope to expose the epididymal duct (tubule) and open it. They then aspirate the flowing sperm using a micropipette. These sperm are then used for subsequent intracytoplasmic sperm injection (ICSI).
- TESE ( = Testicular Sperm Extraction)
In cases of obstruction at the junction between the testis and the epididymis, doctors can retrieve sperm directly from the testis. This requires the surgical removal of a small piece of testicular tissue.
Using specialized processing techniques, they can extract sperm from the testicular tissue, which they then use for further assisted reproduction (ICSI—Intracytoplasmic Sperm Injection). In this procedure, doctors use a microscope to artificially bring the surgically retrieved sperm and eggs together.
After successful fertilization, the embryo begins to develop in the test tube. Approximately 2–3 days after successful fertilization, doctors transfer the embryo back into the uterus. The probability of a successful pregnancy is approximately 25–30% per attempt.
In addition to microsurgical vasovasostomy, there are other microsurgical procedures in urology.
These include:
- Microsurgical varicocelectomy: Used to treat varicoceles (spasmodic dilation of the testicular veins), following unsuccessful surgical treatment attempts, or in cases of varicocele in children.
- Microsurgical neurolysis: Performed for treatment-resistant forms of neuralgia characterized by pain in the spermatic cord region that radiates to the testicles. During the procedure, surgeons sever all structures within the spermatic cord as well as the nerve fibers of the ilioinguinal and genitofemoral nerves.
What is a vasovasostomy
? A vasovasostomy is a surgical procedure in which severed vas deferens are reconnected to restore patency of the vas deferens and male fertility.
When is male fertility restoration recommended
? Male fertility restoration is an option if, following a vasectomy, the man wishes to have children again and his semen contains no sperm.
How is a vasovasostomy performed?
The microsurgical procedure is performed under an operating microscope, usually on an outpatient basis or with a short hospital stay, and is carried out by a specialized urologist.
What is the success rate of vasovasostomy
? The success rate depends on several factors, including how long ago the sterilization took place, the condition of the testicles and epididymis, and the experience of the surgeon.
