OVERVIEW

What is the vas deferens in vas deferens developmental abnormalities, what is its function, and what is its developmental process?

The male reproductive system consists of two parts: external genitalia and internal genitalia. The external genitalia include the scrotum and penis, while the internal genitalia are composed of the gonads (testes), the vas deferens system (epididymis, vas deferens, ejaculatory duct, and urethra), and accessory glands (seminal vesicles, prostate, and bulbourethral glands).

The vas deferens is approximately 30–35 cm long, originating from the tail of the epididymis as a direct continuation of the epididymal duct and terminating at the ejaculatory duct in the prostate. The vas deferens has a thick wall with well-developed muscle layers, a narrow lumen, and feels like a firm, cord-like structure when touched. The vas deferens can be divided into four parts based on its course:

• Testicular part: Extends from the tail of the epididymis to the head of the epididymis.

• Spermatic cord part: Extends to the superficial inguinal ring (a common site for vasectomy).

• Inguinal canal part: Located within the inguinal canal.

• Pelvic part: The longest section, extending from the deep inguinal ring to the ampulla of the vas deferens.

The primary function of the vas deferens is to transport sperm.

A normal vas deferens is a pair of long, slender, and curved ducts. Its smooth muscles produce coordinated rhythmic contractions to propel sperm. Additionally, the vas deferens regulates sperm motility and metabolism and maintains the integrity of the male reproductive system.

Developmental process of the vas deferens:

The vas deferens originates from the mesonephric duct (Wolffian duct) during embryonic development. The mesonephric duct is a paired tubular structure in early embryonic development. In male fetuses, the mesonephric duct gradually develops into the epididymis, vas deferens, seminal vesicles, and ejaculatory duct. In female fetuses, the mesonephric duct regresses.

What is vas deferens developmental abnormality?

Vas deferens developmental abnormality is a condition caused by improper development of the vas deferens during embryonic growth. Current research suggests that it may be a genetic disorder.

Clinically, it often manifests as male infertility. If the testes retain spermatogenic function, sperm retrieval techniques combined with assisted reproductive technologies can help patients conceive. A small number of patients may also undergo vas deferens reconstruction to achieve natural pregnancy.

What are the common types of vas deferens developmental abnormalities?

Abnormalities in the vas deferens due to maldevelopment, regression, or atresia of the mesonephric duct during embryonic development are referred to as congenital absence of the vas deferens (CAVD). This is one of the major causes of obstructive infertility in men and is often associated with the absence of seminal vesicles.

Based on the affected region, it can be classified as:

• Congenital bilateral absence of the vas deferens (CBAVD);

• Congenital unilateral absence of the vas deferens (CUAVD);

• Congenital bilateral segmental absence of the vas deferens.

In practice, doctors often categorize patients simply as having bilateral or unilateral absence. Unilateral absence is less common than bilateral absence, but this may be because patients with unilateral absence retain normal fertility and do not seek medical attention, leading to statistical bias.

SYMPTOMS

What are the symptoms and manifestations of vas deferens developmental abnormalities?

Patients with congenital absence of the vas deferens (CAVD) often have concurrent developmental abnormalities of the seminal vesicles, epididymis, and kidneys, with the primary manifestation being infertility. Different types of CAVD patients exhibit varying symptoms:

• Bilateral absence of the vas deferens: Accounts for 1%–2% of male infertility cases. Semen analysis typically reveals azoospermia.

• Unilateral absence of the vas deferens: The contralateral vas deferens may show segmental absence, obstruction, or normal structure, allowing some patients to retain normal fertility and thus not seek medical attention. Infertile patients often present with contralateral reproductive tract obstruction or testicular developmental abnormalities, and semen analysis may show azoospermia or oligoasthenospermia.

CAUSES

What causes abnormal development of the vas deferens?

Numerous studies at home and abroad have shown that abnormal development of the vas deferens is a genetic disease caused by gene mutations. Approximately 58% to 88% of patients with congenital bilateral absence of the vas deferens have mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

Is abnormal development of the vas deferens hereditary?

Yes.

Mutations in the CFTR gene are associated with abnormal development of the vas deferens. This mutated gene may be passed on to the next generation, leading to the same condition in offspring.

Methods to prevent the hereditary transmission of abnormal vas deferens development can be found in the "Prevention" section below.

DIAGNOSIS

What tests are needed for vas deferens developmental abnormalities?

Physical examination, ultrasound, semen analysis, and seminal plasma biochemical tests are effective methods for diagnosing congenital absence of the vas deferens (CAVD).

Clinicians' neglect of physical examinations and varying ultrasound techniques can easily lead to misdiagnosis or missed diagnosis of CAVD, resulting in an average diagnosis time of 4.3 years for patients.

• Physical examination: If vas deferens developmental abnormalities are suspected, the doctor will assess the patient's growth and development, check for female characteristics, and palpate the size and texture of both testicles as well as the absence of the scrotal segment of the vas deferens. About 3/4 of patients can receive a preliminary diagnosis if the scrotal segment of the vas deferens is not palpable during the scrotal examination. Additionally, the physical examination can determine whether the patient has varicocele or abnormal development and course of the vas deferens.

• Ultrasound examination: Patients suspected of having vas deferens developmental abnormalities should undergo scrotal, abdominal, and transrectal ultrasound (TURS) examinations. Typical ultrasound findings may include dilated changes in the proximal seminal tract, epididymal truncation signs, and the absence or thin linear dysplasia of the corresponding segments of the vas deferens and seminal vesicles. However, ultrasound cannot visualize the entire length of the vas deferens.

• Magnetic resonance imaging (MRI): MRI with a rectal coil provides more precise structural images of the seminal tract and is the gold standard for diagnosing reproductive system diseases. During diagnosis, attention should be paid to any history of recurrent respiratory infections to rule out cystic fibrosis.

• Semen analysis: CAVD patients typically exhibit the "four lows" in semen: azoospermia or oligoasthenospermia, reduced semen volume, low pH, and negative fructose, often due to the absence or dysplasia of the seminal vesicles. Decreased fructose and α-glycosidase levels have diagnostic value for CVAD.

• Seminal tract X-ray contrast imaging: Previously, seminal tract X-ray contrast imaging via seminal vesicle or vas deferens puncture was considered definitive for diagnosing seminal tract obstruction and identifying the specific site of obstruction. However, due to the risks of trauma, obstruction, infection, and radiation exposure, this method is now less commonly used.

TREATMENT

Which department should I visit for abnormal vas deferens development?

You can go to the andrology department, reproductive center, or urology department for diagnosis and treatment.

How is abnormal vas deferens development treated?

The treatment mainly involves various sperm retrieval techniques combined with assisted reproductive technology (ART). ART includes:

• Intrauterine insemination (IUI): A procedure where sperm is artificially injected into the woman's cervix or uterus to facilitate fertilization.
• In vitro fertilization (IVF): Fertilization occurs in a controlled environment outside the body (usually in water), allowing sperm and eggs to combine naturally. The resulting embryo is cultured and then implanted into the woman's uterus.
• Intracytoplasmic sperm injection (ICSI): A microscopic technique where a single sperm is injected directly into an egg for fertilization. The embryo is cultured and later implanted. Patients with congenital absence of the vas deferens often require sperm retrieval (via aspiration or microsurgical extraction) from the testicles before ICSI.

Additionally, patients with unilateral absence of the vas deferens may attempt sperm duct reconstruction surgery for natural conception.

Why do most patients with abnormal vas deferens development require ICSI for fertilization?

Since sperm cannot naturally pass through or be ejaculated from the absent vas deferens, medical intervention is needed to retrieve sperm directly from the testicles.

Whether obtained via aspiration or microsurgical extraction, the retrieved sperm often has issues such as low quantity, immaturity, and poor motility, making natural fertilization impossible. ICSI is necessary to manually inject a single sperm into the egg's cytoplasm for fertilization.

ICSI requires strict medical evaluation by a reproductive specialist to determine suitability.

Which patients with abnormal vas deferens development can attempt sperm duct reconstruction surgery?

Infertile patients with congenital unilateral absence of the vas deferens who desire natural conception may consider reconstruction surgery. A prior exploratory procedure is needed to confirm feasibility.

Patients with bilateral absence (including congenital bilateral or segmental absence) cannot restore sperm duct patency through anastomosis or reconstruction.

DIET & LIFESTYLE

What are the precautions for patients with abnormal vas deferens development in life and diet?

There are no special precautions in life and diet.

PREVENTION

Can Abnormal Development of the Vas Deferens Be Prevented?

Abnormal development of the vas deferens is associated with CFTR gene mutations and may be inherited by the next generation. Therefore:

• If either partner is confirmed to have a CFTR gene mutation, genetic counseling should be sought before attempting pregnancy.

• Men with congenital vas deferens abnormalities should undergo genetic mutation screening with their partner before assisted reproductive procedures. If the female partner does not carry a CFTR mutation, the probability of abnormal vas deferens development in male offspring is extremely low, making assisted reproduction a viable option.

• Additionally, preimplantation genetic testing can be performed on embryos to avoid implanting those carrying the mutated gene, preventing the condition in future generations.