Ejaculatory Duct Obstruction (EDO)

The ejaculatory ducts are two small ducts located within the prostate.

Each is formed where the vas deferens joins the duct of the seminal vesicle.

During ejaculation, sperm travel from the testes and epididymides through the vas deferens. Seminal-vesicle secretions join this pathway before the ejaculatory ducts empty into the prostatic urethra.

If one or both ejaculatory ducts become blocked, sperm and seminal fluid may not enter the urethra normally.

This is called ejaculatory duct obstruction (EDO).

Why does EDO affect fertility?

The seminal vesicles contribute a substantial proportion of normal ejaculate volume.

When both ejaculatory ducts are completely obstructed, sperm may be produced normally inside the testes but cannot reach the ejaculate.

This can result in:

• Low semen volume

• Azoospermia

• Acidic semen

• Reduced or absent seminal-vesicle secretions

This is a form of obstructive azoospermia.

Partial obstruction may produce a different pattern, including:

• Oligozoospermia

• Very poor sperm motility

• Reduced ejaculate volume

• Painful ejaculation

• Haematospermia

Complete vs partial obstruction

EDO does not always completely block sperm passage.

Complete bilateral EDO

Both ducts are fully obstructed.

The classic semen-analysis pattern can include:

• Azoospermia

• Low ejaculate volume

• Acidic semen

• Normal testicular size

• Normal testosterone

• Normal or relatively preserved sperm production

Partial EDO

Some seminal fluid and sperm can still pass through the ducts.

Semen analysis may show:

• Severe oligozoospermia

• Reduced motility

• Low or sometimes near-normal semen volume

• Abnormal semen parameters

Partial EDO can therefore be more difficult to recognize.

Is EDO the same as retrograde ejaculation?

No.

In ejaculatory duct obstruction, semen cannot move normally through the ejaculatory ducts.

In retrograde ejaculation, semen reaches the urethra but travels backward into the bladder instead of exiting through the penis.

These conditions require different diagnostic approaches and treatments.

Is EDO the same as vas deferens obstruction?

No.

The vas deferens carries sperm from the epididymis toward the prostate.

The ejaculatory ducts are farther downstream and pass through the prostate before opening into the urethra.

Identifying the location of an obstruction is important because treatment differs according to where the reproductive tract is blocked.

EDO is diagnosed using a combination of semen analysis, medical history, physical examination, hormonal evaluation, and targeted imaging.

Semen analysis

Semen analysis is one of the most important initial tests.

Classic findings suggesting complete EDO can include:

• Low semen volume

• Azoospermia

• Acidic semen

Partial obstruction may instead cause:

• Severe oligozoospermia

• Very low sperm motility

• Reduced semen volume

AUA/ASRM guidance advises considering distal genital tract obstruction when semen volume is low and acidic, particularly when azoospermia or severe oligozoospermia is present.

Hormonal testing

Hormonal tests may include:

• FSH

• LH

• Total testosterone

Men with purely obstructive infertility may have relatively preserved testicular function and hormone levels.

This can help differentiate obstruction from severe testicular sperm-production failure.

Physical examination

An andrologist or reproductive urologist may assess:

• Testicular size

• Epididymides

• Presence of the vas deferens

• Secondary sexual characteristics

• Other reproductive tract abnormalities

Transrectal ultrasound (TRUS)

TRUS is an important imaging investigation when EDO is suspected.

It can evaluate:

• Seminal vesicles

• Ejaculatory ducts

• Prostate

• Midline prostatic cysts

• Calcifications

• Dilated reproductive structures

The EAU recommends TRUS in infertile men with low seminal volume, acidic pH, and severe oligozoospermia or azoospermia when ejaculatory duct obstruction is suspected.

Pelvic MRI

Pelvic MRI may be useful in selected patients when anatomy remains unclear.

It can provide detailed visualization of:

• Ejaculatory ducts

• Seminal vesicles

• Prostate

• Midline cysts

• Duct dilation

MRI is generally complementary rather than necessary for every patient.

Additional diagnostic procedures

Selected specialist centers may use procedures such as:

• Seminal vesicle aspiration

• Seminal vesiculography

• Chromotubation

• Seminal vesiculoscopy

These are not routine tests for every infertile man but may help confirm obstruction in difficult cases.