Understanding Fallopian Tubes on Ultrasound

The fallopian tubes are essential pathways where fertilization—the meeting of the egg and sperm—actually occurs. While they are a vital part of the reproductive system, their evaluation during a routine fertility scan requires specific expertise and timing.

1. Anatomy of the Fallopian Tubes

Fallopian tubes are paired structures located on either side of the uterus. They are attached near the uterine cornua and extend outward toward the ovaries. Their length typically varies from 7 to 12 cm, and they are divided into four distinct parts:

• Interstitial: The part attached to the uterus.
• Isthmic: The narrow, muscular middle portion.
• Ampullary: The wider section where fertilization usually happens.
• Fimbrial: The free-moving end with finger-like projections that “catch” the egg.

2. Why Normal Tubes Are “Invisible”

In a healthy state, fallopian tubes are very thin and are usually not visualized during a standard ultrasound (USG). However, they become visible under certain conditions:

• Hydrosalpinx: If a tube is blocked and fills with fluid, it appears as a distinct structure on the scan.
• Pelvic Fluid: The presence of free fluid in the pelvic cavity can act as a contrast, making the tubes visible.
• Adnexal Cysts: Occasionally, paraovarian or paratubal cysts (like Cysts of Morgagni) or Gartner’s duct cysts can be detected near the tubes during a routine scan.

3. Screening for Tubal Patency

Because normal tubes aren’t visible on a basic scan, we use advanced diagnostic methods to check if they are open (patent):

• HyCoSy (Hysterosalpingo Contrast Sonography): An ultrasound-based test used to evaluate tubal patency.
• HSG (Hysterosalpingography): An X-ray-based procedure to map the internal structure of the tubes.
• Timing: Tubal assessment is ideally integrated into a basic scan on Day 2 or Day 9 of the menstrual cycle.