Classification of HSG Catheters (Hysterosalpingography Catheters)

HSG catheter is the core consumable used in hysterosalpingography (HSG); it is a single-use interventional catheter employed in infertility screening and serves as an essential instrument for evaluating female infertility.

I. Classification by sealing structure (the primary classification in clinical practice)

1. Dual-Lumen Balloon Type (Mainstream in China)
Structure: Features a working lumen and a balloon inflation lumen, a distal silicone balloon, and dual Luer connectors; metal-reinforced guidewires are available as an option. Available in 5Fr and 7Fr sizes (7Fr is the most commonly used).
Characteristics
✅ Advantages: The balloon inflates to occlude the internal cervical os, preventing the leakage of contrast medium and ensuring the catheter remains securely in place. It is well-suited for patients with a relaxed cervical os or a dilated cervical canal. It allows for simultaneous tubal patency testing and medication administration. Made of single-use silicone, it offers excellent biocompatibility and includes an X-ray radiopaque line.
❌ Disadvantages: The balloon may obscure part of the imaging of the lower uterine segment. If the balloon is too large, it can cause significant distension pain for the patient. There is a very slight risk of the balloon rupturing. The catheter body is relatively thick, which can make insertion difficult in patients with cervical stenosis.

2. Vacuum Cup (Mushroom-Shaped) Type
Structure: Single-chamber design; a silicone, mushroom-shaped cup is placed over the external cervical os and secured via negative-pressure suction. It does not contain an internal balloon.
Characteristics
✅ Advantages: Does not extend deep into the uterine cavity; does not obstruct the view of the uterine cavity, allowing for a complete, unobstructed image; causes less pain; suitable for patients with abnormal uterine cavity morphology or those who wish to avoid the discomfort associated with balloon inflation.
❌ Disadvantages: Requires a specific cervical anatomy for effective use; the negative-pressure seal may fail—leading to fluid leakage—if the cervix is ​​deformed, eroded, or enlarged. Additionally, the procedure requires a negative-pressure suction device.

3. Standard Single-Lumen Catheter (Traditional/Basic Model)
Structure: Features a single infusion lumen; lacks a balloon or negative-pressure sealing mechanism. Requires the use of a metal tenaculum (cervical forceps) to stabilize the cervix.
Characteristics
✅ Advantages: Simple design and low cost; the catheter body is thin, allowing for gentle insertion.
❌ Disadvantages: Lacks a sealing mechanism, making the contrast medium highly prone to backflow and leakage; results in inconsistent imaging quality. It is used with decreasing frequency in clinical practice today.

II. Classification Based on the Presence of a Reinforcing Guidewire

1. Version with a Metal Reinforcing Guidewire
Features: Includes an internal stainless steel guidewire that increases catheter rigidity; the preferred choice for cases involving cervical stenosis or difficult cannulation. The guidewire can be removed. Disadvantage: Improper handling may cause abrasions to the uterine cavity.
2. Standard Version (Without Guidewire)
Features: The catheter body is flexible, resulting in minimal trauma. Suitable for routine imaging procedures where cervical conditions are favorable; however, it may be difficult to insert if there is significant resistance during cannulation.

III. Classification by Raw Material

1. Medical-grade Silicone (Mainstream in the domestic market)
Characteristics: Soft texture with a Shore hardness of 25–40; free from latex allergy risks; excellent balloon-forming properties. Disadvantages: The tube body is relatively soft, offering only moderate structural support.
2. Pebax/Polyurethane (Primarily for export)
Characteristics: Higher hardness, resulting in a stiffer tube body that facilitates smoother insertion; inherently radiopaque (visible under X-ray). Disadvantages: Feels firmer to the touch; higher cost.

IV. By Number of Lumens

1. Dual-lumen: The mainstream option on the market; features a channel for contrast agent and a separate channel for balloon inflation. The two channels are completely independent, with no cross-flow of fluids.
2. Triple-lumen (high-end): Includes an additional channel for pressure monitoring or irrigation. Primarily used for complex cases in reproductive medicine centers; these are higher-priced and see limited usage in the domestic market.