To evaluate the safety and effectiveness of Grency venous stent system in the treatment of iliac vein stenosis or occlusion.

The purpose of this study was to evaluate the safety and effectiveness of a new dedicated venous stent system (Grency) in the treatment of iliac vein stenosis or occlusion. The Grency stent system has a hybrid oblique self-expanding design, which allows precise positioning at the iliocaval confluence.

Inclusion Criteria:

1. subjects aged 18-80 years;
2. CEAP clinical grade C >=3;
3. iliac vein stenosis >=50% or occlusion;
4. patients voluntarily sign informed consent and complete follow-up.

Exclusion Criteria:

1. subjects in pregnancy or lactation;
2. renal insufficiency;
3. subjects are allergic to contrast agents and anesthetics;
4. subjects are allergic to nitinol;
5. the life expectancy of cancer patients is less than 1 year;
6. the length of the stent is expected to exceed the length of the inguinal ligament; 7. both sides of iliac vein stents were required;

8. long term bedridden or wheelchair patients; 9. the target vessel of the subject has been implanted into the iliac vein stent; 10. subjects have anticoagulant contraindications or are unable to receive long-term new oral anticoagulant therapy; 11. the investigator judged that the subjects had poor compliance and could not complete the clinical trial; 12. subjects are participating in clinical trials of other drugs or medical devices and have not yet completed the primary end point of the study.