This study is a multicenter, randomized (each group was assigned 1:1), double-blind controlled trial.

This study aims to investigate if lidocaine injection into the single-use micro-non-invasive injection cervical dilator (short for disposable cervical dilators) leads to better pain control efficacy compared with normal saline injection in intrauterine device(short for IUD) removal surgery. Furthermore, this study aims to compare cervical dilation degree, safety, and patient satisfaction between groups.

Research objects Between August 1, 2023, and August 1, 2025, 74 healthy women who voluntarily request the removal of the intrauterine device under local anesthesia in Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine.

The subjects will be dividied into two groups at random.

1. Trial group: disposable cervical dilator stick combined with lidocaine hydrochloride injection.
2. Control group: disposable cervical dilator stick combined with normal saline injection.

Intervention measures:

The nurse fill the syringe with 5ml of either 2% lidocaine hydrochloride injection or normal saline based on the group allocation specified. The appearance of the two drugs is indistinguishable after loading.

The subject will undergo routine disinfection and receive cervical paracervical nerve block anesthesia. After waiting for 2 minutes, the researcher gently checks the depth of the uterine cavity with a probe and then remove it. After that, the researcher tries to insert a number 10 to 4 metal Hegar dilator in sequence, until passes through the internal cervical orifice without resistance. The nurse connects the disposable cervical dilator to the syringe containing drug. The researcher inserts the disposable cervical dilator into the cervical canal in line with the probe direction, and slowly inject drug from the syringe into it within a minute. The researcher waits for another minute before removing the disposable cervical dilator. After that, the researcher tries to insert a number 10 to 4 metal Hegar dilator in sequence, until passes through the internal cervical orifice without resistance.

The researcher removes the IUD with a ring hook. If necessary, the researcher will use metal Hegar dilators to dilate cervi. The subject uses VAS to evaluate the degree of pain before, during and after surgery. Oral antibiotics were routinely given post-surgery to prevent infection.

Inclusion Criteria:

1. Age ≥18 and <65 years old;
2. Voluntary request for removal of intrauterine device under local anesthesia;
3. No known allergic reactions or sensitivity to lidocaine, physiological saline and polyvinyl formaldehyde polymer materials in the past;
4. Volunteer participation in this study.

Exclusion Criteria:

1. Dysplasia of uterine cavity structure;
2. Known lesions such as uterine fibroids that compress and cause uterine cavity deformation;
3. Presence of untreated acute cervicitis or pelvic inflammatory diseases;
4. History of cervical surgery;
5. Systemic diseases that can affect pain perception;
6. Current or past use of illegal drugs or anesthetic and analgesic drugs;
7. Unable to understand how to score pain using Visual Analog Scale (short for VAS).

If necessary, other researchers can ask us to share the raw data via email after the results are published.