One common reason for difficult IUD removal is that the IUD strings are "missing"—that is, they cannot be located in the vagina near the cervix (342). Usually, the strings have slipped up into the cervical canal, perhaps because they were cut too short at insertion. After ruling out pregnancy, the health care provider can use narrow forceps to probe the cervical canal and draw out the strings. A study in the UK found that missing strings could be retrieved this way in 50% of cases (202). If this fails, the strings may have retracted into the uterine cavity, or the IUD may have been expelled without the woman's knowledge. A sound can be used to check whether the IUD is in place. Vacuum aspiration can be used to find the strings. This usually dislodges the IUD (130). If the strings cannot be retrieved, IUDs can be removed from the uterus with forceps, curettes, or hooks. The provider must be very careful not to injure the uterus.

A less common reason for difficult removal is that the IUD has partially or completely perforated the uterus or become embedded in the uterine wall. Perforation should be suspected particularly if the woman is experiencing abdominal or pelvic pain or irregular bleeding (449). If facilities are available, x-rays, hysterography (x-rays of the uterine cavity after instillation of a contrast medium), hysteroscopy (direct visualization of the uterine cavity with a fiberoptic instrument), or sometimes ultrasound imaging can be used to diagnose perforation and embedding (7, 15, 133, 237, 303, 449). Only experienced clinicians should attempt to remove an embedded or perforating IUD (614).