How should I check the Mirena (levonorgestrel intrauterine system) strings, and what should I do if they are not palpable or appear abnormal?

Mirena String Checking and Management

Patients should be taught to check for Mirena strings by inserting clean fingers into the vagina to feel for the strings protruding from the cervix, and if strings are not palpable or appear abnormal, perform a speculum examination to visualize them—if still not visible, obtain pelvic ultrasound to locate the device and rule out expulsion or perforation. 1

Routine String Checks

Patient Self-Examination

• Instruct patients to periodically check for the presence of IUD strings by inserting clean fingers into the vagina to palpate the strings extending from the cervical os 1
• This can be performed monthly, particularly after menses when expulsion risk may be higher
• Patients should be counseled that inability to feel strings does not necessarily indicate a problem, but warrants clinical evaluation

Clinical Follow-Up

• At routine follow-up visits, consider performing a speculum examination to check for the presence of IUD strings 1
• No mandatory routine follow-up visit is required solely for string checks; patients should be advised to return at any time to discuss concerns 1
• Advise patients when the device needs to be removed based on its duration of effectiveness

Management When Strings Are Not Visible

Initial Assessment

• Perform a careful speculum examination to visualize the cervix and attempt to locate the strings 1
• Use a cytobrush or cotton swab to gently rotate within the cervical canal to retrieve strings that may have retracted
• Rule out pregnancy first with urine or serum testing, as this is a critical differential diagnosis 1

If Strings Cannot Be Retrieved in Office

When strings are not visible and cannot be retrieved safely from the cervical canal:

• Perform or refer for pelvic ultrasound examination to determine the location of the IUD 1
• Ultrasound can confirm intrauterine location, identify expulsion, or detect uterine perforation 1
• If the IUD cannot be located by ultrasound, it may have been expelled or perforated the uterine wall 1

Ultrasound-Guided Removal

• Ultrasound guidance is effective for IUD removal when strings are not visible and conventional office procedures have failed 2
• In one prospective study, ultrasound-guided removal was successful in 33 of 38 cases (86.8%) without complications when office procedures had failed 2
• This approach can avoid the need for more invasive hysteroscopic removal 2

If Device Is Confirmed Intrauterine

• If ultrasonography confirms the IUD is inside the uterus but strings remain non-visible, advise the patient to seek care promptly if they develop heavy bleeding, cramping, pain, abnormal vaginal discharge, or fever 1
• The device can remain in place if properly positioned and the patient is asymptomatic
• Refer for hysteroscopic removal if the patient desires removal or if removal is medically indicated

Critical Situations Requiring Immediate Action

Pregnancy with IUD in Place

If a patient with non-visible strings is found to be pregnant:

• Immediately evaluate for possible ectopic pregnancy 1
• If strings become visible or can be retrieved safely, remove the IUD as soon as possible by pulling gently on the strings 1
• Counsel that leaving the IUD in place substantially increases risks for spontaneous abortion (including life-threatening septic abortion), preterm delivery, and infection 1
• For LNG-IUDs specifically, when not removed during pregnancy, 8 in 10 pregnancies ended in spontaneous abortion in one case series 1

Warning Signs

Advise all patients to seek prompt care if they experience:

• Heavy bleeding
• Cramping or pelvic pain
• Abnormal vaginal discharge
• Fever 1

Common Pitfalls to Avoid

• Do not attempt blind instrumentation of the uterine cavity without ultrasound guidance, as this risks perforation
• Do not assume the device has been expelled without imaging confirmation—uterine perforation must be ruled out 1
• Do not delay pregnancy testing when strings are missing, as management differs significantly if pregnancy is present 1
• Do not use sharp instruments that could cut the retrieval system during attempted removal 3