Intrauterine contraceptive device (IUCD) is the most common method for reversible contraception in women because it is safe, inexpensive and readily available . Uterine perforation and migration of the IUCD into abdominal or pelvic organs is a major complication of IUCD insertion  with an incidence of 1.9–3.6 per 1000 insertions . Factors influencing the risk of perforation include the type of IUCD used, the time of insertion, the insertion technique, and anatomy of the cervix and uterus . The exact mode of uterine perforation and IUCD migration is unclear . However, it is believed that perforation mostly occurs at the time of insertion but may also occur spontaneously at a later time or during puerperium .
The presence of pain and bleeding per vaginam after IUCD insertion suggests that uterine perforation may have occurred at the time of insertion . Secondary perforation may be due to slow migration through the myometrium which may be enhanced by spontaneous uterine contractions . When a pregnancy occurs in a patient with an IUCD, there must be a high suspicion of uterine perforation and possible migration . IUCDs which migrate to the urinary bladder are either located in the bladder wall or within the bladder lumen .
Most patients with intravesical migration of IUCD are symptomatic  with UTI being the most common presentation . The patient in this case presented with persistent UTI.
Transvaginal ultrasonography is the investigation of choice for locating the intravesical IUCD . However, in this case a transabdominal ultrasonography by the radiologist showed the intravesical IUCD as a bladder calculus. Ultrasonography is operator-dependent and this may have accounted for the failure to detect the IUCD by the gynaecologist.
Cystoscopy is another means of visualising the intravesical IUCD and is helpful for its removal .
All IUCDs which have migrated into the urinary bladder must be removed even if they are asymptomatic. This is to prevent complications such as calculus formation and bladder rupture .
An IUCD which has migrated into the urinary bladder is treated by cystoscopic removal or by open suprapubic cystotomy .
Cystoscopic removal is preferred because it has a low morbidity and is highly effective . In this case, cystoscopic removal was done successfully. Open surgery is currently restricted to centres without cystoscopic facilities and also for the removal of IUCDs with calculus formation that are not amenable to cystoscopic removal . Laparoscopic removal, a minimally invasive alternative to open surgery can also be used .