Department of Obstetrics and Gynaecology, Kwong Wah Hospital, Hong Kong.
Address for correspondence: Dr WL Lau, Department of Obstetrics and Gynaecology, Kwong Wah Hospital, 25 Waterloo Road, Kowloon, Hong Kong SAR, China.

Case report

A 41 years old (G9P2) woman with cervical incompetence and repeated cerclages in her four consecutive pregnancies presented to our department. She underwent elective cerclage at 12 weeks of pregnancy, performed by her private obstetrician. Salvage cerclage had to be done at our unit at 22 weeks due to loosened stitch of the previous cerclage and concomitant increased vaginal discharge. During the operation, the cervix was dilated with 2 cm bulging membrane. The posterior cervical lip was 1cm thick, deficient, with evidence of old tear. A MacDonald cerclage was performed with Mersilene tape and the knot was tied at 12 o’clock position. Ultrasound examination was subsequently performed at 23 weeks revealing a herniated sac of 1cm diameter passing through the intact cerclage. The finding was well shown by the 3D render mode image from transperineal approach. The pregnancy ended up with preterm rupture of membrane at 30 weeks and a baby girl weighing 1.18 kg (Apgar score 8, 10) was delivered after removal of the cerclage.

Images 1, 2: 23 weeks - transabdominal view; the image 1 represents a drawing explaining the structures that can be seen on the image 2 (“herniated amniotic sac” passes and bulges out of the cervix).

Images 3, 4: 23 weeks; transperineal scan revealed similar finding as shown on images 1 and 2, with better resolution of the cerclage stitch (arrows).

Images 5, 6: 23 weeks; transperineal 3D scans demonstrate the “herniated amniotic sac” much clearer by multi-planar and render mode. The knot (yellow arrow) was located at 12 o’clock position. The "black hole" within the ring-shaped cerclage stitch represents the herniated sac.

Discussion

The cervix can be visualized clearly by transperineal sonography in about 80% of patients in second trimester [1]. Transperineal scanning could be useful in assessing the cervical status in patients after cervical cerclage. This has the additional advantage of avoiding the discomfort and anxiety of the patient during transvaginal scan and might reduce the potential risk of infection or even vaginal bleeding. To our knowledge, 3D image of the cervical cerclage has been reported only by transvaginal scan [2] but not by transperineal scan. The unique features of the present case are well shown by 3D render image of the cerclage and the herniated sac inside the cerclage.

References

1. Cicero S, Skentou C, Souka A, To MS, Nicolaides KH. Cervical length at     22-24 weeks of gestation: comparison of transvaginal and transperineal-translabial ultrasonography. Ultrasound Obstet Gynecol 2001;17(4):335–340.
2. Bega G, Lev-Toaff A, Kuhlman K, Berghella V, Parker L, Goldberg B, Wapner R. Three-dimensional multiplanar transvaginal ultrasound of the cervix in pregnancy. Ultrasound Obstet Gynecol 2000; 16(4):351-8.