Diagnostic ultrasound ( PDFDrive )

1506 PART IV Obstetric and Fetal Sonography
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FIG. 44.15 Funneling After Cervical Cerclage. (A) Transvaginal scan demonstrates mild protrusion of the membranes. There remains 10-mm
closed cervix length (calipers) above the sutures (arrows). (B) Transvaginal scan demonstrates protrusion of the membranes to the level of the
sutures (arrows). The residual closed cervix length below the cerclage sutures measures 10 mm (calipers). (C) Transvaginal scan demonstrates
protrusion of the membranes beyond the sutures (arrows). H, Fetal head; * indicates amniotic luid sludge.
• Physical examination indicated (“rescue”) cerclage: in
patients presenting with advanced cervical dilation in the
absence of labor or abruptio placentae. Limited data from
one small randomized trial and retrospective studies have
suggested the possibility of beneit from cerclage placement
in these women. 83
• Sonographic inding of a short cervix (<25 mm) before
24 weeks of gestation in patient with singleton pregnancy
and prior history of PTB less than 34 weeks of
gestation.
Numerous studies have compared perinatal outcome in cerclage
patients treated with history-indicated cerclage versus those
monitored with serial TVS examinations that have been treated
with an ultrasound-indicated cerclage as needed. Two recent
summaries of the results of these multiple studies have drawn
the following conclusions, which are limited to singleton
pregnancies:
1. Most patients at risk of cervical insuiciency can be
safely monitored with serial TVS examinations in the
second trimester. 87,88
2. History-indicated cerclage procedures can be avoided in
more than one-half of the patients who undergo serial
TVS cervical length monitoring. 87,89
3. Duration of surveillance should begin at 16 weeks and
end at 24 weeks of gestation. 87
4. Although women with a current singleton pregnancy, prior
SPTB at less than 34 weeks of gestation, and short cervical
length (<25 mm) before 24 weeks of gestation do not meet
the diagnostic criteria for cervical insuiciency, available
evidence suggests that cerclage placement may be efective
in this setting 90,91 Cerclage is associated with signiicant
decreases in PTB outcomes, as well as improvements in
composite neonatal morbidity and mortality.
Sonography has been used in the operating room to guide
the placement of cervical cerclage, especially when the cervix is
short, to ensure that the suture material is placed within the
cervical tissue and does not encroach on bladder mucosa or
rectum. Once in place, the cervical cerclage will appear as one
or more echodense “dots” along the length of the cervical canal
FIG. 44.16 Abdominal Cervical Cerclage. Transvaginal longitudinal
scan demonstrates hyperechoic sutures (arrows) at the internal os in
this woman with a history of incompetent cervix. The cervix is closed
and long, measuring 4.5 cm (calipers).
(Fig. 44.14). Postcerclage evaluation includes location of the
sutures in relation to both the internal and the external cervical
os and measurement of the length of the closed cervical canal
both above and below the level of the suture line. Once the
cerclage has been placed, cervical length assessment continues
to have value in the prediction of SPTB. Several studies reported
that if the residual total closed cervical length ater cerclage
placement was less than 15 mm, or if “funneling to stitch” (open
canal to level of suture line) was present (Fig. 44.15), the patient
was at signiicantly increased risk of delivery before 32 weeks’
gestation, regardless of the indication for stitch placement. 68,92,93
Beyond 30 weeks, there was no predictive value of cervical
assessment in women with a cerclage.
When the vaginal portion of the cervical tissue is absent or
damaged (trachelectomy, cone biopsy, birth trauma), the placement
of a cerclage in the vaginal component of the cervix is not
possible. Alternatively, a cerclage can be placed at the level of
the cervicouterine isthmus either by laparoscopy or laparotomy.
On TVS assessment, the echodense dots of this “abdominal”
cerclage will be visualized close to the bladder and adjacent to
the lower uterine segment (Fig. 44.16).
Who Should Not Get a Cerclage? Incidentally detected
short cervical length in the second trimester in the absence of
a prior singleton PTB is not diagnostic of cervical insuiciency,