Transperineal US

13th July 2024, NIA Diagnostic Imaging

Preterm birth/labour (PTL) is the most common cause of neonatal mortality and morbidity. Preterm birth is defined as delivery prior to 37 weeks of gestation (1). In Australia, the preterm birth rate ranges from 8.3% in 2011 and 8.2% in 2021 with the highest in recent years at 8.7% in 2018 (2). Transvaginal ultrasound (TVUS) is considered as the gold standard in the measurement of cervical length (CL) and is routinely used as part of preterm labour’s risk assessment (4).

Indications for TVUS cervical length measurement in pregnancy (7):

CL <35mm on transabdominal ultrasound (TAUS)
Cervix is not well visualised on TAUS

However, TVUS is invasive and is often described as uncomfortable by patients (8,9). Contraindications of TVUS according to the ASA includes (10):

No consent obtained from patient
Cannot be done if high risk of labour is suspected

Other considerations where TVUS can be done but with great caution:

Placenta praevia +/- per vaginum (PV) bleeding. TVUS should be used discriminately and care must be taken during the advancement of the transducer into the vagina. The relationship between the tip of the transducer and the cervix should be continually assessed in real time.
PPROM (premature rupture of membrane) was considered a contraindication for TVUS as it may pose a risk of infections and reduce the latency period. A small study has shown that TVUS does not increase these risks. However, with little evidence and study available, the decision to use TVUS is dependent on the obstetric care provider and local protocols.

Thus, an alternative technique should be considered in the case when TVUS is contraindicated. Transperineal ultrasound (TPUS) is a non-invasive technique with high correlation to TVUS and is preferred by pregnant women in multiple research studies (5).

TPUS technique:

Informed consent must be obtained.
A low-frequency linear array transducer (4-7 MHZ) with sterile probe cover and gel are used.
The patient is scanned with an empty bladder in a lithotomy position with the hips elevated on a cushion to reduce rectal gas over the external os (7).
The transducer is placed externally on the labia or perineum, just posterior to the symphysis pubis in a mid-sagittal plane along the direction of the vagina (Figure 1).
The transducer is moved in oblique or parasagittal until the cervical canal, external and internal ora are in view (5, 6).
Cervical length measurement is done by placing the callipers at the internal and external ora (5) as shown in figure 2.

Advantages of TPUS

No additional ultrasound transducer required (3)
TPUS is non-invasive as it avoids direct contact with the cervix (3)
More comfortable and tolerable than TVUS (5)
Its non-invasive nature reduces the risk of (3)
- Infection
- Bleeding in the case of placenta previa
- Inaccurate measurement due to probe pressure in TVUS. This can lead to overtreatment and iatrogenic results or under treatment and preterm birth
- Triggering emergency episodes such as rupture membranes or cord prolapse

Reliability of TPUS

TPUS has a 95% sensitivity and a 100% specificity (3)
High correlation with TVUS with interobserver reliability (5)
Estimated difference in CL measurements between TVUS and TPUS was only 0.2mm (5)

Limitation of TPUS

Shadowing caused by pubis symphysis or/and bowel gas. However, elevating the hips can reduce this issue (5).
The inexperience of sonographers. However, this can be eliminated with training (6).

In conclusion, transperineal ultrasound has proven to be a suitable alternative technique in cervical length measurement in obstetric ultrasound.

At NIA Diagnostic Imaging, our sonographers are highly proficient and dedicated to obtaining optimal sonographic images for precise diagnosis. We recognise that transvaginal ultrasound may not be suitable for every female patient’s comfort. Therefore, we are committed to employing alternative techniques to ensure comprehensive measurements and scans, prioritising patient comfort throughout the process.

References

RANZCOG, 2021, “Measurement of cervical length for prediction of preterm birth”, RANZCOG, viewed 5th July 2024, <https://ranzcog.edu.au/wp-content/uploads/2022/05/Measurement-of-cervical- length-for-prediction-of-preterm-birth-C-Obs-27_Board-approved-March-2022.pdf >
AIHW, 2023, Australia’s mothers and babies, AIHW, viewed 5th July 2024 <https://www.aihw.gov.au/reports/mothers-babies/australias-mothers-babies/contents/summary>
Krief, D, Foulon, A, Tondreau, A, Diouf, M, Sergent, F, Gondry, J & Chevreau, J 2023, ‘Transperineal ultrasound in routine uterine cervix measurement’, Archives of Gynecology and Obstetrics, vol. 307, no. 2, pp. 387–393.
Clinical Trial: Evaluation of Transperineal Ultrasound Technic for Diagnostic Shorted Cervical Length for Pregnant Women (2nd and 3rd Trimester) Compared to Endovaginal Technic (Gold Standard) 2020, US Fed News Service, Including US State News, HT Digital Streams Limited, Washington, D.C.
Songserm, V, Komwilaisak, R, Saksiriwuttho, P & Kongwattanakul, K 2019, ‘Transperineal versus transvaginal sonographic measurements of cervical length in pregnant women between 16 and 24 weeks of gestation’, Journal of Clinical Ultrasound, vol. 47, no. 7, pp. 389–393.
Ho, KKW, Wong, CK, Hung, CMW & Lau, WL 2024, ‘Transperineal ultrasound measurement of cervical length to predict preterm delivery in women with threatened preterm labour’, Hong Kong Journal of Gynaecology, Obstetrics, and Midwifery = Xianggang Fu Chan Zhu Chan Ke Za Zhi, vol. 24, no. 1, pp. 8–12.
Newnham JP, White SW, Meharry S, Lee HS, Pedretti MK, Arrese CA, Keelan JA, Kemp MW, Dickinson JE, Doherty DA. Reducing preterm birth by a statewide multifaceted program: an implementation study. Am J Obstet Gynecol 2017;216(5):434-42
Meijer-Hoogeveen M, Stoutenbeek P, Visser GH. Methods of sonographic cervical length measurement in pregnancy: a review of the literature. J Matern Fetal Neonatal Med 2006;19:755-62
Larscheid P, Maass N, Kennes LN, Najjari L (2015) Transperineal ultrasound to measure cervical length of pregnant women in general and in particular with cervical insufciency—a comparison of transabdominal and transperineal ultrasound as alternatives to transvaginal ultrasound. Ultraschall Med 36:59–64
Thoirs, K, O’Hara, S, Quinton, A, Coombs, P, Srayko, S, Spurway, J, … O’Brien, S 2024, ‘Ultrasound assessment of the gravid cervix to assess for risk of spontaneous preterm birth: Introducing an evidence‐based clinical guideline for sonographers’, Sonography, vol. 11, no. 2, pp. 113–125.
Salsi G, Cataneo I, Dodaro G, Rizzo N, Pilu G, Sanz Gascòn M, Youssef A. Three-dimensional/four- dimensional transperineal ultrasound: clinical utility and future prospects. Int J Womens Health. 2017;9:643-656. https://doi.org/10.2147/IJWH.S103789
Amin, M. A., Eltomey, M. A., & El-Dorf, A. A. (2014). Role of transperineal ultrasound measurements in women with prolonged second stage of labor as predictors of the mode of delivery. Egyptian Journal of Radiology and Nuclear Medicine, 45(4), 1295–1299. https://doi.org/10.1016/j.ejrnm.2014.05.01

PFO Closure

Furlan AJ, Reisman M, Massaro J, et al. Closure or medical therapy for cryptogenic stroke with patent foramen ovale. N Engl J Med 2012; 366: 991–

A multicenter, randomized, open-label trial of closure with a percutaneous device, as compared with medical therapy alone, in patients between 18 and 60 years of age who presented with a cryptogenic stroke or transient ischemic attack (TIA) and had a patent foramen ovale. The primary end point was a composite of stroke or transient ischemic attack during 2 years of follow-up, death from any cause during the first 30 days, or death from neurologic causes between 31 days and 2 years.

Results:

Primary end point was 5.5% in the closure group as compared with 6.8% in the medical-therapy group (adjusted hazard ratio, 0.78; 95% confidence interval, 0.45 to 1.35; P = 0.37)

Conclusion:

“In patients with cryptogenic stroke or TIA who had a patent foramen ovale, closure

with a device did not offer a greater benefit than medical therapy alone for the

prevention of recurrent stroke or TIA”

2 Saver JL, Carroll JD, Thaler DE, et al. Long-term outcomes of patent foramen ovale closure or medical therapy after stroke. N Engl J Med 2017; 377: 1022–

A multicenter, randomised, open-label trial ,randomly assigned patients 18 to 60 years of age who had a patent foramen ovale (PFO) and had had a cryptogenic ischemic stroke to undergo closure of the PFO (PFO closure group) or to receive medical therapy alone (aspirin, warfarin, clopidogrel, or aspirin combined with extended-release dipyridamole; medical-therapy group). The primary efficacy end point was a composite of recurrent nonfatal ischemic stroke, fatal ischemic stroke, or early death after randomisation.

Results:

Recurrent ischemic stroke occurred in 18 patients in the PFO closure group and in 28 patients in the medical-therapy group, resulting in rates of 0.58 events per 100 patient-years and 1.07 events per 100 patient years, respectively (hazard ratio 0.55; 0.31 – 0.999; P = 0.046)

Conclusion:

“Among adults who had had a cryptogenic ischemic stroke, closure of a PFO was associated with a lower rate of recurrent ischemic strokes than medical therapy alone during extended follow-up.”

Meier B, Kalesan B, Mattle HP, et al. Percutaneous closure of patent foramen ovale in cryptogenic embolism. N Engl J Med 2013; 368: 1083–

A prospective, multicenter, randomised, event-driven trial, randomly assigned patients to medical therapy alone (anti-platelet or warfarin therapy) or closure of the patent foramen ovale.

Results:

9 patients in the closure group and 16 in the medical-therapy group had a recurrence of stroke (hazard ratio with closure, 0.49; 0.22 – 1.11; P = 0.08). The primary analysis of the intentionto- treat cohort showed a nominal 51% hazard rate reduction with closure, but the reduction did not reach significance.

Conclusions:

” …there was no significant benefit associated with closure of a patent foramen ovale in adults who had had a cryptogenic ischaemic stroke.”

Sondergaard L, Kasner SE, Rhodes JF, et al. Patent foramen ovale closure or antiplatelet therapy for cryptogenic stroke. N Engl J Med 2017; 377: 1033–

Multinational trial involving patients with a PFO who had had a cryptogenic stroke, randomly assigned patients to undergo PFO closure plus antiplatelet therapy or to receive antiplatelet therapy alone.

Results:

During a median follow-up of 3.2 years, clinical ischemic stroke occurred in 6 of 441 patients (1.4%) in the PFO closure group and in 12 of 223 patients (5.4%) in the antiplatelet-only group (hazard ratio, 0.23; 0.09 to 0.62; P=0.002).

Conclusions:

“Among patients with a PFO who had had a cryptogenic stroke, the risk of subsequent ischemic stroke was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone; however, PFO closure was associated with higher rates of device complications and atrial fibrillation.”

Mas JL, Derumeaux G, Guillon B, et al. Patent foramen ovale closure or anticoagulation vs. antiplatelets after stroke. N Engl J Med 2017; 377: 1011–

In a multicenter, randomised, open-label trial patients 16-60 years of age who had had a recent stroke attributed to PFO, to transcatheter PFO closure plus long-term antiplatelet therapy, antiplatelet therapy alone or oral anticoagulation.

Results:

No stroke occurred among patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet- only group (hazard ratio, 0.03; 0 to 0.26; P<0.001). Large number of patients discontinued anti-coagulation in the anti-coagulant group and statistical significance was not analysed because the study was not adequately powered to compare outcomes.

Conclusion:

“Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation.”

Lee PH, Song J-K, Kim JS, et al. Cryptogenic stroke and high-risk patent foramen ovale: the DEFENSE-PFO Trial. J Am Coll Cardiol 2018; 71: 2335–

Patients with cryptogenic stroke and high-risk PFO were divided between a transcatheter PFO closure and a medication-only group.

Results:

No events occurred in the PFO closure group. 12.9% of patients in the medication group had an event (p= 0.023).

Conclusion:

“PFO closure in patients with high-risk PFO characteristics resulted in a lower rate of the primary endpoint as well as stroke recurrence”