Osmotic dilator

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Osmotic dilators prior to expansion. Dilapan-S (left). Laminaria (right) Osmotic dilators 1.jpg
Osmotic dilators prior to expansion. Dilapan-S (left). Laminaria (right)

Osmotic dilators, also known as hygroscopic dilators, are medical implements used to dilate the uterine cervix by swelling as they absorb fluid from surrounding tissue. [1] They may be composed of natural or synthetic materials. A laminaria stick or tent is a thin rod made of the stems of dried Laminaria , a genus of kelp. Laminaria sticks can be generated from Laminaria japonica [2] and Laminaria digitata. [3] Second generation dilators such as Dilapan-S are composed of polyacrylonitrile, a plastic polymer. [4] The hygroscopic nature of the polymer causes the dilator to absorb fluid and expand.

Contents

Use in obstetrics and gynecology

Osmotic dilators are most commonly used to slowly dilate and soften the cervix prior to surgical abortion, a process referred to as cervical preparation. Adequate cervical preparation is important prior to surgical abortions because it helps to prevent complications of dilation and evacuation (D&E), such as laceration of the cervix. [5] Cervical preparation can be accomplished with osmotic dilators, with medications such as prostaglandins and/or mifepristone, or with a combination of these. However, there is no consensus as to which cervical preparation method is superior in terms of safety and efficacy. [6]

At later gestational ages, osmotic dilators, including laminaria, may be used to assist in dilating the cervix. Most abortion providers use laminaria, Dilapan-S, or both for osmotic dilation prior to surgical abortion after 16–18 weeks gestation. [7]

Osmotic dilators may also be used to achieve cervical dilation prior to gynecology procedures, such as hysteroscopy or dilation and curettage of the non-pregnant uterus, [8] although this is uncommon.

Placement

Osmotic dilators after soaking in water for 24 hours. Dilapan-S (left). Laminaria (right). This does not represent the amount of expansion that will be occur when used in humans. Osmotic dilators 3.jpg
Osmotic dilators after soaking in water for 24 hours. Dilapan-S (left). Laminaria (right). This does not represent the amount of expansion that will be occur when used in humans.

Prior to a planned surgical abortion, osmotic dilator(s) may be inserted into a woman's cervix. A speculum is placed in the vagina to allow the provider to see the uterine cervix. A tenaculum may be placed on the anterior lip of the cervix to straighten the cervical canal and hold the cervix steady. Pain medications may be administered via a paracervical block. The dilator is then grasped with a ring forceps and is placed into the cervix so that it spans both the internal cervical os and external cervical os. Over time, the osmotic dilator absorbs fluid and swells to 3-4 times the initial diameter. [9] Most of the increase in size occurs within 6 hours after the dilator are placed in the cervix, though further expansion will continue over 12–24 hours. [7] The number of osmotic dilators placed depends on the degree of cervical dilation that is sought. This may be affected by the gestational age of the pregnancy and history of prior vaginal deliveries. More dilators are generally used with advancing gestational age. [10]

Laminaria tents are usually left in place overnight. [6] [11]

Mechanism of action

Laminaria function by absorbing fluid from the surrounding tissue and expanding. Thus exerts radial pressure on the cervix. They also cause the release of prostaglandins. [12]

Removal

Laminaria are removed prior to initiating the D&E, after they have started the process of dilating the cervix. They are removed by grasping the strings of the dilator and applying gentle traction. The cervix may be dilated further using rigid cervical dilators which serially increase in diameter. [11]

Effectiveness

There is no evidence regarding the risk of not achieving vaginal delivery within 24 hours with laminaria compared to prostaglandin E2 but there may be a lower risk of uterine hyperstimulation with laminaria. It is not certain whether the risks of caesarian section, perinatal death or maternal death are reduced or increased with laminaria compared with vaginal or cervical prostaglandin E2. [13]

Risks

The incidence of complications related to osmotic [1] dilator use prior to abortion has not been systematically studied and reported, but serious complications appear to be very rare. [8] Risks of osmotic dilator insertion include pain, [14] rupture of amniotic membranes, initiation of labor, cervical or uterine perforation, retention of the dilator, and infection. [8] [7]

Original Dilapan dilators were prone to fracturing under tension during removal which sometimes led to retention of dilator fragments within the uterus. [8] Dilapan was subsequently removed from the market and replaced with Dilapan-S which is less prone to fragmentation. [8] Dilapan may expand unevenly within the cervix and develop a dumbbell shape which can result in difficult removal.

Related Research Articles

Dilationand curettage (D&C) refers to the dilation of the cervix and surgical removal of sections and/or layers of the lining of the uterus and or contents of the uterus such as an unwanted fetus, remains of a non-viable fetus, retained placenta after birth or abortion as well as any abnormal tissue which may be in the uterus causing abnormal cycles by scraping and scooping (curettage). It is a gynecologic procedure used for treatment and removal as well as diagnostic and therapeutic purposes, and is the most commonly used method for first trimester abortion or miscarriage.

Intact dilation and extraction is a surgical procedure that terminates and removes an intact fetus from the uterus. The procedure is used both after miscarriages and for abortions in the second and third trimesters of pregnancy. When used to perform an abortion, an intact D&E can occur after feticide or on a live fetus.

<span class="mw-page-title-main">Misoprostol</span> Medication to induce abortion and treat ulcers

Misoprostol is a synthetic prostaglandin medication used to prevent and treat stomach and duodenal ulcers, induce labor, cause an abortion, and treat postpartum bleeding due to poor contraction of the uterus. It is taken by mouth when used to prevent gastric ulcers in people taking nonsteroidal anti-inflammatory drugs (NSAID). For abortions it is used by itself or in conjunction with mifepristone or methotrexate. By itself, effectiveness for abortion is between 66% and 90%. For labor induction or abortion, it is taken by mouth, dissolved in the mouth, or placed in the vagina. For postpartum bleeding it may also be used rectally.

A pessary is a prosthetic device inserted into the vagina for structural and pharmaceutical purposes. It is most commonly used to treat stress urinary incontinence to stop urinary leakage and to treat pelvic organ prolapse to maintain the location of organs in the pelvic region. It can also be used to administer medications locally in the vagina or as a method of contraception.

<span class="mw-page-title-main">Vaginal bleeding</span> Medical condition

Vaginal bleeding is any expulsion of blood from the vagina. This bleeding may originate from the uterus, vaginal wall, or cervix. Generally, it is either part of a normal menstrual cycle or is caused by hormonal or other problems of the reproductive system, such as abnormal uterine bleeding.

<span class="mw-page-title-main">Hysteroscopy</span> Medical procedure

Hysteroscopy is the inspection of the uterine cavity by endoscopy with access through the cervix. It allows for the diagnosis of intrauterine pathology and serves as a method for surgical intervention.

Cervical dilation is the opening of the cervix, the entrance to the uterus, during childbirth, miscarriage, induced abortion, or gynecological surgery. Cervical dilation may occur naturally, or may be induced surgically or medically.

Bloody show or show is the passage of a small amount of blood or blood-tinged mucus through the vagina near the end of pregnancy. It is caused by thinning and dilation of the cervix, leading to detachment of the cervical mucus plug that seals the cervix during pregnancy and tearing of small cervical blood vessels, and is one of the signs that labor may be imminent. The bloody show may be expelled from the vagina in pieces or altogether and often appears as a jelly-like piece of mucus stained with blood. Although the bloody show may be alarming at first, it is not a concern of patient health after 37 weeks gestation.

<span class="mw-page-title-main">Vacuum aspiration</span> Gynaecological procedure

Vacuum or suction aspiration is a procedure that uses a vacuum source to remove an embryo or fetus through the cervix. The procedure is performed to induce abortion, as a treatment for incomplete spontaneous abortion or retained fetal and placental tissue, or to obtain a sample of uterine lining. It is generally safe, and serious complications rarely occur.

Dilation and evacuation (D&E) or dilatation and evacuation is the dilation of the cervix and surgical evacuation of the uterus after the first trimester of pregnancy. It is a method of abortion as well as a common procedure used after miscarriage to remove all pregnancy tissue.

<span class="mw-page-title-main">Cervical effacement</span> Thinning and shortening of the cervix

Cervical effacement or cervical ripening refers to the thinning and shortening of the cervix. This process occurs during labor to prepare the cervix for dilation to allow the fetus to pass through the vagina. While this is a normal, physiological process that occurs at the later end of pregnancy, it can also be induced through medications and procedures.

Cervical weakness, also called cervical incompetence or cervical insufficiency, is a medical condition of pregnancy in which the cervix begins to dilate (widen) and efface (thin) before the pregnancy has reached term. Definitions of cervical weakness vary, but one that is frequently used is the inability of the uterine cervix to retain a pregnancy in the absence of the signs and symptoms of clinical contractions, or labor, or both in the second trimester. Cervical weakness may cause miscarriage or preterm birth during the second and third trimesters. It has been estimated that cervical insufficiency complicates about 1% of pregnancies, and that it is a cause in about 8% of women with second trimester recurrent miscarriages.

<span class="mw-page-title-main">Endometrial ablation</span> Medical procedure

Endometrial ablation is a surgical procedure that is used to remove (ablate) or destroy the endometrial lining of the uterus. The goal of the procedure is to decrease the amount of blood loss during menstrual periods. Endometrial ablation is most often employed in people with excessive menstrual bleeding, who do not wish to undergo a hysterectomy, following unsuccessful medical therapy.

Prostaglandin E<sub>2</sub> Chemical compound

Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and in newborn babies to keep the ductus arteriosus open. In babies it is used in those with congenital heart defects until surgery can be carried out. It is also used to manage gestational trophoblastic disease. It may be used within the vagina or by injection into a vein.

Instillation abortion is a rarely used method of late-term abortion, performed by injecting a solution into the uterus.

<span class="mw-page-title-main">Hematometra</span> Medical condition

Hematometra is a medical condition involving collection or retention of blood in the uterus. It is most commonly caused by an imperforate hymen or a transverse vaginal septum.

A paracervical block is an anesthetic procedure used in obstetrics and gynecology, in which a local anesthetic is injected into between two and six sites at a depth of 3–7 mm alongside the vaginal portion of the cervix in the vaginal fornices. In the United States, the paracervical block is underutilized during insertion of intrauterine devices (IUDs). There is speculation that this is related to the disproportionate under-researching of women's health.

Early pregnancy bleeding is vaginal bleeding before 14 weeks of gestational age. If the bleeding is significant, hemorrhagic shock may occur. Concern for shock is increased in those who have loss of consciousness, chest pain, shortness of breath, or shoulder pain.

A medical abortion, also known as medication abortion or non-surgical abortion, occurs when drugs (medication) are used to bring about an abortion. Medical abortions are an alternative to surgical abortions such as vacuum aspiration or dilation and curettage. Medical abortions are more common than surgical abortions in most places around the world.

Müllerian duct anomalies are those structural anomalies caused by errors in Müllerian duct development as an embryo forms. Factors contributing to them include genetics and maternal exposure to substances that interfere with fetal development.

References

  1. 1 2 "Cervical (Osmotic) Dilator". MyHealth.Alberta.ca. Government of Alberta. Retrieved 6 August 2019.
  2. ↑ "Dilateria - Laminaria - for Cervical Dilation". Cooper Surgical. Retrieved 2019-07-09.
  3. ↑ Kazzi GM, Bottoms SF, Rosen MG (October 1982). "Efficacy and safety of Laminaria digitata for preinduction ripening of the cervix". Obstetrics and Gynecology. 60 (4): 440–443. PMID   7121931.
  4. ↑ Nair, Aiswarya K; Subbaiah, Murali; Maurya, Dilip Kumar (2023). "Comparison of Efficacy of Vaginal Misoprostol versus a Synthetic Osmotic Dilator (Dilapan-S) for Cervical Preparation before Operative Hysteroscopy: A Randomized Controlled Study". Gynecology and Minimally Invasive Therapy . 12 (4): 225–229. doi: 10.4103/gmit.gmit_111_22 . PMC   10683957 . PMID   38034111.
  5. ↑ "Second-Trimester Abortion - ACOG". www.acog.org. Retrieved 2019-07-09.
  6. 1 2 Newmann SJ, Dalve-Endres A, Diedrich JT, Steinauer JE, Meckstroth K, Drey EA (August 2010). "Cervical preparation for second trimester dilation and evacuation". The Cochrane Database of Systematic Reviews (8): CD007310. doi:10.1002/14651858.CD007310.pub2. PMID   20687085. S2CID   205188587.
  7. 1 2 3 Fox MC, Krajewski CM (February 2014). "Cervical preparation for second-trimester surgical abortion prior to 20 weeks' gestation: SFP Guideline #2013-4". Contraception. 89 (2): 75–84. doi: 10.1016/j.contraception.2013.11.001 . PMID   24331860.
  8. 1 2 3 4 5 Lichtenberg ES (July 2004). "Complications of osmotic dilators". Obstetrical & Gynecological Survey. 59 (7): 528–536. doi:10.1097/00006254-200407000-00022. PMID   15199271. S2CID   23835413.
  9. ↑ "Laminaria (Cervical Dilator) by Medgyn Products, Inc". www.medline.com. Retrieved 2019-07-23.
  10. ↑ Diedrich JT, Drey EA, Newmann SJ (May 2020). "Society of Family Planning clinical recommendations: Cervical preparation for dilation and evacuation at 20-24 weeks' gestation". Contraception. 101 (5): 286–292. doi: 10.1016/j.contraception.2020.01.002 . PMID   32007418.
  11. 1 2 Lerma K, Blumenthal PD (February 2020). "Current and potential methods for second trimester abortion". Best Practice & Research. Clinical Obstetrics & Gynaecology. 63: 24–36. doi:10.1016/j.bpobgyn.2019.05.006. PMID   31281014. S2CID   181470281.
  12. ↑ Gelber S, Sciscione A (September 2006). "Mechanical methods of cervical ripening and labor induction". Clinical Obstetrics and Gynecology. 49 (3): 642–657. doi:10.1097/00003081-200609000-00022. PMID   16885669. S2CID   21471309.
  13. ↑ de Vaan MD, Ten Eikelder ML, Jozwiak M, Palmer KR, Davies-Tuck M, Bloemenkamp KW, et al. (March 2023). "Mechanical methods for induction of labour". The Cochrane Database of Systematic Reviews. 3 (3): CD001233. doi:10.1002/14651858.CD001233.pub4. PMC   10061553 . PMID   36996264.
  14. ↑ Lerma K, Blumenthal PD (February 2020). "Current and potential methods for second trimester abortion". Best Practice & Research. Clinical Obstetrics & Gynaecology. 63: 24–36. doi:10.1016/j.bpobgyn.2019.05.006. PMID   31281014. S2CID   181470281.
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