eMedicine Specialties > Clinical Procedures > Radiology

Ultrasonography, Pelvic

Author: Shoreh Kooshesh, MD, Resident Physician, Division of Emergency Medicine, Stanford University School of Medicine
Coauthor(s): Laleh Gharahbaghian, MD, Co-Director, Emergency Ultrasound Fellowship, Associate Director, Emergency Ultrasound, Clinical Instructor, Emergency Medicine, Stanford University Medical Center
Contributor Information and Disclosures

Updated: Nov 19, 2009

Introduction

Background

Pelvic sonography may be viewed as a form or extension of the physical examination. It is one of the best imaging modalities used to evaluate nonspecific pelvic pain, pregnancy complications, anatomy of pelvic organs, and various ovarian pathologies.¹

In transabdominal scanning, using a low-frequency transducer, a full bladder is used to displace bowel gas and serve as an acoustic window to improve image resolution and to allow a large viewing field of the pelvis. Endovaginal scanning, using a high-frequency transducer, is the preferred technique for emergency physicians because a full bladder is not necessary.² It also provides higher resolution, which allows better evaluation of the structure, anatomy, and pathology of pelvic organs.² Endovaginal scanning is preferred over computed tomography because of the absence of radiation exposure with ultrasonography, decreased time of hospital stay, and decreased cost to patient.³

Clinical

History

Clinical indications for pelvic sonography include the following:

• Evaluation of pelvic pain
  • Ultrasonography can be used to evaluate pelvic pain, a common presentation in the emergency department. It evaluates emergent entities such as ovarian cysts and rupture, tubo-ovarian abscesses, uterine fibroids, ectopic pregnancy, uterine rupture, and even ovarian torsion.
  • Endovaginal scanning uses a high-frequency transducer and enables optimal imaging of organs close to the probe, including the endometrium, myometrium, cul-de-sac, and ovaries, which can be seen in detail with better resolution.⁴
  • In a female patient who is obese, pelvic ultrasonography can simplify a difficult physical examination. The endovaginal transducer is preferred for obese patients because it has the ability to visualize pelvic organs far better than any other modality.
  • The differential diagnosis of pelvic pain should be divided into patients who are pregnant and those who are not pregnant.
    • Pregnant patients: The most common cause of pelvic pain with a positive pregnancy test is an ectopic pregnancy. The worldwide incidence is 1 in 200. Once serum beta HCG levels have reached 1,500 IU, a normal gestational sac should be visualized within the uterus using endovaginal ultrasonography. Endovaginal ultrasonography can detect intrauterine pregnancy at a much lower beta HCG level than transabdominal ultrasonography can.⁵
    • Nonpregnant patients: Ovarian torsion is often a difficult diagnosis of intermittent pelvic pain that must be considered in nonpregnant patients.^6,7 Identification of a complex ovarian mass >5 cm increases the probability of torsion.⁸ Endovaginal scanning is the only modality to assess degree of color flow to and from the ovary and diagnose ovarian torsion.⁹
  • Pelvic masses, including uterine fibroids, ovarian cysts, and cancer, can cause pelvic pain. More rare etiologies of pelvic masses include, but are not limited to, pseudomyxoma peritonei, desmoid tumors, and mesothelial tumors.¹⁰ In order to diagnose the specific etiology of the pelvic mass, further imaging and biopsy are needed.
• Evaluation of a pelvic mass
  • Pelvic ultrasonography can be used to determine the etiology of a pelvic mass.
  • Compared with endovaginal ultrasonography, transabdominal ultrasonography uses a lower frequency and can penetrate farther, with a large field of view. Thus, fibroids, ovaries, or cysts located high in the pelvis may be out of the focal range of an endovaginal probe. In addition, pelvic kidneys can be visualized.
  • Uterine fibroids can be diagnosed by pelvic ultrasonography. They may be submucosa, intramural, or subserous. Sometimes they arise from supportive structures of pelvic organs such as broad ligaments. Transabdominal and endovaginal scanning can be done to assess for fibroids. Pelvic masses may also arise from other pelvic organs, including the urinary system, adjacent soft tissues, gastrointestinal system, or even metastases. See below for further discussion on pelvic mass evaluation.
  • Ovarian cysts can get quite large, can cause torsion, and can rupture. They can be nonhemorrhagic or hemorrhagic, simple or complex. Pelvic ultrasonography can provide the information needed to diagnose and delineate the above complications.
  • Nabothian follicles or cysts are caused by a dilation of the endocervical glands; they are located in the uterine cervix and are identified as cystic lesions.¹⁰
• Evaluation of vaginal bleeding in early pregnancy
  • Ectopic pregnancy is the emergent process that must be considered in all pregnant patients who present with vaginal bleeding.¹¹ This indication is well outlined in the eMedicine article Pregnancy, Ectopic. In addition to visualizing an ectopic pregnancy, pelvic ultrasonography can be used to identify a pseudosac. A pseudosac is an empty sac illustrated by an intrauterine fluid collection that forms in response to the hormonal influences of an ectopic pregnancy in the endometrium.
  • Subchorionic hemorrhage (implantation bleeding) is a common cause of spotting. Depending on the size and location of the hemorrhage, pelvic ultrasonography can be used to diagnose this cause of vaginal bleeding in pregnant patients.
  • Intrauterine pregnancy can be illustrated using ultrasonography by visualizing a double-decidual sac sign. Pelvic ultrasonography can show a double layer of echogenic deciduas separated by hypoechoic endometrial cavity.⁵ It can also show a gestational sac with measured fetal pole and yolk sac, or a gestational sac with beating fetal heart illustrating a live intrauterine pregnancy.
• Evaluation of vaginal bleeding post partum
  • Postpartum hemorrhage (PPH) is the leading cause of maternal morbidity.¹² PPH can be defined as primary or secondary. Primary occurs within 24 hours after delivery. Causes include uterine atony, lower genital tract lacerations, and retained products of conception (this usually presents as late-postpartum hemorrhage).¹²
  • Retained products of conception can be evaluated using pelvic ultrasonography.^13,14,15 The ultrasound shows a thickened, heterogeneous stripe or irregular heterogeneous endometrial cavity.¹⁶
• Evaluation of pelvic infection
  • Pelvic inflammatory disease (PID) is one of the most common causes of acute pelvic pain in sexually active women.
  • PID should be suspected in all patients with pelvic pain, cervical motion tenderness, fever, and leukocytosis.
  • Infection can ascend from cervicitis to involve the uterus and fallopian tubes.
  • If treatment is delayed, the infection can ultimately result in tubo-ovarian abscess. Tubo-ovarian abscesses are difficult to diagnose with physical examination alone.
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    Endovaginal ultrasound scan. Endometritis with air in the endometrial cavity and bilateral tubo-ovarian abscesses are shown.

    [ CLOSE WINDOW ]

    

    Endovaginal ultrasound scan. Endometritis with air in the endometrial cavity and bilateral tubo-ovarian abscesses are shown.

  • A normal fallopian tube may not be visualized with endovaginal ultrasonography; however, a fluid- or pus-filled tube can be identified.
  • The resulting tubal damage and scarring increases the risk for long-term complications, including infertility and chronic pelvic pain.⁵
• Localization of an intrauterine device or foreign body
  • Ultrasonography can aid in the localization or detection of an intrauterine device or foreign body.
  • An intrauterine device produces a characteristic acoustic artifact (shadow), which is helpful to the sonographer.¹⁷
• Evaluation of trauma
  • Ultrasonography is used as a screening tool in all trauma patients who present with blunt or penetrating chest trauma or blunt or penetrating abdominal trauma.
  • Views of the sagittal and transverse pelvis using the transabdominal transducer are used to evaluate for free fluid or clotted blood, which can be present in the pouch of Douglas (cul-de-sac).
  • Views of the pelvis obtained before insertion of a Foley catheter are helpful because of the acoustic aid of a full bladder when using the transabdominal transducer.

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