Overview

Internal gynecologic organs commonly evaluated on imaging

• Uterus
• Ovaries
• Fallopian tubes

Studies of choice for gynecologic imaging

• Ultrasound: almost always the initial study of choice
• Pelvic MRI: typically reserved for cases that are indeterminate on ultrasound
• Hysterosalpingography (HSG): a fluoroscopic exam used to assess tubal patency
• Note on CT scans:
  • Generally not used to image the female reproductive organs (poorer resolution than ultrasound)
  • May be indicated as part of an oncology workup to look for evidence of metastasis to the lymph nodes or other abdominal organs
  • Gynecologic pathology may be identified on CT scan (e.g., during a workup for lower abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain in the ED) → typically followed up with pelvic ultrasound for better evaluation

Preparation

Prior to the interpretation of any image, the physician should take certain preparatory steps. The same systematic approach should be followed every time:

• Confirm the name, date, and time on all images.
• Obtain the medical history and perform physical examination.
• Confirm the appropriate exam and technique for the desired pathology.
• Compare any available images of the same area taken in the same modality.
• Determine image orientation:
  • Right or left marker on X-ray
  • In an ultrasound, standard exam views place a marker (dot) on the right.
  • For CT/MRI: on axial view, the image is sliced and viewed from inferior to superior (as if you are looking from the subject’s feet up).

Ultrasonography

Indications

Ultrasound (i.e., sonography) is almost always the imaging modality of choice when evaluating the internal female reproductive organs. Indications include:

• Suspected ovarian or fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum's final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes masses:
  • Cysts
  • Malignancy
  • Ectopic pregnancy Ectopic pregnancy Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Ectopic Pregnancy
• Abnormal uterine bleeding Abnormal Uterine Bleeding Abnormal uterine bleeding is the medical term for abnormalities in the frequency, volume, duration, and regularity of the menstrual cycle. Abnormal uterine bleeding is classified using the acronym PALM-COEIN, with PALM representing the structural causes and COEIN indicating the non-structural causes. Abnormal Uterine Bleeding:
  • Abnormal menstruation Menstruation The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle, including irregularities in frequency, duration, and volume
  • In pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care
  • Postmenopausal bleeding
• Pelvic pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain (looking for structural causes)
• Assessment of the presence and location of intrauterine devices (IUDs)
• Evaluation of congenital anomalies
• Infertility
• Routine pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care assessments:
  • Dating
  • Cervical length
  • Anatomic, fluid, growth, and position assessments of the fetus
• Visual assistance with other invasive procedures, including:
  • Aspiration of ova for in vitro fertilization Fertilization To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. Fertilization and First Week
  • Aspiration of pelvic fluid
  • Indications in obstetrics include:
    • Amniocentesis
    • Chorionic villus sampling

Advantages

• Low cost
• No radiation
• Widespread availability
• Rapid
• Very good visualization of the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall and ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries

Disadvantages

• Lower resolution than MRI
• Technician dependent

Types of routine studies and techniques

Transvaginal ultrasound (TVUS):

• Allows for the best visualization of the female reproductive structures located within the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis
• Positioning: dorsal lithotomy
• Transducer is placed inside the vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor.
• Transducer is typically:
  • At or below the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Posterior Abdominal Wall
  • Angled slightly upward to visualize the reproductive organs

Transabdominal ultrasound (TAUS):

• Positioning: supine
• Performed on a full bladder (pushes away loops of bowel for better visualization of the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall)
• Transducer is placed on the lower abdomen.
• Best for visualizing structures above the true pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis, such as:
  • An enlarged uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall (e.g., during pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care)
  • Large cysts or fibroids extending out of the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis
• Useful in people who cannot tolerate transvaginal exams

Depth and gain:

• Determines the field of view and echogenicity characteristics of the tissue
• Gain should be placed such that the parenchyma is visualized without saturating out (“whitening”) too much signal.

Advanced modalities and techniques

Doppler ultrasound:

• Used to assess blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure:
  • To ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries during evaluation of ovarian torsion Ovarian torsion Ovarian torsion is a clinical emergency in which the ovaries (with or without the fallopian tubes) twist along their axis, leading to partial or complete obstruction of their blood supply. Ovarian torsion is also called adnexal or tubo-ovarian torsion, especially if a fallopian tube is also involved. Ovarian Torsion
  • To an adnexal mass, when evaluating for an ectopic pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care and/or neoplasms
  • Of the fetal cardiovascular system and to the uteroplacenta
• Flow is often shown as:
  • A continuous waveform
  • Color mapping, overlying standard ultrasound images

Saline infusion sonogram (SIS) (sometimes called a sonohysterogram):

• Positioning: dorsal lithotomy
• A catheter is placed into the endometrial cavity.
• A TVUS probe is inserted into the vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor.
• While observing TVUS in real time, sterile saline is injected into the endometrial cavity:
  • Saline distends the cavity, allowing for the evaluation of intracavitary lesions.
  • Although the fluid effluxes through the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall, the tubes are too thin for observation of the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure on TVUS.

3-dimensional (3D) sonography:

• Computerized generation of a 3D image
• Especially useful during:
  • SIS
  • Evaluation of fetal and/or congenital uterine anomalies (CUAs)

Interpretation and evaluation

• Structures are evaluated in both the sagittal and transverse planes.
• Size measurements to obtain:
  • Uterine size in all 3 planes (longitudinal, transverse, anterior/posterior)
  • Endometrial thickness (varies with menstruation Menstruation The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle status)
  • Cervical length
  • Ovarian size in all 3 planes and calculation of overall volume
• Note uterine position: e.g., anteflexed, anteverted, mid position, retroverted, or retroflexed
• Note any free fluid in the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis (small, moderate, significant).
• Note:
  • Fallopian tubes are not visible on ultrasound if normal (though fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum's final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes masses are).
  • Ovaries are often not visible on ultrasound if normal in a postmenopausal woman (too small to definitely find them).
• Note any lesions or abnormalities including:
  • Masses
  • Fluid collection
  • Abnormal echogenicity
  • Structural anomalies

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Magnetic Resonance Imaging

Indications

Although pelvic MRI is rarely a 1st-line test, it is typically ordered for better visualization of abnormalities that are identified on ultrasound. Some reasons to order a pelvic MRI include:

• Differentiation between benign and malignant lesions, for example:
  • Leiomyoma (benign fibroids) versus leiomyosarcoma Leiomyosarcoma Uterine leiomyomas (or uterine fibroids) are benign tumors arising from smooth muscle cells in the uterine myometrium. Leiomyosarcomas, however, are malignant tumors, arising de novo (not from fibroids). Uterine Leiomyoma and Leiomyosarcoma
  • Ovarian cystadenomas versus cystadenocarcinomas
• Better characterization of CUAs
• Other indeterminate lesions noted incidentally on ultrasound and CT
• Assists in preoperative planning (e.g., hysterectomy)

Advantages

• Provides better detail of soft tissue in particular (e.g., can identify fat in an adnexal mass suggesting a dermoid cyst)
• No radiation
• Can be used to evaluate conditions in women who are pregnant

Disadvantages

• ↑ Cost
• Takes much longer to perform than ultrasound (or CT)
• Less readily available
• Not suitable for all cases:
  • Implants (particularly metal) distort image.
  • Requires the subject to be an enclosed space that is loud
  • The subject must stay still for adequate image acquisition.

Positioning

• Supine on the table
• Table is advanced into the scanner.
• The subject is instructed to remain still for the scan.

Types of images

• T1-weighted scan (T1):
  • Fat content (e.g., lipoma Lipoma A lipoma is a benign neoplasm of fat cells (adipocytes) and the most common soft tissue tumor in adults. The etiology is unknown, but obesity is a predisposing factor; genetics also play a role, with multiple lipomas occurring in various inherited disorders. Lipoma) appears bright/white.
  • Water (e.g., simple cyst) appears dark/black.
• T2-weighted scan (T2):
  • Fat still appears bright.
  • Water also appears bright/white.
• Images oriented in 3D “slices”:
  • Coronal
  • Sagittal
  • Axial

Table: Tissue characteristics of T1- versus T2-weighted MRI

Tissue	T1-weighted images	T2-weighted images
Fluid	Dark	Bright
Fat	Bright	Bright
Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation	Dark	Bright

Interpretation and evaluation

Interpretation should follow a systematic and reproducible pattern:

• Observe for “continuity” of structures while scrolling through image slices.
• Identical to ultrasound evaluation:
  • Standard measurements
  • Uterine orientation
  • Comment on free fluid in the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis.
  • Note any lesions or abnormalities.

Normal Findings on Ultrasound and MRI

• Size (normal uterus does not have distinct cutoff values):
  • Approximate uterine size in a reproductive-aged woman: 8 cm x 4 cm x 4 cm + 1 cm in any direction
  • Smaller in postmenopausal women
• Shape: normal contour (inverted pear shape with a smooth fundal curvature)
• Myometrium: homogenous
• Endometrial thickness:
  • Appearance:
    • On ultrasound: a thin hyperechoic line within the myometrium
    • On MRI: appears similar to fluid → darker on T1, brighter on T2
  • During menstruation Menstruation The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle: 2‒20 mm depending on the timing during the menstrual cycle Menstrual cycle The menstrual cycle is the cyclic pattern of hormonal and tissular activity that prepares a suitable uterine environment for the fertilization and implantation of an ovum. The menstrual cycle involves both an endometrial and ovarian cycle that are dependent on one another for proper functioning. There are 2 phases of the ovarian cycle and 3 phases of the endometrial cycle. Menstrual Cycle
  • Postmenopausal women: ≤ 4 mm
    • Without bleeding
    • Slightly thicker endometria may still be normal.
    • If ≥ 5 mm with postmenopausal bleeding → endometrial biopsy is required to rule out neoplasia
• Ovaries:
  • Approximately 4 cm x 2 cm x 1 cm during reproductive years
  • Volume < 10 mL
  • Will typically have follicles (small cysts) during reproductive years
  • On ultrasound: symmetric, bilateral, normal Doppler flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure
• Fallopian tubes: not visualized if normal
• Free fluid: small amount of simple hypoechoic fluid in the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis (difficult to measure definitively)

Abnormal and Other Incidental Findings on Ultrasound and MRI

Simple and/or follicular cysts

• Simple cyst refers to any collection of fluid which has:
  • No septa
  • No solid components
  • Thin walls
• May be large
• Follicular cysts represent normal, developing follicles:
  • Type of simple cyst
  • Typically, a dominant follicle will emerge several days prior to ovulation, which will be 2‒3 cm in size.

Table: Additional imaging findings suggestive of simple/follicular cysts

Ultrasound characteristics

MRI characteristics

Anechoic No increased vascular flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure on Doppler Surrounded by normal ovarian tissue

Homogeneous T1: low signal intensity (dark) T2: very high signal intensity (bright) Post contrast: thin and featureless wall enhancement

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Corpus luteal cyst

• A corpus luteum is the “empty follicle” after ovulation.
• Produces the progesterone required to sustain an early pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care
• Normal finding during the 2nd ½ of the menstrual cycle Menstrual cycle The menstrual cycle is the cyclic pattern of hormonal and tissular activity that prepares a suitable uterine environment for the fertilization and implantation of an ovum. The menstrual cycle involves both an endometrial and ovarian cycle that are dependent on one another for proper functioning. There are 2 phases of the ovarian cycle and 3 phases of the endometrial cycle. Menstrual Cycle in ovulatory women

Table: Imaging findings suggestive of corpus luteal cysts

Ultrasound characteristics

MRI characteristics

Thick rim Usually measures up to 3 cm in size (although can reach sizes up to 15 cm) Peripheral flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure on color Doppler (“ring of fire”) Small central lucency with internal echoes

T1: typically homogeneously hypointense (dark) T2: typically hyperintense (bright) Intense post-contrast wall enhancement

Hemorrhagic cyst

• Bleeding into follicular or corpus luteal cysts
• Resolves spontaneously in 1‒2 menstrual cycles

Table: Imaging findings suggestive of hemorrhagic cysts

Ultrasound characteristics

MRI characteristics

Thin-walled complex cyst Multiple low-level, thin, curvilinear internal echoes arranged in a reticular or lacy pattern

T1: isointense to hyperintense (medium to bright) T2: hyperintense (bright) Weak or no enhancement with contrast Highly variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables based on the timing away from an inciting hemorrhagic event

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Endometrioma

An endometrioma is a collection of endometrial tissue on the ovary.

• Type of endometriosis Endometriosis Endometriosis is a common disease in which patients have endometrial tissue implanted outside of the uterus. Endometrial implants can occur anywhere in the pelvis, including the ovaries, the broad and uterosacral ligaments, the pelvic peritoneum, and the urinary and gastrointestinal tracts. Endometriosis
• Unlike hemorrhagic cysts, endometriomas will not resolve spontaneously in 1‒2 menstrual cycles.

Table: Imaging findings suggestive of endometriomas

Ultrasound characteristics	MRI characteristics
Low-level internal echoes often with a ground-glass appearance With/without septations Poorly vascularized Very similar in appearance to a newly formed hemorrhagic cyst	T1: hyperintense (brighter) Remains bright on T1 fat-saturated images T2: hypointense (darker)

Table: MRI findings differentiating an endometrioma from a hemorrhagic cyst

	Hemorrhagic cyst	Endometrioma
T1	Bright	Bright
T2	Bright	Dark
Resolution	Within 1–2 menstrual cycles → disappears on follow-up scan	Does not resolve spontaneously → persists on follow-up scan

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Dermoid cysts (mature cystic teratomas)

• A type of benign germ cell tumor consisting of tissue from all 3 germ layers
• Frequently contains fat, which is unusual in other types of masses (helps identification on MRI)
• Heterogenous on imaging
• With/without calcifications ( teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth)
• Can be lopsided in nature → ↑ risk of ovarian torsion Ovarian torsion Ovarian torsion is a clinical emergency in which the ovaries (with or without the fallopian tubes) twist along their axis, leading to partial or complete obstruction of their blood supply. Ovarian torsion is also called adnexal or tubo-ovarian torsion, especially if a fallopian tube is also involved. Ovarian Torsion

Table: Imaging findings suggestive of dermoid cysts

Ultrasound characteristics	MRI characteristics
Hyperechoic mass Distal acoustic shadowing With/without hyperechoic lines and nodules Nondependent fluid levels	T1: contain varying degrees of fat → fat is T1 hyperintense (bright) T1 fat suppression: loss of T1 signal T2: hyperintense (bright)

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Other ovarian neoplasms

Ovarian neoplasms: benign (noninvasive) or malignant (invasive) growths arising from a single cell. Ovarian neoplasms are classified according to their cell of origin as either epithelial, germ cell, or stromal tumors (with many different subtypes in each class). Concerning imaging findings include:

• Multinodular heterogeneous tumors
• Presence of papillary projections into a cyst
• Solid component(s)
• Thick, irregular walls
• Septations
• Vascular flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure within septations
• Presence of ascites Ascites Ascites is the pathologic accumulation of fluid within the peritoneal cavity that occurs due to an osmotic and/or hydrostatic pressure imbalance secondary to portal hypertension (cirrhosis, heart failure) or non-portal hypertension (hypoalbuminemia, malignancy, infection). Ascites
• Potentially seen in cases with metastasis:
  • Lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
  • Peritoneal and/or omental nodularity

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Ovarian torsion

Ovarian torsion refers to the acute twisting of the ovary around its blood supply. Ovarian torsion presents with acute pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and is considered a surgical emergency (to untwist/save the ovary). Evaluation is usually only with ultrasound.

• Usually associated with an ovarian mass (commonly dermoids due to their lopsided nature)
• Enlarged heterogenous ovary (often > 4 cm)
• Free pelvic fluid
• With/without Doppler flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure (since torsion can be transient), but absence of flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure confirms torsion/indicates infarction
• Frequently appears as normal

Ectopic pregnancy Ectopic pregnancy Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Ectopic Pregnancy

An ectopic pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care is a pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care outside the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall. A rupture can result in life-threatening hemorrhage. An ectopic pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care is almost always evaluated using ultrasound only.

• Complex heterogenous extraovarian mass with/without Doppler flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure (most common finding on ultrasound)
• Presence of a gestational sac with/without a yolk sac and/or embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week outside the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall (less common)
• Positive pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care test with the absence of a uterine pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care

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Hydrosalpinx

A hydrosalpinx describes the condition of postinflammatory fluid filling the fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum's final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes.

• Tubular hypoechoic extraovarian structure
• May appear to have “septations” (actually due to folds of the wall)

Uterine fibroids

Uterine fibroids (or leiomyomas) are benign uterine neoplasms arising from a single myometrial cell:

• Round or oval mass arising from the myometrium
• Encapsulated → well-defined margins on both ultrasound and MRI
• Usually homogenous
• May be heterogenous if degenerating
• Can be located anywhere in the myometrium, and are classified by location:
  • Submucosal: protruding into the endometrial cavity
  • Intramural: within the myometrium
  • Subserosal: protruding outside the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall, covered by serosa

Table: Imaging findings suggestive of uterine fibroids (leiomyomas)

Ultrasound characteristics	MRI characteristics
Hypoechoic With/without calcifications May contain cystic components (anechoic)	T1: darker normal myometrium T2: dark Variable enhancement (post-contrast administration)

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Adenomyosis Adenomyosis Adenomyosis is a benign uterine condition characterized by the presence of ectopic endometrial glands and stroma within the myometrium. Adenomyosis is a common condition, affecting 20%-35% of women, and typically presents with heavy menstrual bleeding and dysmenorrhea. Adenomyosis

Adenomyosis Adenomyosis Adenomyosis is a benign uterine condition characterized by the presence of ectopic endometrial glands and stroma within the myometrium. Adenomyosis is a common condition, affecting 20%-35% of women, and typically presents with heavy menstrual bleeding and dysmenorrhea. Adenomyosis is a clinical condition in which the endometrium implants/invades into the myometrium, typically resulting in heavy, painful menstruation Menstruation The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle. Findings on both ultrasound and MRI include:

• Enlarged uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall
• Myometrial cystic spaces
• Enlarged and globular uterine appearance
• Asymmetrical thickening of the myometrium (especially a thickened posterior wall)
• Loss of a clear endomyometrial border/thickening of the junctional zone

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Endometrial polyps Endometrial polyps Endometrial polyps are pedunculated or sessile projections of the endometrium that result from overgrowth of endometrial glands and stroma around a central vascular stalk. Endometrial polyps are a few millimeters to a few centimeters in size, can occur anywhere within the uterine cavity, and, while usually benign, can be malignant, particularly in postmenopausal women. Endometrial Polyps

A small growth off the endometrium that is usually pedunculated and often (though not always) benign:

• Thickened endometrium on regular TVUS/TAUS and MRI
• Mass arising from the endometrium and protruding into uterine cavity on SIS (best test to visualize polyps)

Endometrial hyperplasia Endometrial Hyperplasia Endometrial hyperplasia (EH) is the abnormal growth of the uterine endometrium. This abnormal growth may be due to estrogen stimulation or genetic mutations leading to uncontrolled proliferation. Endometrial Hyperplasia and Endometrial Cancer and cancer

• Thickened endometrium based on age and/or menstrual status
• Heterogeneous echogenicity 
• Features suggestive of cancer:
  • Irregular and/or indistinct borders
  • Frank invasion
  • Thickness > 5 mm in postmenopausal women

Hysterosalpingography

Description

• Fluoroscopic examination that allows assessment of:
  • Uterine cavity shape
  • Patency of fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall (best nonsurgical test available)
• A catheter is inserted into the uterine cavity → dye is injected → X-ray

Indications

• Evaluation of CUAs
• Infertility (to look for congenital anomalies and check tubal patency)

Contraindications

• Pregnancy
• Active undiagnosed vaginal bleeding
• Active pelvic infection

Advantages

• Relatively low cost 
• Lower radiation dose (although can become high with prolonged study time)
• Relatively ubiquitous availability
• Dynamic imaging

Disadvantages

• Poor resolution of soft tissue
• Exposure to ionizing radiation
• Discomfort/ pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain to the subject
• Complicated scheduling:
  • Should be performed between the end of menstruation Menstruation The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle and prior to ovulation (to avoid interruption of an early pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-HCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care)
  • Often requires both a gynecologist (to place the catheter) and radiologist (to interpret images) present in the room during the study

Exam technique

• Positioning:
  • Dorsal lithotomy on the fluoroscopy table
  • Board is placed against the back.
  • X-ray beams from the floor → ceiling direction through the subject
• Visualization: Field of view should be focused on the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis.
• Procedure:
  • A speculum is inserted into the vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor and the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Posterior Abdominal Wall is identified.
  • A balloon-tipped catheter is inserted through the cervical canal into the uterine cavity.
  • Contrast is injected slowly and observed in fluoroscopy in real time.
  • Images are acquired.

Interpretation and evaluation

Systematic approach:

• Inside-out approach (central to peripheral):
  • Look at the bowel-gas pattern.
  • Look for solid organ silhouettes if in the field of view ( liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver, spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen, kidney).
  • Look for normal fat planes peripherally.
  • Look for evidence of free intraperitoneal air.
  • Evaluate soft tissues for:
    • Contour of the uterine cavity
    • Patency of fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall
    • Abnormal calcifications (stones, masses)
  • Evaluate osseous structures (vertebral body height, iliac bones, femurs).
• Dynamic approach:
  • Observe the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of contrast through the endometrial canal and note any:
    • Filling defects in the uterine cavity (areas that do not completely saturate with dye)
    • Obstruction
    • Stenosis
    • Extravasation
  • Contrast should flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure through the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall and into the adnexal spaces.

Normal findings

• Normal contour of the uterine cavity:
  • Upside-down triangle
  • No filling defects
• Fallopian tubes fill with dye → dye spills out of the ends of both tubes into the pelvic cavity (“bilateral fill and spill”)

Abnormal or incidental findings

Hydrosalpinx:

• Dilated tubes with collection of contrast in the tubes
• With/without obstruction (i.e., no free spillage)

CUAs:

The uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall forms from the Müllerian ducts, which fuse in the midline to create the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall, cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Posterior Abdominal Wall, and upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor. Therefore, initially, these structures are divided down the midline before the midline septum regresses. Congenital uterine abnormalities typically occur due to abnormal fusion and/or septal regression.

• Septate uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall:
  • Filling defect starting from the uterine apex
  • Length of the septum varies.
• Bicornuate uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall:
  • Filling defect starting from the uterine apex
  • 2 banana-shaped cavities, each draining into a normal fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum's final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes
• Unicornuate uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall: single fusiform uterine cavity draining into a single tube
• Uterus didelphys: 2 completely separate “systems”
  • 2 uterine cavities, each with their own cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Posterior Abdominal Wall and fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum's final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes
  • No communication between sides

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