Gynecologic Imaging - Dr.Heidi Santos
Review: (all pics)
Normal Anatomy of the Pelvis
CT scan of the pelvis, axial plane
Round ligaments on CT scan
Cardinal ligaments on CT scan
Uterosacral ligaments on CT scan
CT scan of the pelvis, sagittal plane
MRI of the uterus
· Endometrium - innermost high signal intensity
· Junctional/transitional zone - middle zone of low signal intensity
· Myometrium - outermost zone of intermediate signal intensity
I. Abnormal Pregnancy
A) Ectopic Pregnancy
· Ultrasound remains the mainstay of evaluation of ectopic pregnancies
· CT scan not routinely used for ectopic pregnancy
o Findings are non-specific
o Associated ionizing radiation is hazardous is a normal intrauterine pregnancy is also present
· MRI should only be used as a problem solving tool in patients in stable condition
o Remember: Ectopic pregnancies are always emergency cases.
o Accurate in tissue characterization and detection, and age determination of blood products
o Findings suggestive of ectopic pregnancy
§ Tubal gestational sac
§ Tubal hematoma
§ Tubal wall enhancement
§ Adnexal mass with hemorrhagic fluid in the peritoneum
o Cases
§ Left tubal pregnancy (9 weeks AOG) in a 44-year old woman.
§ Findings:
ü Dilated fallopian tube with focally enhancing gestational sac; thickened enhancing wall
B) Gestational Trophoblastic Neoplasia
· Affects 1 in every 1,500-2,000 pregnancies
· Increase in serum beta HCG levels
· Hallmark: Vaginal bleeding in the first trimester or early second trimester
· Broad spectrum of placental lesions: hydatidiform mole, invasive mole, choriocarcinoma, placental site trophoblastic tumor
· MRI - useful in assessing extrauterine tumor spread, tumor vascularity, and overall strategy
· CT & PET scan - useful in assessing recurrent and metastatic disease
· Cases: Placental Site Trophoblastic Tumor
o 22 y/o F with irregular menses who reported “passing tissue”.
o CT scan showed a mass with very low attenuation centrally and a slightly higher attenuation process extending through the expected thickness of the myometrium. A thin rim of myometrium is seen surrounding the mass.
o Endometrium appears expanded and displaces the myometrium peripherally.
· Cases: Choriocarcinoma
o Female presents with vaginal bleeding at 9 weeks AOG
§ On ultrasound: Endometrium appears as a heterogenous mass with cystic lucencies. On dilatation & curettage (D&C), this was proven to be a hydatidiform mole.
§ 6 weeks later: Patient presented with nausea, vomiting, and elevated HCG levels. CT scan was nonspecific and showed an enlarged uterus with heterogenous echoes.
§ CT scan of the lung showed pulmonary nodules (metastasis from choriocarcinoma).
o 31 y/o F, presents with choriocarcinoma 4 weeks after an uncomplicated delivery, with acute left hemispheric symptoms. CT scan reveals metastasis to the brain and lungs.
· Cases: Hydatidiform Mole
o Complete hydatidiform mole in 30 y/o F (gravida 6, para 0, aborta 6) with several prior molar pregnancies.
§ On CT scan: Heterogenous densities observed within molar pregnancy.
§ Presence of theca lutein cysts in adnexa (seen in an environment of elevated beta HCG levels).
§ Gross specimen contains vesicles passed out with bleeding.
o 22 y/o F at 10 weeks AOG with elevated beta HCG levels and with no gestational sac on ultrasound. Histopathology confirms complete molar pregnancy.
§ On CT scan: Endometrium appears expanded with high intensity attenuation.
II. Benign Gynecologic Conditions
A) Adnexae
- Dermoid cyst or benign cystic teratoma
· Most common benign germ cell tumor of the ovary
· Affects females of any age (10-30 years old)
· Most lesions discovered incidentally while patient is asymptomatic
· Consists of mature elements derived from ectoderm, mesoderm and endoderm including bone, teeth, and hair
· Cystic teratoma
o Gross pathology
§ Unilocular
§ Filled with sebaceous material lined by squamous epithelium
§ Hair follicles, skin glands, muscle, and other tissue lie within the wall
§ Raised protuberance projecting into the cyst cavity known as the Rokitansky nodule
o Imaging: purely cystic
§ Mixed density mass with components of all 3 germ cell layers
§ Non-cystic masses are composed predominantly of fat
o CT & MRI - demonstrate lipid material within the cyst
· Dermoid cyst
o CT findings
§ Complex-appearing cystic mass with smooth, well-defined surface and focus of calcification that resembles teeth
§ Sebaceous contents: same as fat attenuation (hypoechoic)
· Mature teratoma
o X-ray - large mass with fat opacity and multiple tooth-like calcifications
o CT scan (without contrast) - hypodense mass in the pelvis; mass contains a rim of hyperdense calcifications along its left anterior wall; Rokitansky nodules appear as hyperdense enhancements on contrast administration.
o MRI - high signal intensity on both T1W and T2W; may have fat suppression; Rokitansky nodules also have high signal intensity
· Immature teratoma
o Contrast-enhanced pelvic CT scan will show a large heterogenous mass with soft tissue components, a cystic portion, small foci of fat, and scattered calcifications (teeth).
- Endometrioma
· Functional endometrial tissue outside the boundaries of the uterine musculature that is implanted on the surface of other organs.
· Implants respond to hormone stimulation - recurrent bleeding, inflammation, and fibrosis.
· Endometriosis has been found everywhere in the body.
· Most common sites of implants: ovaries, pouch of Douglas, rectosigmoid, uterine ligaments, fallopian tubes.
· Less common sites of implants: vagina, cervix, bladder.
· Hallmark:
o Numerous tiny implants of endometrial tissue on peritoneal surfaces
o Endometriomas (chocolate cysts filled with hemorrhage)
o Adhesions between surrounding tissues
· MRI
o Cystic mass with high signal intensity on T1-weighted images
o Loss of signal intensity on T2-weighted images
§ Phenomenon of “shading” - a result of the high iron concentration of hemoglobin or blood products contained within as a result of hemorrhage; very specific for an endometrioma on MRI.
· CT scan
o Complex cystic masses, usually with high density fluid components
o Prominent inflammation and fibrosis
o Multiple pelvic organs may be incorporated into a mass
- Corpus luteum cyst
· Residual follicle after ovulation - can cause pain and bleeding
· Appear as very well defined (with rim enhancement), low intensity, hypodense cysts
· Case: Hemorrhagic ovarian cyst in a 25 y/o F who presented with sudden onset of pelvic pain. CT scan revealed a cyst with wall thickening and enhancement, (+) hemoperitoneum within the cul-de-sac as a result of rupture of the cyst.
- Hydrosalpinx
· May occur as an isolated adnexal lesion or as a component of a complex adnexal lesion that has caused distal tube occlusion.
· Most common cause: Pelvic Inflammatory Disease
· Can be associated with early stage tubo-ovaritis and pyosalpinx - pus forms within the tube; inflammation of ovaries can occur later on with abscess formation
· Other causes: endometriosis, peritubal adhesions from previous surgeries, tubal cancer, tubal pregnancy.
· CT & MRI findings may reveal sausage-shaped, C or S-shaped, tortuous or tubular adnexal structures distended because of fluid collection.
· MRI
o May be useful for determining the cause of a hydrosalpinx or its associated adnexal process by characterizing the nature of the contents of the dilated tube-like structure.
§ Pyosalpinx - if the wall of the tube is thickened with variable signal intensity
§ Malignancy - enhancing solid mass within a dilated tube
§ Tubal pregnancy - enhancement of the wall surrounding a sac-like cystic mass
B) Vagina
· Gartner cysts
o Remnants of mesonephric (wolffian) ducts, which in women are present in the uterus, vagina and hymen until the 3rd month of gestation and which give rise to the ureters.
o Remains of the Gartner duct may be detected in up to ¼ of adult women.
o Most cysts are small (<3 cm), and are usually paravaginal and found in the anterolateral position.
C) Uterus/Endometrium
- Leiomyoma (Fibroid)
· Benign neoplasms derived from smooth muscle cells of the uterine myometrium
· Most common uterine tumor affecting 50% of females of reproductive age
· Usually asymptomatic; but may cause bleeding, pelvic pain, mass symptoms, and infertility
· Categorized by location:
o Subserosal - beneath the serosa; may appear pedunculated
o Intramural - within myometrial wall; most common
o Submucosal - beneath the endometrium; usually bleed; may appear pedunculated
· Degeneration due to inadequate blood supply
o Hyaline, myxomatous, cystic, fatty, hemorrhagic, or malignant
· CT scan
o Limited role in diagnosis
o Homogenous or heterogenous mass that may be hypo/iso/hyperdense relative to the myometrium
o Coarse calcifications within mass
o Diffuse uterine enlargement; lobulated contour
o Bladder may appear compressed
o Pedunculated myoma - may be be mistaken for an adnexal rather than uterine mass
· MRI
o Best characterization of size, number and location
o Characteristic low signal intensity on both T1W and T2W imaging
o Well circumscribed with well-defined margins
o ~ 1/3 surrounded by a high signal intensity rim on T2W that correlates with peritumoral
lymphatics, veins, and edema
· Endocavitary leiomyoma
o T2W image will show a mixed-signal intensity heterogenous mass within and distending the endometrial cavity, a finding characteristic of an endocavitary leiomyoma.
- Adenomyosis
· Sometimes called internal endometriosis
· Migration of glands from the basal layer of the endometrium to within the myometrium; the focus of basal endometrial glands is surrounded by smooth muscle hyperplasia
· Can cause pain, uterine tenderness, meno/metrorrhagia
· Usually affects parous women aged 40-50 years old
· May be focal or diffuse
· MRI
o Best for detection of the disease
o Low intensity areas with asymmetrical thickening of the myometrium as whole, specifically the junctional zone - glands tend to overlap between the endometrium and myometrium in this zone; this is where adenomyosis usually begins.
o Focal or diffuse thickening of the junctional zone is a hallmark of the disease. The zone looks like it is replaced by a mass with cystic foci within.
o High signal foci within myometrium in 50% of cases (due to cystic changes of hemorrhage).
o Focal form: oval ill-defined low signal masses (adenomyomas) on T2W; often bright foci on both T1W and T2W within the masses
· In cases where adenomyosis and leiomyoma are both present, the leiomyoma will appear as hypoechoic area on T2W while the adenomyosis will present as a thick high intensity area.
III. Malignant Gynecologic Conditions
- Carcinoma of the Cervix
· Most common gynecologic malignancy
· Peak age of onset: 45-55 years old
· Squamous cell CA (95%); Adenocarcinoma (5%)
· Spread:
o Direct extension to vagina, paracervical, parametrial, bladder, rectum
o Obstruction of ureter by proximity
o Lymph metastasis
o Hematogenous metastasis: lung, bone brain
· CT scan
o Local staging by CT is limited; 50% of tumors are isodense to cervical tissue
o Primary tumor - enlarges the cervix; appears as hypodense mass
o Fluid collection within endometrial cavity because of the obstruction created by the mass (fluid is unable to drain out).
o Direct extension - thick irregular tissue strans; mass fanning out of parametria
o Late spread to lungs, bones, brain
- Ovarian Cancer
· Wide range of histologic tumor types: 2/3 cystic, 25% bilateral, 85% endocrinologically non-functional.
· Spread
o Primary diffusion throughout peritoneal cavity (most common pattern of spread) - unique for ovarian cancer
o Direct extension to pelvic organs and lymph nodes
o Hematogenous spread to lung, liver, bones
· CT scan
o Imaging of choice; will show tumor response to treatment and post-op recurrence
o Findings
§ Primary tumor is usually cystic with thick irregular walls, internal septations, and prominent soft tissue components.
§ Direct tumor extension to involve uterus, colon, bowels, bladder.
§ Peritoneal implants: soft tissue nodules on peritoneal surface appearing as “omental cakes”
§ Ascites = peritoneal spread
§ Lymphatic spread
§ An ovarian heterogenous mass should always be suspected for ovarian cancer.
o “Omental caking”
§ Appears as thickened band of omentum anterior to the bowels; implantation of tumor into omentum
§ Due to a metastatic tumor
- Endometrial Cancer
· Now most common invasive gynecologic malignancy
· Peak age of onset: 55-62 years old
· Key symptom: post-menopausal bleeding
· Spread
o Initially invades myometrium and cervix
o Followed by lymphatic and hematogenous spread
· CT scan
o Primary tumor appears as a large hypodense mass within endometrial cavity or invading the myometrium surrounded by fluid (ascites)
o Parametrial and sidewall extension: same as carcinoma of the cervix
· MRI
o T2W image of non-invasive endometrial cancer is nonspecific. The uterus may appear normal on MRI.
o Thickening of the endometrial stripe - focal or diffuse, hyperintense or isointense, homogenous or heterogenous - may be seen.
· Leiomyosarcoma (uterus)
o 3% of uterine body tumors
o Very invasive neoplasms; frequently present at an advanced stage
o CT will show a large, irregular uterine tumor with invasion of the surrounding pelvic organs, peritoneum and omentum.
- Vaginal Cancer
· Can invade the vagina muscularis and infiltrate the rectovaginal fat planes.
IV. Infertility
- Polycystic Ovarian Syndrome
· The association of amnorrhea with bilateral polycystic ovaries was first described by Stein and Leventhal and was known for decades as Stein-Leventhal Syndrome.
· Diagnostic criteria of PCOS: hyperandrogenism and chronic anovulation; exclude secondary causes such as neoplasms, hyperprolactinemia, and adult-onset congenital adrenal hyperplasia.
· An elevated luteinizing hormone-follicle stimulating hormone ratio is often but not always present, and cystic ovarian changes are usually present but not essential for diagnosis (indicates hypothalamic-pituitary dysfunction).
· T2W imaging may show bilateral ovarian enlargement with multiple peripheral follicles.
- Fallopian Tube Carcinoma
· Can appear as an enhancing solid intraluminal mass within a dilated fallopian tupe on T2W imaging.
· There is heterogenous enhancement of the solid mass lesion within the dilated fallopian tube.
Summary
· Primary imaging modality is still ultrasound
· MRI and CT are used to stage and follow-up pelvic malignancies
o Supplemental ultrasound can provide additional characterization of lesions
o MRI has excellent capacity to different tissue types (pus, blood, calcifications, etc.)
o Many uterine and adnexal lesions may be discovered incidentally by pelvic CT or MRI performed for other reasons.