Diagnostic Ultrasound - Abdomen and Pelvis

Cystic Adnexal Mass
Differential Diagnoses: Female Pelvis
DIFFERENTIAL DIAGNOSIS
Common
• Physiologic Cysts
○ Follicular Cyst
○ Corpus Luteal Cyst
• Paraovarian/Paratubal Cyst
• Postmenopausal Adnexal Cyst
• Inclusion Cyst, Ovary
Less Common
• Serous Cystadenoma
• Hydrosalpinx
• Theca Lutein Cysts
• Peritoneal Inclusion Cysts
• Dermoid (Mature Cystic Teratoma)
Rare but Important
• Serous Cystadenocarcinoma
• Anechoic Adnexal Cyst (Mimic)
○ Loop of Bowel
○ Bladder Diverticulum
○ Tarlov Cyst
○ GI Duplication Cyst
○ Complex Cyst (Mimic)
○ Solid Lesion (Mimic)
○ Nabothian Cyst
• Adnexal Torsion
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Thin-walled, anechoic cysts are benign
○ Solid elements increase risk of malignancy
• Rule of 1-2-3
○ 1 cm cyst in 1st week of menstrual cycle is follicle
○ 2 cm cyst in 2nd week of menstrual cycle is dominant
follicle
○ 3 cm cyst in 3rd week of menstrual cycle is corpus luteum
• Size is important
○ Cyst < 3 cm in premenopausal woman is likely
physiologic
○ Cyst > 7 cm is potentially neoplastic
• Follow-up sonogram in 6 weeks often shows resolution of
physiologic cysts but is almost always unnecessary
• Pain can be due to size of cyst or torsion of cyst
• Is cyst separate from ovary?
○ Paraovarian cyst
○ Hydrosalpinx
○ Loop of bowel
Helpful Clues for Common Diagnoses
• Physiologic Cysts
○ Premenopausal women
– Resolve over time
○ Birth control pills can decrease formation of new cysts
while current cyst resolves
• Paraovarian/Paratubal Cyst
○ Separate from ovary
○ Thin walled
○ Anechoic
○ Tend to not change in size over time
• Postmenopausal Adnexal Cyst
○ Cysts may be present in postmenopausal women
○ If thin walled and anechoic (simple), highly likely benign
(99%) up to 10 cm (many are serous cystadenomas)
○ May change in size over time
○ Use of tamoxifen associated with adnexal cysts
• Inclusion Cyst, Ovary
○ Invagination of ovarian cortical surface epithelium with
lost connection to surface
○ Typically small caliber (1-13 mm) but may be up to 10 cm
○ Thin, smooth wall
○ Typically within 1-2 mm of outer surface of ovary
Helpful Clues for Less Common Diagnoses
• Serous Cystadenoma
○ Thin-walled cyst
○ Usually unilocular
○ May have thin septation
• Hydrosalpinx
○ Elongated "cyst" with tubular or coiled shape
○ "Cysts" connect
○ Prior pelvic inflammatory disease or endometriosis
○ Longitudinal folds show classic cogwheel appearance
when tube imaged in cross section
• Peritoneal Inclusion Cyst
○ History of prior surgery, endometriosis, pelvic
inflammatory disease
○ Ovary at edge or surrounded by cyst
○ Irregularly shaped with poorly defined walls (formed by
adjacent organs)
• Dermoid (Mature Cystic Teratoma)
○ Rare for dermoid to present as purely anechoic cyst but
can occur if predominately sebum component
○ Calcifications in wall or echogenic nodule (dermoid plug)
raise suspicion of dermoid
○ May see
– "Dot-dash-dot" appearance of hair in sebum
– "Tip of the iceberg" sign in which "dirty" shadowing
from dermoid obscures visualization of deep margins
of mass
Helpful Clues for Rare Diagnoses
• Serous Cystadenocarcinoma
○ Extremely rare for serous cystadenocarcinoma to
present as anechoic cyst
○ If cyst is large, small solid element could be missed at
imaging
• Anechoic Adnexal Cyst (Mimic)
○ Use transvaginal scanning to assess for internal
echotexture to exclude solid elements or septations
○ At real-time scanning assess for peristalsis
○ Ensure that gain is set appropriately to detect solid
elements
○ Assess for flow within presumed cyst to ensure it is not
homogeneous, hypoechoic, solid lesion
○ Ensure that lesion is in adnexa and not related to bowel
or spine
○ Complex Cyst (Mimic)
– May appear anechoic due to transabdominal
technique or gain set too low
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