Pathology of the Ovaries, Part I Study Notes

PATHOLOGY OF THE OVARIES, Part I

Anatomy of the Ovaries

• The ovaries are paired, almond-shaped structures situated one on each side of the uterus, close to the lateral pelvic wall.
• Their positioning can vary, influenced by the location of the uterus and the attachments of ligaments.
• In cases of an anteflexed midline uterus, the ovaries are typically identified laterally or posterolaterally.

Key Anatomical Features

• Uterine Components:

  • Uterine fundus
  • Fallopian tubes
  • Ovarian ligament
  • Endocervix and ectocervix
  • Cavity of the uterus
  • Myometrium and endometrium
  • Uterine isthmus
  • Lateral fornix
  • Vagina

• Ovary Composition:

  • Germinal epithelium
  • Cortex and medulla
  • Primary ovarian follicles
  • Secondary ovarian follicles
  • Oocyte and Graafian follicle

• The ovaries are ellipsoidal in shape, with their craniocaudad axes paralleling the internal iliac vessels located posteriorly.

Normal Sonographic Appearance

• The normal ovary exhibits a homogeneous echotexture and may show a central, more echogenic medulla.
• Small anechoic or cystic follicles can appear peripherally in the cortex.
• The appearance of the ovaries can vary based on the individual’s age and menstrual cycle.

Sonographic Images Displayed

• Visual representations of the left and right ovaries along with the uterus across multiple scans demonstrate their echotexture and positioning.

Cyclic Changes of the Ovary

• The ovary undergoes several changes throughout the menstrual cycle, recognizable sonographically:
  • Corpus luteum of pregnancy
  • Dominant follicle of the ovary
  • Menstruating ovary
  • Menopausal atrophied ovary
  • Prepubertal ovary
  • Degenerating corpus luteum

Sonographic Evaluation

• During reproductive years, three phases can be recognized sonographically during each menstrual cycle:
  • Early Proliferative Phase:
  • Multiple follicles develop and increase in size until roughly day 8 or 9 of the cycle, stimulated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
  • At this point, one follicle becomes dominant, typically growing to 2.0 to 2.5 cm by ovulation.
  • Cumulus Oophorus:
  • Occasionally visible as an eccentrically located cyst-like 1-mm internal mural protrusion, indicating a mature follicle and imminent ovulation.
  • Follicular Cyst Formation:
  • If fluid in nondominant follicles is not reabsorbed, a follicular cyst may develop.
  • The dominant follicle usually disappears immediately post-ovulation.
  • Occasionally, the follicle may shrink and develop a scalloped wall appearance.
  • Post-Ovulation Changes:
  • The mature corpus luteum can be seen as a small hypoechoic or isoechoic structure within the ovary after ovulation, often appearing irregular with echogenic crenulated walls.
  • The presence of fluid in the cul-de-sac is common following ovulation, peaking in the early luteal phase. The corpus luteum begins to involute approximately 8 or 9 days post-ovulation and often disappears shortly before or at the onset of menstruation.

Key Points on Ovarian Volume

• The volume of a normal ovary in an adult menstruating female can be as large as 22 cc, with a mean volume of 9.8 ± 5.8 cc.
• Any volume exceeding 8.0 cc is considered abnormal for postmenopausal patients.
• An ovary significantly larger than its counterpart (more than double the volume of the opposite side) is also classified as abnormal.
• Ovarian size is best determined using measurements based on the prolate ellipse formula: $ext{Volume} = 0.523 imes ext{length} imes ext{width} imes ext{height}$.

Ovarian Cysts

• Simple cysts are the most common ovarian masses, usually benign.
• They form as ovaries mature oocytes under the influence of luteinizing hormone and follicle-stimulating hormone, synthesizing androgens that are converted to estrogens, and producing progesterone post-ovulation to maintain early pregnancy until placental support.

Types of Cystic Masses

• Follicular cysts develop when the dominant follicle fails to ovulate, growing 1 to 24 mm in the mid to late follicular phases. They can persist as simple or complex cystic structures measuring between 1 and 10 cm.
• If a cyst larger than 6 cm persists beyond 8 weeks, surgical intervention is advised, and ultrasound-guided needle aspiration is an option for recurrent simple ovarian cysts in select cases.
• The majority of simple cysts have thin walls, anechoic contents, and exhibit acoustic enhancement on ultrasound.

Postmenopausal Cysts

• Small, anechoic cysts may be detected in postmenopausal ovaries and can change in size over time; monitoring via serial sonographic studies is recommended.
• Surgery is generally advised for postmenopausal cysts larger than 5 cm, or with internal septations or solid nodules.

Complex Ovarian Masses

• Complex masses may arise from simple cysts undergoing hemorrhage during involution.
• Differential diagnoses for complex adnexal masses in reproductive-aged patients include:
  • Ectopic pregnancy
  • Endometriosis
  • Pelvic Inflammatory Disease (PID)
  • Dermoids and other benign tumors

Common Complex Masses

• Cysts that present as complex lesions include:
  • Cystadenoma
  • Dermoid cyst
  • Tubo-ovarian abscess
  • Ectopic pregnancy
  • Granulosa cell tumor

Doppler Investigations of Ovarian Masses

• Doppler Ultrasound:
  • Can differentiate potential cystic lesions from adjacent vascular structures.
  • Pulsed Doppler is utilized to analyze flow velocity to ovarian masses and nearby vascular structures, including the uterine and ovarian arteries.
  • Indices such as the Resistive Index (RI) and Pulsatility Index (PI) help assess the likelihood of malignancy based on blood flow characteristics.

Ovarian Hyperstimulation Syndrome (OHS)

• A common iatrogenic complication arising from ovulation induction that can manifest in mild, moderate, or severe forms, characterized by:
  • Mild: Enlarged ovaries measuring less than 5 cm, pelvic discomfort without significant weight gain.
  • Severe: Notably enlarged ovaries (>10 cm), severe pelvic pain, abdominal distension, and associated ascites and pleural effusions. Treatment usually resolves within 2-3 weeks.

Polycystic Ovarian Syndrome (PCOS)

• PCOS, also known as Stein-Leventhal syndrome, is characterized by:
  • Bilaterally enlarged polycystic ovaries
  • Often develops during late teens to 20s, potentially indicating endocrine imbalance
  • Clinical manifestations include amenorrhea, obesity, infertility, and hirsutism.
  • Sonographic findings are consistent with multiple tiny cysts surrounding the ovary, which may be normal or enlarged in size.

Endometriosis

• A condition where functioning endometrial tissue is found outside the uterus, potentially in the ovaries, fallopian tubes, or pelvic cavity.
• The tissue may cyclically proliferate and bleed, leading to pelvic pain, and is categorized into diffuse and localized forms (localized form -> endometrioma).
• Sonographic appearances range from cysts to solid formations depending on blood organization during the menstrual cycle.

Ovarian Torsion

• An acute condition resulting from the rotation of the ovarian pedicle, leading to an enlarged, edematous ovary typically measuring greater than 4 cm.
• Radiological findings include:
  • Multiple tiny follicles around a hypoechoic mass
  • Potential free fluid in the pelvis
  • Doppler examination generally shows absent blood flow to the torsed ovary.
• This condition accounts for 3% of gynecologic emergencies, requiring prompt intervention to prevent loss of ovarian tissue. The torsed ovary typically appears enlarged, heterogeneous, and may have associated abnormalities or masses.