Ovarian Cyst

An ovarian cyst is a fluid-filled sac that develops within or on the surface of an ovary. They are extremely common, most are benign and self-limiting, but some require investigation and intervention depending on their type, size, and the patient's age and symptoms.

Classification

1. Functional (Non-Neoplastic) Cysts

These are the most common type and arise from normal ovarian physiology. They are benign and usually resolve spontaneously.

a. Follicular Cysts

Most common functional cyst
Form when a follicle fails to rupture and release the ovum, continuing to grow
Rarely exceed 8 cm; defined as a follicular cyst when diameter > 3 cm
Usually found incidentally on examination or imaging
Typically resolve in 4-8 weeks with expectant management

b. Corpus Luteum Cysts

Less common than follicular cysts
Form when the corpus luteum fails to involute and continues to grow after ovulation
More likely to rupture and cause hemoperitoneum
Rupture is more common on the right side, often occurs during intercourse, most commonly on cycle days 20-26
Patients on anticoagulants or with bleeding diatheses are at particular risk

c. Theca Lutein Cysts

Least common functional cysts
Usually bilateral
Associated with: molar pregnancy, choriocarcinoma, multiple gestations, diabetes, Rh sensitization, clomiphene citrate, human menopausal gonadotropin use, GnRH analogs
Up to 25% of complete molar pregnancies have theca lutein cysts, which regress spontaneously

2. Other Benign Ovarian Cysts

Endometriomas ("chocolate cysts"): fluid-filled ovarian cysts filled with old blood from endometriosis; can enlarge to 6-8 cm
Benign cystic teratomas (dermoid cysts): most common neoplasm to undergo torsion
Paraovarian/paratubal cysts: arise adjacent to the ovary or tube

Epidemiology and Risk Factors

Annual hospitalization rate for functional ovarian cysts: up to 500 per 100,000 woman-years (US)
Increased risk: cigarette and marijuana smoking (though attenuated in overweight/obese women)
Decreased risk: combined oral contraceptive (OCP) use suppresses follicular development and ovulation; however, low-dose pills have an attenuated effect
OCPs do NOT hasten resolution of existing cysts - Berek & Novak's Gynecology, p. 452

Causes of Pelvic Mass by Age

Age Group	Most Common Cause
Infancy	Functional cyst, germ cell tumor
Prepubertal	Functional cyst, germ cell tumor
Adolescent	Functional cyst, pregnancy, benign cystic teratoma
Reproductive	Functional cyst, pregnancy, fibroids
Perimenopausal	Fibroids, epithelial ovarian tumor
Postmenopausal	Ovarian tumor (benign or malignant), functional cyst

(Berek & Novak's Gynecology, p. 449)

Clinical Presentation

Asymptomatic: most functional cysts are found incidentally on pelvic exam or imaging.

Symptoms when cysts cause complications:

An ovarian cyst that is NOT undergoing torsion, rapidly enlarging, infected, or leaking does not usually cause acute pain
Rupture of corpus luteum cyst: sudden onset pelvic pain progressing to generalized abdominal pain, dizziness or syncope if significant hemoperitoneum develops; can mimic ruptured ectopic pregnancy
Rupture of endometrioma or dermoid: similar pain but WITHOUT dizziness/signs of hypovolemia (blood loss minimal)
Leaking cyst: pain from peritoneal irritation by blood, follicular fluid, or cyst contents

Complications

Rupture

Functional cysts are more likely to rupture than benign or malignant neoplasms
Mittelschmerz (midcycle pain at ovulation) = small bleed from ruptured follicle
Hemorrhagic cyst rupture can produce significant hemoperitoneum
Surgical exploration indicated if: significant hemoperitoneum (corpus luteum), chemical peritonitis (endometrioma or dermoid), acute abdomen (abscess)

Adnexal Torsion

Twisting of the vascular pedicle causes ischemia
Benign cystic teratoma is the most common neoplasm to undergo torsion
83% of torsions occur in ovaries ≥ 5 cm
Pain is usually severe and constant; nausea, vomiting, tachycardia are common autonomic responses
Can occur in children even without an ovarian lesion

Diagnosis

Blood tests:

Pregnancy test (essential - to exclude ectopic pregnancy)
CBC (hematocrit decreased with active bleeding)
Type and screen (if orthostasis present)
Leukocytosis is uncommon with simple cyst rupture

Imaging:

Transvaginal ultrasound is the primary modality - characterizes the cyst (dermoid, endometrioma, corpus luteum, abscess), quantifies free fluid
Features concerning for malignancy: ascites, cysts > 10 cm, multiloculations, solid components, irregular septations, Doppler flow within septa
MRI: useful for uterine anomalies; rarely justified over ultrasound for most pelvic masses due to cost

Culdocentesis: historically used; now largely replaced by pelvic ultrasound, image-guided aspiration, or diagnostic laparoscopy.

Management

Functional / Suspected Benign Cysts

Expectant management is the standard: most functional cysts resolve in 4-8 weeks
OCPs do NOT accelerate resolution of existing cysts but reduce risk of future cysts
Mildly symptomatic masses suspected to be functional: analgesics, avoid surgery (risk of adhesions affecting fertility)
Surgical intervention warranted for: severe pain, suspicion of malignancy, torsion

Ruptured Cyst

Hemodynamic Status	Management
Stable, no orthostasis, small amount of free fluid	Observation (ED or inpatient), repeat imaging
Orthostasis, significant anemia, large free fluid	Surgical management (laparoscopy or laparotomy)

Adnexal Torsion

Surgical emergency: diagnostic and therapeutic laparoscopy with detorsion

Endometriomas

Excision preferred over ablation for fertility outcomes
Asymptomatic endometriomas do not need removal prior to ART if diagnosis is not in question

Differential Diagnosis of Acute Pelvic Pain (including ovarian cysts)

Ectopic pregnancy
Hemorrhagic functional ovarian cyst
Adnexal torsion
Ruptured ovarian cyst (functional, neoplastic, inflammatory)
Pelvic inflammatory disease / tubo-ovarian abscess
Appendicitis
Ureteral stone

Sources:

Berek & Novak's Gynecology, pp. 449-465, 556-561
Creasy & Resnik's Maternal-Fetal Medicine, p. 3092-3163

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