Ovarian cysts:
when they need evaluation or treatment.

An ovarian cyst is a fluid-filled sac on or inside an ovary. During a normal cycle, the ovary grows a follicle that releases an egg and then becomes a structure called the corpus luteum; either one can fill with fluid and linger for a few weeks. These are functional cysts, and the Office on Women's Health notes that most women make at least one follicle or corpus luteum cyst every month, usually without ever knowing it. ACOG puts it simply: ovarian cysts are very common, most are benign, and most go away on their own without treatment.

Other kinds are less common and behave differently. An endometrioma is a cyst caused by endometriosis, filled with old blood. A dermoid cyst (teratoma) is a benign growth present from early development that can contain tissue such as skin or hair. A cystadenoma grows from the surface of the ovary, is usually benign, and can become quite large. Unlike functional cysts, these don't come and go with the cycle, which is one reason a cyst that persists over several months gets a closer look. Rarely, a cyst is malignant, and the risk rises with age, especially after menopause.

Sources: ACOG, Ovarian Cysts · Office on Women's Health, Ovarian Cysts

In most cases, nothing. ACOG notes that many cysts are found during a routine pelvic exam or on imaging done for another reason, and the Office on Women's Health describes most as small and symptom-free. When a cyst does cause symptoms, it is usually a dull or sharp ache low in the abdomen on one side, a feeling of pressure or bloating, pain with sex, or pain during certain activities. A corpus luteum cyst can delay a period or cause spotting. These symptoms overlap with many other conditions, which is why a cyst is confirmed by ultrasound rather than by symptoms alone.

Two complications turn a quiet cyst into an emergency. A cyst can rupture, which causes sudden, severe pain and occasionally significant internal bleeding. A larger cyst can cause ovarian torsion, in which the ovary twists on its blood supply; the pain is typically one-sided, may come and go before becoming constant and severe, and often comes with nausea and vomiting. Torsion threatens the ovary itself and is treated surgically, ideally quickly enough to untwist and save it. The Office on Women's Health lists the signs that call for immediate care: pain with fever and vomiting, sudden severe abdominal pain, faintness, dizziness, or weakness, and rapid breathing.

Sources: ACOG, Ovarian Cysts · Office on Women's Health, Ovarian Cysts

Transvaginal ultrasound is the test that matters. ACOG's guidance on adnexal masses calls it the recommended imaging for a suspected or incidentally found pelvic mass, and no other imaging has proven superior enough to replace it. The scan measures the cyst and, more importantly, characterizes it: whether it is a simple cyst, a thin-walled sac of clear fluid, or a complex one with solid areas, internal walls, debris, or irregular borders. Simple cysts are almost always benign regardless of a woman's age or the cyst's size. Features that raise concern, in ACOG's words, include size greater than 10 centimeters, papillary or solid components, irregularity, fluid in the abdomen, and high blood flow on Doppler.

Blood tests play a supporting role. CA-125 is a protein that can be elevated with ovarian cancer, but it is also raised by endometriosis, fibroids, infection, and even menstruation, so in women who are still cycling it causes more confusion than clarity. After menopause it is more useful: ACOG notes that an elevated CA-125 together with a pelvic mass in a postmenopausal woman is highly suspicious and should prompt referral to a gynecologic oncologist. A pregnancy test is checked when it applies, since early pregnancy and ectopic pregnancy can look like a cyst. MRI is reserved for the uncommon case where ultrasound leaves a question. At Sparrow Women's Health in Winter Garden, Florida, Dr. Megan Luciano, a board-certified gynecologist, performs transvaginal ultrasound in the office, so a cyst found at a visit can be characterized the same day and followed with the same eyes over time.

Source: ACOG Practice Bulletin No. 174, Evaluation and Management of Adnexal Masses

For a simple or functional-appearing cyst in a woman who is still having periods, the standard approach is watchful waiting: a repeat ultrasound after a cycle or two to confirm the cyst has shrunk or disappeared. ACOG describes this as monitoring with repeat ultrasound to see whether the cyst has changed in size or appearance, and it notes that functional cysts often resolve within six to eight weeks. A cyst that has clearly shrunk needs no further follow-up. One that is unchanged is rechecked later; one that has grown or changed in character prompts a different conversation.

Size alone does not decide. ACOG states that no definitive size cutoff for surgery has been established, that simple cysts up to 10 centimeters can be safely monitored with repeat imaging even in postmenopausal women, and that even larger simple cysts often regress on their own. Radiology groups have published more detailed follow-up schedules based on size and menopausal status; those are reporting guidelines rather than ACOG recommendations, and your clinician will translate them into a plan for you. One common misconception is worth correcting: hormonal birth control does not shrink a cyst that already exists. A Cochrane review found that birth control pills did not speed the resolution of functional cysts in any trial. What the pill does do is suppress ovulation, which can reduce the formation of new functional cysts in women who get them repeatedly.

Sources: ACOG, Ovarian Cysts · ACOG Practice Bulletin No. 174 · Cochrane Review, Oral contraceptives for functional ovarian cysts (2014)

ACOG lists the situations in which surgery may be recommended: a cyst that is very large, one that is causing symptoms, or one in which cancer is suspected. The Office on Women's Health adds the practical markers that move a cyst from waiting to acting: it does not go away after several cycles, it gets larger, it looks unusual on ultrasound, or it causes pain. Torsion and a rupture with significant bleeding are surgical emergencies. Endometriomas and dermoid cysts are often removed when they are symptomatic or growing, since they will not resolve on their own.

When surgery is needed and the cyst is thought to be benign, ACOG recommends a minimally invasive approach, typically laparoscopy through small incisions. For women who want to preserve fertility, the goal is usually a cystectomy, removing the cyst and leaving the ovary, and even a twisted ovary is untwisted and preserved whenever possible. Removing the whole ovary is considered when a cyst has destroyed it, after menopause, or when cancer is a concern, in which case ACOG recommends the surgery be done by or with a gynecologic oncologist. Dr. Luciano maintains surgical privileges at a local surgery center for minor gynecologic procedures and provides trusted referrals for major surgery.

Sources: ACOG, Ovarian Cysts · Office on Women's Health, Ovarian Cysts

After menopause the ovaries stop making functional cysts, so a new cyst has no monthly explanation, and ACOG notes that while most masses in postmenopausal women are still benign, the risk of malignancy is considerably higher than before menopause. That does not mean every cyst after menopause needs surgery. Small simple cysts are common in postmenopausal women and are very likely benign; ACOG's guidance supports monitoring simple cysts with repeat ultrasound even after menopause. What changes is the threshold for concern: a complex cyst, a cyst with solid parts, a growing cyst, fluid in the abdomen, or an elevated CA-125 alongside a mass each prompts prompt referral. Persistent bloating, pelvic pressure, feeling full quickly, or new urinary urgency in a postmenopausal woman deserve an evaluation that includes an ultrasound, even without a known cyst.

Source: ACOG Practice Bulletin No. 174, Evaluation and Management of Adnexal Masses