Family doctor

What is an ovarian cyst?

An ovarian cyst is a fluid-filled sac-like structure that forms from one of the ovaries. Although the finding of an ovarian cyst is often upsetting to the patient, the majority of ovarian cysts are not tumours, but rather are simple structures termed functional or physiological cysts. These occur as part of the normal physiological functions of the ovary throughout the menstrual cycle.

Occasionally ovarian cysts occur as part of an ovarian tumour; such tumours may be benign (non-cancerous) or malignant (cancerous) and usually have a complex structure. Benign ovarian (non-functional) cysts include cystic teratomas and endometriomas ('chocolate cysts').

This article focuses primarily on functional ovarian cysts.

How common are ovarian cysts?

Ovarian cysts are very common and can develop at any age . They are most common in pre-menopausal women, in whom ovarian cysts occur in 30% of those with regular periods and 50% of those with irregular periods. In addition, ovarian cysts occur in 6% of post-menopausal women; these are not functional cysts (as there is no ovulation) but may be simple in structure.

What causes ovarian cysts?

Functional ovarian cysts develop during the course of the menstrual cycle. In a normal menstrual cycle the ovary develops small follicles on its surface, one of which enlarges to 2-3 cms. At ovulation (mid-cycle), the dominant follicle ruptures and releases the egg (ovum). The follicle then transforms to a structure called the corpus luteum, the function of which is to produce the pregnancy hormone progesterone if fertilization takes place (until the placenta takes over this role). If fertilization does not occur, the corpus luteum shrivels and disappears.

Functional cysts arise from either the follicle or the corpus luteum (depending on the stage in the menstrual cycle at which they occur). Follicular cysts develop when ovulation does not occur, and the follicle continues to grow. Functional cysts can also occur if the corpus luteum persists after ovulation beyond its normal 2-week phase.

Functional cysts may be stimulated by excessive amounts of the female hormones FSH and hCG. These and other agents may be used to induce ovulation in infertility patients, who thus have an increased risk of developing functional cysts. In contrast, combined oral contraceptive (OC) pills reduce the likelihood of developing functional cysts because they suppress ovulation.

How are ovarian cysts diagnosed?

Ovarian cysts are usually diagnosed by chance, either during a regular pelvic examination or as an unexpected finding during an ultrasound examination of the pelvis.

If the examining doctor detects a mass during a regular pelvic examination, she/he will usually refer the patient for an ultrasound examination of the pelvis in the first instance. This may be performed over the abdomen (similar to a pregnancy scan) or via the vagina using a special ultrasound probe. An ultrasound examination can determine if the mass is a cyst, and if so, whether it has a simple structure (usually a functional cyst) or a more complex one (more likely to be an ovarian tumour). If the cyst is not simple in nature, other imaging studies may be performed, including MRI and CT scans.

In addition to ultrasonography, a blood test for CA-125 may be performed. CA-125 is known as a tumour marker, and is often markedly increased in ovarian cancer, although it may also be raised in other conditions.

What are the symptoms of ovarian cysts?

Most simple ovarian cysts do not produce symptoms unless they have associated complications. Symptoms that may occur with ovarian cysts include:

• lower abdominal pain or discomfort
• fullness or bloating
• pain with sexual intercourse
• urinary frequency or difficulty with bowel movements (because of pressure on adjacent pelvic anatomy)
• irregular periods or spotting.

Are there any complications associated with ovarian cysts?

Ovarian cysts may rupture, twist, bleed or become infected, all of which are likely to cause severe pain and may cause nausea and vomiting. Rupture of a cyst often occurs after exercise, sexual intercourse, trauma or even a pelvic examination. Torsion (twisting) and haemorrhage are more likely in right-sided ovarian cysts.

Simple cysts are unlikely to become malignant (cancerous).

How are ovarian cysts managed?

The management of ovarian cysts depends on a number of factors, including age of the woman, size of the cyst, type of cyst as determined by ultrasound (simple or complex), level of CA-125 and the presence or not of symptoms.

If ultrasound identifies that the cyst is simple, a wait-and-see plan ('expectant management') may be appropriate, because many simple ovarian cysts resolve spontaneously. In fact one study of 278 women aged 14 to 81 years with simple cysts found that 44% of cysts resolved with no treatment.

With expectant management, the woman has a repeat ultrasound 6-8 weeks after the simple cyst was first diagnosed. In the past, combined oral contraceptives were often prescribed to pre-menopausal patients during this time, but it is now accepted that these agents only prevent the development of functional cysts and do not suppress them. If the cyst has persisted after the observation period, then the patient is usually referred for surgical evaluation.

Expectant management is not recommended in women with large cysts, symptoms, elevated CA-125 or if other specific female hormones are increased. Some specialists suggest aspirating persistent simple cysts as a second step before surgery, whilst others prefer to proceed directly to surgery in those who are not suitable for expectant management. Surgery is also usually necessary for women presenting with ovarian cyst complications.

The aims of surgery are to confirm the diagnosis of an ovarian cyst, assess whether there is any cancerous appearance, and remove the entire cystic structure for laboratory analysis of the tissue. Surgery may be performed by an abdominal operation or by laparoscopy; the latter approach is appropriate for those thought to have a non-cancerous simple cyst (unless it is too big). If the patient wishes to retain her ovary, it does not have to be removed along with a simple cyst; however, those with an increased risk of later developing ovarian cancer may be advised to sacrifice their ovaries(if they have completed child-bearing or are approaching or post-menopausal).

Bibliography:

• Helm CW. Ovarian cysts. Emedicine; available from: http://www.emedicine.com/med/topic1699.htm. Accessed July 2001
• Kazzi A. Ovarian cysts. Emedicine: available from http://www.emedicine.com/emerg/topic352.htm. Accessed June 2001
• Rice LW. The ovary. In: Ryan KJ, Berkowitz RS, Barbieri RL, Duanif A, eds. Kistner's Gynecology & Women's Health:, 7th ed. St Louis: Mosby Inc, 1999: 166-90
• Salat-Baroux J, Merviel P, Kuttenn F. Management of ovarian cysts. British Medical Journal 1996;313:1098
• Thach AM, Young GP. Pelvic pain. In: Rosen P, editor-in-chief, Barkin R, Danzl DF, Hockberger RS, editors. Emergency Medicine: Concepts and Clinical Practice. 4th ed. St Louis: Mosby-Year Book Inc, 1998: 2293-2304
• Zanetta G, Lissoni A, Torri V, et al. Role of puncture and aspiration in expectant management of simple ovarian cysts: a randomised study. British Medical Journal 1996;313:1110-3