A cyst is a closed sac-like structure, an abnormal pocket of fluid similar to a blister that contains liquid, gaseous, or semi-solid material.
A cyst is located within the tissue, and can develop anywhere in the body and may vary in size – some are so tiny they can only be observed through a microscope, while others may become so large that they displace normal organs.
If the sac is filled with pus it is not a cyst, it is an abscess. Some cysts are solid and may be called tumours.
An ovarian cyst is an accumulation of fluid within an ovary that is surrounded by a very thin wall. Any ovarian follicle that is larger than approximately 2cm is an ovarian cyst.
The majority of ovarian cysts are benign (harmless) and they typically occur most frequently during a female’s reproductive years (child-bearing years).
However, ovarian cysts may affect a woman of any age. In some cases, ovarian cysts cause pain and bleeding.
If the cyst is over 5cm in diameter, it may need to be surgically removed.
There are two main types of ovarian cysts:
- Functional ovarian cysts – These are the most common type. They are harmless and form part of the female’s normal menstrual cycle. They are short-lived.
- Pathological cysts – These are cysts than grow in the ovaries; they may be benign or cancerous (malignant). There is no definite way of preventing ovarian cyst growth. However, regular pelvic examinations, which allow for early treatment if needed, usually protect the woman from complications. As most ovarian cysts present no signs or symptoms, they frequently go undiagnosed. This also makes it difficult to estimate incidence and prevalence of the condition.
The causes are different for each type of ovarian cyst, so we have to look at them one type at a time.
Functional ovarian cysts
There are two types of functional ovarian cysts:
- Follicular cysts – Follicular cysts are the most common type of ovarian cyst. A female human has two ovaries which release an egg every month. The egg moves into the uterus (womb), where it can be fertilized by a male sperm. The egg is formed in the follicle, which contains fluid to protect the growing egg. When the egg is released, the follicle bursts. In some cases, the follicle either does not shed its fluid and shrink after releasing the egg, or does not release an egg. The follicle swells with fluid, becoming a follicular ovarian cyst. Typically, one cyst appears at any one time and normally goes away within a few weeks.
- Luteal ovarian cysts – These are much less common. After the egg has been released it leaves tissue behind (corpus luteum). Luteal cysts can develop when the corpus luteum fills with blood. In most cases, this type of cyst goes away within a few months. However, it may sometimes split (rupture), causing sudden pain and internal bleeding.
Dermoid cysts are the most common type of pathological cyst for women under 30 years of age. Cystadenomas are more common among women aged over 40 years.
- Dermoid cysts – Dermoid cysts are bizarre tumours, usually benign. They develop from a totipotential germ cell (a primary oocyte) – in other words, the cell can give rise to all orders of cells necessary to form mature tissues. These cysts need to be removed surgically.
- Cystadenomas – Cystadenomas are ovarian cysts that develop from cells that cover the outer part of the ovary. Some are filled with a thick, mucous substance, while others contain a watery liquid. Rather than growing inside the ovary itself, cystadenomas are usually attached to the ovary by a stalk. Although they are rarely cancerous, they need to be removed surgically.
The following conditions may increase the risk of developing ovarian cysts:
- Polycystic ovarian syndrome
- Pelvic pain – A ruptured ovarian cyst may present similar signs and symptoms to those of appendicitis or diverticulitis.
- Irregular menstruation – Periods may also become painful, heavier or lighter than normal.
- Dyspareunia – Pelvic pain during sexual intercourse.
- Pain when passing a stool
- Pressure on the bowels
- Pregnancy symptoms, including breast tenderness and nausea
- Bloating, swelling, or heaviness in the abdomen
- Problems fully emptying the bladder
- Pressure on the rectum or bladder
- Hormonal abnormalities
Sometimes watchful waiting, also known as observation, is recommended, especially if the woman is pre-menopausal, and she has a small functional cyst (2cm to 5cm).
If the cyst is large, does not look like a functional cyst, is growing, or persists through two or three menstrual cycles, the doctor may recommend that the patient have it surgically removed.