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. Ovarian cysts can range widely in size; from being as small as a pea to larger than an orange - in rare cases ovarian cysts can become so large that the woman looks pregnant.
The majority of ovarian cysts are benign (harmless). According to the Centers for Disease Control and Prevention (CDC), USA, most premenopausal women and up to 14.8% of postmenopausal women are found to have ovarian cysts.
Ovarian cysts typically occur most frequently during a female's reproductive years (childbearing 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 - the most common type. These harmless cysts form part of the female's normal menstrual cycle and are short-lived.
- Pathological cysts - these are cysts than grow in the ovaries; they may be harmless (benign) or cancerous (malignant).
Contents of this article:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on ovarian cysts
Here are some key points about ovarian cysts. More detail and supporting information is in the main article.
- An ovarian cyst is a buildup of fluid within an ovary surrounded by a thin "shell".
- A cyst is a closed sac-like structure like a blister. It consists of liquid, gaseous, or semi-solid substance.
- A cyst is not a normal part of the tissue, it has a separate membrane. The outer section of a cyst is called the cyst wall.
- Ovarian cyst size can range widely from being as small as a pea to larger than an orange.
- Ovarian cysts are usually benign (harmless).
- Ovarian cysts occur most frequently during a female's reproductive years.
- There are two main types of ovarian cysts: functional ovarian cysts and pathological cysts.
- In most ovarian cyst cases, they will cause no signs or symptoms.
- Complications of ovarian cysts include torsion, bursting and in rare cases, cancer.
- Treatment options for ovarian cysts include "watchful waiting", birth control pills or surgery.
What is a cyst?
A cyst is a closed sac-like structure - an abnormal pocket of fluid, similar to a blister - that contains either liquid, gaseous, or semi-solid material.
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.
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.
In anatomy, a cyst can also refer to any normal bag or sac in the body, such as the bladder. In this text, cyst refers to an abnormal sac or pocket in the body that contains either liquid, gaseous or semi-solid substances.
A cyst is not a normal part of the tissue where it is located. It has a distinct membrane and division on nearby tissue - the outer or capsular portion of a cyst is called the cyst wall.
If the sac is filled with pus it is not a cyst, it is an abscess. Some cysts are solid and may be called tumors (pathological cysts). The word tumor does not necessarily mean it is cancerous - a tumor is a medical term for a swelling.
Causes of ovarian cysts
In this section we look at the causes of ovarian cysts. As the causes are different for each type of ovarian cyst, we will look at each type one at a time.
Functional ovarian cysts
There are two types of functional ovarian cysts:
1) Follicular cysts
Follicular cysts are the most common type of ovarian cyst. A female human has two ovaries, small round organs 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 (without treatment).
2) 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 (cystic teratomas)
A dermoid cyst a bizarre tumor, usually benign. This type of cyst develops 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. Dermoid cysts contain hair, skin, bone and other tissues (sometimes even teeth). A totipotential germ cell can develop in any direction. They are formed from cells that make eggs. These cysts need to be removed surgically.
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. By existing outside the ovary, they have the potential to grow considerably. Although they are rarely cancerous, they need to be removed surgically.
The following conditions may increase the risk of developing ovarian cysts:
Endometriosis is a condition in which cells that are normally found inside the uterus (endometrial cells) are found growing outside of the uterus. That is the lining of the inside of the uterus is found outside of it. Endometrial cells are the cells that shed every month during menstruation, and so endometriosis is most likely to affect women during their childbearing years. Women with this condition have a higher risk of developing ovarian cysts.
Polycystic ovarian syndrome (PCOS)
In this condition many small and harmless cysts develop on the ovaries, caused by a problem with hormone balance produced by the ovaries. People with PCOS have a higher risk of developing ovarian cysts.
Symptoms of ovarian cysts
A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.
A ruptured ovarian cyst may present similar signs and symptoms to those of appendicitis or diverticulitis.
In the vast majority of cases, ovarian cysts are small and benign (harmless); there will be no signs or symptoms.
Even if there are symptoms, they alone cannot determine whether a patient has an ovarian cyst. There are several other conditions with similar signs and symptoms, including endometriosis, pelvic inflammatory disease, ectopic pregnancy or ovarian cancer. A ruptured ovarian cyst may present similar signs and symptoms to those of appendicitis or diverticulitis.
Signs and symptoms of an ovarian cyst may include:
- Irregular menstruation - periods may also become painful, heavier or lighter than normal
- A pain in the pelvis. This may be persistent pain or an intermittent dull ache that may spread to the lower back and thighs
- Pelvic pain may appear just before menstruation begins
- Pelvic pain may occur just before menstruation ends
- Dyspareunia - pelvic pain during sexual intercourse. Some women may experience pain and discomfort in the abdomen after sex
- Pain when passing a stool (doing a poo)
- Pressure on the bowels
- Some 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 - the patient may have to go to the toilet more often, either to urinate or pass a stool
- Hormonal abnormalities - in some rare cases the body produces abnormal amounts of hormones, resulting in changes in the way the breasts and body hair grow.
Complicated cyst signs and symptoms
- Torsion - the stem of an ovary can become twisted if the cyst is growing on the stem, blocking the blood supply to the cyst and causing severe pain in the lower abdomen
- Bursting - if the ovarian cyst bursts, the patient will experience severe pain in the lower abdomen. If the cyst is infected pain will be worse. There may also be bleeding
- Cancer - in rare cases an ovarian cyst may be an early form of ovarian cancer.
On the next page we look at how ovarian cysts are diagnosed, plus prevention and treatment options for ovarian cysts.