The ovaries are the two small organs located on either side of the uterus which produce female hormones and produce and release an oocyte ("egg") each month, a process called ovulation.
An ovarian cyst is a fluid filled pouch within the ovary. It is normal for the ovaries to contain small fluid filled cysts at any given time. Occasionally a cyst can become large and dysfunctional and cause pain and other symptoms. Occasionally a tumor can have a cystic appearance. For this reason, all cysts should be checked out by a health care provider.
1. Functional Cysts
Under normal circumstances the ovaries are always producing cysts throughout the cycle:
The ovaries produce hundreds of tiny cysts (follicles) each month. Each contains an egg. Within a few days one of these becomes the "dominant follicle", ie the one that will ovulate. The dominant cyst (follicle) produces hormones that cause all the other follicles that developed that month to shrivel up and go away. (Yes, ovulation is a naturally a very wasteful process). The remaining egg develops within the fluid filled dominant follicle ("simple follicular cyst") each month. This cyst continues to get larger until it reaches 2 to 4cm in diameter, then it typically bursts ("ovulation"). After ovulation, the cyst partially collapses and produces progesterone for the last 2 weeks for the cycle. This collapsed cyst is called a "corpus luteal cyst". Sometimes the cyst can bleed into itself and form a small clot after ovulation, that slowly resolves. This is called a "hemorrhagic cyst".
Most of these cysts cause no problems at all. Occasionally they can grow abnormally large, or not actually ovulate (these simple cysts are suppose to burst at the time of ovulation when they release the egg). If they get to be larger than 5cm, the risk of torsion (twisting on the stem that brings blood to the ovary) is increased, so often they are drained at this point.
Polycystic ovaries are normal ovaries' reaction to being in an insulin resistant body. When you are insulin resistant, the dominant follicle does not form, and the many tiny follicles remain in a state of partial development early in the process at the surface of the ovary. The cysts themselves are not a problem, except that they produce high levels of estrogen and testosterone. They are more a symptom of a more concerning condition, insulin resistance.
These are collections of endometriosis that build-up within the ovary. Endometriosis is a condition that occurs when the lining of the uterus travels outside of the uterus and reimplants itself elsewhere in the pelvis and cycles there. If it burrows into an ovary and cycles and bleeds within the ovary, the blood typically has nowhere to go. It builds up and eventually turns a chocolate brown color as it begins to disintegrate within the uterus. These have been nicknamed "chocolate cysts" for that reason. They have a classic ultrasound appearance and are often associated with a lot of cyclic menstrual pain.
4. Benign Tumors
a. Dermoid Cysts
These are benign tumors that arise from the germ cells within the ovary that would normally eventually form the egg cells (oocytes) that ovulate each month. When they divide abnormally as a tumor, they form a cystic structure in the ovary that contains hair, sebaceous glands and sebaceous material, and sometimes even teeth (all skin structures, hence the name "dermoid"). They may stay small and not cause any symptoms, or become large and cause discomfort.
These benign (ie not cancerous) cystic tumors arise from cells on the outside surface of the ovary and contain a gelatinous material. Some stay small, while others are capable of becoming very large, actually distending the abdomen and weighing several pounds (some have been reported to be as large as 20 pounds). If they get large, they can cause discomfort.
c. Peritubal Cysts
These are not ovarian cysts, but cysts from the tubes that are present from birth, and thought to be remnants of the male genital system (both male and female genital systems form when you are a fetus, and one disintegrates as you develop). On ultrasound they can be difficult or impossible to distinguish from ovarian cysts.
Rarely an ovarian cyst might represent a cancerous growth. Ovarian cancer is uncommon in young women but risk does increase with age. Currently the lifetime risk of ovarian cancer is 1/52, with most of these occurring after menopause. Cysts are more likely to be cancerous if they are associated with free fluid in the pelvis, and have a complex appearance on ultrasound (thick septations, thickening in the wall of the cyst) and are bilateral or occur after menopause.
Typically functional ovarian cysts produce no symptoms. They get blamed for a lot of unrelated symptoms in fact. That's because there is (and should be) almost always an ovulatory cyst present on the ovaries at some stage of development, unless you are on the pill, which suppresses ovulation, or in menopause. Often when you have pelvic pain, and someone sees this normal ovulatory cyst, the pain is blamed on the cyst, but it isn't usually the cause.
In the unusual cases where ovarian cysts cause symptoms it is usually because they are particularly large. In this case they produce a dull ache, sometimes place pressure on the bladder. Occasionally they can tort (twist) on their blood supply, especially if they are larger than 5cm, and produce more intense dull pain, or burst and produce a few hours of sharp pain. Every normal ovulatory cyst bursts at ovulation (that's how you ovulate) and usually this does not produce intense pain unless the cyst was very large.
Would my symptoms be different if the ovarian cyst were really a cancer?
Typically not. One of the problems with ovarian cancer is that it can grow silently (ie with no symptoms at all) until it is very advanced. However there are subtle warning signs of early ovarian cancer. They are non-specific, and common with many conditions, including simple benign ovarian cysts, but one condition that will cross your gynecologist's mind is ovarian cancer when you describe these. That's why a pelvic ultrasound is commonly ordered when you mention these symptoms.
Sometimes ovarian cysts can be felt on pelvic exam. An experienced gynecologist who has been in practice more than 10 years can detect an enlarged ovarian cyst, when it is present, about 50% of the time in most studies. Ability to detect cysts and masses on ovaries during a routine exam decreases as weight increases, and currently 70% of the American population is overweight, so physical exam is fairly limited.
Pelvic ultrasound is usually the best way to look at ovaries. This procedure uses sound waves to create a picture image. A very slender instrument called a "transducer" is placed in the vagina and the ovaries carefully examined by ultrasound for location, size and features of the cysts.
Laparoscopy is an outpatient surgery in which a small camera is placed through an incision in the belly button and the cyst examined by directly looking at it. Laparoscopy is also the preferred way to remove many benign ovarian tumors or functional cysts that are causing symptoms.
CA-125 is a blood test that can be useful for detecting whether or not an ovarian cyst is cancerous in post-menopausal women. It is not at all useful in pre-menopausal women because there are far too many false positives and negatives. There are even some false positives and negatives in post-menopausal women (although less than in younger women), so you can't rely on it too much even in that age group.
Most cysts are observed for 2 cycles or so because most functional cysts disappear during that period of time. Usually an ultrasound is repeated 6 weeks after the cyst has been observed, to be sure that it has resolved (gone away). Cysts that persist beyond that period of time are usually removed surgically (usually by laparoscopy) because they are less likely to be functional.
If you are having trouble with recurrent functional ovarian cysts that give you symptoms, the oral contraceptive pill often helps by stopping you from ovulating. It does not make an existing cyst go away faster, but it prevents new ones from forming.
If your cyst is large, persistent, has concerning features or is causing too many symptoms for you, your gynecologist may recommend removing it surgically.
The aim is to remove the cyst in the most minimally invasive way, while at the same time not compromising your outcome in the rare event that the cyst is a cancer. If the risk for cancer is low, which it usually is, then your physician will usually choose to remove the cyst through the laparoscope and spare the rest of the ovary if possible. Most of the time, this is how we handle cysts that need surgical management. Sometimes a simple cyst causing problems is simply drained laparoscopically.
Occasionally, it will be recommended that the entire ovary be removed, or sometimes even both ovaries. In some circumstances, it is in your best interest to have the cyst removed through a larger incision in your abdomen, even though the recovery may be longer.
The type of surgery recommended depends on your age, the type of cyst and location, the extent of concern that it might be a cancer, and your desire for future childbearing. Sometimes your physician will not know what the best course of action is until after the surgery has started and they've had a chance to have a good look at the cyst and the pelvis.
For more information, please see the American College of Ob/Gyn's brochure: Ovarian Cysts.