Ovarian cysts are fluid filled sacs in the ovary
Ovarian cysts are usually diagnosed by ultrasound
They may be asociated with pelvic pain or abnormal bleeding
Expert ultrasound is the key to treatment
Types of ovarian cysts
The most common cysts are functional, related to the normal function of the ovaries. These can be either fimbrial cysts or luteal cysts, depending upon which part of the ovarian cycle they arise. The good things about physiological cysts are that they are completely benign, and usually resolve completely without treatment.
Cysts that arise from the surface skin of the ovaries are called epithelial cysts. These can be benign, borderline or malignant. The benign ones are called cystadenomas, and the malignant ones cystadenocarcinomas. Epithelial ovarian cancer is the most common type of malignant ovarian cancer.
Germ cell tumours
Ovarian cysts can arise from the egg cells and give rise to benign tumours called dermoid cysts. This is one of the most common benign cysts. Malignant tumours can also arise from egg cells and are called malignant teratomas.
Tumours from granulosa and theca cells
Tumours can arise from the cell layers in the follicle surrounding the egg cells. These may be benign. The malignant tumours in this group tend to be lest aggressive than epithelial ovarian cancers.
Other conditions that give rise to ovarian cysts
Polycystic ovarian syndrome
This syndrome is characterised by multiple peripheral cysts on the ovary, usually seen on ultrasound. The cysts seen are not important, and the condition is more a metabolic condition rather than anything related to the ovarian cysts. The syndrome may be associated with menstrual irregularities, acne, hirsuitism and infertility.
Endometriosis is a condition where tissue that looks like the lining of the uterus is found in other sites, most commonly on the side of the pelvis. Endometriosis on the ovary may form cysts that can be seen on ultrasound.
Ovarian cyst mimics
Occasionally cysts in other structures will ‘mimic’ ovarian cysts. Common examples of this are fimbrial cysts on the end of the fallopian tube, and a hydrosalpinx which is a fluid collection within the fallopian tube. Fibroids sometimes occur in the tissue next to the ovary called the broad ligament and so appear to be attached to the ovary.
Secondary ovarian tumours
Cysts may develop in the ovaries as a result of malignant tumours in other organs, most commonly the large bowel, the breast or thyroid. These tumours may be difficult to differentiate from ovarian tumours that originate in the ovaries.
What is Polycystic Ovarian Syndrome?
This is a condition where a hormone imbalance is associated with the formation of many small cysts around the surface of the ovaries. The cysts themselves do not cause any problem and are merely a manifestation of the underlying imbalance, and therefore do not need to be treated.
How are ovarian cysts diagnosed?
An ultrasound scan, is the simplest and best way to diagnose an ovarian cyst. In expert hands, an ultrasound scan will give very accurate information about the nature of the cyst and will likely give a diagnosis. Most scans are not of this quality and may need to be repeated by a more experienced operator.
In a small number of cases, an MRI scan may give additional information.
A transvaginal scan usually gives better information than a transabdominal scan
What symptoms do ovarian cysts cause?
Most ovarian cysts cause no symptoms at all and many are discovered because of scans for other reasons. The following symptoms may be noticed.
- Lower abdominal pain which may be intermittent, but more usually constant
- Irregularity of the menstrual cycle or bleeding between periods
- Pain with sex
- Abdominal swelling or a lump in the abdomen
Can cysts cause any problems?
An ovarian cyst can…
- …burst. This may cause sudden pain that settles after a few hours without treatment. This usually occurs in simple fluid filled cysts and is not dangerous as the fluid is just absorbed by the body. Rarely, the ovary may continue to bleed and may need treatment.
- …be bled into. This causes a sudden onset of pain that may last for many hours. This most commonly occurs in luteal cysts and will usually stop spontaneously. Providing this can be correctly diagnosed it often does not require any treatment. It may need careful monitoring in hospital.
- …undergo torsion. When this happens the whole ovary is twisted with the cyst and the blood supply is quickly blocked. The ovary may untwist by itself which will restore the blood flow, but otherwise it is an emergency since the lack of blood will cause the ovary to die within a few hours.
These are all called “cyst accidents”.
Diagnosing an Ovarian Cyst
An ultrasound scan is the most common investigation for an ovarian cyst. The scan shows some of the characteristics of the cyst and points to the likely type of cyst. An abdominal scan may be performed first, and is useful if the cyst is large. An abdominal scan also allows other structures in the abdomen to be visualised. A full bladder improves visualisation of the pelvic structures as the fluid in the bladder makes a kind of “window” to the pelvis. A transvaginal scan brings the ultrasound probe much closer to the pelvic organs and usually gives better detail of the ovaries, fallopian tubes and uterus. This scan should not cause any discomfort and does not require a full bladder.
Ultrasound characteristics of ovarian cysts
- Thickness of the outer wall of the cyst. A simple cyst has a thin outer wall.
- Irregularities in the cyst wall. A simple cyst has a smooth wall whereas a complex cyst may have some irregular nodules or thickening of the wall.
- Internal divisions or “septae” are found only in complex cysts. These may be thin or thick and may also contain irregularities.
- Solid areas are seen in some complex cysts.
- The nature of the “fluid” filling the cysts varies and ultrasound can give some insight into this. Blood often looks very different to the thin fluid of a follicular cyst.
- If similar cysts are present on both ovaries this may be significant.
- Blood flow through various parts of the cyst can be measured by Doppler scanning and helps determine the nature of the cyst.
All the above characteristics are taken into account by the ultrasonographer who may be able to form a judgement on the type of cyst present. Such judgements are never 100% accurate and are sometimes very difficult. However they may give some guidance as to how to manage the cyst.
The information gained by an ultrasound examination is very dependent on the skill of the person performing the scan. Most radiologists have areas of the body they are particularly interested in and develop skills in those areas specifically. Choice of the right person to perform a scan is important, particularly if the diagnosis is difficult.
If a cyst appears simple, the ultrasound scan may be repeated at an interval of 4 to 6 weeks to see whether the cyst has resolved or increased in size.
This blood test measures the presence of a tumour antigen. The CA125 level may be elevated in ovarian cancer, although in 30% of early cancers it is not elevated at all. It is also elevated in many other circumstances including endometriosis. The CA125 level changes with the normal menstrual cycle and is therefore more useful after the menopause.
Magnetic Resonance Imaging is an alternative method of scanning the ovaries. It provides information that complements the ultrasound findings. The MR image differentiates between different tissue types by imaging the molecular characteristics of tissue. It can identify fat, blood and other tissues. If the cyst is complex MRI may be useful in helping to determine what type of cyst is present.