An ovarian cyst is a fluid-filled sac in an ovary. Ovarian cysts may arise at any time from the neonatal to postmenopausal period, although they occur most often during active periods of development, such as puberty.
1. Types of cyst
Ovarian cysts that arise as the result of ovulation are termed functional cysts; they may be follicular or luteal and can be stimulated by gonadotrophins. Functional cysts tend not to cause symptoms and resolve in six to eight weeks. If there is excessive gonadotrophin stimulation, multiple functional cysts may be produced.
Neoplastic cysts may arise from all ovarian cell types, but mostly from the surface epithelium. The incidence of epithelial ovarian cystadenocarcinomas, sex cord stromal and mesenchymal tumours rises exponentially with age until the sixth decade of life.
Teratomas or dermoid cysts are a form of germ cell tumour containing elements from all three embryonic germ layers; these represent up to 10% of ovarian neoplasms.
Germ cell tumours are most common in adolescence.
Endometriomas are cysts filled with blood arising from ectopic endometrium. The ovary often contains multiple cystic follicles 2-5mm in diameter in polycystic ovary syndrome. Ovarian cysts may be detected on transvaginal ultrasonography; most of these will be functional and therefore benign.
2. Symptoms
Benign cysts do not usually cause pain but this is dependent on their size and pressure on adjacent structures. Other symptoms include dyspareunia, bowel and/or urinary symptoms. Furthermore, cysts may undergo torsion, rupture and haemorrhage.
Torsion or rupture may present with severe abdominal pain. Moreover, malignant ovarian cystic tumours may be associated with abdominal distension, bowel obstruction, nausea, vomiting, early satiety and heartburn.
Cyst rupture may cause haemodynamic compromise; it may present with a surgical abdomen with rebound tenderness and guarding. A large cyst may be palpable on abdominal or bimanual examination. Gross ascites may prevent palpation of an intra-abdominal mass. There may be adnexal tenderness or cervical excitation.1
3. Investigations
Ultrasonography is the main imaging modality for investigating ovarian cysts. MRI and CT are less commonly used.
Simple cysts are unilocular and have a uniformly thin wall surrounding a single cavity that contains no internal echoes. These cysts are likely to be functional.
In contrast, complex cysts are multilocular and may have a thickened wall; these cysts may be benign or neoplastic. Haemorrhagic cysts, endometriomas and dermoid cysts tend to have a characteristic sonographic appearance.
Cancer antigen 125 (CA125) is a protein expressed on the cell membrane of normal ovarian tissue and ovarian carcinomas. Local reference ranges may vary but according to the Royal Collage of Obstetricians and Gynaecologists (RCOG), if a cut-off level of 30 units/ml is used, the test has a sensitivity and specificity of 81 and 75% respectively.2
This test is a useful adjunct in assessing a postmenopausal woman with an ovarian cyst. Ovarian cysts are present in 6% of asymptomatic postmenopausal women.
4. Management
Simple unilateral, unilocular ovarian cysts less than 5cm in diameter have a low risk of malignancy. The RCOG recommends that in the presence of normal serum CA125 levels, these cysts can be managed conservatively.
Persistent simple ovarian cysts larger than 3-5cm, especially if symptomatic, as well as complex ovarian cysts, should be considered for surgical removal.
The RCOG recommends that a 'risk of malignancy index' (RMI) be used to select women who require surgical intervention (see box below). If the RMI is less than 25, the cyst may be monitored; a score of 25-250 should prompt referral for laparoscopy or laparotomy.
| Risk of malignancy index |
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RMI = ultrasound score x menopausal score x CA125 level Notes:
- Multilocular cyst.
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It is recommended that laparoscopic management of ovarian cysts in postmenopausal women should usually involve bilateral oophorectomy rather than cystectomy.
The aims of surgery include confirming the diagnosis and assessing whether there is malignant potential, obtaining fluid for cytology and assessing other intra-abdominal organs including the contralateral ovary.
If a malignancy is revealed during laparoscopy or subsequent histology, referral of the patient to a cancer centre for further management is recommended.
In conclusion, treatment for ovarian cysts should be based on age, whether the woman is premenopausal or postmenopausal, the size of the cyst and whether the cyst is unilocular or multilocular. In premenopausal women, a conservative approach may be preferred for cysts that appear benign.
- Dr Kochhar is a GP principal in St Leonards-on-Sea and Miss Sinha is a consultant obstetrician and gynaecologist, Conquest Hospital, East Sussex
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References
1. Salat-Baroux J, Merviel P, Kuttenn F. BMJ 1996; 313: 1098.
2. Royal College of Obstetricians and Gynaecologists. Green-top Guideline 34. London, 2003.
