2006-06-05-14 Ovarian cyst © Cuillier www.thefetus.net/
Fabrice Cuillier, MD*, Denies J, MD**
* Department of Obstetrics and Gynecology, Hôpital Félix Guyon ** Sonograhpher, Bourbon avenue, Reunion Island, France
Definition: Ovarian cysts are rare benign anomalies that usually resolve spontaneously. These cysts originate from the follicle epithelium. They can also be a theca-lutein cyst, corpus luteum cysts and simple cysts. Small follicular or functional theca-lutein cysts are a common finding in fetal and neonatal ovaries. We described a case report of an ovarian cyst diagnosed at 30 weeks.
Case report: A 35-year-old woman, G3P2, was referred at 30 weeks due to a fetal abdominal cyst. There was no previous relevant family history of genetic or structural abnormalities. At 8, 12 and 24 weeks, the scans were normal. The nuchal translucency was also normal. At 30 weeks, a pelvic cyst was seen in a routine scan. A left-sided unilocular fetal ovarian cyst was identified, separate from the bladder and the stomach, measuring 25 x 30 x 30 mm. An MRI confirmed the diagnosis. At 34 weeks, the cyst had the same size. The delivery occurred at 38 weeks. The clinical examination was normal. A scan was performed at day 15. A right ovarian cyst was present (1,4 x 1,6 x 1,8 mm) without any associated kidney anomaly.
Transverse view of the ovarian cyst at 31 weeks
Note the relationship between the cyst and the bladder
MRI longitudinal section at 32 weeks showing the cyst with a thin wall
MRI transverse section at 32 weeks showing the cyst
History: The first publication about antenatal ovarian cysts was in 1989. The first prenatal sonographic description of an ovarian cyst was performed by Valentin (1975) (1). Since then, ovarian cysts have also been increasingly recognized in newborns.
Prevalence: Fetal and neonatal ovarian cysts are an uncommon finding. Foley, in 2004, described that only 53 cases were reported since 1971 (2). But since the advent of routine prenatal scanning, fetal ovarian cysts are detected more frequently. Kirkinen described the incidence of the cysts at about 1:2625. According to Heling, ovarian cysts represent 5% of female abdominal tumors. A review of the literature reveals that 85% of total fetal ovarian masses are cystic (follicular or luteinic etiologies) and 15% are organic (< 3% are carcinomas). 12% of all ovarian cysts are represented by teratomas and mucinous/serous cystadenomas. According to Brandt’s series, torsion occurred prenatally in 38% of the cases.
Etiology: Stimulation of the fetal ovary by both placental human chorionic gonadotropin and maternal estrogen is generally considered to be responsible for the cysts. It also explains why the majority of these ovarian cysts are benign follicular and functional theca-lutein. After delivery, the decrease of hormonal stimulation may lead to spontaneous resolution of the ovarian cyst. The association of fetal ovarian cysts with maternal diabetes and hypothyroidism has also been described (3).
Pathogenesis: Small physiological follicular cysts are present in normal neonatal ovaries. The ovarian cyst develops from these follicles and may either remain simple or become a complex mass. Follicular ovarian cysts can be found in 1/3 of female babies (4). All fetal ovarian cysts begin as simple follicular cysts or follicular-luteinic. They are the consequence of HCG hypersecretion or gonadotropin activity perturbation. This explains the increased incidence of ovarian cysts in infants of mothers with diabetes, preeclampsia or rhesus isoimmunization (5). An ovarian cyst can only appear if the gonad is mature enough to respond to hyperstimulation. This explains why ovarian cysts generally appear only during the third trimester. Nevertheless, Meizneir described eight cases diagnosed before 28 weeks (two before 19 weeks) (5). Perrotin described four cases before 24 weeks (6).
Complications like torsion, hemorrhage (8) or rupture may occur pre or postnatally and results in a complex ovarian cyst. When this happens there is a risk of loosing the ovary (7). Whereas prenatal complications do not appear to cause clinical problems, perinatal and postnatal complications seem to be associated with serious morbidity and mortality (9).
Sonographic findings: The diagnosis of fetal ovarian cysts is most common during a routine scan or following an obstetrical complication caused by the ovarian cyst. The detection of ovarian cysts has been increased with the use of prenatal and postnatal sonography. Fetal ovarian cysts are usually unilateral and the average size is about 3 to 5 cm in diameter at diagnosis.
The ultrasound finding is an anechoic abdominal mass without peristalsis. The Doppler reveals little peripheric vascularization. The diagnosis of ovarian cyst is confirmed if the diameter is larger than 20 mm (9). The bladder must be seen surrounded by the two umbilical arteries to make the differential diagnosis. The ovarian cysts are located above the bladder and below the stomach and the gallbladder. An abnormality involving the intestinal and urinary tracts should be excluded.
The sonographic features of complicated and uncomplicated ovarian cysts are different:
Uncomplicated: Anechoic, round, homogeneous with posterior echogenic intensify, > 20 mm in diameter, unilocular, pelvic or more often intra-abdominal, unilateral or seldom bilateral, thin-walled. The color Doppler flow is normal.
Complicated: Heterogeneous with fluid and hyperechogenic components, thick walled with sedimentation and fluid levels, with or without intracystic clots, containing free-floating material with intracystic septations, mobile after adnexal torsion. The absence of color Doppler flow occurs in almost 100% of cases that are complications of torsion. There is no established correlation between the sonographic findings and the histological nature of the ovarian cyst. Nevertheless, prenatal histological diagnosis does not affect the management. Quarello et all described recently the "daughter cyst sign", which consists of the existence, within or outside the main cyst, of small (2-8 mm), round, anechoic structures. This feature confirms the ovarian origin of the cysts in Lee’s study with a sensitivity of 82% and specificity of 100% (1). However, the main differential diagnosis is the ureterocele. This "daughter cyst sign" might be explained by the hormonal dysfunctions responsible for the genesis of follicular or luteinic cysts, which are the most common (1).
Implications for targeted examinations: During a fetal scan, it is important to look for signs of complications. In a French series (Saint Vincent de Paul), 30 cysts (in 56 cases described) were not complicated. The complication signs include:
Signs of compression: Large ovarian cysts can compress other viscera but can resolve spontaneously. The appearance of polyhydramnios, as a result of partial obstruction of the gastro-intestinal tract, as well as that of ascites, as the result of transudation, have been described in the literature (3).
Signs of torsion: Torsion may happen with any size of ovarian cyst. A possible sign of torsion is the emergence of fetal tachycardia due to peritoneal irritation (3). Enucleation of the ovarian cyst has also been described.
Signs of rupture (4): Some fluid can be seen in the fetal abdomen.
Signs of hemorrhage: Thilaganathan described one case of fetal anemia due to a hemorrhage into an ovarian cyst (8). The volume of blood loss was enough to result in significant fetal anemia. Serial scans and Doppler assessment can reveal the development of fetal anemia (middle cerebral Doppler study).
Digestive duplications: The bowel wall is different in appearance and shows peristalsis.
Cystic lymphangioma or mesenteric cyst: These cysts are usually multilocular, without peristalsis.
Choledochal cyst or hepatic hamartoma: localized near the liver.
Cyst of the urachus: This cyst is near the bladder, medial, adjacent to the anterior wall.
Hydrocolpos or hydrometrocolpos: The major cause is hymeneal imperforation or vaginal duplication.
Sacrococcygeal teratoma: This is more posterior or an abdominal-pelvic finding.
Ovarian teratoma: The presence of calcifications is suggestive of an ovarian teratoma or hemorrhagic necrosis. Nevertheless, the two majors differential diagnosis are digestive dilatation and urinary dilatation.
Prognosis: In the Perrotin’s series (52 ovarian cysts), ovarian cysts were diagnosed at 32 weeks. The medium dimensions were 43 mm. Among 35 ovarian cysts, none were complicated during the fetal period, however, 43% had a complication postnatally. In total, 56% of the ovarian cysts required surgical interventions. All the cysts were folliculus-luteinic.
Observation only, with serial scans.
Antenatal aspiration of simple ovarian cysts to prevent complications. Aspiration of ovarian cysts is not a universal practice and not proven to be a good option. There is a potential for fetal morbidity and mortality, including preterm delivery, particularly if the intervention is early. According to Heling (3), prenatal aspiration of ovarian cysts seem to be of no advantage and should be carried out only in special individual cases, in particular if the ovarian cyst is huge and likely to impair spontaneous delivery.
A cyst diameter greater than 5 cm has been used as a criteria for antenatal aspiration. Foley (2) disagrees, particularly about the prediction risk of ovarian loss. But certainly, successful in utero aspiration of large ovarian cysts may reduce the ovarian cyst volume and lessen the chance of torsion. According to Borrione (11), the antenatal ovarian cyst puncture must not be indicated.
Resection of all complex ovarian cysts in the neonatal period. According to Foley (2), complex ovarian cysts can cause serious postnatal complications. Complex ovarian cysts can be managed conservatively, although many authors describe an early postnatal resection to avoid potential future complications. When torsion of the ovarian cyst is suspected, delivery in a perinatal center, which offers the availability of postnatal care, is recommended. Usually, a cesarean section is not necessary. There is one report in the literature describing a case of an ovarian cyst rupture during the delivery. Generally, the antenatal fetal ovarian cyst does not change the pregnancy management.
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2- Foley P.T., Ford W.D.A., McEwing R., Furness M.- Is conservative management of prenatal and neonatal ovarian cysts justifiable ? Fetal Diagn Ther 2005 ; 20 : 454-8.
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