Introduction
Neonatal ovarian cysts are rare, but they are the most common cystic abdominal finding in neonatal imaging. Cysts are usually discovered in the third trimester at 28 weeks gestation or later. The cyst may be simple (fluid filled) or complex (heterogenous appearing) and is usually a result of maternal and placental hormone exposure. Regardless of appearance, almost all cysts in this period are benign and spontaneously resolve. Of those that do not resolve or that are large, there is variation in management practices. Antenatal cyst aspiration has scant outcome data and therefore should not be routinely done. If a cyst persists with certain characteristics past the neonatal period, surgery should be considered. Of those operated on as infants, the most common pathology is remote torsion. Other pathology includes functional cysts, cystadenomas, and mature teratomas/dermoid cysts.
Disease definition
Neonatal ovarian cysts are masses on the ovary that are found during the antenatal period through the first 28 days of life. They can be simple or complex. Because of the nature of ultrasound, they can be confused with cysts of gastrointestinal or genitourinary origin.
Prevalence and epidemiology
About 30% of female neonates have notable ovarian follicles. , However, antenatal diagnosis of prominent ovarian cysts (>4 cm) is rare, occurring in about 1/2500 female fetuses. Because of the advances in imaging capabilities, this incidence is increasing. Risk factors for neonatal ovarian cysts include maternal preeclampsia, maternal diabetes, polyhydramnios, and rhesus isoimmunization. It is not clear if these risk factors are directly related to ovarian cyst development or instead are incidentally found because of increased third-trimester antenatal fetal surveillance.
Etiology and pathophysiology
Although the etiology is not completely understood, neonatal ovarian cysts are likely driven by maternal and placental hormones. These circulating hormones stimulate the fetal ovaries, which subsequently develop functional cysts. Most functional cysts will spontaneously resolve (slowly involuting) usually by month 12 of life. , However, some will develop a hemorrhagic component and/or may undergo torsion, both of which are more likely with cysts greater than 4 cm, have complex components, and are persistent.
Testing
Neonatal ovarian cysts are typically identified during routine antenatal ultrasounds. Cysts <2 cm are presumed follicles and do not need follow-up testing. Most experts suggest surveillance ultrasounds for masses >4 cm. The interval for this surveillance is variable, but most agree that a postnatal ultrasound and a follow-up ultrasound no more than 6 months later are reasonable. , , If a mass is >6 cm and appears complex, it is more likely to be surgically managed. , 
Because of the extreme rarity of malignancy in this age group and maternal-placental transfer of traditional ovarian tumor markers, there are no recommended serum markers for neonatal ovarian masses.
Manifestations of disease
The majority of neonatal ovarian cysts are asymptomatic. Of those that have symptoms, they include mass effect with compression of surrounding viscera (including inferior vena cava compression or urinary obstruction), rupture or hemorrhage of the cyst (with or without secondary effects on surrounding anatomy), or symptoms of torsion.
Clinical presentation and evaluation
Most neonatal ovarian cysts are found during routine antenatal ultrasounds. Depending on the size and characteristics of the mass, follow-up ultrasounds may be appropriate.
There is no classic clinical picture of the neonate or infant with an ovarian cyst, but when referring or evaluating this child, the provider should inquire about the baby’s demeanor (are they consolable when fussy), their urine output, and review their growth curve. Similarly, there is no standardization of surveillance. Experts recommend follow-up imaging based on the baby’s clinical picture, cyst size, and cyst characteristics.
Imaging technique and findings
When identified on neonatal ultrasound, cysts are typically simple, anechoic, and <3 cm. Of the neonatal cysts that are larger, the majority are between 3 and 6 cm. When performing serial ultrasounds, it is important to compare the progression of the cyst characteristics, including size, contour, echogenicity, and location, to help elucidate the pathophysiology and need for repeat imaging or surgical management. Cysts that are persistent in size and changing from simple to heterogenous are more likely to undergo surgical evaluation. A pediatric radiologist should note any signs pointing to nonovarian origin (such as the “gut signature”). The “gut signature” is five alternating echogenic layers of the bowel wall. When seen around a cyst that abuts more bowel, as in Fig. 28.1 , this suggests an enteric duplication cyst. Enteric duplication cysts are congenital cysts that have a gastrointestinal tract epithelium with a smooth muscle envelope and abut the alimentary tract. They are often symptomatic within the first 2 years of life, but can pose life-threatening complications; therefore an expedited pediatric surgery consult is recommended.
Physical examination
On physical examination of a neonate or infant, start by assessing their growth curve to confirm appropriate weight gain. On abdominal examination, the mass may or may not be appreciated. If there is adnexal torsion, it is likely remote (in utero); therefore peritoneal signs should prompt evaluation for nonovarian pathology.
Differential diagnosis
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Ovarian mass: follicle, hemorrhagic component with or without torsion, cystadenoma, dermoid
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Genital anomalies: hydrometrocolpos, cloacal anomaly
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Urologic anomalies: urinary outflow tract obstruction (with enlarged bladder and/or hydroureter), renal cyst, urachal cyst
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Gastrointestinal anomalies: mesenteric cyst, enteric duplication cyst, duodenal atresia, volvulus
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Neoplasms: presacral teratoma, neuroblastoma, lymphangioma
Management and treatment options
There is no clear guidance on management of neonatal cysts. Management is either expectant with serial imaging or surgical with aspiration of the cyst contents or removal of the mass. Removal of the mass may be with a cystectomy or an oophorectomy if autoamputation from remote torsion has already occurred. 
However, given that most cysts will resolve by 12 months with expectant management, this should be the first line of treatment. In addition, because neonatal ovarian masses are usually asymptomatic and the risk of malignancy is exceedingly rare, surgical intervention should be timed to balance the need for intervention, risks of general anesthesia, and the risks of the need for postoperative analgesics. Intrauterine aspiration of fetal ovarian cysts has been studied and “did not lead to a significant reduction of neonatal interventions.” By 6 months of age, if a mass is persistently >4 cm or complex, surgery should be considered; however, clinical context is needed. In general, when surgery is performed, torsion is found about 20% of the time. The risk of torsion was also increased if the cyst was >4 cm (odds ratio [OR] 30.8, 95% confidence interval [CI] 8.6–110.0) or complex appearing (OR 59.1, 95% CI 24.7–141.0). At the time of surgery, ovarian-sparing surgery should be performed if possible. Historically, though, there are higher rates of oophorectomy if undergoing surgery (25.1%, 95% CI 17.2%–34.0%) and if the mass is >4 cm (OR 58.9, 95% CI 19.2–181.0) or complex (OR 35.1, 95% CI 17.0–72.7), likely because of autoamputation. Autoamputation will appear as a strictured infundibulopelvic ligament with separate adnexa in varying stages of necrosis. The higher rates of autoamputation likely reflect the remote or antenatal torsion event.
Expectant management of some infants with complex masses has shown complete resolution of autoamputation by 12 months. A case of premenarchal ovarian torsion also had signs of what was likely unrecognized neonatal torsion.
Special considerations for this population
Intrauterine cyst aspiration has not been shown to reduce further neonatal interventions.
Although general anesthesia is relatively safe, it is not without risks. The Pediatric Perioperative Cardiac Arrest (POCA) Registry was formed to characterize the patients associated with perioperative cardiac arrest. The registry found that cardiac arrest was rare (1.4/10,000), but more common in children less than 1 year old and those with severe underlying disease. , Other anesthetic and surgical risks include respiratory and cardiovascular depression from intraoperative and postoperative medications. , Because of these findings, postanesthesia management is individualized and based on postconception age of the infant, their gestation at delivery, other comorbidities, and type of surgery. Postanesthesia management may require admission for monitoring, including of analgesics.
A laparoscopic approach is preferred in the neonate for an adnexal mass. During umbilical entry, there should be extra attention to increased risk of umbilical vein complications. Stab incisions with direct placement of instruments are often used instead of trocars for the assisting ports. If an open approach is needed, a mini laparotomy around the umbilicus should be done rather than a Pfannenstiel incision.
Research gaps
There is no data-driven consensus on management for neonatal adnexal masses. Textbook guidance is based on expert opinion from prior retrospective case series and cohort studies.
