In Utero Fetal Ovarian Torsion Alena Levit, MD, and Susan L. Voci, MD CLINICAL HISTORY A 1-month-old female with ovarian cyst was seen on prenatal ultrasound (US).

DISCUSSION Fetal ovarian cysts are the most common abdominal masses in fetuses and neonates. Their incidence has increased in the past decade due to availability and prevalent use of US.1 Most are identified toward the end of the second trimester. Stimulation of the fetal ovary by placental and maternal hormones leads to the development of ovarian cysts. Therefore, they tend to regress shortly after birth. Complications such as hemorrhage, rupture, and torsion can develop. Most cysts are benign and are classified with regard to their ultrasonographic features as ‘‘simple’’ or ‘‘complex’’ and with regard to their size as ‘‘small’’ or ‘‘large’’ cysts.2,3 Simple cysts, also referred to as follicular cysts, are usually unilocular and completely anechoic on US. Complex cysts can have an echogenic wall, internal septae, fluid-debris level, or a blood clot. Complicated cysts tend to be more concerning for an underlying ovarian torsion. Simple cysts less than 4 cm tend to spontaneously regress within a few months after birth.4 Larger cysts (94 cm) have susceptibility for torsion, and surgical treatment is recommended.

FIGURE 1. Transverse gray scale image of the right side of the pelvis demonstrates an enlarged 4.3-cm right ovary (A). Transverse power Doppler image of the right side of the pelvis demonstrates complete absence of flow in the right ovary (B).

Ovarian torsion is the most common complication of fetal ovarian cysts. It results from either partial or complete twist of the ovary and fallopian tube. Initially, there is compromise of

FIGURE 2. Axial (A), sagittal (B), and coronal (C) T2 fat-saturated images demonstrate an enlarged right ovary with hyperintense afollicular central stroma and absence of enhancement on postcontrast images (D).

lymphatic drainage leading to lymphatic edema, which causes enlargement of the ovary. Torsion of the ovarian pedicle produces circulatory stasis that is initially venous but becomes arterial as the torsion and resultant edema progress. If the torsion is complete and obstructs the arterial blood supply, gangrenous and hemorrhagic necrosis results. Early diagnosis and treatment may make it possible to conserve normal ovarian structures and fertility. Ultrasound is the imaging modality of choice to evaluate for ovarian torsion. When torsion of a cyst occurs, US features will reflect that by demonstrating increase in the size of the cyst and becoming complex in appearance. Another commonly reported presentation of the ovarian torsion is a unilaterally enlarged ovary with peripheral cysts containing fluid-debris level.1 If the US findings are equivocal, an MRI can be performed for further characterization (Figs. 1, 2).

TEACHING POINTS University of Rochester, Rochester, NY. The authors declare no conflict of interest. Reprints: Alena Levit, MD, University of Rochester, 601 Elmwood Ave, Box 648, Rochester, NY 14642 (e

In utero fetal ovarian torsion.

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