Abdominal Cysts

Definition

Ovarian cysts are fluid-filled sacs arising from the ovary.

Prevalence and Epidemiology

After the kidneys and bowel, the ovaries are the third most frequent organ giving rise to abdominal cysts. The first case was reported by Valenti et al. in 1975. The incidence was initially estimated to be 1 : 2625 pregnancies. With improving image quality the number of cases diagnosed prenatally might have increased, but the incidence of 1 : 2500 is confirmed in more recent reports.

Etiology and Pathophysiology

The fetal ovary is sensitive to the maternal gonadotropins. Fetal ovarian cysts are usually functional, mostly follicles enlarged as a result of stimulation by maternal and placental hormones. A higher prevalence of these cysts is noted in pregnancies complicated by diabetes, preeclampsia, and rhesus immunization, i.e., in pregnancies with an increased release of placental human chorionic gonadotropin.

Manifestations of Disease

Imaging Technique and Findings

Ultrasound.

The ultrasound (US) appearance depends on the size of the cyst and the possible complications, such as torsion of the ovary or intracystic bleeding. Uncomplicated cysts typically appear as a unilocular, thin-walled cystic mass ( Fig. 24.1 ). Ovarian cysts may appear as a complex mass (with internal echoes, septations, or debris; Fig. 24.2 ) or as a solid mass when complicated by torsion or internal bleeding.

Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) is not required to diagnose ovarian cysts. An ovarian cyst can be an incidental finding on fetal MRI; in T2-weighted images it appears as a white cystic structure.

Classic Signs

A simple intraabdominal cystic structure (2 to 5 cm) in a female fetus, typically unilateral, with normal urinary tract (kidneys and bladder clearly seen) and intestinal tract (no dilated bowel).

Prenatal

Options for prenatal management include observation and, in the case of a simple cyst, aspiration. The conservative approach is usually preferred. Authors favoring prenatal aspiration claim to prevent ovarian torsion and its complications (i.e., necrosis and intraabdominal inflammation). The procedure has to be weighed against the risk of complications (i.e., preterm rupture of membranes, infection, and bleeding). No randomized trial comparing invasive and conservative approaches exists. Periodic follow-up to check the size and appearance of the cyst can be recommended. A puncture with aspiration of the cyst may be reasonable for very large cysts likely to impair vaginal delivery. Otherwise fetal ovarian cysts do not present a contraindication for vaginal delivery.

Postnatal

Postnatal US confirms the diagnosis. Other imaging modalities (MRI or computed tomography [CT]) are usually not required. Depending on the size and the appearance of the cyst, the choice is between conservative and invasive management. A recent metaanalysis including 34 studies with a total of 954 fetuses showed that 54.6% (95% confidence interval [CI] 47.0–62.0) of the cysts regressed either during pregnancy or after birth. Resolution occurred significantly less often in complex versus simple cysts (odds ratio [OR]: 0.15, 95% CI 0.10–0.23) and in cysts ≥ 40 mm compared to smaller ones (OR: 0.03, 95% CI 0.01–0.06). An observed change in ultrasound pattern on follow-up examination was associated with an increased risk of eventual ovarian loss (positive predictive value [PP]: 57.7%, 95% CI 42.9–71.8). The risk of ovarian torsion was also significantly higher in cysts ≥ 40 mm (OR: 30.8, 95% CI 8.6–110). Larger and complex cysts tended to have surgery more often. In cases with prenatal aspiration 38% recurred (95% CI 14.8–64.3), torsion and hemorrhage (diagnosed after birth) complicated 10.8% (95% CI 4.4–19.7), and 9.7% (95% CI 3.7–18.3), respectively. Eighteen percent of fetuses undergoing prenatal aspiration also had surgery after birth.

In the neonate it seems reasonable to operate (laparoscopically, if possible) on cysts larger than 40 mm, or complex and symptomatic cysta. Cystectomy is preferred over oophorectomy. Large simple ovarian cysts in neonates can also be aspirated under US guidance. Smaller cysts and simple cysts are often managed conservatively. Accompanying videos show a laparoscopic marsupialization of a simple ovarian cyst in a neonate ( Video 24.1 ) and a laparoscopic retrieval of a spontaneously detached ovarian cyst ( Video 24.2 ).

Definition

Enteric duplications comprise two layers of epithelium and share the vascular supply with the adjacent intestinal tract. They are typically in immediate contact, but not in continuity, with the intestinal tract.

Prevalence and Epidemiology

Enteric duplication cysts are commonly found postnatally but are rarely detected prenatally. Males are affected twice as often as females.

Etiology and Pathophysiology

There are multiple theories that explain the development of enteric duplications, but no definitive theory accounts for all known variants. Theories involve partial or abortive twinning, the split notochord theory and anomalous adhesion occurring in the third week of gestation, diverticula and canalization defects between 6 to 8 weeks of life, and even environmental factors such as trauma and hypoxia.

Histologic evaluation of the cysts shows full replication of the mucosal, muscular, and serosal layers.

Manifestations of Disease

Imaging Technique and Findings

Ultrasound.

Enteric duplication cysts are elongated, tubular, or spherical cystic masses, usually unilocular and anechoic ( Fig. 24.3 ). Multiple septations and “sludge” may be seen ( Table 24.2 ). The location and mass effect on adjacent bowel can suggest the diagnosis. If present, peristaltic movement of the muscular wall can aid in the diagnosis.

TABLE 24.2

ULTRASOUND CRITERIA OF AN OVARIAN CYST VERSUS AN ENTERIC DUPLICATION CYST

Modified after Giorlandino C, Rivosecchi M, Bilancioni E, et al.: Successful intrauterine therapy of a large fetal ovarian cyst. Prenat Diagn 10:473–475(10), 1990.

	Ovarian Cyst	Enteric Duplication Cyst
Gender	Female	Male and female (ratio 2 : 1)
Location	Lower abdomen	Entire abdomen
Structure	Cystic	Elongated, thick-walled
Internal structure	Smooth, isolated or heterogeneous	Smooth, “sludge”
Kidneys and bladder	Visible	Visible
Peristalsis	No	Possible

Magnetic Resonance Imaging.

MRI can provide a global overview of the abdomen and can be helpful in the differential diagnosis, enabling better tissue differentiation.

Classic Signs

Anechoic, unilocular, tubular, or spherical cystic mass close in relationship with adjacent bowel