Fetal abdominal cysts in the first trimester: prenatal detection and clinical significance
Abstract
Objective
In order to determine the clinical significance of fetal abdominal cysts detected in the first trimester, we reviewed our experience with such cases collected over a 5-year period.
Methods
Five cases in which a fetal abdominal cyst was detected by ultrasound in the first trimester were identified. Information on the ultrasound findings, antenatal course and perinatal outcome was obtained in all cases.
Results
The abdominal cyst was confirmed by an early second-trimester scan at 14–16 weeks in all cases, at which time no associated anomalies were detected. The standard detailed second-trimester scan at 18–22 weeks demonstrated complete resolution in three cases. These women had an uneventful antenatal course, and normal newborn infants were delivered at term. However, one of these infants had intestinal malrotation, chronic abdominal distension and midgut volvulus requiring surgery at the age of 7 months. Among the remaining two cases in which the abdominal cyst persisted, one required prenatal aspiration at 19 weeks owing to significant enlargement and resolved. The other remained stable in size and was managed conservatively, but the infant required surgery at the age of 7 weeks owing to a choledochal cyst causing intermittent episodes of acholia.
Conclusion
Abdominal cysts in early pregnancy often resolve spontaneously or remain small and are usually associated with a good outcome. Nevertheless, as they can also be associated with serious underlying gastrointestinal pathological conditions, close surveillance in the perinatal period is advocated. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Introduction
The ultrasound detection of a fetal abdominal cyst in the second and third trimesters, although rare, is a well characterized finding representing a wide variety of clinical and surgical conditions1-4. Among them, the main differential diagnoses include cystic structures originating from either the gastrointestinal tract (mesenteric or omental cysts, intestinal duplication cysts, hepatic or choledochal cysts, and dilated bowel loop secondary to atresia or obstruction) or the genitourinary tract (ovarian, renal, urachal, and adrenal cysts)1-4.
In recent years the progressive incorporation of first-trimester ultrasound screening into routine clinical practice has allowed the early detection of a significant number of fetal structural abnormalities5-7. However, there is a paucity of reports dealing with the diagnosis and significance of an abdominal cyst detected at this early gestational age. In this report we present our experience with the prenatal diagnosis, subsequent management, and perinatal outcome in cases in which an abdominal cystic mass was detected by ultrasound in the first trimester.
Patients and Methods
Cases in which an abdominal cystic mass was detected by ultrasound in the first trimester were prospectively collected for this study. In order to be included, the cystic structure had to be clearly differentiated from the fetal bladder by ruling out the presence of the umbilical arteries alongside the mass with color-flow mapping8. Color Doppler ultrasound was also used to exclude the possibility of a vascular structure by ruling out the presence of blood flow within the cystic mass. Once the diagnosis had been established, the parents were informed on the prenatal findings, differential diagnoses, and probable natural course, and offered ultrasound follow-up, including an early second-trimester scan at 14–16 weeks and the standard detailed second-trimester scan at 18–22 weeks. Information on maternal demographics, ultrasound findings, subsequent antenatal course and perinatal outcome was obtained by reviewing the medical records, ultrasound reports and neonatal charts. If the woman delivered in another institution, the referring obstetrician was contacted to obtain the pertinent perinatal information for analysis.
Results
During the 5-year period from June 2002 to July 2007, five cases of first-trimester fetal abdominal cyst were diagnosed by the authors (estimated prevalence). Table 1 displays the most relevant clinical and ultrasound findings in these cases. All the women were younger than 35 years and two (40%) were primigravidas. Gestational age at the time of diagnosis ranged from 10 + 4 weeks to 13 + 2 weeks, with the fetal crown–rump length measuring between 36 and 77 mm. The nuchal translucency thickness was measured in four cases and reported to be within the normal range for gestational age in all of them. The cystic mass was single in all cases, with the largest diameter at the time of detection measuring between 5 and 11 mm (Figures 1-4). An early second-trimester follow-up scan confirmed the presence of the abdominal cystic mass, but no associated anomalies, in all cases.
Ultrasound image of a first-trimester fetal abdominal cyst. The bladder is seen as a separate anechoic structure in the lower abdomen, caudal to the abdominal cyst. The infant had intestinal malrotation (Case 1).
Transverse views of the fetal upper abdomen of Case 2, showing a cystic structure adjacent to the stomach at 13 weeks' gestation (a) and at 18 weeks, when it had doubled in size (b). The infant was diagnosed neonatally with choledochal cyst.
A 12-week fetus (Case 3) with a large cyst located in the upper abdomen.Two-dimensional sagittal view (a) and three-dimensional image (b), showing the location and relative size of the abdominal cyst. The cyst increased in size, was aspirated at 19 weeks and resolved. The presumptive diagnosis was hepatic cyst.
Transverse (a) and parasagittal (b) ultrasound images of Case 4 at 12 weeks' gestation, showing a large cyst in the lower fetal abdomen. There was complete resolution by the time of the detailed second-trimester scan.
| Case | MA (years) | GA (weeks) | CRL (mm) | NT (mm) | Abdominal cyst (mm) | Remarks |
|---|---|---|---|---|---|---|
| 1 | 27 | 13 + 2 | 77 | 2.3 | 8 × 7 | Resolution. Term delivery of male infant with intestinal malrotation, midgut volvulus, necrotizing enterocolitis, mesenteric thrombosis, intestinal resection, short bowel syndrome |
| 2 | 20 | 13 + 1 | 72 | 1.1 | 5 × 4 | Term delivery of female neonate. Surgery for choledochal cyst at 7 weeks of postnatal life |
| 3 | 17 | 12 + 1 | 60 | 0.7 | 10 × 8 | Cyst aspiration at 19 weeks with subsequent resolution. Preterm rupture of membranes and delivery at 33 weeks. Normal female neonate discharged on day 17 |
| 4 | 31 | 11 + 5 | 53 | 1.0 | 10 × 9 | Resolution. Term delivery of normal female neonate |
| 5 | 28 | 10 + 4 | 36 | ND | 11 × 11 | Resolution. Term delivery of normal male neonate |
- CRL, crown–rump length; GA, gestational age; MA, maternal age; ND, no data available; NT, nuchal translucency thickness.
Spontaneous resolution of the cyst was documented at the time of the detailed second-trimester scan in three cases. Among them, two newborn infants had an uneventful neonatal course, and after a normal abdominal scan both were discharged with their mother, and remained asymptomatic at the pediatric follow-up examinations. The other infant developed chronic abdominal distension, which was managed medically. However, at 7 months he had an intestinal pseudo-obstruction and underwent surgery confirming intestinal malrotation and a midgut volvulus. The postoperative course was complicated with mesenteric thrombosis requiring small bowel resection, which led to short bowel syndrome. In the remaining two cases, the abdominal cyst was again identified at the time of the detailed second-trimester scan. One was managed with a single percutaneous ultrasound-guided aspiration at 19 weeks because of significant enlargement of the cyst, with subsequent resolution documented from 20 weeks onwards. The further antenatal course was uncomplicated, and the infant was delivered at 33 weeks by Cesarean section owing to rupture of membranes and suspicion of chorioamnionitis unrelated to the prenatal invasive procedure. Subsequently the infant did well, and at the time of writing was 12 months old and thriving. The other case was managed expectantly; the cyst doubled in size from 5 × 4 mm to 11 × 9 mm and remained stable in size until term. The infant had an uncomplicated neonatal course and was discharged with her mother. However, this infant underwent laparoscopic surgery at the age of 7 weeks for excision of a choledochal cyst causing intermittent episodes of acholia.
Discussion
This report describes the prenatal ultrasound detection of an abdominal cyst in five first-trimester fetuses, together with its subsequent management and perinatal outcome. The abdominal cyst was confidently identified independent of the fetal bladder and kidneys, and confirmed as such during the follow-up scan in the early second trimester, thus reducing the possibility of an ultrasound artifact. The subsequent detailed second-trimester scan demonstrated that the abdominal cyst resolved spontaneously in three cases, one of which was associated with serious gastrointestinal complications after birth. Two others persisted throughout the second trimester, one of which required percutaneous cyst aspiration owing to significant enlargement, and the other underwent surgery because of a symptomatic choledochal cyst. The etiology of the abdominal cyst in three of our cases, in the absence of surgical or pathological proof, remains therefore speculative.
First-trimester ultrasound examination at 11–14 weeks has been shown to be an important tool for the screening of chromosomal abnormalities5-7. With significant improvements in image resolution and a better systematic anatomic assessment protocol, evaluation of the early fetal anatomy with greater detail is now possible9, 10, making the detection of several structural anomalies at this stage of pregnancy possible11-15. Among them, megacystis is the most common condition presenting as an abdominal cystic mass in the first trimester, and the differential diagnosis can easily be established with color Doppler ultrasound, as the bladder is normally surrounded by the intra-abdominal umbilical arteries8. In contrast, there are only a few reports describing the finding of an abdominal cyst in the first trimester, the majority of them being isolated case reports invariably describing different associated gastrointestinal malformations including distended sigmoid colon and intestinal malrotation16, 17, hepatic cyst18, ileal duplication cyst19, and anal atresia or imperforate anus17, 20. We are also aware of reports describing complete resolution of an abdominal cyst detected early in pregnancy in the presence of a serious underlying gastrointestinal pathology manifesting only in the neonatal period. Teele et al.21 described two cases of intestinal malrotation presenting as an abdominal cyst at 15 weeks that subsequently resolved in utero. Gilbert et al.22 also described the presence of a cystic mass in the lower fetal abdomen at 12 weeks, which had resolved by 17 weeks. At birth, the male infant had multiple anomalies including anorectal agenesis, rectourethral fistula, horseshoe kidney and an anomalous sacrum. These authors hypothesized that an intra-abdominal cyst in early pregnancy may have effects on the rotation and fixation of the bowel, and recommended close neonatal follow-up even if the cystic mass disappears before birth21, 22.
In conclusion, the detection of a fetal abdominal cyst in the first trimester is usually an isolated finding and is associated with a good perinatal outcome in the majority of cases. In these cases, the abdominal cyst probably represents a transient finding with no clinical significance. However, some other cases can be associated with serious gastrointestinal malformations, even in cases in which the mass resolves spontaneously in utero, so close perinatal surveillance is advocated.
Acknowledgements
We are grateful to Drs R. Cassis, M. Ivankovic, V. Rodriguez and C. Schnapp for their significant contribution to the antenatal care of the patients reported in this study. This work was supported by Sociedad Profesional de Medecina Fetal ‘Fetalmed’ Limitada, Chile.
