Postnatal Outcome of Prenatally Diagnosed Intra-Abdominal Cysts

Abstract

Aim

This article compares the antenatal diagnosis of fetal intra-abdominal cysts with postnatal diagnosis and determines the diagnostic accuracy of ultrasound in correctly diagnosing the origin of prenatal abdominal cysts.

Methods

A prospective study of antenatally diagnosed fetal intra-abdominal cysts was conducted from January 2022 to December 2023. Cases of fetal intra-abdominal cysts that fulfilled the criteria were included in the study. The imaging characteristics of various types of cysts were summarized and compared with postnatal follow-up results.

Result

In our study, the fetal intra-abdominal cysts were prenatally diagnosed in 24 cases. Of 24 cases, postnatal follow-up was available for 19 (79.16%) cases. The antenatal diagnosis was confirmed postnatally in 18 cases (94.73%). Five cases could not be examined postnatally, as in two cases pregnancy was terminated, two babies died after birth before investigations, and one case was lost to follow-up.

Conclusion

An appropriate ultrasound examination, combined with comprehensive analysis and careful judgment, leads to an accurate diagnosis and proper postnatal management.

Keywords

fetus - intra-abdominal cyst - ultrasound - congenital abnormality - postnatal follow-up

Introduction

Fetal abdominal cysts are rare. With recent advances in ultrasound (US) techniques and increasing clinical experience, routine US screening has facilitated the early detection of fetal structural abnormalities.[1] [2] [3] [4] The abnormal cystic structure mainly originates from either the gastrointestinal (GI) tract or the genitourinary tract.[5] [6] [7] [8] [9] However, since abdominal cysts may originate from different reproductive, urinary, and digestive systems,[6] [7] [8] [9] it is challenging to accurately determine the origin of cysts antenatally via US and predict postnatal outcome. Most of the GI tract is located in the abdominal cavity, which contains other structures such as the liver, choledochal system, pancreas, mesentery, and omentum.

Genitourinary tract related organs are the kidneys, adrenals, and ovaries in females. One of the main difficulties in the sonographic examination of the fetal abdomen is establishing the origin of an intra-abdominal cyst during examination, which could be from any of the structures mentioned here or from abnormal development of early embryonic structures and embryonic abdominal totipotential cells, such as teratomas. Location, sonographic appearance, associated anomalies, gestational age at diagnosis, and fetal sex provide important information directing toward a possible diagnosis. In many cases, it remains difficult to be certain about the origin of the cyst until delivery. Assessment of the fetal sex is necessary when an abdominal cyst is detected, as some cysts are sex-related (ovarian cysts or hydrometrocolpos occur exclusively in females) or may present a sex predominance (choledochal cysts are more frequent in female fetuses). Finally, a cyst may be differentiated by the assessment of its sonographic appearance (shape, echogenicity, wall margins, or other specific features), and it is mandatory to carefully examine to detect other possible associated sonographic findings. The use of color Doppler allows examination of the vascular supply to the cyst, its anatomic relations with the abdominal blood vessels, and the possible diagnosis of its vascular origin. This is helpful in cases of umbilical vein varix or hepatic arteriovenous malformation.

Risk factors associated with intra-abdominal cystic lesions include:

• Gonadal cyst: Placental human chorionic gonadotropin, fetal gonadotropins, Rh isoimmunization, and preeclampsia.

• Adrenal cyst: Congenital adrenal hyperplasia and ambiguous genitalia.

• Extralobar pulmonary sequestration: Idiopathic.

• Mesenteric cyst: Small bowel lymphangioma.

• Megacystis: Male fetus (posterior urethral valve), neurologic syndromes, genetic syndrome (MMIH-megacystis microcolon intestinal hypoperistalsis syndrome).

Aim of the Study

This article aims to compare the antenatal diagnosis of the intra-abdominal cyst with the postnatal diagnosis and to determine the diagnostic accuracy of US in correctly diagnosing the origin of prenatal abdominal cyst.

Methods

This is a prospective study of all cases of intra-abdominal cysts diagnosed in a tertiary fetal medicine center. US scanning for all cases was performed on a GE Voluson E8 or E10 machine equipped with a 2 to 9 MHz curvilinear, RAB 6 probe, and the Mindray Neuva I9 machine with SC6-1S probe. All antenatally diagnosed cases of intra-abdominal cyst from the period between January 2022 and December 2023 were monitored for their progress/resolution, any change in the appearance of the cyst, and any newly developed ultrasonography findings.

Cysts were differentiated by assessment of their sonographic features like size, shape, echogenicity, cyst wall, single cyst or multiple, vascularity, proximity to other abdominal organs, or other specific features.

In all cases where the cyst had not resolved antenatally, postnatal scans (US, computed tomography [CT] scan, or magnetic resonance imaging) were conducted. Antenatal diagnosis, postnatal diagnosis, and the ultimate outcome were recorded.

Only solitary cysts were included in the study. Cysts were divided into subgroups according to their prenatal suspected origin, like ovarian, GI, gallbladder, renal, mesenteric, and vascular.

Result and Discussion

[Table 1] shows that 144 intra-abdominal cysts were identified over a 2-year study period, with 120 cases involving multiple cysts and 24 cases involving solitary cysts. Cases with solitary cysts were included in the study.

Table 1 Distribution of cases with intra-abdominal cyst

Total intra-abdominal cyst	144
Solitary cyst	24
Multiple cyst	120

[Table 2] shows that out of 24 antenatally diagnosed cases of intra-abdominal solitary cyst, 12 were gonadal cysts, 3 were choledochal cysts, 1 was an adrenal cyst, 1 was a hepatic cyst, 1 was an extralobar pulmonary sequestration, 1 was a renal cortical/mesenteric cyst, 1 was megacystis, 3 were umbilical vein varix, and 1 was an enteric duplication cyst.

Table 2 Distribution of cases with intra-abdominal cyst as per their location

Type of cyst based on location	Number of cases
Gonadal cyst	12
Choledochal cyst	03
Adrenal cyst	01
Hepatic cyst	01
Extralobar pulmonary sequestration	01
Renal cortical/mesenteric cyst	01
Megacystis	01
Umbilical vein varix	03
Enteric duplication cyst	01

[Table 3] shows that the origin of fetal intra-abdominal cysts was prenatally diagnosed in 24 cases.

Table 3 Follow-up of antenatal diagnosis with postnatal outcome

Antenatal diagnosis	Number of cases	Associated anomaly	Postnatal outcome
Gonadal cyst	12	No	11 babies are alive and healthy and 1 baby died after birth 11/11 gonadal cysts were correctly diagnosed by antenatal US
Choledochal cyst	03	No	2 cases confirmed postnatally, 1 case diagnosed as enteric duplication cyst All 3 babies are alive and healthy
Adrenal cyst	01	No	Findings confirmed postnatally. Baby is alive and healthy
Hepatic cyst	01	B/L enlarged kidneys, Meckel–Gruber syndrome	Pregnancy was terminated
Extralobar pulmonary sequestration	01	No	Findings confirmed postnatally. Baby is alive and healthy
Renal cortical cyst/mesenteric cyst	01	No	The patient was lost to follow-up
Megacystis	01	B/L enlarged echogenic dysplastic kidneys	Pregnancy was terminated
Umbilical vein varix	03	No	All 3 babies are alive and healthy
Enteric duplication cyst	01	No	The baby died after birth.

Abbreviation: US, ultrasound.

Out of 24 cases, postnatal follow-up was available in 19 (79.16%) cases. The antenatal diagnosis was confirmed postnatally in 18 cases (94.73%), and in one case, the postnatal diagnosis was different. Five cases could not be examined postnatally, as in two cases pregnancy was terminated (hepatic cyst and megacystis), in two cases the baby died after birth (ovarian cyst and enteric duplication cyst), and one case was lost to follow-up (mesenteric cyst).

Gonadal cysts were typically seen in female fetuses only. They were all ovarian cysts. Ovarian cyst represents the response of fetal ovaries to increased maternal hormones (estrogen, human chorionic gonadotropins) and fetal gonadotropins. They are usually located in the lower abdomen close to the urinary bladder. The shape of cysts is generally regular, round/oval and cyst wall is generally thin with smooth contour. Intracapsular bleeding may occur in the cyst and hemorrhage makes the appearance of the cyst “complex” with diffuse echogenicity ([Fig. 1]). The presence of daughter cyst in ovarian cyst pathologically represents a stimulated ovarian follicle and is diagnostic of ovarian origin of the cyst[10] ([Fig. 2A]). Ascites may result from rupture of the cyst or transudation due to partial obstruction of the GI tract. Complication such as polyhydramnios develops due to impaired fetal swallowing occurring due to increased pressure on the bowel from the cyst ([Fig. 3A–F]). Majority of cases are benign. In the present study, the gonadal cyst was seen in 12 cases. All were found in female fetuses. One case was seen at 21 week, 3 cases were seen between 32 and 34 weeks, 6 cases between 35 and 37 weeks, and 2 cases between 38 and 40 weeks. Mean gestational age of presentation was 32.6 weeks. Out of 12 gonadal cysts, 3 cysts persisted even after 2 months postnatally and 1 cyst was ruptured causing ascites (follow-up scan at 27 weeks) and 8 cysts were resolved within 1 month after birth. In the present study, the accuracy of antenatal US in diagnosing gonadal cyst is 91.66%.

Fig. 1 Shows antenatal and postnatal images of case 1. (A) Axial section of fetal abdomen and pelvis, a thick walled cyst with homogeneously hyperechoic content, measuring 26 × 44 × 26 mm was located anterior to left kidney, superior, and to the left of urinary bladder, most likely hemorrhagic ovarian cyst. (B) Postnatal ultrasound (US) confirming the antenatal diagnosis.

Fig. 2 Shows antenatal images of two different cases. (A) Tomographic ultrasound imaging (TUI) axial section of fetal abdomen + pelvis showing a left gonadal cyst with daughter cyst (case 2). (B) Parasagittal section of fetal lower abdomen + pelvis showing unilocular, thin walled, anechoic gonadal cyst below the left kidney and above the urinary bladder (case 3).

Fig. 3 Shows antenatal images of case 4. (A–C) Images showing a well defined parasagittal section. An echoic gonadal cyst of size 19 × 19 mm below the left kidney (gestational age [GA] 21 weeks). (D–F) Images showing follow-up scans done at 27 weeks with ascites and polyhydramnios developed due to rupture of the cyst.

A choledochal cyst is also known as congenital bile duct dilatation, primary bile duct dilatation, or bile duct cystic dilatation. It is a rare condition occurring due to pancreaticobiliary maljunction that may cause pancreatic enzyme reflux into the bile ducts and result in bile duct dilatation. Choledochal cysts are found in the right upper quadrant of the abdomen near the gallbladder. They are predominantly oval in shape and have thick walls. A definitive diagnosis can be made by demonstrating the communication between the bile duct and the cyst. In the present study, three intra-abdominal cysts were diagnosed as choledochal cyst antenatally ([Figs. 4] [5] [6]). In the third case, postnatal US was suggestive of enteric duplication cyst ([Fig. 5A–C]), the patient underwent surgery for resection and anastomosis. Postoperatively, baby is alive and healthy. In the present study, accuracy of antenatal US in diagnosing choledochal cyst is 66.66%.

Fig. 4 Shows antenatal image of case 1. The axial view of fetal abdomen, a thick walled anechoic cyst measuring 14.9 × 10.6 mm was seen in the right upper quadrant of the abdomen, at the lower edge of the liver originating from the gallbladder.

Fig. 5 Shows antenatal and postnatal images of case 2. (A) Coronal section showing anechoic, thick-walled cyst located below the diaphragm, near to the gallbladder, and separate from urinary bladder and stomach most likely choledochal cyst. (B) Axial section showing the cyst is avascular. (C) Postnatal ultrasound (US) showing the characteristic “signature gut sign,” so the diagnosis was changed to enteric duplication cyst.

Fig. 6 Shows antenatal and postnatal images of case 3. (A) Coronal section showing a thickwalled, anechoic cyst originating from the gallbladder (GB) located superior to the urinary bladder. (B) Coronal section showing cyst is avascular. (C) Multiplanar view showing the cyst is in continuation with the wall of GB s/o choledochal cyst.

Fetal adrenal glands are located on the superior pole of the kidneys. The adrenal cortex is of lower echogenicity adjacent to the liver or kidney and the medulla is more echogenic than the cortex. They have a classic inverted V-shape appearance in the longitudinal section. The adrenal anomalies include cyst, hemorrhage, hypertrophy, and tumors. An adrenal cyst can be detected in the third trimester in a characteristic location, cephalad to the kidney, with an anechoic, smooth margin and a clear boundary. In the case of hemorrhage, the cyst becomes hypoechoic with an organized blood clot. In the present study, one case was diagnosed with an adrenal cyst ([Fig. 7A] and [B]). Postnatal US confirmed the diagnosis of adrenal cyst ([Fig. 7C]). In the present study, the accuracy of antenatal US in diagnosing an adrenal cyst is 100%.

Fig. 7 Showing antenatal and postnatal images. (A) Axial section of fetal abdomen showing a thick walled, anechoic cyst at the upper pole of the left kidney of size 19 × 11 mm. (B) Coronal section showing the cyst is in close relation to the renal cortex likely to be renal cortical/adrenal cyst. (C) Postnatal ultrasound (US) finding s/o adrenal cyst.

The hepatic cyst usually develops due to canalicular maldevelopment. They are more commonly unilocular and are visualized on the left side. In our study, there was one case of hepatic cyst ([Fig. 8A] and [B]) with associated findings of bilateral dysplastic kidneys ([Fig. 8C] and [D]), suggestive of Meckel–Gruber syndrome, at 20 weeks of gestation. Patient terminated pregnancy.

Fig. 8 Showing antenatal images. (A) Axial section of the fetal upper abdomen showing a large anechoic cystic lesion involving the liver of size 33 × 26 mm. (B) Coronal section showing the cyst is below diaphragm involving the right lobe of liver, s/o hepatic cyst. (C) Showing coronal section and (D) showing parasagittal sections showing enlarged kidneys.

Subdiaphragmatic extralobar pulmonary sequestration appears as a well-defined, homogenously hyperechoic lesion supplied by systemic circulation. In the present study, one case was diagnosed with extralobar intra-abdominal pulmonary sequestration (Figure ). It consisted of an island of lung parenchyma that did not communicate with the bronchial tree ([Fig. 9A–C]) and was fed by systemic circulation ([Fig. 9D]). Postnatal contrast-enhanced CT thorax confirmed the antenatal findings of intra-abdominal extra lobar pulmonary sequestration ([Fig. 9E]).

Fig. 9 Showing antenatal images and postnatal contrast enhanced computed tomography (CECT) report. (A) Coronal section and image (B) showing axial sections of fetal abdomen, echogenic mass with cystic structure within measuring 21 × 14 × 19 mm was located near the left adrenal gland. (C) Coronal section showing the mass is located above the left kidney and left adrenal gland. (D) Axial section showing a feeding vessel to mass originating from the descending aorta s/o extralobar pulmonary sequestration. (E) Postnatal CECT thorax confirming the antenatal diagnosis.

The mesenteric cyst is generally unilocular/multilocular, hypoechogenic with variable size, thin wall, and devoid of peristalsis, located anywhere in the abdominal cavity. In the present study, one case was diagnosed as a mesenteric cyst ([Fig. 10]); however, the patient was lost to follow-up.

Fig. 10 Showing antenatal images. (A) Axial section of the fetal lower abdomen showing round shaped, anechoic, thin-walled cyst located anterior to the right kidney and superior to the urinary bladder. (B) Coronal section showing the cyst is intra-abdominal but not directly related to any abdominal organs s/o mesenteric cyst/renal cortical cyst.

Megacystis is defined as a longitudinal urinary bladder diameter ≥ 7 mm (in the first trimester, 11 to 13 + 6 weeks), and ≥ 30 mm in the second trimester. It may be due to an obstructive or nonobstructive cause. In the present study, megacystis was diagnosed at 13 weeks ([Fig. 11A]), with hydroureter ([Fig. 11B]), left dysplastic kidney, and right echogenic kidney ([Fig. 11C]). The bladder wall becomes thick and hyperechoic ([Fig. 11D]). The patient opted for the termination of pregnancy.

Fig. 11 Showing antenatal images. (A) Parasagittal section of fetus showing distended urinary bladder. (B) Axial section of the pelvis showing dilated ureter. (C) Parasagittal section showing echogenic dysplastic kidneys. (D) Distended bladder measuring 17 mm with echogenic walls s/o megacystis.

Umbilical vein varix is a focal dilatation of the intra-abdominal part of the umbilical vein. It is usually anechoic, located between the anterior abdominal wall and the lower edge of the liver, confirmed by color Doppler and pulsed Doppler examination. The measurement of the cyst should be > +2 standard deviation of the mean for gestational age. If it presents before 26 weeks, there is an increased incidence of spontaneous fetal death.[11] The present study showed three cases of umbilical vein varix at the gestational age of 37 ([Fig. 12A]), 28 ([Fig. 12B]), and 27 ([Fig. 12C] and [D]) weeks. The postnatal outcome was favorable in all three.

Fig. 12 Shows antenatal images. (A) Axial section showing anechoic cyst measuring 8 × 6.7 mm (> 5.1 mm, i.e., > 95th centiles) with flow in color Doppler s/o umbilical vein varix. (B) Coronal section showing anechoic cyst of 11.4 mm (> 7.3 mm, i.e., > 95th centiles) with flow in color Doppler at the level of urinary bladder s/o umbilical vein varix. (C and D) Axial and coronal section showing elongated, slightly irregular cyst measuring 27 × 12 mm (> 7.3 mm, i.e., > 95th centiles) umbilical vein varix at the entry point of umbilical cord in the anterior abdominal wall.

Enteric duplication cysts are either spherical or tubular structures with a thick wall, usually sharing a common wall with the normal GI tract. They may be anechoic or hyperechoic and with/without septations ([Table 4], and [Fig. 13A, B]). In the present study, one case with an enteric duplication cyst was diagnosed. The baby was delivered preterm 33 weeks and admitted to the neonatal critical care unit for respiratory distress. As baby was in the neonatal intensive care unit on ventilator, further investigations were not done. The baby died on day 5 after birth.

Fig. 13 Showing antenatal images. (A) Axial section of fetal abdomen showing heterogeneous cystic lesion measuring 77 × 60 × 88 mm (volume 219 cm³), located anterior to the left kidney with solid-cystic components, appeared to be related to bowel loops. (B) Internal septations were seen within the cyst. The characteristic “signature gut sign” present.

Factors associated with poor outcome:

1. Anatomical location of the cyst[12]

2. Size of the cyst > 40 mm[12]

3. Number of the cyst

4. Trimester at the time of diagnosis[12]

5. Associated abnormalities

6. Gender of fetus[13]

7. Those who require postnatal surgical treatment[13]

According to Sanna et al,[14] the most common presentation of fetal abdominal cyst is unilocular anechoic mass with no vascularity, and it is most frequently diagnosed in the third trimester, which is consistent with our findings.

Compared to Garcia-Aguilar et al,[15] in our study we have reported hepatic cyst, umbilical vein varix, and extralobar pulmonary sequestration.

Agreement between pre- and postnatal diagnosis is around 65 to 70% according to other authors,[16] which is consistent with our results.

Conclusion

In the present study, out of 24 cases, in 19 cases, postnatal follow-up was available (79.16%). The antenatal diagnosis was confirmed postnatally in 18 cases (94.73%). There are various types of fetal intra-abdominal cysts that are distinguished by their location, gestational age, sex, sonographic appearance, vascularity, and associated anomalies. Prenatal US is important to identify the cause and nature of the cyst, its progress, assessment of disease outcome, and to determine the choice of treatment. An appropriate US examination with comprehensive analysis and careful judgment therefore leads to accurate diagnosis and proper postnatal management. Advancements in imaging, that is, CT scan, significantly enhanced diagnostic accuracy, allowing better characterization and informed perinatal/postnatal management. Where most cystic lesions are benign and self-resolving, some may require postnatal surgical management and a multidisciplinary approach involving obstetricians, fetal medicine experts, neonatologists, and pediatric surgeons. Continued research and long-term follow-up are mandatory for a better understanding of the natural history of lesions and improved management protocols.

Table 4 Location and features of intra-abdominal cyst

Cyst type	Location	US features	Postnatal outcome
Gonadal	Lower abdomen/Pelvis of female fetus	Late 2nd/ 3rd trimester anechoic Unilocular Thin-walled	Most of them resolve without sequelae within 6 months
Choledochal	Right upper quadrant of liver	Anechoic, unilocular, thick walled	Spontaneous resolution
Adrenal	Upper pole of kidney	Upper pole of kidney
Hepatic	They usually occur in the right lobe of the liver More common in females (F:M 4:1)	Unilocular, solitary cyst
Extralobar pulmonary sequestration	Basal region of left hemithorax, 10% located in the upper abdomen below the diaphragm	Hyperechoic lesion with typical feeding vessel from thoracic/ abdominal aorta	Excellent outcome after postnatal surgical correction
Mesenteric	Intestinal	Thick walled, heterogeneous	Spontaneous resolution
Megacystis	Lower abdomen and pelvis, common in male fetus[17]	Large urinary bladder > 7 mm in sagittal section with thick wall > 2 mm	Bladder length ≥ 7 mm and 7–15 mm between 11 and 14 weeks, it is associated with chromosomal abnormalities, remaining group shows 90% spontaneous resolution, 10 % develop renal problems[18]
Umbilical vein varix	Focal dilatation between anterior abdominal wall and lower edge of liver	Anechoic, measuring +2 SD of the mean GA, confirmed by color Doppler and pulse wave Doppler	If diagnosed early in pregnancy, fetuses are at high risk of in utero death, UV thrombosis.[14] [19] Those diagnosed later in pregnancy careful monitoring required
Enteric duplication	40% will involve the ileum,[12] rectum, and colon	Anechoic, thick walled, “signature gut sign”	Postnatal surgical correction

Abbreviations: F, female; GA, gestational age; M, male; SD, standard deviation; US, ultrasound; UV, umbilical vein.

Conflict of Interest

None declared.

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Publication History

Article published online:
09 January 2026