**2.3. Abnormal structures present in the abdomen: cystic or hypoechoic masses**

The presence of cystic lesions in the fetal abdomen can have many underlying conditions. The diagnosis can be made upon their appearance: unique or multiple, the situs of the abnormal structure, and its relations with the abdominal viscera, the aspect of the wall and content. In most cases, the correct prenatal diagnosis of these structures is difficult to make and their origin can be determined only after birth.

Single cystic masses can be:

• megacystis,

The differential diagnosis should include other anomalies of the kidney, associated with oli-

When bilateral renal agenesis is suspected, a detailed examination of the fetal anatomy should

• Cardiovascular malformations (14%): tetralogy of Falloch, ventricular septal defect, atrial septal defect, hypoplastic left ventricle, coarctation of the aorta, dextrocardia, single ventricle, transposition of the great vessels, total anomalous pulmonary venous drainage, tricuspid

• Musculoskeletal malformations (40%): absent radius and fibula, digital anomalies, lumbar

• Central nervous system malformations (11%) include hydrocephaly, microcephaly, menin-

• Gastrointestinal malformations (19%): duodenal atresia, imperforate anus, esotracheal fis-

The prognosis is usually lethal due to the association of pulmonary hypoplasia and growth

Bladder exstrophy as well as cloacal exstrophy arise from the abnormal growth of the caudal fold, resulting in a anterior abdominal wall defect. The absence of the anterior abdominal wall and the anterior bladder wall will expose the posterior bladder wall to the amniotic fluid. Small defects result in epispadias, but a larger one might expose the posterior bladder wall. The incidence of bladder exstrophy is 1:30,000 births, with male fetuses being more affected [16]. These anomalies are frequently sporadic, although familial transmissions have been reported [16].

Positive and differential ultrasonographic diagnosis of bladder exstrophy should be suspected whenever the bladder cannot be visualized, even though the amniotic fluid volume is normal (the cycle of the bladder filling is 15 min)—**Figure 5**. Others ultrasound signs useful are:

Bladder exstrophy must be differentiated from gastroschisis and omphalocele. In those conditions, despite the abdominal wall defects, the bladder is still present within the fetal pelvis [17]. The risk of association with chromosomal and nonchromosomal syndromes is low. Perinatal counseling depends on the association with other anomalies. If the prenatal diagnosis of blad-

• a solid hyperechoic mass that comes in close contact with the umbilical arteries.

tula, intestinal malrotations, absent stomach or gallbladder, and omphalocele.

gohydramnios as polycystic kidney disease, multicystic kidneys, etc.

atresia, and hypoplastic aorta.

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• Single umbilical artery.

*2.2.4. Bladder exstrophy*

be performed considering the high risk of other anomalies association [15]:

hemivertebrae, cleft palate, sacral agenesis, and diaphragmatic hernia.

gocele, cephaloceles, holoprosencephaly, and iniencephaly.

retardation, the fetuses die in utero or in the first days of life.

• the absence of the bladder within the fetal pelvis.

• genital ambiguity (duplication and division of the penis).

der exstrophy is made, therapeutic abortion must be offered as an option.

• normal volume of the amniotic fluid.


Multiple cystic lesions can be more frequent:


of liquid and delaying the dilatation of the intestine. Sometimes, the only consistent sign at repeated scans is a dilated stomach. Differential ultrasonographic diagnosis should be made

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Duodenal atresia has a high risk (62%) of association with chromosomal anomalies and associated anomalies mainly with Down syndrome. Duodenal atresia is a sporadic anomaly, but it has been demonstrated that it can be transmitted in an autosomal recessive manner. Almost half of the fetuses with duodenal atresia manifest other anomalies: skeletal defects (vertebral and rib abnormalities, sacral agenesis, esotracheal fistula, intestinal malrotation, Meckel's diverticulum, and anorectal atresia), renal and cardiac defects. Because of the close vicinity with the Vater Ampulla, in 1% of cases biliary duct anomalies are present. Gall bladder atresia is impossible to diagnose before birth, but it can be suspected, if duodenal atresia is present

with other cystic structures present in the upper or inferior abdomen:

• choledocal cyst.

• intestinal duplication cyst.

**Figure 6.** Duodenal atresia—double bubble sign.

• kidney cyst or multicystic dysplastic kidney.

and the gall bladder cannot be visualized [18].

• hepatic cyst.

• ovarian cysts.

• mesenteric cysts.

• urachal cyst.

• ureterocele.

• pyelectasis.

• persistent right umbilical vein or varicose veins pertaining to the umbilical vein.


The differential diagnosis of the cystic abdominal proliferations includes:


#### *2.3.1. Duodenal atresia*

It is defined as the obstruction of the bowel produced by a degenerated middle segment of the duodenum. It can be also extrinsic due to a malformed annular pancreas or fibrous peritoneal bands that cause compression. The most frequent affected segments are the 2nd and the 3rd segment of the duodenum. With an incidence is 1:10,000 births, it is the second main cause of small bowel obstruction [18].

The diagnosis is suspected in the presence of polyhydramnios and it is based on the "double bubble" sign (**Figure 6**) formed by the stomach and the proximal part of the duodenum, both appearing dilated. This sign may be present from 19 weeks, but usually it is seen in the second part of the pregnancy or even later due to the fetal capacity of swallowing small amounts

**Figure 6.** Duodenal atresia—double bubble sign.

of liquid and delaying the dilatation of the intestine. Sometimes, the only consistent sign at repeated scans is a dilated stomach. Differential ultrasonographic diagnosis should be made with other cystic structures present in the upper or inferior abdomen:


• bowel volvulus,

• ascites,

• polycystic kidney, • hydronephrosis,

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• meconium peritonitis,

• liver calcification.

• mesenteric cysts,

• choledochal cysts,

• intestinal obstruction, • intestinal duplication,

• meconium peritonitis-related cysts,

• anterior meningomyelocele,

• the persistence of the cloaca.

small bowel obstruction [18].

• omental cysts,

• renal cysts,

• ovarian cysts,

• megacystis,

• hydrometrocolpos,

*2.3.1. Duodenal atresia*

• dilated megaureter in uretero-pelvic junction obstruction,

Other complex aspects involving hypo and hyperechoic structures can be found in:

It is defined as the obstruction of the bowel produced by a degenerated middle segment of the duodenum. It can be also extrinsic due to a malformed annular pancreas or fibrous peritoneal bands that cause compression. The most frequent affected segments are the 2nd and the 3rd segment of the duodenum. With an incidence is 1:10,000 births, it is the second main cause of

The diagnosis is suspected in the presence of polyhydramnios and it is based on the "double bubble" sign (**Figure 6**) formed by the stomach and the proximal part of the duodenum, both appearing dilated. This sign may be present from 19 weeks, but usually it is seen in the second part of the pregnancy or even later due to the fetal capacity of swallowing small amounts

The differential diagnosis of the cystic abdominal proliferations includes:


Duodenal atresia has a high risk (62%) of association with chromosomal anomalies and associated anomalies mainly with Down syndrome. Duodenal atresia is a sporadic anomaly, but it has been demonstrated that it can be transmitted in an autosomal recessive manner. Almost half of the fetuses with duodenal atresia manifest other anomalies: skeletal defects (vertebral and rib abnormalities, sacral agenesis, esotracheal fistula, intestinal malrotation, Meckel's diverticulum, and anorectal atresia), renal and cardiac defects. Because of the close vicinity with the Vater Ampulla, in 1% of cases biliary duct anomalies are present. Gall bladder atresia is impossible to diagnose before birth, but it can be suspected, if duodenal atresia is present and the gall bladder cannot be visualized [18].

The prognosis of isolated duodenal atresia is favorable, the rate of survival after corrective surgery is over 95%. The incidence of early postoperative mortality is between 3 and 5%, and the long term postoperative mortality rate is 6%. Considering the high risk of chromosomal anomalies association, the karyotype analysis is mandatory whenever duodenal atresia diagnosis is made prenatally, and also a careful examination of the fetus anatomy. Polyhydramnios can cause preterm birth and although vaginal delivery is allowed, it must take place in a tertiary unit to assure proper care for the neonate.

Intestinal obstruction is usually sporadic, but it can have a genetic transmission when the affected areas are multiple. Anorectal atresia is associated in 80% of cases with vertebral defects, genitourinary, cardiac and other gastrointestinal abnormalities. The association with chromosomal or

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Ultrasound diagnosis is usually possible beyond 25 weeks of gestation, due to the slowly dilation progression. The size of the intestinal lumen does not exceed 2–7 mm. The jejunum and ileum obstructions aspect is of dilations of the intestinal loops with active peristalsis. The fetal abdomen is fully distended and the majority of cases also present polyhydramnios, especially in the case of proximal obstructions. Similar images of the fetal abdomen can be found in Hirschsprung's disease. Transitory ascites or meconium peritonitis can appear when intestinal perforations occur [5]. When intestinal obstruction is diagnosed, the work-up to exclude other intestinal tract anomalies, ovarian cysts, mesenteric cysts, or intestinal duplication cysts is mandatory. Anorectal atresia is difficult to diagnose prenatally due to the great distension of the proximal bowel and the normal amount of amniotic fluid. Occasionally, calcification of

The prognosis depends on the type and location of the obstructed site and on the association of other anomalies. Considering that polyhydramnios that can occur, preterm births are common and the birth should take place in a tertiary unit. After birth, the affected babies develop emesis and abdominal distention, and can require immediate surgery repair. For isolated obstructions, requiring small resections of the intestine, the survival rates are over 95%. The resection of a large intestinal segment can lead to a lethal syndrome—short gut syndrome.

It is caused by the congenital absence of intramural parasympathetic ganglia of the colon. The deficiency is caused by the lack in neuroblast migration from the neural crest, which occurs between the 6th and the 12th week of development. Also, the degeneration of the already migrated neuroblasts, which can occur before or after birth, may be involved. The incidence is approximately 1:3000 births. This disease is usually sporadic, but in 5% of cases there is a familial transmission.

Ultrasound diagnosis can be suspected in the presence of the dilatation of the intestinal lumen produced by abnormal peristaltic movements. At the ultrasound scan, images are similar to those found in anorectal atresia, in which the colon is also affected. Similarly, when the small intestine loops are affected, the images are of an obstruction with dilated intestinal loops and polyhydramnios. The prognosis depends on the postnatal postoperative evolution, which aims to resect the affected intestinal segment, and can include a temporary colostoma with a neonatal mortality rate of 20%. Considering the prematurity risk due to associated polyhydramnios and the need for postnatal surgery, the birth must take place in a tertiary unit, but cesarean birth is not mandatory.

They are defined as cystic dilatations of the common bile duct; they are rare and are usually of unknown etiology. The diagnosis is made in the presence of a transonic image located in

In a small number of cases, Hirschsprung's disease is associated with Down syndrome.

the fetal meconium may be present within the fetal pelvis.

other anomalies is rare.

*2.3.3. Hirschsprung's disease*

*2.3.4. Choledochal cysts*

#### *2.3.2. Intestinal obstruction*

Intestinal obstruction is defined by the total or partial intestinal obstruction, which can occur in an intrinsic or extrinsic manner. The intrinsic lesions are caused by intestine stenosis or atresia. In the case of atresia, the two intestinal segments can be completely separated or tied by a fibrous band. In the case of intestinal stenosis, the two segments can be separated by a septum or a central diaphragm or the intestinal lumen is very narrow. "Apple-peel" atresia is characterized by the absence of an important intestinal segment that can include the distal duodenum, the entire jejunum, or the proximal ileum—**Figure 7**. Conditions that can produce extrinsic obstruction are most frequently represented by:


The intestinal areas affected in the order of frequency are: the distal ileum (35%), the proximal jejunum (30%), distal jejunum (20%), proximal ileum (15%), or it can be multicentric in approximately 5% of cases. Anorectal atresia results from an abnormal cloacal division in the 9 weeks of gestation [5]. The incidence of intestinal obstruction is 1:2000 births. In half of the cases, obstruction of the small intestine is present, and the other half is made up by anorectal atresia.

**Figure 7.** Duodenal stenosis—in utero image.

Intestinal obstruction is usually sporadic, but it can have a genetic transmission when the affected areas are multiple. Anorectal atresia is associated in 80% of cases with vertebral defects, genitourinary, cardiac and other gastrointestinal abnormalities. The association with chromosomal or other anomalies is rare.

Ultrasound diagnosis is usually possible beyond 25 weeks of gestation, due to the slowly dilation progression. The size of the intestinal lumen does not exceed 2–7 mm. The jejunum and ileum obstructions aspect is of dilations of the intestinal loops with active peristalsis. The fetal abdomen is fully distended and the majority of cases also present polyhydramnios, especially in the case of proximal obstructions. Similar images of the fetal abdomen can be found in Hirschsprung's disease. Transitory ascites or meconium peritonitis can appear when intestinal perforations occur [5]. When intestinal obstruction is diagnosed, the work-up to exclude other intestinal tract anomalies, ovarian cysts, mesenteric cysts, or intestinal duplication cysts is mandatory. Anorectal atresia is difficult to diagnose prenatally due to the great distension of the proximal bowel and the normal amount of amniotic fluid. Occasionally, calcification of the fetal meconium may be present within the fetal pelvis.

The prognosis depends on the type and location of the obstructed site and on the association of other anomalies. Considering that polyhydramnios that can occur, preterm births are common and the birth should take place in a tertiary unit. After birth, the affected babies develop emesis and abdominal distention, and can require immediate surgery repair. For isolated obstructions, requiring small resections of the intestine, the survival rates are over 95%. The resection of a large intestinal segment can lead to a lethal syndrome—short gut syndrome.
