**8. Urogenital tract**

Urogenital malformations are the most often diagnosed anomalies with a birth prevalence of 0.5%. Fetal kidneys can be first visualized with ultrasound at 14 weeks of pregnancy beside the spine and by 18 weeks, their structure can be analyzed too [44].

In the first 18 weeks of development, the amniotic fluid is derived from the placenta and membranes, but after 16 weeks, fetal kidneys gradually take over the production. Therefore, anomalies of the fetal urinary tract may result in impaired production of the amniotic fluid and eventually oligohydramnios. However, when one kidney is functional, the quantity of the amniotic fluid can be normal as well [44].

Renal agenesis is the absence of one or both kidneys. The birth prevalence of this abnormality is 1:4000. The fetal kidney or kidneys cannot be visualized with ultrasound, only the enlarged adrenal glands (lying down adrenal sign). When both kidneys are absent, the filling of the bladder is missing and oligohydramnios is severe. The severe oligohydramnios may cause Potter-syndrome: flattened nose and ears, peculiar look, hip dysplasia, club-foot, hypomelia, sirenomelia, arthrogryposis, fetal growth retardation and pulmonary hypoplasia (due to the impaired secretion and resorption of the amniotic fluid and compression) [5, 44–46].

Potter type I polycystic kidney is usually bilateral and shows an autosomal recessive inheritance pattern. It occurs in 1:10,000–1:40,000 birth. The cysts are small, 1–2 mm, originated from the collecting ducts. Cysts can also appear in the liver and renal and hepatic fibrosis may also occur. The cysts are too small to be detected with ultrasound, but the enlargement and hyperechogenicity of the kidneys are seen. Furthermore, oligohydramnios and the absence of the filling of the bladder are also usually present. Potter-sequence may also appear due to the severe oligohydramnios [5, 44, 46].

Morphological types:

**8. Urogenital tract**

can be normal as well [44].

• Type 1: The intestines are intact after the atresia

12 Congenital Anomalies - From the Embryo to the Neonate

• Type 3: multiplex anomalies of the intestines

intestines based on the ultrasound findings [5].

of the esophagus was diagnosed in only one-fifth of the cases.

the spine and by 18 weeks, their structure can be analyzed too [44].

• Type 2: There is a narrowing after the atresia and the intestines are often shortened

Intestinal atresia mostly occurs due to teratogenic effects. Polyhydramnios and dilated intestinal loops are usually seen on ultrasound. Atresia of the large intestines and of the anus is harder to detect due to the lack of polyhydramnios and less distended intestines. The dilated rectum that is filled with water may be visualized between the sacrum and the bladder [5, 36, 43].

Hirschsprung's disease is a congenital aganglionosis of the intestines that causes the distal large intestines to dilate. It occurs in 1:5000 live birth, mostly in boys. Dilated intestines and polyhydramnios are the most important signs on ultrasound after the second trimester. However, it is hard to differentiate between Hirschsprung's, cystic fibrosis and the atresia of the large

In our study, duodenum atresia was diagnosed with a high sensitivity of 94.74%, while atresia

Urogenital malformations are the most often diagnosed anomalies with a birth prevalence of 0.5%. Fetal kidneys can be first visualized with ultrasound at 14 weeks of pregnancy beside

In the first 18 weeks of development, the amniotic fluid is derived from the placenta and membranes, but after 16 weeks, fetal kidneys gradually take over the production. Therefore, anomalies of the fetal urinary tract may result in impaired production of the amniotic fluid and eventually oligohydramnios. However, when one kidney is functional, the quantity of the amniotic fluid

Renal agenesis is the absence of one or both kidneys. The birth prevalence of this abnormality is 1:4000. The fetal kidney or kidneys cannot be visualized with ultrasound, only the enlarged adrenal glands (lying down adrenal sign). When both kidneys are absent, the filling of the bladder is missing and oligohydramnios is severe. The severe oligohydramnios may cause Potter-syndrome: flattened nose and ears, peculiar look, hip dysplasia, club-foot, hypomelia, sirenomelia, arthrogryposis, fetal growth retardation and pulmonary hypoplasia (due to the

Potter type I polycystic kidney is usually bilateral and shows an autosomal recessive inheritance pattern. It occurs in 1:10,000–1:40,000 birth. The cysts are small, 1–2 mm, originated from the collecting ducts. Cysts can also appear in the liver and renal and hepatic fibrosis may also

impaired secretion and resorption of the amniotic fluid and compression) [5, 44–46].

• Type 4: The dorsal mesentery is absent and the intestines are shortened

In multicystic renal dysplasia, there is no normal parenchyma, but 10–20 mm cysts and connective tissue fill the kidneys. The anomaly is unilateral in two-third of the cases. The quantity of the amniotic fluid is usually normal, but oligohydramnios can appear in bilateral and sometimes polyhydramnios in unilateral cases. The incidence of this malformation is around 1:10,000 birth and it is more prevalent in boys. Most cases are diagnosed with ultrasound at 18 weeks as the cysts can be visualized and they are not connected to the renal pelvis. Also, the kidneys usually have an abnormal shape. Bilateral dysplasia is often fatal [44–46].

Obstructions of the urinary tract usually results in the dilatation proximally. Obstruction of the ureteropelvic junction is the main cause of hydronephrosis in the neonate. Pyelectasis is the dilatation of only the renal pelvis and the calyces, while when the parenchyma is also affected by the compression, we talk about hydronephrosis. The dilatation of the pyelon and calyces can be seen in pyelectasis, while hydronephrosis appears as a solid cyst or sac. Pyelectasis is defined as a pyelon larger than 4 mm before 20 weeks or larger than 7 mm after 34 weeks of gestation. The anomaly is often diagnosed (2–5.5% of all fetuses), but spontaneous regression is common [6, 7, 45, 47].

In the obstruction of the ureterovesical junction, the ureter distends as well, creating a megaloureter. This anomaly is 4 times more prevalent in boys. In the presence of a posterior urethral valve, the bladder, ureter and renal pelvises dilate too and the distention damages the kidneys as well. It may cause severe oligohydramnios and Potter-sequence. Also, the dilated organs may stretch the abdominal wall, causing rectus diastasis (prune belly syndrome) [5, 44, 45].

Ovarian cyst is the most common abdominal mass in female fetuses with a birth prevalence of 1:2600. The malformation is more and more often diagnosed prenatally. The etiology of the anomaly is unknown and the cyst is usually benign. Ovarian cysts are more prevalent in fetuses of mothers with diabetes, eclampsia or Rh isoimmunisation. Complications are rare: compression of other organs, rupture, bleeding. The most common complication is the torsion of the cyst may cause the ischemia and eventually necrosis of the ovary [47, 48].

Malformations of the female organs are mostly caused by the impaired development of the Müllerian duct. When the two ducts do not fuse properly it causes the female organs to be septate or doubled. MRKH (Mayer-Rokitansky-Küstner-Hauser) syndrome is a malformation of the Müllerian duct when the upper two-third of the vagina and the uterus are missing [49].

Malformations of the urogenital tract were diagnosed with ultrasound in 54.55% of the cases. The sensitivity of the ultrasound was high in polycystic kidney (100%), obstructions of the urinary tract (88.89%), multicystic renal dysplasia (80.57%), and pyelectasis (67.21%). However, genital malformations were harder to diagnose and a correct diagnosis was made in only 19.7% of the cases.
