**2.2. Classification**

and nonobstructive dilatation of the urinary tract that can be associated with alterations in the

We will discuss the congenital anomalies of the urinary and genital tract, with a short review of kidney abnormalities. These malformations may coexist within the same case, and this is

The reno-urinary anomalies occur more frequently in males than in females, the ratio being 2.5:1 (M-F), and there are many cases with family aggregation. The incidence is 3–4 at 1000 lives or 1–5% of all pregnancies [4, 5]. If including all cases detected at post-mortem fetal

The urogenital system is represented by two major components: the urinary system and the genital system. Embryological and fetal kidneys, genital tract and the urinary system develop from intermediate mesoderm. The rhythm of growth and development of the collector tubes differs greatly during pregnancy. Until 15 weeks of gestation, the rhythm of development is

The urinary tract is almost entirely developed from the intermediate mesoderm. The evolution implies different stages in development: pronephros, mesonephros and metanephros. These stages will appear successively in the craniocaudal direction and coexist over time. Intermediate mesoderm is divided in the upper cervical and thoracic region, resulting in

The mesonephric duct will give rise to the ureteral bud after the formation of the pronephros. This, after 15 generations of divisions, will lead to the formation of the ureter, the calves, the collector tubes and the kidney pelvis. The lack of formation or agenesis of the pronephros or of the mesonephric duct can lead to the total or partial absence of the kidney or to other

CAKUT (congenital anomalies of kidney and urinary tract) may be part of multi-organ processes in single-gene disorders, with dominant or recessive inheritance, as we can find in Fraser syndrome, the branchiootorenal syndrome, Kallmann syndrome, Ehlers-Danlos syn-

The genitalia differentiation, which leads to female or male gender, starts at 7–8 weeks of pregnancy and finalizes at 12–13 weeks. Every fetus will develop female characteristics, because at the beginning of gestational period, the Mullerian and Wolffian structures coexist. If the Mullerian structure will suffer atrophy, due to testosterone and anti-Mullerian hormone effects, male sex structures will develop from the Wolffian structure, and the fetus will

number, size and/or position of the kidneys [1, 2].

**2. Congenital anomalies of urinary tract**

**2.1. Relevant embryology**

nephrotomes [2, 3].

drome and others [5, 6].

very rapid and later decreases [1, 2].

anomalies of the reno-urinary tract [4, 5].

autopsies, the prevalence of these malformations is much higher [2].

due to their common embryonic origin [3].

288 Congenital Anomalies - From the Embryo to the Neonate

Congenital urinary abnormalities are often associated with the kidney anomalies, and there is a wide range of malformations resulting from disorders in the normal development process [9].

Malformations of renal parenchyma may occur due to the abnormal nephron development—in cases of renal dysplasia, renal agenesis and renal polycystic disease. The migration abnormalities of kidney embryo buds are found in renal ectopy and in the mismatched malformations [10].

Abnormalities in the development of the urinary tract system cause duplicated collective systems, posterior urethral valves and obstructions of the pyeloureteral junction. Defects may be unilateral or bilateral, and several types of defects may be associated [1–3, 6, 7].

The anomalies of the urinary system can be divided into nephropathies and uropathies:


For a better understanding of urinary tract abnormalities, we will summarize the classification of kidney malformations that may accompany these anomalies:


**d.** *Supernumerary kidney* is the rarest anomaly and consists of a third kidney with excretory cavities and its own vascularity, completely separated from the other kidney [1–8].

In the first trimester of pregnancy, the kidneys appear as an ovoid structure located on both

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Renal urine production begins during week 9 of embryonic life, making it possible to visualize the bladder, as a fluid collection in the fetal pelvis. The bladder appears spherical and transonic and is located between the iliac bone centers of ossification, in the lower pelvis. It can be visualized starting with the ninth week of pregnancy, and the umbilical arteries can be visualized laterally next to the bladder. Beyond the first trimester, the bladder will fill and empty in an intermittent manner, every 25–30 minutes, due to the influence of hormonal fac-

Normal ureters cannot be visualized by means of echography. The ratio of renal circumference to abdominal circumference is 0.27–0.30 and remains constant during pregnancy [8].

Evaluation of the urinary tract also requires the evaluation of the amniotic fluid volume. After the 14th week of intrauterine life, the amniotic fluid comes mainly from the production of fetal

For a correct diagnosis, the clinician has to perform a complete examination in all of the three planes, the coronal, the sagittal and the longitudinal plane, using 2D grayscale and color Doppler. The examination should be complete. Sometimes, the ultrasound examination has to be completed by another screening method. Due to the association between renal malformations and other congenital defects or chromosomal anomalies, performing an invasive

The renal pelvic dilatation (RPD) is the most common of the abnormalities that can be detected during antenatal ultrasonography and is probably the most frequent sign of a reno-urinary

urine and only one-third of its quantity comes from the pulmonary fluid [2, 5].

sides of the spine (**Figure 1**) [1–4].

tors on the bladder (**Figure 2**) [2, 3].

diagnosis method may be required [14].

**Figure 1.** Fetal kidneys in the first trimester of pregnancy.


**III.** Kidney's shape abnormalities


**VI.** Renal position abnormalities

	- **V.** Multicystic renal dysplasia

These are large and hyperechogenic kidneys, including renal ciliopathies. These conditions may be divided into autosomal dominant diseases and autosomal recessive disorders, including the polycystic kidney disease, renal dysplasia, glomerulocystic kidney disease (trisomy 13 and trisomy 18, Beemer syndrome), multicystic dysplastic kidneys (MCDK), medullary cystic dysplasia (Meckel-Gruber and Beckwith-Wiedemann syndromes, as well as congenital infections) [10–13].
