**2.5. Ureteral malformations**

In medical practice many abnormalities can occur, like:


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**Figure 5.** Coronal section and high-definition power color Doppler, in a supernumerary kidney cases. Visualization of the double renal artery.

**b.** The ureteropelvic junction obstruction

Many studies show that a right or left prenatal AP renal pelvic diameter > 4 mm is associated with a higher risk of postnatal hydronephrosis compared with a right and left prenatal AP renal pelvic diameter ≤ 4 mm [15, 16]. Male neonates have a higher risk of postnatal hydronephrosis than females. These results can assist in establishing the appropriate follow-up

• Ureteral agenesis is accompanied by the absence of the ipsilateral kidney. It may be uni- or

• Incomplete ureteral duplication (ureter fissus or ureter bifid)—a double-sided pyeloureteral system: the ureters bend before opening into the bladder through a single orifice. • Complete ureteral duplication (duplex ureter)—a double-sided pyeloureteral collection system: the ureters open through separate boreholes in the bladder, one in orthoposition

method and evaluation of fetuses with renal pelvic dilatation [18, 19].

In medical practice many abnormalities can occur, like:

**Figure 4.** Hydronephrosis in the third trimester of pregnancy.

294 Congenital Anomalies - From the Embryo to the Neonate

**2.5. Ureteral malformations**

• Number abnormalities

• Structure abnormalities

• Calibration abnormalities

**a.** Ureteral abnormalities

• Vesicoureteral reflux (VUR)

• Abnormalities of the pyeloureteral junction

• Position and opening abnormalities [1, 2, 14]

bilateral, the latter being incompatible with life.

and the other in the ectopic position (**Figure 5**) [15–17].

Obstruction of the ureterobladder junction (obstructive megaureter) or obstruction on pyeloureteral junction is one of the most common causes of hydronephrosis found in children, its incidence being 1 case in 1000–2000 newborns. In this situation, hydronephrosis may be caused by an abnormal shape of the ureteral junction—the existence of the ureteral valves and the mucosal fold at this level. Like many other abnormalities, this pathology occurs much more frequently in males, usually unilaterally and especially on the left side [10, 14].

The ultrasound diagnosis is based on the observation of the increase of the anteroposterior diameter of the kidney, a degree of kidney pyelectasis. If the obstruction is unilateral and the filling of the bladder is normal, the normal amount of amniotic fluid will be preserved. When the damage is bilateral, the oligoamnios/oligohydramnios may appear.

In most cases this condition does not produce symptoms after birth; in 10–15% of the cases, it regresses spontaneously, but sometimes repeated evaluation is needed [1–8].

**c.** Obstruction of the ureterobladder junction

This condition is the cause of approximately 5–10% of all cases of dilatation of the urinary tract. Ultrasound diagnosis is based on dilated urethra, with renal pelvis dilatation and normal bladder image. The cause of the disease is the dysfunction of the lower ureter, the outcome is favorable and the pathologic aspects disappear postnatally in many cases [16] (**Figure 6**).

The normal ureter size in children is up to 5 mm. Normal ureter cannot be detected during prenatal ultrasound examination. It can only be detected if it is dilated to a size greater than 7 mm and is observed like a translucent structure. The dilated ureter should be differentiated from full intestinal loops. Pathological dilatation of the ureter is more common in male patients, usually appearing to be unilateral (**Figure 7**) [15–17].

**Figure 6.** Contralateral pyelectasis in a unilateral MCDK case.

The dilatation of the ureter may be partial or total, and this pathology can be classified into the following conditions:

• Grade II reflux: reflux reaches the renal pelvis, without dilatation of the collector system,

**Figure 7.** (a) First trimester: both renal arteries visualized in color Doppler, normal kidney images on both sides of the cross section and a kidney highlighted in the coronal section. (b) Second trimester (same case): asymmetrical bilateral

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pyelectasis, left kidney longitudinal diameter and hydroureter on the right side.

• Grade III reflux: moderate dilatation of the ureter, with or without sinusitis; moderate dila-

• Grade IV reflux: moderate dilatation of the ureter with or without sinuosity; moderate dilatation of the collector system; calyces are flattened but with the impression of the papilla still visible. • Grade V reflux: severe dilatation with ureter sinuosity and marked dilatation of the collec-

• The prognosis is good. The prenatal diagnosis is important. Forty percent of the newborns

As many other kidney abnormalities, ureterocele is more common in male patients. This pathology appears as a thin wall cyst or sept on the bladder wall [1, 16]. In many cases the diagnosis may be omitted when the bladder is full, the filling masking the cyst. There have been described cases of ureterocele shed in the urethra. This phenomenon may lead to acute obstruction of the lower urinary tract [1, 2]. The prognosis is favorable, but its evolution must be assessed postnatally, by residual renal function testing and reflux tests (**Figure 8**) [20].

tor system; reflux in the parenchyma, with parenchymal thinning [10–15, 18].

the papillae being normal.

tation of the collector system.

develop severe kidney damage [2].

**e.** Ureterocele


Vesicoureteral reflux (VUR) is characterized by the return of urine from the bladder to the kidney which often causes hydronephrosis and sometimes even abnormalities in kidney development (renal dysplasia). Causes include transient obstruction of bladder discharge, delayed maturation of the vesicoureteral junction and high bladder evacuation pressure. Patients with vesicoureteral reflux have a high risk of pyelonephritis, hypertension and progressive renal failure. Vesicoureteral reflux is represented by the retrograde passage of urine from the bladder to the ureter and subsequently to the kidneys, due to the incompetence of antireflux mechanisms [17, 19, 20].

This condition is usually easy to diagnose prenatally, when visualizing renal pelvis and calyces dilatations that vary in size, associated with unilateral or bilateral ureteral dilatations. RVU reveals a nonprogressive hydronephrosis with normal amniotic fluid index [10–13, 18].

VUR classification:

• Grade I reflux: reflux is only present in the ureter that has various degrees of dilatation.

**Figure 7.** (a) First trimester: both renal arteries visualized in color Doppler, normal kidney images on both sides of the cross section and a kidney highlighted in the coronal section. (b) Second trimester (same case): asymmetrical bilateral pyelectasis, left kidney longitudinal diameter and hydroureter on the right side.


The dilatation of the ureter may be partial or total, and this pathology can be classified into

Vesicoureteral reflux (VUR) is characterized by the return of urine from the bladder to the kidney which often causes hydronephrosis and sometimes even abnormalities in kidney development (renal dysplasia). Causes include transient obstruction of bladder discharge, delayed maturation of the vesicoureteral junction and high bladder evacuation pressure. Patients with vesicoureteral reflux have a high risk of pyelonephritis, hypertension and progressive renal failure. Vesicoureteral reflux is represented by the retrograde passage of urine from the bladder to the ureter and subsequently to the kidneys, due to the incompe-

This condition is usually easy to diagnose prenatally, when visualizing renal pelvis and calyces dilatations that vary in size, associated with unilateral or bilateral ureteral dilatations. RVU reveals a nonprogressive hydronephrosis with normal amniotic fluid index [10–13, 18].

• Grade I reflux: reflux is only present in the ureter that has various degrees of dilatation.

the following conditions:

• Obstructive-type megaureter

• Megaureter without reflux and without obstruction

**Figure 6.** Contralateral pyelectasis in a unilateral MCDK case.

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tence of antireflux mechanisms [17, 19, 20].

• Obstructive- and reflux-type megaureter

• Reflux-type megaureter

**d.** Vesicoureteral reflux

VUR classification:

As many other kidney abnormalities, ureterocele is more common in male patients. This pathology appears as a thin wall cyst or sept on the bladder wall [1, 16]. In many cases the diagnosis may be omitted when the bladder is full, the filling masking the cyst. There have been described cases of ureterocele shed in the urethra. This phenomenon may lead to acute obstruction of the lower urinary tract [1, 2]. The prognosis is favorable, but its evolution must be assessed postnatally, by residual renal function testing and reflux tests (**Figure 8**) [20].

• The bladder mucosa is exposed to the external environment, with the ureteric holes and

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• Some patients have rectal prolapse and anal incontinence; this phenomenon is due to

The most common obstructive cause of the lower urinary tract is the posterior urethral valve (PUV). PUV is due to the existence of membranes in the posterior urethra. Echography shows dilated bladder and urethral dilatation, giving a classic echographic sign—'the keyhole sign'. Dystriation of ureters and troughs also occurs [14]. In advanced forms, oligohydramniosassociated pulmonary hypoplasia and urinary ascites may also appear. These fetuses require prenatal intervention to avoid kidney damage. Some authors tried to demonstrate that creating a vesicoamniotic passage may lead to a better outcome, but this has not yet been fully

**1.** Urethral agenesis (absence of urethra) is a rare malformation, incompatible with life unless an alternative communication between the bladder and amniotic sac exists. The urine is discharged through abnormal communication with other organs (between bladder and

**3.** Rear urethral valves: mucosal lining located in the posterior urethra originating from the

**4.** Epispadias: abnormality characterized by opening the urethra on the dorsal face of the penis at variable distance of the gland, dorsal curvature of the penis and foreskin abnor-

• Penopubian: a complete defect, often associated with bladder exstrophy. In this situation, a distinct pathological condition appears: the exstrophy-epispadias complex [19].

• Hypospadias: the anomaly is characterized by opening the urethra on the ventral side of the penis, at any level between the gland and the perineum, causing a ventral penis (chord). Patients with hypospadias have often abnormalities of the foreskin and cryptorchidic scrotum, inguinal hernia and hydrocele. Studies have shown a higher presence of hypospadias in patients with fetal growth restriction (**Figures 9**

seminal colonic and insertion on the anterior wall of the urethra [14–17].

the inner urethra opening visible.

**4. Urethral malformations**

demonstrated [16].

• Vesicoureteral reflux is present in all cases.

In the prenatal life, other malformations may be seen:

malities. There are many forms of epispadias:

• Balanic: distal incomplete defect.

• Penian: incomplete proximal defect.

bowels or by umbilical fistula).

**2.** Congenital structures.

and **10**) [19]

the malposition of sphincter structures [1–4, 15–17, 19, 20].

**Figure 8.** Ureterocele and hydroureter.
