**8. Pelvis dilatation**

Definition: the dilatation of the pelvis is the most common anomaly detected by ultrasound. It can present as a mild pelviectasis or as hydronephrosis. Though numbers may vary in different sources, generally values are around these figures:


Limits of normal size for gestational age have also been described [2]:


Incidence: 1–5:500 newborns.

Pathology: mild pelviectasis has been associated with aneuploidy (minor marker), especially trisomy 21. The mechanism for unilateral hydronephrosis may be obstruction of the ureteropelvic junction, vesicoureteral reflux, and obstruction of the vesicourethral junction. Bilateral hydronephrosis may be caused by bilateral vesicoureteral reflux or by urethral obstruction.

Ultrasound findings: renal scanning reveals a dilated renal pelvis above the cutoff for the respective gestational age. Frequently, when hydronephrosis is installed, the calyces are also

Pathology: mesoblastic nephroma is a benign mesenchymal tumor with spindle-shaped cells. It is frequently associated with polyhydramnios through mechanisms that are not yet fully understood; polyuria caused by hypercalcemia and bowel obstruction by mass effect are

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Ultrasound findings: examination usually reveals a tumor/mass that occupies part or the entire kidney. Mesoblastic nephromas have ill-defined margins and may present on color Doppler ultrasound as a vascular mass. When there are arteriovenous shunts, fetus may pres-

• Risk of nonchromosomal anomalies: Wilms' tumor may be associated with Beckwith-

• Surgical removal of the tumor or nephrectomy is indicated in the neonatal period (**Figure 8**).

among the most accepted theories.

• Adrenal mass (tumor or hemorrhage).

• Renal collecting system duplication.

• Risk of chromosomal anomalies is very low.

Wiedemann or Denys-Drash syndrome [5].

• You should look for Beckwith-Wiedmann signs.

• May have a–v shunts and hydrops, or cardiac failure may appear.

• The first sign may be polyhydramnios.

• Tumor may have rapid growth.

**Figure 8.** Nephroblastoma.

ent hydrops.

Clinical facts:

Differential diagnosis:

• Crossed fused ectopia.

**Figure 7.** Bilateral hydronephrosis.

dilated. Sometimes, the dilatation is isolated (as in ureteropelvic junction stenosis) or includes dilatation of the ureters. In rare cases dilatation may lead to urinoma (only in cases of severe obstruction). Amniotic fluid is usually normal and in one-third of the cases may even be increased (impaired concentration ability).

Clinical facts:

