**9. Renal tumors**

Definition: renal tumors in the fetus are more commonly mesoblastic nephroma (a benign tumor) with rare occurrence of Wilms' tumor (which is malignant).

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 among the most accepted theories.

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 present hydrops.

Differential diagnosis:


#### Clinical facts:

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

• Risk of chromosomal anomalies is low, though mild pelviectasis has been associated with

• Risk of nonchromosomal syndromes (VACTERL, Schinzel-Giedion syndrome, camptom-

• Eighty percent of mild pelviectasis resolve antenatally, and half of the rest resolve postna-

• Pelviectasis that is slowly progressing to hydronephrosis usually has an underlying pathol-

• Poor prognosis may appear in cases of bilateral renal pathology or associated anomalies

Definition: renal tumors in the fetus are more commonly mesoblastic nephroma (a benign

• Even with hydronephrosis the prognosis is excellent if there is no renal impairment.

• Postnatal following is recommended with scans and evaluation of the renal function.

• In the presence of mild pelviectasis, screening for T21 markers is recommended.

increased (impaired concentration ability).

282 Congenital Anomalies - From the Embryo to the Neonate

ogy that would have to be addressed postnatally.

• Prenatal intervention is rarely needed (**Figure 7**).

tumor) with rare occurrence of Wilms' tumor (which is malignant).

Clinical facts:

trisomy 21.

tally [2].

elic dysplasia).

**Figure 7.** Bilateral hydronephrosis.

(syndromic or not).

**9. Renal tumors**


**Figure 8.** Nephroblastoma.
