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liver; N, node; S, stomach. B: Celiac axis neuroblastoma. Enhanced CT section of the abdomen
at level of the kidney shows a large lobulated mass with irregular margins and calcification
displacing the right kidney inferoposterior and laterally. Note encased inferior vena cava (IVC)
and aorta. The IVC is displaced laterally and ventrally and to the right the superior mesenteric
artery and celiac axis are completely surrounded by the mass. A, Aorta; I, IVC; K, kidney; L,
liver; S, spleen; white arrows, mass.

Wilms Tumor
Wilms tumor is the most common intrarenal tumor seen in children. The tumor
can be massive before its discovery. Wilms tumor should be considered in any
child who has unexplained hematuria.
A solid renal mass demonstrated by US in infants and children is usually a
Wilms tumor. Because of the high frequency of tumor extension into the renal
veins and inferior vena cava, these vascular structures should be examined by US.
Because Wilms tumors are usually large and expansive, the inferior vena cava
often is extrinsically displaced by the tumor mass. CT with bolus contrast
enhancement may be required for confirmation of equivocal invasion in a patient
suspected of having Wilms tumor. CT scan can define the presence of an
intrarenal mass and extent of tumor, visualizes vascular structures, identifies
nodal involvement, defines internal hemorrhage and necrosis, evaluates the
presence or absence of liver metastases, and provides some measure of renal
excretory function. Also, CT can determine whether a tumor is initially
nonresectable or bilateral ( Fig. 116.24 ). Chest CT is also performed at the initial
evaluation to identify pulmonary metastases.