Which radiography findings are characteristic of Wilms tumor?

Updated: Mar 04, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Answer

Conventional radiography is a noninvasive and economical way to demonstrate lung and bone metastases. Plain radiographs are also used in following up radiation therapy and in looking for pulmonary complications associated with chemotherapy. A plain abdominal radiograph often shows displacement of the abdominal viscera and, in less than 10% of cases, streaky or irregular calcification. Calcification is more apparent on CT than on radiographs. The calcification usually is on the edge of the tumor, whereas the calcification associated with a neuroblastoma is speckled throughout. [9]

IVU shows an intrarenal mass confined within the renal outline (see the image below). The mass is often associated with splaying, distortion, and displacement of the calyces. Three-dimensional assessment can be achieved by using frontal and lateral radiographs. Upper and posterior tumors increase calyceal distortion, as these sites offer little room for exophytic expansion because of their rigid surrounding structures.

An IVU shows a nonfunctioning left kidney with a s An IVU shows a nonfunctioning left kidney with a suggestion of ill-defined mass in the left loin due to a biopsy-proven Wilms tumor. Note the functioning right duplex renal collecting system. The chest radiograph in the same child shows a lung metastatic deposit (arrow). Images courtesy Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com

With IVU, an inadequate dose of contrast medium often causes nondiagnostic results, with subsequent errors in diagnosis. Relatively large doses of contrast agent (4 mL/kg) should be used to obtain diagnostic IVUs.

Tumors are commonly large at presentation and often cross the midline. Because large tumors may virtually replace the excretory renal tissue, IVU may show little opacification. This is true in approximately 10% of children with a Wilms tumor, but it does not appear to affect their prognosis.

Tumors at the lower pole and anterior tumors have more room for exophytic growth. Therefore, their associated calyceal deformity is less pronounced than that observed with upper and posterior tumors. A central tumor may cause hydronephrosis and calyceal distortion.

In the developed world, conventional radiography (apart from chest radiography) has a limited role in the workup of Wilms tumor to detect and follow up lung metastases. However, in the developing world, much more reliance may be placed on conventional radiography and perhaps ultrasonography, because these modalities are more readily available. Chest radiography, IVU, and ultrasonography provide the best combination in parts of the world where CT and MRI are not available.

A preoperative imaging protocol that relies predominantly on chest radiography and abdominal ultrasonography does not reduce survival. [29] More sophisticated imaging, particularly CT, is not required in most cases, and it is warranted only when results of chest radiography or ultrasonography are not helpful for resolving relevant management problems. Lung and bone metastases are easily missed on plain radiographs. Moreover, plain radiographs have low specificity.


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