Case contributed by Dr. Foryoung


Patient is an infant with no past medical history. Unremarkable review of systems according to mom and dad. On physical exam, the left side looks larger than the right. Left arm is longer than the right. The girth of the left upper and lower arm is a larger than the right. On the left, the girth of the left thigh and the left calf is larger than the right.

Patient Data

Age: 11 months
Gender: Female

Ultrasound at presentation


MRI at presentation

Multiple nodular lesions of varying sizes and shapes in bilateral kidneys, left greater than right, predominantly peripherally located, with features most consistent with bilateral nephroblastomatosis.


Study one year later

Pre and Post contrast MRI at a follow up study 1 year from initial presentation which demonstrates multiple hypointense nodules in both kidneys have increased in size as described above. Left lower pole lesion shows faint internal and peripheral enhancement. Findings are concerning for malignant transformation of the previously identified perilobar nephrogenic rests.

Case Discussion

Nephrogenic rest (NR): persistent metanephric blastema 1

  • in the periphery: perilobular
  • within the kidney: intralobular
  • multiple NRs: nephroblastomatosis

NRs are important to diagnose and follow because they are precursors to Wilms tumor.

In some studies, up to 35% of diffuse hyperplastic perilobar NR transform to Wilms Tumor. This is considered the most at risk group 

The patient in this case demonstrates this in the initial ultrasound images.

Other syndromes associated with NRs (and Wilms tumor) are

On imaging the NRs appear homogeneous on all imaging modalities. This is a very important distinction to Wilms tumor, which is heterogeneous. The NRs do not enhance to same degree as the surrounding kidney

The patient in this case demonstrates homogeneous enhancement less that kidney parenchyma on the initial MRI images.

Unfortunately, a repeat MRI one year later demonstrates increased peripheral and internal enhancement, findings concerning for malignant transformation.

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Case information

rID: 39984
Published: 30th Sep 2015
Last edited: 15th Jun 2017
Inclusion in quiz mode: Included

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