Elastography is a emerging imaging technique that has demonstrated high reliability in the assessment of tissues stiffness and quantification of fibrosis particularly in adult's livers. This ultrasound exploration has no secondary effects. There is no study published in the pediatric population concerning the role of ultrasound elastrography in kidney. The aim of this study is to look for a correlation between the elastography's results and the kidney fibrosis on children who have to undergo a renal biopsy. Elastography may play a potential diagnostic and/or prognostic role in the management of these patients which would limit invasive biopsy procedures.

Inclusion Criteria:

• Male children or feminine from 5 to 18 years old to whom is indicated a renal biopsy by the néphrologue paediatrician whatever is the initial pathology, whatever are one or several current or previous treatments and whatever is their associated comorbidity

Exclusion Criteria:

• Children of less than 5 years old or more than 18 years
• Children for whom a draining renal biopsy is not or more indicated by néphrologues
• Refusal or withdrawal of the consent lit by the holders of the exercise of the parental authority or by the child if he is capable of receiving the information
• Contraindication in the realization of a draining renal biopsy (current infection, disorder of the coagulation.)