The hypothesis of our study is that a correlation exists between the couple ultrasound elastography- renal perfusion estimated with contrast-enhanced ultrasound and the degree of fibrosis estimated in a semi-quantitative way in 4 stages (0; 25 %; 25-50 %; > 50 %), as elastography alone did not allow to differentiate moderated fibrosis at 3 months in our feasibility study.

Kidney transplant patients are exposed to long-term immunosuppressive therapy, and have an increased risk of infections and cancer, while a lack of treatment increases the risk of rejection. The development of imaging techniques to characterize the status of the graft remains a challenge in transplantation. Ideally, they should identify complications (acute rejection, chronic allograft nephropathy, nephrotoxicity ...) without the need for invasive procedures and thus lead to better customization of immunosuppressive therapy.

The post-transplant follow-up is based on the monitoring of graft function. Impaired function suggests the possibility of a complication, but requires confirmation by an invasive procedure such as renal biopsy. In addition, the diagnosis remains complex at a relatively advanced stage of the process due to damage to the graft parenchyma. To anticipate the altered function and detect subclinical lesions, screening biopsies have been used to diagnose chronic rejection. By definition, screening for subclinical lesions can not be based on any biological parameter; the diagnosis of subclinical complications thus requires performing multiple systematic biopsies, which are scheduled at 3 months and 1 year.

Doppler ultrasound is an imaging method of choice for the study of renal transplant, but it cannot diagnose the NCT due to the absence of specific findings. The lack of early diagnostic test for NCT is a major obstacle to the development and evaluation of new therapeutic options to prevent, slow or stabilize renal fibrosis. It is therefore necessary to develop a non-invasive imaging technique for the early diagnosis of NCT.

Ultrasound elastography is a technique that allows tissue stiffness measurements and provides a parametric picture.

The main objective of our study is to evaluate the performances of elastography and measurement of renal perfusion (area under the ROC curve) to diagnose the NCT and determine for each both measures a threshold to maximize the sensitivity. These performances will be evaluated at 3 months and 12 months. The results can also be compared to other imaging modalities such as functional MRI, and to clinical events (obstruction, infection…).

Functional ultrasound imaging should identify diagnostic and prognostic criteria of NCT, and enable the development of less invasive therapeutic protocols to evaluate new therapeutic approaches

Inclusion Criteria:

• Age ≥ 18 years;

• Patient with informed consent;

• Recipient of a living donor graft or cadaveric donor patient;

• No contraindication for biopsy of the graft;

• No contraindication to the injection of SonoVue ®:

  • hypersensitivity to sulfur hexafluoride
  • acute coronary syndrome, unstable ischemic heart disease (myocardial infarction phase formation or evolution, typical resting angina in the previous 7 days, significant worsening of cardiac symptoms in the previous 7 days, recent intervention on the coronary arteries or another factor suggesting clinical instability (eg, recent deterioration of ECG changes in clinical or laboratory parameters), acute heart failure, stage III or IV heart failure, severe arrhythmias.
  • right-left shunt, severe pulmonary hypertension (PAP> 90 mmHg), uncontrolled systemic hypertension, respiratory distress syndrome

• Affiliated to a social security scheme

Exclusion Criteria:

• Refusal to participate in the study;
• Inability / refusal to give informed consent;
• contraindication for biopsy testing graft;
• Presence of a contraindication to the injection of SonoVue ®.
• Presence of a peripheral venous access in a non-restricted already infused patient, not pickable under ultrasound
• Breastfeeding, pregnancy