Evaluation of Hepatic Rigidity by Ultrasonic Impulse Elastography in Liver Transplant Patients

Interventional study with minimal risks and constraints, prospective, mono-centric.

Ultrasonic impulse elastography is a technique for studying non-invasive tissue rigidity. In particular, it is used in hepatology to assess the degree of fibrosis in a simple manner, by eliminating, in a number of cases, liver biopsy. The investigation of fibrosis is an essential element in the follow-up of patients with hepatic transplant since it is the indirect sign of a post-transplant complication or a recurrence of the initial disease. Several elastography devices are available on the market, using different technologies to measure the rigidity of tissues. Studies have shown that the first hepatic elastography devices, Fibroscan® and Acoustic Radiation Force Impulse (ARFI) can detect significant fibrosis on hepatic grafts accurately and reproducibly. However, there are several factors related to patients or to the elastography apparatus itself, limiting its use by making the collection of measurements impossible or by giving outliers. In addition, first-generation devices (Fibroscan®) are not coupled to a conventional ultrasound system and are dedicated to the measurement of hepatic rigidity, so patients must undergo systematic ultrasound as part of graft follow-up . Supersonic® (SuperSonic Imagine, Aix-en-Provence, France) is part of the latest generation of elastography devices and is based on ultrafast shearwave elastography (SWE) technology. This device is a conventional ultrasound system for routine ultrasound scanning with an integrated module for measuring tissue stiffness, and has the advantage of establishing real-time mappings of tissue rigidity over a large area. Several studies have shown that the measurements were reliable and reproducible, especially in the assessment of liver stiffness. In the literature, only one study addressed the measurement of hepatic rigidity with the Supersonic® ultrasound system in liver transplant patients and was designed to diagnose viral hepatitis recurrence or acute cellular rejection. In the secondary results, the authors found a significantly higher hepatic rigidity of healthy hepatic grafts compared to healthy native livers. It is proposed to add to the ultrasound of systematic follow-up of the hepatic grafts carried out in clinical routine an elastographic measurement in order to assess the hepatic rigidity in these patients in a non-invasive way.