Sánchez, William

Abstract Ultrasound and magnetic resonance elastography techniques are used to assess mechanical properties of soft tissues. Tissue stiffness is related to various pathologies such as fibrosis, loss of compliance, and cancer. One way to perform elastography is measuring shear wave velocity of propagating waves in tissue induced by intrinsic motion or an external source of vibration, and relating the shear wave velocity to tissue elasticity. All tissues are inherently viscoelastic and ignoring viscosity biases the velocity-based estimates of elasticity and ignores a potentially important parameter of tissue health. We present attenuation measuring ultrasound shearwave elastography (AMUSE), a technique that independently measures both shear wave velocity and attenuation in tissue and therefore allows characterization of viscoelasticity without using a rheological model. The theoretical basis for AMUSE is first derived and validated in finite element simulations. AMUSE is validated against the traditional methods for assessing shear wave velocity (phase gradient) and attenuation (amplitude decay) in tissue mimicking phantoms and excised tissue. The results agreed within one standard deviation. AMUSE was used to measure shear wave velocity and attenuation in 15 transplanted livers in patients with potential acute rejection, and the results were compared with the biopsy findings in a preliminary study. The comparison showed excellent agreement and suggests that AMUSE can be used to separate transplanted livers with acute rejection from livers with no rejection.

Although short‐term risks of living donor hepatectomy have been well defined, little is known about the longterm impact. We aimed to perform a systematic follow‐up to screen for unanticipated health consequences of liver donation. All donors who were more than 1 year from donation were invited for a systematic evaluation including physical and laboratory assessment, quality of life questionnaire, and magnetic resonance imaging (MRI)/magnetic resonance cholangiopancreatography (MRCP). Those unable to return were offered the questionnaire and laboratory assessment at home. Out of our total of 97 donors, 45 returned for a full assessment and 23 completed labs and survey locally (total n = 68; 70%) after a median of 5.5 years (1.5‐10.9 years) after donation. The only laboratory abnormality was a significant decrease in platelet count (median 198 ×109/L versus 224 ×109/L before donation; P < 0.001), whereas 93% of patients were still above normal limits. No late biliary strictures or other structural abnormalities were found on MRI/MRCP. Liver regeneration was complete. Spleen volume did significantly increase (median 278 cm3 versus 230 cm3 before donation; P < 0.001) without resulting in lowered platelets (P = 0.73). The most common complaints were persistent incisional numbness and changed bowel habits. Seven donors (11%) reported problems obtaining insurance. The vast majority (97%) would have donated again. In conclusion, longterm outcome following liver donation appears satisfactory. None of our donors have developed occult biliary strictures, failure of regeneration, abnormal liver function, or other important health consequences after a median of 5.5 years from surgery. These findings can be used when counseling potential donors in the future. Liver Transplantation 22 934–942 2016 AASLD