Robot-assisted surgery is often carried out through master-slave teleoperation. With the progress of robotic technology and development of novel surgical procedures, new challenges emerge like need for haptic feedback and time delay in teleoperation communication channels, etc. Most existing bilateral teleoperation works in literature emphasize more on maintaining system stability at the cost of degraded transparency, with time variant communication delay further worsening the situation. In this paper, we present a nonlinear Hunt-Crossley model-mediated bilateral teleoperation scheme with targeted applications in robot-assisted surgery. The system stability is guaranteed by decoupling the master and slave subsystems and the system transparency is enhanced with online environment parameter estimation using recursive least squares (RLS) technique. Simulation studies have been carried out for both constant and time varying interaction environments. The proposed teleoperation scheme is shown to be efficient in providing stable and transparent performance and robust against communication delay and environment parameter variance.