Abstract
Combined spinal-epidural anaesthesia is an excellent technique for providing intraoperative and postoperative analgesia in patients undergoing total knee arthroplasty. Epidural catheters threaded through a Tuohy needle with a cephalad needle bevel orientation follow a winding pattern within the epidural space. Caudal or downward migration of an epidural catheter may lead to unsatisfactory anaesthesia and epidural failure. Colour flow Doppler sonography is emerging as an effective technique to determine the epidural catheter tip position. We report an interesting case of caudal migration of a lumbar epidural catheter confirmed by colour flow Doppler ultrasound.