Ultrasonographic anatomy of the sacrococcygeal region and ultrasound-guided epidural injection at the sacrococcygeal space in dogs.

Sacrococcygeal epidural anaesthesia allows selective desensitisation of the sacral plexus. Ultrasound is used for guidance in human anaesthesia to facilitate sacrococcygeal epidural injections. The aims of this study were to describe the sonographic appearance of the sacrococcygeal region in dogs and a technique for performing epidural injection at this location under ultrasound guidance. In the preliminary part of the study four cadavers were used to describe the sonoanatomy of the sacrococcygeal space and to develop the ultrasound-guided puncture technique. In the second phase of the study this technique was repeated in four dogs under general anaesthesia. In all dogs the sacrococcygeal space appeared as a circular hypoechoic region, located caudal to the sacral caudal articular processes, delimited by bony hyperechoic structures such as body and arch of the first caudal vertebra. Ultrasound guidance allowed the operator to visualise and position the spinal needle into the sacrococcygeal epidural space. No complications were reported during this procedure. Preliminary results indicate that ultrasound-guided sacrococcygeal epidural anaesthesia may be considered as an alternative to a blind approach technique.