• Flavio Augusto Vieira Freitag / University of Guelph - Ontario Veterinary College - Department of Clinical Studies; Guelph, ON, Canada.

• Alexander Valverde / University of Guelph - Ontario Veterinary College - Department of Clinical Studies; Guelph, ON, Canada.

• Monica Jensen / University of Guelph - Ontario Veterinary College - Department of Clinical Studies; Guelph, ON, Canada.

• Andrea Sanchez Lazaro / University of Guelph - Ontario Veterinary College - Department of Clinical Studies; Guelph, ON, Canada.

• Diego Gomez-Nieto / University of Guelph - Ontario Veterinary College - Department of Clinical Studies; Guelph, ON, Canada.

• Craig Bailey / University of Guelph - Ontario Veterinary College - Department of Biomedical Sciences; Guelph, ON, Canada.

Introduction Epidural injections are a common regional anesthetic technique used to provide analgesia of the pelvic limbs, pelvis and abdomen. The rostral spread of epidural drugs can be affected by gravity and friction forces, and the volume of injectate. The volume can be calculated based on body weight (mL/kg) or on the length of the vertebral column (mL/cm). Methods In a cadaveric model, 22 dog cadavers were paired for similar weights and length of the vertebral column, and within each pair, dogs were randomly assigned to receive a lumbosacral epidural volume based on weight (GW; 0.2 mL/kg) or length (GL; 0.05 to 0.11 mL/cm based on vertebral length), using dye (yellow tissue dye) mixed with contrast media (iopamidol) injected through an epidural catheter. The rostral spread was evaluated by anatomical dissection. Results In small ( 25, < 45 kg) and giant dogs (> 45 kg), there was no obvious difference in volume and rostral spread. Conclusion The results of this cadaveric study corroborate findings of a previous hypothetical mathematical model that predicts that the volume of injectate and rostral spread is larger in small and medium dogs when the volume is calculated based on length of the vertebral column, and similar for large and giant dogs.