['This study was designed to assess changes in blood flow of the dog cauda equina after lumbar sympathectomy using an experimental chronic cauda compression model.', 'The cauda equina was compressed at 10 mm Hg with a plastic balloon in all animals (n = 12). One week later, bilateral lumbar sympathectomy was carried out in the LSX group (n = 7), and vessels of the cauda equina were thereafter observed for 90 minutes using a specially designed microscope supplied with a video camera. Five animals did not undergo sympathectomy and were used as controls. The volume of blood flow was calculated from two parameters: velocity (mm/s) and diameter (microm) of a vessel observed in each animal.', 'The increment in vessel diameter in the LSX group was pronounced at 30 and 45 minutes after sympathectomy compared with the control group (P < 0.05). Blood flow in the LSX group was increased at 30 minutes depending on dilation of the vessel diameter compared with the control group (P < 0.05). The velocity in the observed vessels remained unchanged throughout the measurements.'] Does lumbar sympathectomy increase blood flow in a dog model of chronic cauda equina compression?