Postoperative computed tomography and low-field magnetic resonance imaging findings in dogs with degenerative lumbosacral stenosis treated by dorsal laminectomy.

Objectives: To describe postoperative computed tomography (CT) and magnetic resonance imaging (MRI) findings in dogs with degenerative lumbosacral stenosis (DLSS) treated by dorsal laminectomy and partial discectomy.

Methods: Prospective clinical case study of dogs diagnosed with and treated for DLSS. Surgical and clinical findings were described. Computed tomography and low field MRI findings pre- and postoperatively were described and graded. Clinical, CT and MRI examinations were performed four to 18 months after surgery.

Results: Eleven of 13 dogs were clinically improved and two dogs had unchanged clinical status postoperatively despite imaging signs of neural compression. Vacuum phenomenon, spondylosis, sclerosis of the seventh lumbar (L7) and first sacral (S1) vertebrae endplates and lumbosacral intervertebral joint osteoarthritis became more frequent in postoperative CT images. Postoperative MRI showed mild disc extrusions in five cases, and in all cases contrast enhancing non-discal tissue was present. All cases showed contrast enhancement of the L7 spinal nerves both pre- and postoperatively and seven had contrast enhancement of the lumbosacral intervertebral joints and paraspinal tissue postoperatively. Articular process fractures or fissures were noted in four dogs.

Clinical Significance: The study indicates that imaging signs of neural compression are common after DLSS surgery, even in dogs that have clinical improvement. Contrast enhancement of spinal nerves and soft tissues around the region of disc herniation is common both pre- and postoperatively and thus are unreliable criteria for identifying complications of the DLSS surgery.