Received: 1 September 2019 Revised: 31 March 2020 Accepted: 2 April 2020 DOI: 10.1111/vru.12891 ORIGINAL INVESTIGATION Dynamic MRI is reliable for evaluation of the lumbosacral spine in healthy dogs Rachel Lampe 1 Kari D. Foss 1 Devon W. Hague 1 Cintia R. Oliveira 1 Rebecca Smith 2 1 Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 2 Department of Veterinary, Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois Correspondence Kari D. Foss, Department of Veterinary Clinical Medicine, University of Illinois at Urbana- Champaign, 1001 W. Hazelwood Dr, Urbana, IL 61822. Email: karifoss@illinois.edu Funding information This study was funded by the University of Illinois Companion Animal Research Grant Program: Dr. Allan L. and Mary L. Graham Fund and the Companion Animal Memorial Fund. Abstract Magnetic resonance imaging (MRI) is commonly used to diagnose degenerative lum- bosacral stenosis; however, studies show limited correlation between imaging and clinical signs. The purpose of this prospective observer agreement study was to use dynamic MRI of the lumbosacral (LS) spine of healthy dogs to determine reliable ref- erence ranges. Twenty-two healthy large breed dogs were prospectively enrolled. MRI of the LS spine was performed in T2-weighted, T1-weighted, and T2-weighted SPACE sequences in neutral, flexed, and extended positions. Four observers performed image analyses. Measurements included LS angle, vertebral canal height and area, and LS foraminal areas. Ordinal categorical assessment of loss of fat signal in the foramina, LS compression, intervertebral disc (IVD) degeneration, spondylosis, and IVD protrusion was also performed. The majority of values were significantly larger in flexion versus neutral position, and significantly smaller in extension versus neutral position (P < .05). Subclinical compression and IVD protrusion was noted in a neutral position in 45% and 55% of dogs and in an extended position in 85% and 73% of dogs, respectively. Inter- observer agreement was strong (intracluster correlation coefficient [ICC] > .5) except for the L7:LS vertebral canal area ratio (ICC ≤ .03). Intraobserver agreement was high (rho > .5) for all measurements except for the mid-L6:LS vertebral canal height ratio (rho = .38). There was poor interobserver agreement for loss of fat signal in the foram- ina and evidence of compression. This study provides the groundwork for future stud- ies using dynamic MRI to evaluate dogs with signs of clinical LS disease. KEYWORDS canine, compression, foramina, stenosis 1 INTRODUCTION Degenerative lumbosacral stenosis is a common cause of back pain and neurologic dysfunction, especially in working dogs. 1 The most common Abbreviations: 3D, three-dimensional; ACVIM, American College of Veterinary Medicine; DLSS, degenerative lumbosacral stenosis; EMG, electromyography; ICC, intracluster correlation coefficient; LS, lumbosacral; MPR, multiplanar reconstruction; SPACE, Sampling Perfection with Application optimized Contrasts using different flip angle Evolution EQUATOR network disclosure: Authors followed the STROBE guidelines. This study was presented in abstract form at the 2019 ACVIM conference, Phoenix, AZ. clinical signs are back pain, difficulty rising or jumping, pelvic limb lame- ness, and incontinence. 1 This condition can be debilitating, especially in the working dog population. One retrospective study of 976 military working dogs revealed that degenerative lumbosacral stenosis (DLSS) was the cause of euthanasia or death in 15% of the population. 2 Clinical signs are suspected due to narrowing of the vertebral canal and compression of the cauda equina. This compression can be secondary to a number of pathologies, including Hansen type 2 intervertebral disc (IVD) herniation, lumbosacral (LS) instability, local proliferation of bone and soft tissue, and vascular compromise. 1 Vet Radiol Ultrasound. 2020;1–11. © 2020 American College of Veterinary Radiology 1 wileyonlinelibrary.com/journal/vru