Medical information retrieved for each case included breed, sex, date of birth, weight, date of procedure, surgical procedure performed, anatomical location of surgery, a summary of findings from any medical imaging performed (Myelography, Computed Tomography, CT, Magnetic resonance Imaging, MRI, or Radiography), and a description of disc material from the surgery report. All non-disc related cases were excluded based on findings indicated in the surgery reports. All breed information was owner reported when presenting at the VMTH. All Miniature and Toy Poodles were treated as one breed, and all Dachshund varieties were treated as one breed; however, based on weight, all but two Dachshunds were miniature in size. The total numbers of dogs from the affected breeds were counted from the DNA repository in order to determine the relative breed representation of the surgical cases in the repository.
Breed-specific allele frequencies for the FGF4 retrogenes were determined using 2333 samples from the UC Davis DNA repository irrespective of IVDD diagnosis. Additional samples for breed-specific allele frequencies were acquired from the Vetsuisse Biobank, University of Bern DNA repository without health information. Additional samples for the Dachshund breed in the United Kingdom (UK) were genotyped from a collection from the Animal Health Trust.