Dachshunds have a higher lifetime risk of disc herniation than many other breeds. As such, there as been a lot of interest in trying to mitigate this risk through breeding practices throughout the world.
Remarkably, interest in radiographs as an observational tool has surged in literature again recently. What do we know radiographs on dachshunds? Based on several studies, it appears that dachshunds begin calcification of their discs by age 1 and hit a “peak” calcification between 2-5 years of age, before the number of calcified discs begins to decrease. The peak actually refers to a steady state with little change in calcification between the ages of 2 and 5 years old. Along the way a “K number” (Kn) or calcification number was coined which linked the number calcified discs noted on radiographs between ages 2-5 with a lifetime risk of symptomatic disc herniation. Dachshunds with a Kn = 5 or more, had a 70% lifetime chance of a symptomatic disc herniation. Conversely, dogs with a Kn of 3, had a 20% lifetime chance of a symptomatic disc herniation. Taken on an individual basis, one might argue that knowing the Kn of a given dog will only result in anxiety and stress for the owner because there is little that they can do to reduce the dog’s chance of disc herniation. Keeping dogs fit and trim, avoiding jumping, and minimizing work does not appear to be related to a lower risk of disc herniation in at risk populations. However, for breeders, this information could be a big part of the puzzle when deciding the breeding pair to arrange. In many European countries dachshund breeders are required to determine the Kn before breeding.
Researchers have gone further and identified the retrogene insertion responsible for the short legs (chondrodystrophy) and risk of disc herniation in dachshunds. It is called FGF4L2 (known in the general population as the CDDY gene) and appears to be present in about 95% of dachshunds. Breeding this gene out would be challenging given the high frequency of the gene, but reducing it to only 1 pair might be possible. Furthermore, when this gene was eliminated (dogs with N/N genotype) the resulting dog had longer legs and was no longer within the breed standard. Yikes! Dr. Sullivan et al (JVIM 2025; 39 )(1): e17281) correlated the FGF4L2 gene with the Kn and found that dogs that carried only 1 (FGF4L2/N) or both wild genotype (N/N) were more likely to be Kn =0 than those with two sets of the FGF4L2 genotype. No Kn >3 dogs were noted with (N/N) genotype.
Take away
If a client wants to know their dog’s risk of disc herniation, take radiographs between ages 2-5. Count up the number of calcified discs. If it is >3 the risk is high and <3 the risk is lower.
Genetic testing to identify the CDDY genotype would be useful for dachshund breeders but may not be useful for the general population.
I hope you enjoyed the Tidbit Tuesday and look forward to working with you soon! I hope you’re staying safe and cool during this wild weather!