Calcification of intervertebral discs in the dachshund: a radiographic and histopathologic study of 20 dogs

The purpose of the study was to compare the accuracy of radiographic and histologic study of calcified disks.  

Intervertebral disc disease (IDD) affects 19% of dachshunds, and 48% of cases of IDD are found in dachshunds. Calcified disks (overgrowth of calcification on vertebrae) are the first step to IDD, so it is important to be able to identify calcification in order to treat or study the disease. The hypothesis was that radiographic study could be less sensitive than a pathologic study to identify calcified discs.

The vertebral columns from 20 euthanized dachshunds were obtained, ranging from 10 months to 13 years of age at death. The dachshunds were not euthanized for the study but for unrelated reasons. Then, radiographs were taken within 24 hours of death and analyzed. Three classifications of calcification were defined: slight, moderate, and severe. If classification was in doubt, then additional radiographs were taken. Then immediately after radiography, each intervertebral disc between the C2 and S1 were removed and fixed in a preserving solution, and stained using a method that helps demonstrate calcium. Then 503 discs were analyzed under a light microscope. A small amount of calcification was defined as slight, with moderate, the calcification was on most of the area, and severe had widespread or total calcification.

Radiography was found to identify calcification on 148 discs while the histopathologic examination found 230. Using histopathology as the gold standard, radiology has a sensitivity of 0.6 and a specificity of 1.0, meaning that it found 60% of the calcified disks but rated them (as slight, moderate, severe) with almost 100% accuracy.

Therefore, the hypothesis was confirmed. The authors acknowledged a few errors in their study, however. The study had much higher numbers of dogs with calcified disks: probably because they all died in a clinical setting, and many from neurological dysfunction. In addition, the radiographs were highly technical because they were taken of spines removed from the bodies and motion blurring was not an issue. In addition, the radiographs and histological sections were only evaluated by one person each, which could mean a lot of variation between the observers. The authors admit that this could have been fixed if 2 or more people evaluated each, and say that a sensitivity of 0.6 represents an underestimate.

 

Øyvind Stigen and Øyvor Kolbjørnsen, 2007. “Calcification of intervertebral discs in the dachshund: a radiographic and histophathologic study of 20 dogs”. Acta Veterinaria Scandinavica 49: 39.

https://actavetscand.biomedcentral.com/articles/10.1186/1751-0147-49-39

Reviewed by: Anna Day

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