Date Published: December 21, 2007
Publisher: BioMed Central
Author(s): Øyvind Stigen, Øyvor Kolbjørnsen.
The purpose of the study was to compare radiographic and histopathologic findings with regard to number and extent of calcified discs in the dachshund.
The intervertebral discs of 20 dachshunds were subjected to a radiographic and histopathologic examination. The dogs were selected randomly from clinical cases euthanased for reasons unrelated to research at the Norwegian School of Veterinary Science. Lateral radiographs were taken of the vertebral columns after removing them from the carcasses. The histopathologic examination included 5 μm thick sections in the transverse plane, stained with hematoxylin-eosin and von Kossa. Radiographs and histological sections were evaluated independently.
A total of 148 (28.5%) calcified discs were identified at the radiographic and 230 (45.7%) at the histopathologic examination. Of 92 discs found to be calcified by histopathology, but not by radiography, the degree of calcification was evaluated as ‘slight’ in 84 (91.3%). All the intervertebral discs (n = 138) that were found to be calcified by radiography were also found to be calcified by histopathology.
A sensitivity of 0.6 and specificity of 1.0 for radiography was calculated when using histopathology as the gold standard.
Intervertebral disc disease (IDD) is the most common cause of neurologic dysfunction in the dog . The disease is most often diagnosed in dachshunds, and in 8117 canine cases of IDD, Priester  found 3898 (48.0%) to occur in this breed. The breed prevalence of IDD in the dachshund has been estimated to be 19.0% .
The vertebral columns were obtained from 20 dachshunds that were euthanased for reasons unrelated to research at the Department of Companion Animal Clinical Sciences, Norwegian School of Veterinary Science. The case material, including size and coat varieties, sex, age and reason for euthanasia is presented in Table 1. The age of the dachshunds ranged from ten months to 13 years (mean 5.3 years) and there were twelve (60.0%) females.
At the radiographic examination, calcification was found in 148 (28.5%) of the 520 discs. Of all affected discs, a severe degree of calcification was found in 15, a moderate degree in 43 and a slight degree in 90 discs. Calcified discs were identified in 18 (90.0%) of the dogs and the number of calcified discs in each affected dog ranged from one (dog no. 19) to 20 (dog no. 15).
The present study shows that a significantly higher number (45.7% versus 27.4%) of calcified discs are identified by a histopathologic examination compared to a radiographic examination of intervertebral discs in dachshunds. This finding verifies the hypothesis presented at the beginning of the present paper.
A histopathologic examination is superior to a radiographic examination in identification of calcified intervertebral discs in the dachshund. A sensitivity of 0.6 and a specificity of 1.0 for radiography is calculated using number of calcified discs as parameter and histopathology as the gold standard. Calcification of the nucleus pulposus and/or the annulus fibrosus is a significant sign of disc degeneration in dachshunds and the distribution of detectable calcification in affected discs represents the distribution of a continuous variable.
The author(s) declare that they have no competing interests.
ØS conceived of the study, carried out the radiographic examination and is the main author of the paper. ØK carried out the histopathologic examination. Both authors read and approved the final manuscript.