Radiographical Survey of Osteochondrodysplasia in Scottish Fold Cats caused by the TRPV4 gene variant.

The unique appearance of Scottish Fold cats is caused by a single gene variant in TRPV4, which impacts the development of cartilage. This results in the ears folding forward and variable effects on articular cartilage and bone. While some find this appearance desirable, early work demonstrated that homozygous cats with two copies of this variant develop severe radiographic consequences. Subsequent breeding programs have mated heterozygous cats with straight-eared cats to ensure an equal mix of heterozygous (fold) and wild-type (nonfolded) offspring, in the hope of raising healthy cats. More recent radiological surveys suggest that these heterozygous cats may also have medical problems consisting of deformed distal extremities in the worst cases and accelerated onset of osteoarthritis. However, these previous studies were undermined by selection biases, lack of controls, unblinded assessment and lack of known genotypes. Our aim was to determine if heterozygous cats exhibit radiological abnormalities when controlling for these limitations. Specifically, DNA and radiographs were acquired for 22 Scottish Fold cats. Four reviewers, blinded to the ear phenotype, assessed the lateral radiographs. Genotyping showed that all 10 folded-ear cats were heterozygous, and none of the straight-ear cats (n = 12) had the abnormal TRPV4 variant. Although each reviewer, on average, gave a numerically worse 'severity score' to folded-ear cats relative to straight-ear cats, the images in heterozygous cats showed much milder radiological signs than previously published. This study provides additional information to be considered in the complicated debate as to whether cats with the TRPV4 variant should be bred for folded ears given the potential comorbidities.

Interpretation of cardiac chamber size on canine thoracic radiographs is limited and may result in the false identification of right-sided cardiomegaly in the presence of severe left-sided cardiomegaly.

Qualitative assessment of individual cardiac chamber enlargement on thoracic radiographs was assessed using echocardiography as the gold standard in dogs. Using this method, the presence of severe left-sided cardiomegaly was hypothesized to contribute to the false identification of right-sided cardiomegaly on radiographs. 175 dogs with three-view thoracic radiographs were retrospectively included in this diagnostic accuracy study if echocardiography was done within 24 h, and no rescue therapy was provided in the interim. All radiographic studies were reviewed by two groups of five board-certified veterinary radiologists with greater and less than 10 years of experience for grading of cardiac chamber enlargement as normal or mildly, moderately, or severely enlarged. The agreement, sensitivity, and specificity of the radiologists' interpretation of cardiac chamber size on thoracic radiographs to measured echocardiographic grades were evaluated. A total of 147 cases had complete echocardiographic data available for analysis. Intragroup agreement was moderate for the evaluation of left atrial enlargement and slight to fair for all other cardiac chambers. Between the mode of the radiologists' responses in the two groups and the echocardiographic grades, there was slight agreement for all cardiac chambers with higher severity grades reported using echocardiography. When moderate to severe left-sided cardiomegaly was identified on echocardiography, the sensitivity, specificity, and accuracy of radiographs were low, identifying dogs with radiographic evidence of right-sided cardiomegaly in the absence of corresponding right-sided cardiomegaly on echocardiography. Therefore, thoracic radiographs should be used with caution for the evaluation of cardiac chamber enlargement, particularly in the presence of severe left-sided cardiomegaly.

Computed Tomography for the Diagnosis and Characterization of Dermoid Sinuses in Two Dogs.

A 6 mo old male castrated bloodhound-Rhodesian ridgeback mix (case 1) presented for a mass suspected to be a dermoid sinus in the thoracolumbar region, and a 2.5 yr old male castrated Rhodesian ridgeback (case 2) presented for a mass suspected to be a dorsal cervical dermoid sinus. Both dogs underwent single-phase contrast computed tomography (CT) to characterize the extent of the dermoid sinus prior to surgical excision. Soft tissue and bony abnormalities of the vertebral spine associated with the dermoid sinuses were confirmed in both dogs prior to surgery, demonstrating communication with the dura of the spinal cord. Surgical exploration and excision of the dermoid sinus was performed in each dog, including partial laminectomy. Both cases had resolution of the sinus and an uncomplicated recovery. These cases show that single-phase contrast CT was accurate in characterizing the extent of the dermoid sinus without adjunctive tests or more invasive diagnostics. Single-phase contrast CT should be considered as a preoperative method to characterize the extent of dermoid sinuses, avoiding the risks associated with myelography or fistulography and the expense of MRI. This is also the first report of a dermoid sinus in the thoracolumbar region and the first in a bloodhound and Rhodesian ridgeback mix.