Diagnostic imaging of the respiratory system in exotic companion mammals

Computed tomographic features of clinically suspected rhinitis in domestic rabbits (Oryctolagus cuniculus)

BACKGROUND

The aim of this study was to characterise the computed tomographic (CT) findings in domestic rabbits with clinically suspected rhinitis and compare them with CT findings in rabbits without clinical signs of rhinitis.

METHODS

CT images of rabbits that underwent a CT of the head were retrospectively reviewed and any CT abnormalities were described. Statistical analysis was performed to detect any association between the CT findings and clinical signs of rhinitis, and also to assess if there was any association between rhinitis and otitis media, otitis externa or dental disease.

RESULTS

Thirty-three of the 133 rabbits included in the study had soft tissue-attenuating material within their nasal cavities and were therefore classified as having CT findings compatible with rhinitis. CT evidence of rhinitis was correlated with the presence of clinical signs of rhinitis and with the presence of otitis media. There was no statistical association between CT evidence of rhinitis and the presence of otitis externa or dental disease.

LIMITATIONS

The retrospective nature of the study, small sample size and lack of aetiological confirmation limit the conclusions that can be drawn from the findings.

CONCLUSION

Clinical signs of rhinitis were associated with CT abnormalities consistent with rhinitis and CT evidence of otitis media. The results of this study provide useful information for CT assessment of the nasal cavities of domestic rabbits and can be used as a reference for the diagnosis of rhinitis in this species.

Diagnostic Accuracy of Lung Ultrasound in Rabbit Subclinical Lung Lesions

Rabbits are commonly affected by subclinical lung diseases. Computed tomography (CT) is the gold standard for diagnosing rabbit lung diseases but is not widely available and requires anesthesia, delaying diagnosis. Lung ultrasound (LUS) has emerged as a radiation-free, bedside diagnostic tool in human and veterinary medicine, though its use in rabbit medicine is not routine. This study aimed to evaluate LUS for detecting subclinical lung lesions in rabbits. Thirty healthy, five-month-old male New Zealand white rabbits underwent lung ultrasound, exploring four regions in each hemithorax, followed by thoracic CT under sedation with midazolam and butorphanol. The ultrasound images were scored as positive or negative, and the CT exams were assessed for aeration using threshold masks. The results showed that 63% of rabbits had one or more affected regions in the ultrasound images, and 19% of the regions were positive. CT identified 54% of the regions as positive for poorly aerated tissue, with 26/30 rabbits showing at least one positive region. The sensitivity and specificity of LUS were 33.33% and 93.48%, respectively, with an accuracy of 67.92% for detecting subclinical lesions. While LUS demonstrated a high specificity, its sensitivity was low compared to CT, highlighting the need for further refinement in its use for rabbit respiratory disease diagnosis.

Age and Diet-Related Associations With Acquired Dental Disease in Pet Rabbits

The aim of this study was to investigate the prevalence of acquired dental disease (ADD) in pet rabbits, as well as the association between disease development, age, and the feed type. Sixty-two rabbits were divided into 3 groups based on feed type and age. All rabbits underwent general clinical examination, followed by radiographic imaging of the skull and endoscopic examination of the oral cavity. Based on the degree of ADD, the rabbits were then classified into 5 groups, based on the grade of ADD. The results found that 64.52% of rabbits suffered from some degree of ADD. The group of rabbits classified as grade 4 ADD had the highest median age. A positive correlation was found between the grades of ADD and the age of the rabbits. Rabbits fed a different diet type showed various levels of significance when comparing grades 0, 1, and 2 ADD with grade 3 ADD. The data suggests that age and feed type may be a factor affecting the degree of ADD.

Evaluation of sectional anatomic, micro-computed tomographic, and magnetic resonance imaging features of the thorax in Syrian hamsters (Mesocricetus auratus)

Clinically, the rodent thorax is important because of the variety of problems that may affect the heart, lungs, and other thoracic structures. Syrian hamsters are the most common pet and experimental hamster species. Sectional imaging of small mammals is widely increasing in use for clinical and research settings; however, no reports on the thoracic sectional imaging anatomy in this species have been made. Therefore, this study aimed at evaluating micro-computed tomography (MCT), magnetic resonance image (MRI), and gross sections of the Syrian hamster thorax. Eight healthy adult male and female Syrian hamsters were examined. Anesthetized hamsters were evaluated by MCT and 3 Tesla MRI. After imaging, the frozen slab sections were photographed, and identified anatomic structures were matched with structures on corresponding MCT and/or MRI images. Clinically relevant anatomic features of the Syrian hamster thorax that were identified on transverse and sagittal anatomic sections could be discerned on the corresponding MCT and MRI scans. The three matched images were exhibited the following features: (1) the narrow thoracic cavity and small lung space, (2) the heart positioning ventral and medial to lung, (3) heart ventricles locating towards the left side, and (4) parallel cardiac position relative to the sternum. The obtained results were similar to those have only been reported in rabbits, regardless of heart orientation and lung lobe covering the heart. The results of this study support the use of MCT and MRI as diagnostic tools in Syrian hamsters and provide reference values for the clinically relevant anatomic structures of thorax.

Evaluation of the Effects of Sedation and Anesthesia on Total Lung Volume and Attenuation in Rabbit Lung CT Exams

Respiratory disease is common in rabbits, but subclinical conditions can be challenging to diagnose and may cause respiratory problems during anesthesia. CT is the preferred method for diagnosing lung diseases, but anesthesia can alter lung volume and cause lung lobe collapse. In this study, seventeen healthy 5-month-old male New Zealand white rabbits underwent thoracic CT scans under different conditions. Rabbits were sedated with midazolam and butorphanol and scanned in a sphinx position; they were then anesthetized with dexmedetomidine and ketamine and scanned again in sternal recumbency during spontaneous breathing. Lastly, apnea was induced using intermittent positive pressure ventilation (IPPV) for a final scan. Lung volume and density were measured using the 3D Slicer version 5.6.2 software, with thresholds set between -1050 and -100 Hounsfield Units (HU). Sedated animals had significantly higher total lung volume (69.39 ± 10.04 cm3) than anesthetized (47.10 ± 9.28 cm3) and anesthetized apnea rabbits (48.60 ± 7.40 cm3). Mean lung attenuation during sedation was -611.26 HU (right) and -636.00 HU (left). After anesthesia induction, values increased to -552.75 HU (right) and -561.90 HU (left). Following apnea induction, attenuation slightly decreased to -569.40 HU (right) and -579.94 HU (left). The results indicate that sedation may be preferable for rabbit lung CT to minimize anesthesia-related changes.

Cardiology in Rodents, Rabbits, and Small Exotic Mammals-Diagnostic Workup

The incidence of cardiac diseases in pet rabbits and rodents increased over the past decade as these species live longer and diagnostics methods are more precise to diagnose heart diseases even in small-sized animals. The article summarizes diagnostics of cardiac diseases in selected exotic companion mammals, particularly in rabbits, guinea pigs, chinchillas, and rats. The emphasis of the paper is given on clinical examination, thoracic radiography, electrocardiography, and echocardiography.

Lateral rhinostomy for treatment of severe chronic rhinosinusitis in two rabbits

CASE DESCRIPTION 2 client-owned rabbits were evaluated for signs of chronic upper respiratory tract disease. CLINICAL FINDINGS Clinical signs had been present for 3 weeks and 4 years and included mucopurulent nasal discharge, right-sided maxillary swelling, recurrent dacryocystitis, and intermittent sneezing. One rabbit had been treated with nasolacrimal duct lavage and topical and systemic antimicrobial administration without resolution of clinical signs. Results of CT of the head in both cases indicated severe rhinosinusitis. TREATMENT AND OUTCOME Both rabbits underwent unilateral rhinostomy by means of a lateral approach. Access was established via the facies cribrosa of the maxillary bone. Purulent material was removed from the affected nasal cavity and the maxillary sinus by means of debridement and lavage. After endoscopic exploration, marsupialization was performed to create a stoma. Both rabbits recovered from surgery without apparent complications, and the surgical site healed within 1 month in both. Computed tomography was repeated 5 months after surgery in one rabbit and 13 months after surgery in the other and indicated patent nasal passages and no evidence of recurrence or persistence of disease. CLINICAL RELEVANCE Results suggested that lateral rhinostomy should be considered for treatment of chronic severe rhinosinusitis in rabbits. Such an approach may be less technically demanding and could decrease the likelihood of postsurgical complications reported with other techniques.

Computed tomography of the thorax in rabbits: a prospective study in ten clinically healthy New Zealand White rabbits

Background

Literature investigating the normal cross-sectional anatomy of rabbits with computed tomography (CT) is sparse and incomplete. The purpose of the present study was to investigate the normal thoracic structures, in particular the cranial thorax, with CT angiography in 10 clinically healthy New Zealand White (NZW) rabbits.

Results

Absolute and relative measurements of the trachea, heart, thoracic caudal vena cava and aorta, right and left principal bronchi, right and left caudal lobar bronchi and the accompanying branches of the right and left pulmonary artery and vein, right and left lung volume and lung density were taken. The three lobes of the thymus (right ventral, right dorsal and left thoracic lobes) were identified in all rabbits. Both the right dorsal and left thoracic lobes of the thymus extended between the heart and thoracic wall in all individuals with the left lobe reaching more caudally in seven animals. Consequently, the craniocaudal extension of the left lung was smaller than the right lung in these rabbits. Volume of the left lung was significantly smaller than the right (P = 0.005). The cranial mediastinal, right and left tracheobronchial and the aortic thoracic lymph nodes were very small and identified in four, four, seven and ten rabbits, respectively. The heart took up a median of 4.0 intercostal spaces, and in seven rabbits, it was located in the 2nd–5th intercostal space. Median relative cardiac height and width measured 74 and 88%, respectively. The median angle of the trachea to the spine was 5°. Median density between the right and left lung did not significantly differ (− 549 and − 583 Hounsfield units, respectively). In all but one rabbit, atelectasis was present and classified as mild, moderate or severe in six, two and one individuals, respectively. Mild subclinical bronchopneumonia was diagnosed in seven rabbits.

Conclusions

The present study provides species-specific anatomical CT information and reference values for structures in the thorax of the NZW rabbit. Subclinical bronchopneumonia appears to be a common CT finding.

Diagnostic Imaging of Dental Disease in Pet Rabbits and Rodents

Diagnostic imaging techniques are of paramount importance for dentistry and oral disorders of rabbits, rodents, and other exotic companion mammals. Aside from standard radiography, stomatoscopy is a complementary tool allowing a thorough and detailed inspection of the oral cavity. Computed tomography (CT) generates multiple 2-dimensional views and 3-dimensional reconstructions providing superior diagnostic accuracy also useful for prognosis and treatment of advanced dental disease and its related complications. MRI is a diagnostic imaging technique additional to CT used primarily to enhance soft tissues, including complex odontogenic abscesses.