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.

Experimental evaluation of four airway devices in anaesthetized New Zealand White rabbits.

OBJECTIVE: To compare airway management during induction of anaesthesia, spontaneous ventilation (SV) and controlled mechanical ventilation (CMV), using an endotracheal tube (ETT), laryngeal mask (LM), rabbit-specific supraglottic airway device (v-gel) or facemask (FM). STUDY DESIGN: Prospective randomized crossover experiment. ANIMALS: Ten New Zealand White rabbits. METHODS: After premedication, rabbits were randomly allocated to four groups: 1) ETT; 2) LM; 3) v-gel or 4) FM. The required dose of propofol, duration and number of attempts to place an airway device and leakage during SV and CMV at different peak inspiratory pressures (6, 10, 12, 14 and 16 cmH2O) were recorded. Computed tomography (CT) of the head, neck and abdomen were performed before and after CMV. RESULTS: Significantly less propofol and time [2.0±0.5 mg kg-1, 82±34 seconds, p<0.001] were needed to place the FM compared to the three other groups [v-gel 5.1±2.1 mg kg-1, 302±124 seconds; LM 4.8±1.2 mg kg-1, 275±89 seconds; ETT 5.5±1.4 mg kg-1, 315±147 seconds]. A leak > 25% of the tidal volume occurred at the lowest pressure in FM [median (range), 6 (6-8) cmH2O], which was significantly lower than with v-gel [16 (6-no leak at 16) cmH2O], LM [>16 (6-no leak at 16)] or ETT [>16 (no leak at 16) cmH2O] (p<0.001). On CT images, the height and width of the larynx were significantly smaller with v-gel in comparison to FM and LM (p=0.004). A significant increase in the amount of gas in the stomach (p=0.007), but not gastric volume, was detected in FM and LM. CONCLUSIONS AND CLINICAL RELEVANCE: The v-gel is a practical alternative to LM and ETT for airway management and CMV, but can compress the larynx. The FM is easily placed, but significant leakage occurs during CMV.

Magnetic resonance imaging anatomy of the rabbit brain at 3 T.

BACKGROUND: Rabbits are widely accepted as an animal model in neuroscience research. They also represent very popular pet animals, and, in selected clinical cases with neurological signs, magnetic resonance imaging (MRI) may be indicated for imaging the rabbit brain. Literature on the normal MRI anatomy of the rabbit brain and associated structures as well as related reference values is sparse. Therefore, it was the purpose of this study to generate an MRI atlas of the normal rabbit brain including the pituitary gland, the cranial nerves and major vessels by the use of a 3 T magnet. RESULTS: Based on transverse, dorsal and sagittal T2-weighted (T2w) and pre- and post-contrast 3D T1-weighted (T1w) sequences, 60 intracranial structures were identified and labeled. Typical features of a lissencephalic brain type were described. In the 5 investigated rabbits, on T1w images a crescent-shaped hyperintense area caudodorsally in the pituitary gland most likely corresponded to a part of the neurohypophysis. The optic, trigeminal, and in part, the facial, vestibulocochlear and trochlear nerves were identified. Mild contrast enhancement of the trigeminal nerve was present in all rabbits. Absolute and relative size of the pituitary gland, midline area of the cranial and caudal cranial fossa and height of the tel- and diencephalon, 3rd and 4th ventricles were also determined. CONCLUSIONS: These data established normal MRI appearance and measurements of the rabbit brain. Results provide reference for research studies in rabbits and, in rare instances, clinical cases in veterinary medicine.