Comparative assessment of left atrial volume in healthy cats by two-dimensional and three-dimensional echocardiography.

BACKGROUND: The left atrium (LA) is an important prognostic parameter in cardiac pathologies of cats. Its size is currently measured in one-dimensional methods, while human medicine considers two- and three-dimensional echocardiography as standard. The objectives of this study were to compare monoplane, biplane, triplane and real-time three dimensional echocardiography for volumetric measurement of the left atrium in healthy cats and establish a reference interval for further studies on cats with heart disease. Additionally, the influence of age, sex and weight on left atrial volume (LAV) was tested. RESULTS: One dimensional monoplane Simpson method of discs (SMOD) in the right parasternal four chamber view (r4) and the left apical 2 chamber view (l2) as well as biplane SMOD had no significant difference for left atrial maximum volume (LAMax). They can be used as equivalent in future studies and one common reference range was set up (1.96 ± 0.54 ml). Those three methods produced significantly higher volumes than triplane echocardiography (RTTPE) and real time three dimensional echocardiography (RT3DE) using TomTec® software. LA volumetry with RTTPE and RT3DE-TomTec™ was more feasible than expected, but low RT3DE image quality was the main reason for excluding patients. Neither age nor weight had an influence on LA volume in healthy cats. Male LAV results were only slightly, but in 2D and RTTPE significantly higher than those of female cats with a range of + 10.46% to + 19.58%. CONCLUSIONS: Monoplane, biplane, triplane and real-time three dimensional echocardiography were feasible for LA volumetry in healthy cats and showed acceptable intra- and interobserver variability. One common LAMax reference range for monoplane r4, l2 and biplane SMOD was set up. Raw data can be used for LA volumes and does not need to be correlated with the cat's weight or age. Male cats have only slightly but significantly larger atria than females in 2D and RTTPE. Therefore, under reservation, also sex related limit values were defined.

Good Inter- and Intra-Observer Reliability for Assessment of Radiographic Femoral and Tibial Frontal and Sagittal Planes Joints Angles in Normal Cats.

OBJECTIVE: The aim of this study was to evaluate the inter- and intra-observer reliability of plain digital radiographs for assessing normal feline femoral and tibial joint reference angles in the sagittal and frontal planes. STUDY DESIGN: This was a cadaveric radiographic anatomical study. that involved 20 short-haired domestic adult cats. MATERIALS AND METHODS: Sagittal and frontal plane tibial and femoral joint angles of 40 limbs were measured twice by three observers with different levels of experience. Inter- and intraobserver reliability was determined by the intra-class correlation coefficient (ICC). An ICC > 0.75 was considered high correlation, 0.74 > ICC > 0.60 good correlation, 0.59 > ICC > 0.4 fair correlation and an ICC < 0.40 poor correlation. RESULTS: Mean ± standard deviation angles were anatomic lateral proximal femoral angle (aLPFA) 110.6 ± 3.6; anatomic lateral distal femoral angle (aLDFA) 91.9 ± 2.1; mechanical lateral proximal femoral angle; mLPFA (mLPFA) 107.3 ± 3.6; mechanical lateral distal femoral angle (mLDFA) 95.5 ± 1.7; femoral neck anteversion (FNA) 121.9 ± 4.1; anatomical caudal proximal femoral angle (aCPFA) 156.1 ± 3.9; anatomical caudal distal femoral angle (aCDFA) 101.4 ± 1.4; mechanical medial proximal tibial angle (mMPTA) 93.5 ± 1.2; mechanical medial distal tibial angle (mMDTA) 100.5 ± 2.3; mechanical cranial proximal tibial angle (mCrPTA) 113.1 ± 3.2; tibial plateau angle (TPA) 23.1 ± 3.2; mechanical cranial proximal tibial angle (mCrDTA) 86.7 ± 3.1.The intra-observer ICC indicated high correlation for 70% or more of the measurements. The inter-observer agreement among observers was high. These results show that the radiographic method for measuring femoral and tibial joint angles was good or high, except for FNA and mCrDTA. CONCLUSIONS: This study provides some radiographic anatomical and mechanical joint angles of the femurs and tibias of normal domestic short-haired cats. We found good reliability for both intra- and interobserver measurements.

Anatomical assessment of intrathoracic cardiovascular structures using fast spin-echo double inversion recovery and steady-state free precession magnetic resonance imaging in a normal cat.

In human medicine, non-contrast cardiac magnetic resonance imaging (CMRI) is routinely used to assess the cardiovascular system. In this study, using non-contrast CMRI, we provide a thorough description of the normal appearance of the intrathoracic cardiovascular structures in one healthy cat using a magnet operating at a field of 1.5-Tesla. The CMRI protocol was based on the use of fast spin-echo double inversion recovery and steady-state free precession pulse sequences in oblique short-axis, vertical long-axis, and horizontal long-axis imaging planes. After imaging the feline heart, four cadaver cats injected with latex substance into their arterial and venous systems were sectioned to facilitate interpretation of the intrathoracic cardiovascular structures to the corresponding CMRI. The fast spin-echo double inversion recovery images showed the best evaluation of gross intrathoracic anatomy, giving excellent contrast of the myocardium and vessels walls as they appeared with intermediate signal intensity compared to the lumen that appeared with low signal intensity. By contrast, steady-state free precession images showed details of the heart cavities and vascular lumen due to the high signal intensity of fast-flowing blood. The results of this study provide some anatomic detail for the heart and associated vessels as seen by non-contrast CMRI in the domestic cat.

Morphological assessment of cat kidneys using computed tomography.

There are numerous publications about feline renal imaging information; however, none have established reference values for kidney size using computed tomography (CT). This study aimed to determine renal size and shape as well as the morphology of renal-related structures in clinically normal cats (Felis catus) that underwent CT. Twenty-seven healthy cats underwent pre- and post-iodinated contrast-enhanced CT. Most cat (59%) kidneys were located at the same level. The average pre-contrast dimensions of the left kidney included a width of 2.46 ± 0.28 cm, a length of 3.52 ± 0.44 cm and a height 2.19 ± 0.31 cm, whereas those of the right kidneys were 2.45 ± 0.27 cm, 3.54 ± 0.46 cm and 2.05 ± 0.23 cm, respectively. After contrast enhancement, kidneys were slightly enlarged though not significantly. Additionally, renal length (LK or RK) was compared with second lumbar vertebra (L2) length and abdominal aorta diameter (AO). AO was significantly larger in male cats whereas L2 length appeared longer in male cats, but was not statistically different from the female cats. The LK/L2 and RK/L2 ratios were 2.29 ± 0.23 and 2.36 ± 0.20, respectively, and the LK/AO and RK/AO were 11.72 ± 1.37 and 12.05 ± 1.47, respectively. Renal vessels were examined. The renal vein was obviously larger than the renal artery, and paired renal veins were observed periodically. This study provides CT information about the feline kidney, which may help to establish reference values and information regarding renal structure prior to surgery in practice.

An assessment of the role of the falx cerebri and tentorium cerebelli in the cranium of the cat (Felis silvestris catus).

The falx cerebri and the tentorium cerebelli are two projections of the dura mater in the cranial cavity which ossify to varying degrees in some mammalian species. The idea that the ossification of these structures may be necessary to support the loads arising during feeding has been proposed and dismissed in the past, but never tested quantitatively. To address this, a biomechanical model of a domestic cat (Felis silvestris catus) skull was created and the material properties of the falx and tentorium were varied for a series of loading regimes incorporating the main masticatory and neck muscles during biting. Under these loading conditions, ossification of the falx cerebri does not have a significant impact on the stress in the cranial bones. In the case of the tentorium, however, a localized increase in stress was observed in the parietal and temporal bones, including the tympanic bulla, when a non-ossified tentorium was modelled. These effects were consistent across the different analyses, irrespective of loading regime. The results suggest that ossification of the tentorium cerebelli may play a minor role during feeding activities by decreasing the stress in the back of the skull.

The cat's meow: A high-field fMRI assessment of cortical activity in response to vocalizations and complex auditory stimuli.

Sensory systems are typically constructed in a hierarchical fashion such that lower level subcortical and cortical areas process basic stimulus features, while higher level areas reassemble these features into object-level representations. A number of anatomical pathway tracing studies have suggested that the auditory cortical hierarchy of the cat extends from a core region, consisting of the primary auditory cortex (A1) and the anterior auditory field (AAF), to higher level auditory fields that are located ventrally. Unfortunately, limitations on electrophysiological examination of these higher level fields have resulted in an incomplete understanding of the functional organization of the auditory cortex. Thus, the current study uses functional MRI in conjunction with a variety of simple and complex auditory stimuli to provide the first comprehensive examination of function across the entire cortical hierarchy. Auditory cortex function is shown to be largely lateralized to the left hemisphere, and is concentrated bilaterally in fields surrounding the posterior ectosylvian sulcus. The use of narrowband noise stimuli enables the visualization of tonotopic gradients in the posterior auditory field (PAF) and ventral posterior auditory field (VPAF) that have previously been unverifiable using fMRI and pure tones. Furthermore, auditory fields that are inaccessible to more invasive techniques, such as the insular (IN) and temporal (T) cortices, are shown to be selectively responsive to vocalizations. Collectively, these data provide a much needed functional correlate for anatomical examinations of the hierarchy of cortical structures within the cat auditory cortex.

Doppler ultrasonographic assessment of maternal and fetal arteries during normal feline gestation.

The aim of this study was to describe Doppler parameters of uterine, umbilical, fetal abdominal aorta, fetal renal and fetal internal carotid arteries, as well as fetal heart rate (FHR), during normal feline gestation. Fifteen, 1-4 years of age, weighing 2.5-3.9kg, domestic short-hair pregnant queens, which were born in our institutional cat colony were included in this study. Color and pulsed-wave Doppler evaluations of uterine arteries were performed every 10 days (Day 0, 10, 20, 30, 40, 50, 60) from mating. Fetal Doppler and M-mode ultrasonography were performed to assess umbilical, fetal abdominal aorta, fetal renal, fetal internal carotid arteries and FHR. Both peak systolic velocity (PSV) and end diastolic velocity (EDV) of uterine artery increased up to parturition (P<0.01), while resistance index (RI) decreased from Day 10 onwards (P<0.01). From Day 40 onwards, RI of umbilical artery diminished, while PSV and EDV augmented (P<0.01). Fetal abdominal aorta (P<0.01), renal (P<0.01) and internal carotid (P<0.01) arteries diminished their RI from Days 40, 60 and 40 onwards, respectively. Both PSV and EDV of these three arteries increased progressively. Fetal heart rate was first registered on Day 20 when it began to increase up to Day 40 and then diminished to the end of gestation (P<0.01). It is concluded that blood flow of uterine, umbilical, fetal abdominal aorta, fetal renal and fetal internal carotid arteries progressively increased during normal feline pregnancy, while FHR rose to mid gestation and then decreased up to parturition.

Pelvic differences between brachycephalic and mesaticephalic cats and indirect pelvimetry assessment.

Pelvic measurements were carried out in cats with various cranial conformations to (1) determine pelvic morphometry, (2) compare any pelvic differences with cranial conformation and gender and (3) determine whether body biometrics can be used to predict pelvic measurements. Thirteen brachycephalic and 14 mesaticephalic female cats and 17 brachycephalic and nine mesaticephalic male cats were used. Body and external pelvic measurements, as well as pelvic radiographs, were performed. Brachycephalic females all had external pelvic and radiographic measurements that were significantly smaller than those of the mesaticephalic females, including smaller pelvic inlet and outlet areas and a smaller pelvic canal shape. Brachycephalic females had wider and flatter heads than do mesaticephalic females. Similarly, brachycephalic males all have radiographic pelvic measurements that are smaller than those of mesaticephalic males. Males had larger pelvis measurements than did their female counterparts for both cranial types, and indirect pelvimetry did not demonstrate good predictive value in determining the internal pelvic measurements. Thus, we conclude that pelvic differences exist between genders and between brachycephalic and mesaticephalic cats. Furthermore, body biometric measurements do not have good predictive value for determining internal pelvic measurements.

Impact of fine needle aspiration (FNA) and of the number of punctures on the feline testis: clinical, gross anatomy and histological assessment.

The safety of testicular fine needle aspiration (FNA) has been proven in dogs but has not been fully established in men, while studies in rats have given contradictory results. Furthermore, the extent of damage inflicted by multiple punctures is unknown. The aim of this study was to determine the impact of FNA and of the number of punctures on the feline testis with clinical, gross anatomy and histological examinations. Twenty-seven sexually mature healthy laboratory Domestic Shorthair cats were randomly assigned to two groups: 5 cats in which no FNA was performed (control group), and 22 cats which had their left and right testis punctured with a 26 ga needle towards 3 and 8 directions, respectively (experimental group). Two cats at a time were orchiectomized 5 or 30 min, 1, 2, 4, 7 or 14 days or 1, 2, 3 or 4 mo post-aspiration. The cats of the control group were also orchiectomized. During the first week post-aspiration clinical examination revealed vaginal cavity hematoma (8/44 testes), while the histological findings were focal hemorrhagic areas (20/24 testes), erythrocytes inside the seminiferous tubules' lumen (9/24 testes), and germinal cell degeneration in <1.94% of the seminiferous tubules (15/24 testes). After the first week the histological findings were germinal cell degeneration in <2.14% of the seminiferous tubules (19/20 testes) and enlargement of the lumen of <5.16% of the seminiferous tubules (7/20 testes). The germinal epithelium and interstitium had an overall normal appearance. No significant differences were observed between the left and right testis. The results of the study indicate that testicular FNA should be considered a safe procedure in the cat when up to 8 punctures are performed.

Sonographic assessment of gallbladder volume in normal cats.

We quantified gallbladder volume in 30 clinically healthy, fasted, cats, using an ellipsoid formula. All cats had a complete blood count and serum chemistry profile performed. Fasting times before sonography ranged from 12 to 16 h. The median gallbladder volume was 2.42 ml, with a range of 0.84-4.50 ml. The mean gallbladder volume was 2.41 ml. This reference range will assist clinicians when evaluating cats with hepatobiliary disease or suspected extrahepatic biliary obstruction.

Corneal innervation in mesocephalic and brachycephalic dogs and cats: assessment using in vivo confocal microscopy.

OBJECTIVE: To determine the density of the canine and feline corneal neural network in healthy dogs and cats using in vivo confocal microscopy (IVCM). ANIMALS EXAMINED: A total of 16 adult dogs (9 Mesocephalic breeds, 7 Brachycephalic breeds) and 15 cats (9 Domestic Short-haired cats (DSH), 6 Persian cats) underwent IVCM. PROCEDURE: Animals were examined with a confocal corneal microscope (HRTII/RCM; Heidelberg Retina Tomograph II/Rostock Cornea Module, Heidelberg Engineering, Dossenheim, Germany). The investigations focused on the distribution of the corneal nerves and quantification of central subepithelial and subbasal nerve plexus. RESULTS: The corneal stromal nerve trunks, subepithelial and subbasal nerve plexus were observed. The nerve fiber density (NFD) quantified in nerve fiber length in mesocephalic dogs were 12.39 +/- 5.25 mm/mm(2) in the subepithelial nerve plexus and 14.87 +/- 3.08 mm/mm(2) in the subbasal nerve plexus. The NFD of the subepithelial nerve plexus in DSH cats was 15.49 +/- 2.7 and 18.4 +/- 3.84 mm/mm(2) in the subbasal nerve plexus. The subbasal NFD of DSH cats was significantly higher than in mesocephalic dogs (P = 0.037). The subepithelial NFD in brachycephalic dogs, and Persian cats were 10.34 +/- 4.71 and 9.50 +/- 2.3 mm/mm(2), respectively. The subbasal NFD measured 11.80 +/- 3.73 mm/mm(2) in brachycephalic dogs, and 12.28 +/- 4.3 mm/mm(2) NFD in Persian cats, respectively. The subepithelial and subbasal NFD in Persian cats were significantly lower than in DSH cats (P = 0.028, respectively, P = 0.031), in contrast to brachycephalic vs. mesocephalic dogs. CONCLUSION: The noninvasive IVCM accurately detects corneal innervation and provides a reliable quantification of central corneal nerves.

Ultrasonographic assessment of the feline mammary gland.

The aim of this study is to characterise the feline mammary echotexture using B-mode ultrasonography, which is not routinely used to examine the feline mammary gland. Using a 5-9 MHz linear transducer the ultrasonographic appearance of non-stimulated and stimulated mammary glands was determined in 35 mature intact non-pregnant, pregnant and lactating queens aged from 16 months to 8 years. In intact non-pregnant queens, mammary glands are fairly underdeveloped and on the ultrasonograms they appear with a regular hypoechoic texture and generally show a thickness of less than 2.0mm. The stimulated mammary tissue typically presents a more hyperechoic appearance compared to the non-stimulated gland and a fine granular echotexture. Maximum echogenicity of the mammary gland is reached during lactation. In late pregnancy, the mammary glands reach 6-9 mm in thickness. During lactation, the size of the glands depends on the existence of a suckling stimulus, with the suckled glands reaching about 11 mm in thickness. Ductal structures can only be imaged during late pregnancy and lactation. Ultrasonographic evaluation of the feline mammary gland can become a valuable diagnostic tool to characterise physiological changes and may further contribute to a better characterisation of diseased mammary tissue.

Quantitative assessment of renal cortical echogenicity in clinically normal cats.

In this study, we assessed the renal cortical echogenicity of clinically normal adult cats by histogram analysis to obtain basic ultrasonographic data. Ultrasound images were taken under the following sets of conditions: (1) high contrast and low gain setting using a convex probe, (2) low contrast and high gain setting using a convex probe, (3) high contrast and low gain setting using a linear probe and (4) low contrast and high gain setting using a linear probe. Echogenicity of the region of interest (ROI) in the right and left renal cortices, liver and spleen was determined by histogram analysis; kidney/spleen (Kid/Sp) and kidney/liver (Kid/Liv) echogenicity ratios were calculated. Kid/Sp and Kid/Liv values varied among different ROI sites in the kidney when obtained using the convex probe, but were constant when obtained using the linear probe. Kid/Sp measured in the middle sites of the kidney showed similar values for the different settings; however, Kid/Liv differed between probes. The present findings suggest that determination of Kid/Sp using a linear probe is a feasible method for quantitative evaluation of renal cortical echogenicity in cats.

Assessment of the posterior segment of the cat eye by optical coherence tomography (OCT).

OBJECTIVES: To assess the feasibility of optical coherence tomography (OCT) for examining the cat ocular fundus, to provide normative data on retinal thickness in different fundus regions, and to demonstrate selected surgically induced vitreoretinal pathologies in the cat. ANIMAL STUDIED: Forty-five eyes of 28 healthy domestic cats and two eyes of domestic cats that had undergone subretinal implantation surgery for a visual prosthesis were examined. PROCEDURES: An optical coherence tomograph (Zeiss-Humphrey) was used to examine the anesthetized animals. At least five vertical and five horizontal scans in regular distribution were recorded for each cat including (1) the peripapillary region, (2) the area centralis, and (3) the peripheral retina. Thickness was measured manually at five locations in each scan. Retinal thickness was compared in the three above-mentioned fundus regions, between eyes and between vertical and horizontal scans. OCT was additionally performed in animals with retinal detachment and a subretinal visual prosthesis. RESULTS: OCT measurements required only minimal adjustments of human settings and yielded high quality images. In comparison to humans intraretinal layers were more difficult to differentiate. Retinal thickness was highest in the peripapillary region (245 +/- 21 microm), followed by the peripheral retina (204 +/- 11 microm) and the area centralis (182 +/- 11 microm; all P < 0.0001). There was no statistically significant difference between right and left eye or between vertical and horizontal scans. OCT demonstrated retinal detachment, an iatrogenic break and a subretinal prosthetic device in high detail. CONCLUSIONS: Retinal thickness was measurable with high precision; values compare well to older histologic studies. OCT bears significant advantages over histology in enabling one to repeat measurements in living animals and thus allowing longitudinal studies. Various vitreoretinal pathologies common in feline eyes are detectable and quantifiable by OCT.

Assessment of location of the celiac and cranial mesenteric arteries relative to the thoracolumbar spine using magnetic resonance imaging.

Exact localization of thoracolumbar lesions can be harder with magnetic resonance (MR) imaging than with radiography. The celiac and cranial mesenteric arteries are easily seen on MR images and are always included in sagittal thoracolumbar studies. This study was undertaken to establish whether their location was sufficiently consistent to enable them to be used as anatomic landmarks. It was found that their location varied considerably, and there was no useful relationship to breed, gender, age, or body weight. They are therefore unreliable for use in establishing initial localization of a spinal lesion although they can be helpful when comparing multiple image planes.

Assessment of body composition in cats and dogs.

The assessment of body composition in any species is important to the understanding of subjects such as the control of obesity, the realimentation of sick animals and the evaluation of energy requirements. In most cases our requirement is to assess the chemical constituents of the body by the measurement of the fat and fat-free mass (FFM) of the subject. There may also be a requirement to break down the FFM mass into its component parts and measure the tissue distribution within the body. Clearly in the understanding of the causes and effects of obesity in companion animals, the evaluation of the actual level of obesity is fundamental. Similarly, whilst classifying the effectiveness of a weight loss programme it is vital that the reduction in weight loss and the distribution of tissue types can be accurately recorded by the veterinary surgeon or clinician. This review covers the theory of body composition measurement and the techniques which have been developed, together with their relevance to studies with companion animals. Most techniques are based on indirect methods which use the model of the body being at least two chemically distinct compartments, the fat and the FFM. In more complex analyses four and even six compartment models are considered which include concepts such as protein content, cell and osseous mineral content. The techniques to be covered include the measurement of total body water (for example by the use of isotope dilution), anthropometric techniques (skinfold thickness and dimensional evaluation), densitometry, total body potassium, muscle metabolite markers, absorptiometry, neutron activation analysis, electrical conductance, ultrasound, near infrared interactance, computed tomography and magnetic resonance imaging.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the interbulbar connections in the cat using the Fink-Heimer and HRP methods.

The anterograde degeneration technique, using the Fink-Heimer method, and retrograde cell tracing with horseradish peroxidase (HRP) were used to analyze the afferent and efferent fiber projections of the olfactory bulb complex, consisting of the main olfactory bulb (MOB), the anterior olfactory nucleus (AN) and the accessory olfactory bulb (AO) in the cat. The results reveal that the ipsilateral and contralateral fibers running via the anterior commissure to join the internal plexiform layer of both the ipsilateral and contralateral MOBs originate from the AN, whereas the ipsilateral fiber terminals running into the outer part of the plexiform layer of the pyriform cortex originate from the MOB and AOB. In consideration of the olfactory functional relays, it is suggested that the AN, both in the dorsolateral part and external layer, most likely stimulates some afferent and efferent impulses of the olfactory impact in the mammal.