The size and shape of the foramen magnum were studied in skulls from 75 adult and 5 juvenile Pekingese dogs. After maceration of the skulls, the height, width, and area of each foramen magnum were measured, and various skull indices were determined. The shape of the foramen varied from ovoid to rectangular and had a dorsal notch in aU but 2 skulls. Prolapse of cerebellum or brain stem through the enlarged opening was prevented by a fibrous membrane covering he dorsal notch. Mean +/- SD area of the foramen was 138.1 +/- 26.1 mm(2); its mean total height was 15.0 +/- 2.9 mm, and its mean maximal width was 13.3 +/- 1.1 mm. Statistically, variability in the area of the foramen was mainly correlated with total height of the foramen, including the dorsal notch. Total height of the foramen was not correlated with age or gender. The degree of dysplasia, notch index, and occipital index of each foramen magnum were determined. To allow a more accurate evaluation of the morphology of the foramen, the foramen magnum index, defined as the ratio between the maximal width and the total height of the foramen, was also computed. Mean +/- SD foramen magnum index was 91.8 +/- 17.1 in the adult Pekingese dogs. Foramen magnum index was not significantly correlated with age, but was significantly larger in male than in female dogs. The large variability in the shape and size of the foramen magnum and the absence of any neurologic problems in dogs of this study indicate that the dorsal notch of the foramen magnum in brachycephalic dogs is a normal morphologic variation, rather than a pathologic condition.

The position, dimensions, and structure of the thyroid gland, the portion of the esophagus in the neck the cervical lymph nodes, and the major blood vessels of the neck were determined via ultrasonography in cattle. The left and right ventral neck regions of 30 healthy Swiss Braunvieh cows were examined ultrasonographically, using 3.5- and 5.0-MHz linear transducers and a 3.5-MHz convex transducer. The external jugular vein was situated directly beneath the skin in the upper and middle parts of the neck and 2.7 to 6.6 cm from the body surface in the lower part of the neck. In contrast, the common carotid artery was located further from the body surface along the entire ventral neck region; depending on the measuring point, this distance varied from 2.6 to 10.9 cm. The external jugular vein narrowed from caudad to craniad. The diameter of the common carotid artery remained fairly constant along its course in the ventral part of the neck and varied from 0.9 to 1.4 cm. The thyroid gland was identified via ultrasonography caudodorsal to the larynx It appeared as an echogenic spindle-shaped structure with finely granular echogenic pattern. The esophagus appeared as a band-shaped structure in longitudinal section, and it could be followed to the thoracic inlet. Its width increased from craniad to caudad, and mean +/- SD diameter was 2.9 +/- 0.23 cm. The medulla, hilus, cortex, and capsule of the cervical lymph nodes could be clearly differentiated via ultrasonography. Mean length and width of the left cervical lymph node were 3.0 +/- 0.45 and 1.8 +/- 0.23 cm, respectively. To determine reproducibility and reliability of the results, 10 cows were examined by ultrasonography 10 times within 2 weeks. The interassay coefficients of variation determined from these examinations varied from 3.0 to 12.3%; most of the coefficients of variation ranged from 5 to 10%. The smallest coefficients of variation were determined for diameter of the common carotid artery, and the largest were for diameter of the external jugular vein. Description of the ultrasonographic appearance of the structures of the ventral neck region in healthy cattle represents the basis for use of diagnostic ultrasonography in cattle with suspected diseases involving this area. The technique is noninvasive and can be performed on cattle in standing position.

Pharmacologically induced splenic contraction might be useful during certain medical or surgical procedures in horses. The effects of phenylephrine, an alpha 1-adrenergic receptor agonist, on hemodynamic function and splenic dimensions were examined in 6 healthy adult horses. Phenylephrine infusion (1, 3, or 6 microgram/kg of body weight/min for 15 minutes) resulted in a dose-related increase in mean pulmonary artery pressure; right atrial pressure; systolic, mean, and diastolic arterial pressures; and packed cell volume (P = 0.0001). Concurrent decreases in heart rate and specific cardiac output (P = 0.0001) were detected, but stroke volume did not vary significantly. The rate-pressure product was increased only at the highest phenylephrine dosage (P = 0.012). Bradycardia was observed at all dosages during drug infusion, and second-degree atrioventricular block was detected in 88% of horses during infusion. Phenylephrine administration caused dose-dependent splenic contraction, as detected by ultrasonographic measurements of splenic area and thickness (P = 0.0001). At the 3- and 6-microgram/kg/min infusion rates, splenic area was reduced to 28 and 17% of baseline measurement, respectively. Splenic dimensions had returned to baseline values by 35 minutes after the end of infusion. Infusion of phenylephrine at a dosage of 3 microgram/kg/min for 15 minutes can be used to induce splenic contraction in horses.

Twelve resected canine gallbladders (in vitro) and the gallbladder in each of 14 dogs (in vivo) were ultrasonographically examined. Gallbladder volume was calculated from ultrasonographically measured geometric dimensions, using 4 volumetric model formulas: cone, ellipse, biplanar ellipse, and prolate ellipse. Calculated volume was compared with true gallbladder volume, as measured by water displacement. AU examined models for calculation of gallbladder volume were closely associated with true gallbladder volume (P < 0.005), and all models provided accurate predictions of true gallbladder volume (r2 > 0.80). Calculated volumes can be corrected mathematically by use of the regression coefficient and constant for each model. Body weight was not significantly associated with gallbladder volume in any of the models considered. Use of ultrasonography to accurately measure gallbladder volume could be combined with synthetic cholecystokinin-stimulated gallbladder emptying to provide information about biliary function and patency in icteric animals. Such information could aid the clinical decision between surgical or medical treatment. Correction of calculated volumes would not be necessary in association with induced emptying studies, because volume change is more important than absolute volume.

To determine the position, dimensions, and structure of the right kidney in cattle by use of ultrasonography, the right kidney of 11 healthy Brown Swiss cows was examined 10 times within 2 weeks. A 3.5- and 5.0-Mhz linear and convex transducer was placed on the right side of the cow in the lumbar region, in the paralumbar fossa, and in the last intercostal space. The echogenicity of various renal structures differed. The lobulation of the kidney in cattle could be visualized ultrasonographically; however, the cortex and medulla could not be differentiated. The distance between body surface and the right kidney was almost 3 times larger (5.3 +/- 1.71 cm, mean +/- SD) in the lumbar region than in the paralumbar fossa (1.8 +/- 0.52 cm). The vertical diameter of the kidney was remarkably smaller (5.1 +/- 0.47 cm) than the horizontal diameter (9.4 +/- 0.98 cm). In 7 cows, the thickness of the renal cortex and medulla was between 1.9 and 2.1 cm. The medullary pyramids could be visualized when the transducer was placed in the paralumbar fossa. Fourteen of 19 variables measured had a coefficient of variation between 8 and 14%. It was concluded that the ultrasonographic values determined in this study can be used as references for the diagnosis of morphologic changes in the right kidney of domestic dairy cattle.

In a 5-year prospective study, computed tomographic (CT) morphometry of the lumbosacral vertebral canal was performed on 42 large-breed dogs (21 controls and 21 dogs with lumbosacral stenosis). Dogs were allotted to 4 groups. Group 1 (n = 13) consisted of cadaver specimens obtained from dogs that died or were euthanatized for reasons unrelated to the spine; group 2 (n = 8) consisted of live dogs with no history of clinical signs related to the spine and with normal neurologic examination findings; group 3 (n = 10) consisted of dogs with surgically confirmed lumbosacral stenosis; and group 4 (n = 11) consisted of dogs with suspected lumbosacral stenosis that were managed conservatively. The CT scans were performed, using 5-mm contiguous slices obtained perpendicular to the vertebral canal, from the midbody of the 5th lumbar vertebra through the caudal endplate of the sacrum (L5-S3). Lumbosacral lordosis was minimized in all dogs by positioning them in dorsal recumbency with the hind limbs flexed. A tuberculin syringe calibration phantom was placed within the scanning field of view, parallel to the axis of the spine. In each dog, 11 CT slice locations within the lumbosacral spine were evaluated. At each slice location, sagittal plane diameter, dorsal plane diameter, and transverse area of the vertebral canal, vertebral body, and calibration phantom were measured, using the CT computer's software programs for distance and area calculation. Window/level settings were constant, and all measurements were made by the same operator (JCJ). Accuracy of calibration phantom CT measurements was 100% for sagittal and dorsal plane diameter and was 85% for transverse area. In control dogs (groups 1 and 2), vertebral canal dimensions were significantly (r greater than or equal to 0.50, P less than or equal to 0.0001) correlated with vertebral body dimensions, but not with dog weight or age. There were no significant differences between group 1 vs group 2, and group 3 vs group 4 for all absolute vertebral canal dimensions and for 5 ratios of vertebral canal to correlated vertebral body dimensions (general linear model for ANOVA). Pooled control dogs (n = 21) and those with lumbosacral stenosis (n = 21) were compared, and significant differences were not identified for absolute canal dimensions. Significant differences between control dogs and those with lumbosacral stenosis were identified in the ratios of vertebral canal transverse area to vertebral body sagittal diameter (P less than or equal to 0.01) and vertebral canal transverse area to vertebral body transverse area (P less than or equal to 0.001). For both these ratios, analysis by slice location identified significant differences (P < 0.05) between pooled groups at the caudal pedicles of L5 and L6. For the ratio of transverse canal area to sagittal vertebral body diameter, differences (P less than or equal to 0.05) also were found at the cranial pedicle of L7. These results indicate that: CT is an accurate method for performing morphometry of the canine lumbosacral spine; vertebral canal dimensions can be corrected for differences in dog size by calculating ratios of vertebral canal to vertebral body dimensions; statistical comparisons, using such corrected vertebral canal dimensions, may reveal differences not evident when absolute vertebral canal dimensions are used; and corrected transverse area of the vertebral canal differs in large-breed dogs with lumbosacral stenosis vs normal controls. Morphometric differences identified at more than 1 vertebral level support a theory that multilevel congenital or developmental stenosis of the lumbosacral vertebral canal may be a predisposing or contributing factor in large-breed dogs with acquired lumbosacral stenosis.

Although power analysis is of important tool research, investigators in veterinary medicine are unaware of the concepts of the statistical power. Two types of error occur in classical hypothesis testing and, those errors should be avoided, if possible. Since power is highly dependent on the sample size, whenever declaring non-statistically significant result they should consider the potential for committing a Type Ⅱ error in their studies, which refers to the probability of falsely stating that two treatments are equivalent despite true difference between them. Also, sample size determination is one of the most important tasks facing the researcher when planning a diagnostic study, and provides valuable information on the characteristics of a test performance. This type of analysis forms the basis for proper interpretation of test results. The aim of this article was to re-evaluate some selected studies on diagnostic test reported in the domestic veterinary publications to determine the power and necessary sample size for inequality testing to ensure the desired power. Power calculations were illustrated using real-life examples of comparison of a new test and a reference test for detecting antibodies of various animal diseases. Factors affecting to the power were also discussed.

Tissue variation in microscope slides made for spermatozoon analysis and variation introduced by the subjective techniques used to analyze these slides reduce the statistical power of studies that seek to use spermatozoon morphology to predict fertility. A simple specimen preparation method was developed to standardize stallion spermatozoon morphologic smears, and a new, automated spermatozoa morphometry instrument was used to objectively analyze the efficacy of the specimen preparation technique. The method achieved a standard spermatozoon concentration and reduced field-to-field variation in the number of spermatozoa analyzed. Metric measurements of spermatozoon head dimensions from clinically normal, fertile stallions revealed small, but highly significant, differences between stallions. The variation in metric measurements between replicate slides within stallions was small, indicating that replicate slide analysis probably is not necessary for clinically normal stallions. Coefficients of variation were generally less than 11% for metric measurements between stallions, and were less than 4% within stallions. This study revealed that a high degree of statistical power can be achieved when using these new, standardized specimen preparation and objective analysis techniques. Such power makes possible the detection of subtle differences between clinically normal stallions, and may facilitate accurate detection of abnormal fertility (ie, subfertility) in stallions.