Abdominal ultrasonography in small animals: Examination of the liver, spleen and pancreas

Ultrasonography is an important diagnostic technique in veterinary medicine. It may be used to examine most structures in the small animal ahdomen, providing a rapid, non-invasive means of supplementing information obtained by physical examination and radiography. Limitations of ultrasonography include the non-specific nature of many observed abnormalities, which prevents a specific diagnosis, and the difficulty of identifying certain normal organs such as the pancreas. This paper reviews ultrasonography of the liver, spleen and pancreas, and ultrasound-guided biopsy in small animals, and indicates areas of potential future development.     

TRUNCATION ARTIFACT IN MAGNETIC RESONANCE IMAGES OF THE CANINE SPINAL CORD

The truncation artifact in magnetic resonance (MR) images is a line of abnormal signal intensity that occurs parallel to an interface between tissues of markedly different signal intensity. In order to demonstrate the truncation artifact in sagittal images of the canine spinal cord and the effect of changing spatial resolution, we conducted an experimental in vitro study. A section of fixed canine spinal cord was imaged using a 1.5T magnet. Spatial resolution was increased by increasing the acquisition matrix and reconstruction matrix, producing series of T2‐weighted (T2w) images with the following pixel sizes: A, 1.6 (vertical) × 2.2 mm² (horizontal); B, 1.2 × 1.7 mm²; C, 0.8 × 1.1 mm²; D, 0.4 × 0. 6 mm². Plots of mean pixel value across the cord showed variations in signal intensity compatible with truncation artifact, which appeared as a single, wide central hyperintense zone in low‐resolution images and as multiple narrower zones in high spatial resolution images. Even in images obtained using the highest spatial resolution available for the MR system, the edge of the spinal cord was not accurately defined and the central canal was not visible. The experiment was repeated using an unfixed spinal cord specimen with focal compression applied to mimic a pathologic lesion. Slight hyperintensity was observed within the spinal cord at the site of compression although the cord was normal histologically. Results of this study suggest that caution should be applied when interpreting hyperintensity affecting the spinal cord in T2w sagittal images of clinical patients because of the possibility that the abnormal signal could represent a truncation artifact.     

Plasma adrenocorticotropin (ACTH) concentrations and clinical response in horses treated for equine Cushing's disease with cyproheptadine or pergolide

Plasma ACTH levels have been variable in horses with a positive clinical response for therapy for equine Cushing's Disease (ECD). Therefore, our purpose was to determine the value of monitoring plasma adrenocorticotropin (ACTH) levels during treatment of equine Cushing's disease (ECD) with either cyproheptadine (n = 32) or pergolide (n = 10). First, we validated the chemiluminescent ACTH assay (specificity, precision, accuracy, intra-assay and interassay variations) and tested methods of handling the whole blood from the time of collection to when the ACTH was assayed. The sensitivity and specificity of high plasma ACTH levels for detecting ECD was determined in a retrospective study on hospitalised horses (n = 68). Surveys were sent to veterinarians who submitted equine ACTH levels that were high initially and had at least 2 ACTH samples to determine the value of monitoring ACTH levels during therapy of ECD. The ACTH chemiluminescent assay was valid. The ACTH was stable when whole blood was collected and held in plastic tubes for 8 h before separating the plasma. The sensitivity and specificity of plasma ACTH levels for detecting ECD were 84% (n = 19,95% CI 60,97) and 78% (n = 49,95% CI 63,88), respectively. Treated horses generally showed a decrease in plasma ACTH. Plasma ACTH levels may be helpful when monitoring therapy of ECD, although improvement in clinical signs should be considered most important. There were no differences between cyproheptadine and pergolide in terms of improvements in any of the clinical signs.     

Evaluation of the Breeding Soundness of Male Camels (Camelus dromedarius) via Clinical Examination,Semen Analysis,Ultrasonography and Testicular Biopsy: A Summary of 80 Clinical Cases

Male camel infertility is a heterogeneous disorder. A variety of factors may adversely affect sperm production and function and impair fertility. This study was designed to evaluate the sensitivity and specificity of ultrasonography and testicular biopsy in the evaluation of the breeding soundness of male dromedaries compared with results obtained by clinical examination and semen analysis. Eighty‐four male dromedary camels (5–15 years old) were used in this study during the rutting season (November–May). Four sexually mature male camels were used as controls. These animals were apparently healthy and had histories of normal fertility. Eighty infertile male camels were subjected to an algorithmic approach based on information collected during careful examinations of the camels' breeding histories, clinical examinations, testicular evaluations, testicular ultrasonographies, the results of the semen analyses and testicular biopsies to diagnose the camels' infertilities. The differences in the semen parameters between the control and infertile male camels were highly significant (p < 0.01). Regarding the diagnoses of male camel infertility, the results of testicular ultrasonographies and biopsies were compared with those from the semen analyses, and the accuracies of these tests were 92.5% and 90%, respectively. Additionally, the results of the testicular ultrasonographies were matched with those of the testicular biopsies of the infertile animals, and this comparison resulted in 85% accuracy. Testicular biopsy is a promising method that, along with a carefully performed history, clinical examination, an appropriate testicular ultrasonography procedure and semen analysis, can afford veterinarians the opportunity for more precise diagnosis and treatment of many dromedary infertility disorders.     

Correlation of Plasma Insulin Concentration with Laminitis Score in a Field Study of Equine Cushing's Disease and Equine Metabolic Syndrome

This study aimed to investigate endocrinologic test values and the response to treatment of two commonly encountered causes of endocrinopathic laminitis, equine Cushing's disease (ECD) and equine metabolic syndrome (EMS), in a veterinary practice setting. In particular, the study aimed to determine whether insulin concentration correlated to the severity of clinical laminitis in horses with EMS or ECD. Twenty-five horses were included in the study and assigned to one of three groups: ECD (n = 6), EMS (n = 10), and controls (n = 9). Blood samples were collected at an initial visit and then at regular intervals for the next 12 months. Plasma concentrations of adrenocorticotropin (ACTH), cortisol, and insulin and serum concentrations of glucose and total thyroxine (T4) were obtained. Horses with ECD had significantly higher plasma ACTH concentrations than EMS horses or controls. Horses with EMS and ECD both had significantly higher plasma insulin concentrations than control horses, which was correlated with the Obel grade of laminitis (r = 0.63). After treatment, there was a trend for a reduction in plasma ACTH concentration in horses with ECD. A program of diet and exercise for horses with EMS resulted in reductions in both plasma insulin concentrations and bodyweight, which was variable, depending on the individual. There was a significant correlation between the change in plasma insulin concentration and Obel grade of laminitis (r = 0.69). This study has highlighted the importance of baseline plasma insulin concentration as a potential indicator of the susceptibility of horses to laminitis and the response to a program of diet and exercise.     

CANINE MENINGEAL DISEASE: ASSOCIATIONS BETWEEN MAGNETIC RESONANCE IMAGING SIGNS AND HISTOLOGIC FINDINGS

In order to compare the accuracy of MR sequences for diagnosis of meningeal disease, MR images of the brain, and histopathologic specimens including the meninges of 60 dogs were reviewed retrospectively by independent observers in a cross‐sectional study. MR images included T1‐weighted pre‐ and postgadolinium images, subtraction images, T2‐weighted images, and T2‐weighted fluid‐attenuated inversion‐recovery (FLAIR) images. Pathologic changes affected the pachymeninges in 16 dogs, leptomeninges in 35 dogs, and brain in 38 dogs. The meninges were normal in 12 dogs. Meninges were classified histopathologically as normal (grade 0), slightly or inconsistently affected (grade 1), or markedly affected (grade 2). When applying relaxed pathologic criteria (grades 0 and 1 considered normal), the results of ROC analysis (area under curve, AUC) were: T1‐weighted postcontrast images 0.74; subtraction images 0.7; T2‐weighted images 0.68; FLAIR images 0.56. The difference in AUC between T1‐weighted postgadolinium images and FLAIR images was significant (P = 0.04). AUC for FLAIR images was not significantly different from 0.5. When applying strict pathologic criteria (only grade 0 considered normal), none of the MR sequences had AUC significantly different from 0.5. On the basis of T1‐weighted postgadolinium images and subtraction images, correct anatomic classification of lesions occurred more often for pachymeningeal than leptomeningeal lesions (P < 0.001). Overall, MR imaging had low sensitivity for diagnosis of meningeal pathology in dogs, particularly for changes affecting the leptomeninges. Subtraction images had similar accuracy to T1‐weighted postgadolinium images for meningeal lesions in dogs. T2‐weighted FLAIR images appear to have limited diagnostic utility for meningeal lesions.     

Evaluating the accuracy of mapping weeds in seedling crops using airborne digital imaging: Avena spp. in seedling triticale

Airborne multispectral imaging has been used to map patches of Avena spp. (wild-oats) in a field of seedling triticale (X Triticosecale , Wittmack). Images of the target field were acquired using a four-camera airborne digital imaging system, recording in the infrared, red, green and blue wave-bands. Spectral information derived from images of 0.5-, 1.0-, 1.5- and 2.0-m spatial resolution were correlated with detailed on-ground weed density measurements to investigate the effect of image resolution on mapping accuracy. Comparisons between normalized-difference vegetation index (NDVI) or soil-adjusted vegetation index (SAVI) images and weed data achieved correlations of up to 71%. The highest correlation was achieved with the 0.5-m-resolution images and the lowest with the 2.0-m-resolution images. At 0.5-m resolution, NDVI images could not reliably discriminate weed populations of less than 28 weeds m^–2 from weed-free regions, while SAVI images could not discriminate populations of less than 17 weeds m^–2. At 1.0-, 1.5- and 2.0-m resolution, SAVI images could not discriminate populations of less than 23 weeds m^–2, while NDVI images again demonstrated a higher discrimination threshold. Results suggest that airborne multispectral imaging could be used as part of a stratified weed sampling system.     

In situ provision of drinking water to grazing dairy cows improves milk production

AIMS: To determine the effect of providing water within the area grazed by dairy cows on milk yield and quality, compared to requiring cows to walk to a distant water trough, on a dairy farm in the Pampa region of Argentina during summer.

METHODS: Holstein dairy cows were allocated to two herds with similar parity, days in milk and milk production. They were grazed in one paddock that was divided in two, with a fixed water trough at one end. Cows were moved twice daily to grazing plots within the paddock. Control cows (n=66) could only access water from the fixed trough, whereas supplemented cows (n=67) also received water from a mobile trough within the grazing plot. Milk production of each cow, and water consumption of the two herds were measured daily over 62 days. Milk composition for each herd was determined weekly from Days 18 to 60 of the study, and grazing behaviour was observed between 08:00 and 16:00 hours on Days 11–15, 19–22 and 39–43.

RESULTS: Over the 62 days of the study, supplemented cows produced 1.39 (SE 0.11) L/cow/day more milk than Control cows (p=0.027). Estimated mean daily water intake was 50.4 (SE 2.1) L/cow/day for supplemented cows and 58.2 (SE 2.7) L/cow/day for Control cows (p=0.004). Percentage total solids in milk was higher for supplemented (12.5 (SE 0.06)%) than Control (12.4 (SE 0.04)%) cows (p=0.047). During the periods of behavioural observation, a higher percentage of cows in the water supplemented than the Control herd were observed in the grazing area (p=0.012).

CONCLUSIONS AND CLINICAL RELEVANCE: This preliminary study demonstrated that provision of water to dairy cows within the grazing plot was beneficial for milk production and composition, and may be associated with longer periods spent within the grazing area, during hot weather in the Pampa region of Argentina.