Thyroid imaging in the dog: current status and future directions

This review describes the advantages and disadvantages of radiography, ultrasonography, and nuclear medicine in the 2 most frequent thyroid pathologies of the dog: acquired primary hypothyroidism and thyroid neoplasia. Ultrasonography and scintigraphy remain the 2 most indicated imaging modalities for these thyroid abnormalities. However, as in human medicine, computed tomography and magnetic resonance imaging also have potential indications. This is especially the case in the evaluation of the extent, local invasiveness, and local or distant metastases of thyroid neoplasia. Based on experience with different imaging modalities in people, we suggest future directions in the imaging of the canine thyroid gland.     

A review of methods for assessment of the rate of gastric emptying in the dog and cat: 1898-2002

Gastric emptying is the process by which food is delivered to the small intestine at a rate and in a form that optimizes intestinal absorption of nutrients. The rate of gastric emptying is subject to alteration by physiological, pharmacological, and pathological conditions. Gastric emptying of solids is of greater clinical significance because disordered gastric emptying rarely is detectable in the liquid phase. Imaging techniques have the disadvantage of requiring restraint of the animal and access to expensive equipment. Radiographic methods require administration of test meals that are not similar to food. Scintigraphy is the gold standard method for assessment of gastric emptying but requires administration of a radioisotope. Magnetic resonance imaging has not yet been applied for assessment of gastric emptying in small animals. Ultrasonography is a potentially useful, but subjective, method for assessment of gastric emptying in dogs. Gastric tracer methods require insertion of gastric or intestinal cannulae and are rarely applied outside of the research laboratory. The paracetamol absorption test has been applied for assessment of liquid phase gastric emptying in the dog, but requires IV cannulation. The gastric emptying breath test is a noninvasive method for assessment of gastric emptying that has been applied in dogs and cats. This method can be carried out away from the veterinary hospital, but the effects of physiological and pathological abnormalities on the test are not known. Advances in technology will facilitate the development of reliable methods for assessment of gastric emptying in small animals.     

Frequency of pulmonary mineralization and hypoxemia in 21 dogs with pituitary-dependent hyperadrenocorticism

The purpose of this study was to determine the frequency of hypoxemia and pulmonary mineralization using ^99mTc-methylene diphosphonate (^99mTc-MDP) in dogs with pituitary-dependent hyperadrenocorticism (PDH). Twenty-one dogs with PDH were pro-spectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using ^99mTc-macro-aggregated albumin [^99mTc-MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco-lumbar vertebrae from lateral thoracic ^99mTc-MDP images. Thoracic: vertebral ratios were calculated using ^99mTc-MDP studies from 21 control dogs. The thoracic: vertebral ratios were compared between the 2 groups (PDH and control). The mean age (±SD) of the 21 PDH dogs was 10.2 (±3) years, whereas the mean age of the control group was 9.8 (±3) years. Seven of the 21 dogs with PDH were hypoxemic (denned as an arterial partial pressure of oxygen [PaO₂] <80 mm Hg) with an average PaO₂ (±SD) of 62 (±15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using ^99mTc-MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic. The average quantitative thoracic: vertebral ratio was not significantly different between the PDH and control dogs (0.5 ± 0.4 versus 0.4 ± 0.1, P = .16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hypoxemia in dogs with PDH.     

Association of racing performance with specific abnormal radiographic findings in Thoroughbred yearlings sold in Texas

The objective of this prospective study was to determine the association between presence of abnormal radiographic findings attributed to orthopedic disorders of development (ARF) with subsequent performance among yearlings in Texas. The study population was 348 yearlings offered for sale at the Texas Summer Yearling Sale during 2002 and 2003 for which presale radiographs of limbs were available for review. Radiographs of yearlings were reviewed and presence of ARF were recorded. Additionally, the following data were recorded for each horse: identifiers [name of dam, name of sire, hip number, and name (when available)], year of sale, state of birth, and sales price. Subsequent performance data were obtained for each horse at the conclusion of their 2^nd and 3^rd years of life. Results indicated that no ARF was significantly associated with performance outcomes. Lesions of the proximal dorsal aspect of the sagittal ridge of the 3^rd metacarpus/metatarsus resulted in significantly lower sales prices than either horses without this ARF or horses without any ARF. In conclusion, multiple radiographic abnormalities of Thoroughbred yearlings were not associated with reduced performance during the first 2 years of the racing careers of horses studied. Presence of some abnormalities, however, may be associated with reduced sales price.     

Intermuscular Heterotopic Ossification in the Shoulder Region Associated with a Hopping-type Forelimb Lameness

Heterotopic ossification has not previously been described in the horse. An event horse was investigated due to poor performance and development of a hopping-type forelimb lameness when ridden. Comprehensive local analgesic techniques did not alter the hopping-type lameness. Radiological assessment revealed an osseous plate between the biceps brachii and brachiocephalicus muscles of the lame limb. Ultrasonographic examination verified that there was no involvement of the intertubercular bursa or tendon of biceps brachii or the muscles themselves. The horse was humanely destroyed because of multilimb lameness, with multiple sources of pain. Postmortem examination revealed a large plate of bone with very sharp, pointed margins, which was easily dissected from the adjacent muscles. The radiological and gross appearances of the bone plate were typical of heterotopic ossification in human beings.     

Two-dimensional cardiothoracic ratio for evaluation of cardiac size in German shepherd dogs

ObjectivesTo evaluate cardiac size in normal German shepherd dogs (GSD) using the two-dimensional cardiothoracic ratio (CTR) and to use this measure for diagnosing GSD with altered cardiac size.AnimalsOne hundred clinically normal GSD as well as 46 GSD with altered cardiac size (microcardia or cardiomegaly).MethodsThe CTR was computed as the percentage area of the cardiac silhouette relative to the area of the dog's thorax. Measurements were performed using a digital software program on lateral and ventro-dorsal radiographs at the points of peak inspiration and expiration. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic accuracy of the CTR for diagnosing cardiomegaly or microcardia.ResultsThe mean (±SD) CTR on lateral radiographs of normal dogs was 27.60% ± 1.10% and 30.13% ± 1.42% at the points of peak inspiration and expiration, respectively. For ventro-dorsal radiographs, mean CTR was 30.45% ± 1.39% at peak inspiration and 33.34% ± 1.46% at peak expiration. The cutoff value of the CTR for diagnosing microcardia on lateral radiographs was 22.98% (inspiration) and 25.06% (expiration), compared to 25.03% (inspiration) and 23.97% (expiration) on ventro-dorsal radiographs. Cutoff values for diagnosing cardiomegaly were 30.28% (inspiration) and 33.44% (expiration) on lateral radiographs and 36.80% (inspiration) and 37.99% (expiration) on ventro-dorsal radiographs.ConclusionsCTR may provide a clinically useful tool for evaluating cardiac size in dogs.     

Digital Agenesia in Martina Franca Donkey Foal: A Case Report

A 4-day-old male Martina Franca donkey foal was evaluated for a forelimb alteration. Clinical examination and radiographs revealed the agenesia of the distal digit. Biochemical parameters were normal, and ultrasonographic evaluation did not identify any relievable organ alteration. Karyotype study revealed an abnormality on chromosome 1. The foal was discharged with a distal limb bandage in which a palmar splint was applied. A poor prognosis for the functionality of the limb was given. In endangered species, such as the Martina Franca donkey, the excessive inbreeding could result in an increase in genetic disorders. These findings shed new light on the possible pathogenesis of the digital dysgenesia. The study of the karyotype could be a useful approach to detect genetic alterations that could or could not be expressed in the animal, especially in endangered species in which a risk of an excessive inbreeding is considerable. These defects should be considered in the choice and selection of the breeders.     

Atypical Radiologic Appearance of a Second Cervical Vertebral Fracture in a Horse

This report presents the case of a 21-year-old Warmblood mare referred to the clinic with neurological dysfunctions and considerable signs of discomfort. A fracture of the caudal vertebral body of C2 with a very unusual radiographic appearance was diagnosed, and the mare was euthanized due to deterioration in neurological status. Histology revealed no evidence of neoplasia or pathological fracture.