In vivo axial dynamization of canine tibial fractures using the Securos external skeletal fixation system.

Bilateral transverse mid-shaft tibial osteotomies, with a 4-mm gap, were performed in purpose-bred research dogs and stabilized using a Securos Type 2 external skeletal fixotor (ESF). Full (100%) axial dynamization of one randomly selected ESF in each dog was performed at 31 days postoperatively. Caudo-cranial radiographs were obtained at weekly intervals, which were qualitatively and quantitatively evaluated (densitometry and ImageJ analysis). The dogs were euthanatized 13 weeks postoperatively, at which time dual energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), mechanical testing in torsion, and qualitative histological analysis were performed. A two-tailed paired Student's t-test was performed for statistical analysis of all parameters of interest, with significance set at p < 0.05. Three of five dynamized bones bridged quicker, and four of five dynamized bones appeared to have greater callus formation, however, statistically significant differences could not be definitively determined. Statistically significant differences were not found with densitometry (any time frame), DEXA, pQCT, torsional stiffness or maximum torque. Despite the lack of statistically relevant data, trends were observed with larger callus size and density in the dynamized tibiae. The dynamized tibiae appeared to fracture more consistently outside of the area of the healing callus as compared to the control tibiae. Histological evaluation showed greater remodelling in four of five control limbs when compared to the dynamized limb. Dynamization at 31 days post-operatively may delay bone remodelling, despite a trend towards a larger callus size. The results of this study failed to show a definitive role for early full axial dynamization.

Cross-sectional imaging techniques in veterinary ophthalmology.

Ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) are useful, complementary cross-sectional imaging modalities of the eye and orbit. High-resolution US provides excellent morphological information of ocular structures but offers limited information on the periocular tissues. CT and MRI provide valuable morphologic and topographic images of both ocular and periocular structures, thereby giving a more complete picture of the pathological process. US can be performed on awake patients, whereas CT and MRI require general anesthesia. In addition, US equipment is readily available and less costly than CT or MRI units. Fine-needle aspirations and biopsies under US or CT guidance can also be performed. This article reviews the technique and normal findings of ocular and orbital structures as displayed in each of these imaging modalities. Representative clinical cases are presented to illustrate the interpretation principles as well as to provide an illustrative reference for common ocular and orbital changes.

MR imaging findings in a dog with intravascular lymphoma in the brain.

Intravascular lymphoma (malignant angioendotheliomatosis, angiotrophic lymphoma) is a rare neoplastic disorder in dogs. The literature contains few reports in dogs and a single report in a cat. Intravascular lymphoma is characterized by an intravascular proliferation of malignant lymphocytes. This unique angiocentric distribution of neoplastic cells leads to the characteristic clinicopathologic feature of thromboses and infarctions. In people, intravascular lymphoma has a predilection for vessels in the central nervous system (CNS) and skin. Typically, affected patients have episodic symptoms that coincide with the timing of infarctions. This report details the clinicopathologic description and magnetic resonance (MR) images of a dog with intravascular lymphoma that resulted in multiple CNS infarctions. Abnormalities identified with MR imaging consisted of multifocal hyperintensities observed in pre-contrast T1-weighted, T2-weighted, intermediate-weighted, and FLAIR pulse sequences. Lesions were most conspicuous on the FLAIR images. In addition, there was mild enhancement of the lesions seen in post-contrast T1 weighted images.

Retrospective review of the ultrasonographic features of adrenal lesions in 21 ferrets.

Clinical signs and follow-up information were recorded. Histopathologic diagnoses were obtained for 25 adrenal glands in 21 ferrets. Adrenal lesions included ten adenocarcinomas, nine adenomas, one hyperplasia and one cortical cyst. Four adrenal glands (all right-sided) were diagnosed as unspecified adrenal tumors but lacked a definite histopathologic diagnosis (adenoma vs. adenocarcinoma) due to incomplete surgical resection and consequent small sample sizes. Bilateral adrenal lesions were identified in 4 ferrets (19%). Adrenal shape, size, echogenicity, laterality, and the presence of vascular invasion were evaluated with ultrasound. Size and shape were variable and not specific to lesion type. Both benign and malignant adrenal tumors (adenomas, adenocarcinomas) appeared most often as masses with increased thickness and a normal length (11/23), less frequently as larger masses with increased thickness and length (4/23) or as nodules focally deforming the normal adrenal shape (6/23). The only cortical cyst appeared as a nodule. Three adrenal glands had a normal size and shape and were diagnosed as adenomas (2) or hyperplasia (1). Therefore treatment may be warranted based solely on clinical signs if adrenal glands are ultrasonographically normal. Vascular invasion was not identified ultrasonographically. However, focal absence of periglandular fat resulting in contact of 8 adrenal glands with either caudal vena cava (6), aorta (1) or liver (1) identified ultrasonographically, correlated with incomplete surgical resectability (6/8) and histopathologic diagnoses of carcinoma (4/8) or unspecified tumors (4/8). Therefore, a focal absence of periglandular fat between the adrenal gland and the large vessels or liver, deviation or compression of the large vessels by the adrenal lesion may indicate malignancy. Adrenal tumors (benign and malignant) were often associated with a prominent uterus, uterine stump or prostate with or without prostatic cysts.

Advanced imaging concepts: a pictorial glossary of CT and MRI technology.

This article serves as an illustrative glossary of concepts related to computed tomography (CT) and magnetic resonance imaging (MRI) technology. The principles of tomography, digital processing, image resolution, CT windowing, CT gray levels, contrast enhancement, and MRI spin echo pulse sequences are reviewed. Techniques not commonly described for use in animal patients are also introduced, and include gradient echo, short time of inversion recovery, fluid attenuated inversion recovery and fat saturation pulse sequences, fast imaging, MRI angiography, perfusion and diffusion imaging, brain activation, CT angiography/functional CT, interventional procedures, and three-dimensional CT.

Alternative imaging of the lung.

This article illustrates the roles of ultrasonography, scintigraphy, and computed tomography (CT) as alternative techniques for pulmonary imaging in small animals. The advantages and limitations of each modality, normal anatomic features, and technical considerations will be discussed. Selected applications will be examined and include pulmonary consolidation, neoplasia and other masses, atelectasis, pneumothorax, dystrophic mineralization, diffuse infiltrative disease, and pulmonary embolism. The use of ultrasound and CT-guided interventional procedures will also be briefly discussed.

Ultrasonography of the thorax (excluding the heart).

Until recently, ultrasonography has had a subordinate role in the evaluation of the thorax in both small animals and humans, most likely due to the inability of sound to penetrate air-filled lung. When pathologic processes such as pleural effusion and lung consolidation provide an acoustic window to the thorax, however, thoracic ultrasonography becomes feasible. As this article illustrates, ultrasonography may be effectively employed in the diagnosis and management of various thoracic wall, pleural, mediastinal, pulmonary, and diaphragmatic diseases by providing valuable information not obtainable with routine radiography and enabling percutaneous aspiration or tissue core biopsy of lesions.

Computed tomography and magnetic resonance imaging of cavernous sinus enlargement in a dog with unilateral exophthalmos.

Computed tomography (CT), magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) were performed on a dog with a two year history of unilateral exophthalmos occurring two years following head trauma. On CT images, an expansile enhancing mass was present along the right intracranial cavernous sinus and extended through the orbital fissure into the retrobulbar space. With MRI, the structure appeared as a signal void due to the presence of rapidly flowing blood. Gadolinium enhancement of the adjacent brain was not present. A vascular origin of the lesion was confirmed with MRA. Based on the CT and MRI findings, the enlarged cavernous sinus and associated ophthalmic plexus were believed to represent an arterialized aneurysm, most likely the result of traumatic arteriovenous fistulization. Treatment consisted of surgical enucleation. At the time of this report, 29 months later, the dog remains free of clinical signs.

Imaging of adrenal gland disorders.

In recent years, diagnostic imaging has become an important adjunct to conventional endocrine testing in the evaluation of adrenal gland dysfunction. This article discusses the role of imaging in the diagnostic workup of the following adrenal gland disorders: hypercatacholaminism, hyperaldosteronism, hyperadrenocorticism, and hypoadrenocorticism. The strengths and limitations of radiography, ultrasonography, scintigraphy, CT scanning, and MR imaging are addressed.

Behavioral changes associated with suspected complex partial seizures in bull terriers.

OBJECTIVES: To identify and treat a range of abnormal behavior, including tail chasing, unprovoked aggression, and extreme irrational fear, in Bull Terriers and to correlate the behavioral signs with electroencephalogram (EEG) or anatomic evidence of abnormal brain geometry or deafness. DESIGN: Prospective clinical study. ANIMALS: 8 affected and 5 unaffected (control) Bull Terriers. PROCEDURE: All dogs were examined neurologically, including use of EEG, brainstem auditory-evoked response, and computed tomography or postmortem examination of the brain. In addition, plasma concentrations of zinc, copper, and iron, and the activity of zinc- and copper-dependent enzymes (alkaline phosphatase and ceruplasmin oxidase) were measured in affected and control dogs. RESULTS: An abnormal EEG was found in 7 of 7 affected dogs and in none of the control dogs subjected to this examination. Seven of 8 affected dogs and 2 of 3 controls had various degrees of hydrocephalus. Metal ion and enzyme concentrations were not different between affected and control dogs. Treatment with phenobarbital was effective in 5 of 7 dogs. CLINICAL IMPLICATIONS: Bull Terriers with compulsive tail chasing and extreme affective disorders should be regarded as neurologically disturbed, with partial seizures perhaps underlying their behavior. Treatment with anti-convulsants is a logical first step in treatment.

Pediatric neuroimaging.

In this article, some of the common and not-so-common neuropediatric disorders were discussed. As in the full-grown animal, abnormalities of the CNS in the pediatric animal patient may be classified according to the type of insult present (eg, malformation, injury, neoplasia, inflammation, or degeneration). To recognize the imaging manifestations of such disorders, an appreciation of normal anatomy, the pathological response of nervous system tissue to insult, and the principles of image interpretation is required. These fundamentals may then be applied to any CNS disease, regardless of frequency and to any animal patient, regardless of age.

Correction of mandibular nonunion and malocclusion by plate fixation and autogenous cortical bone grafts in two dogs.

Two dogs were treated for severe malocclusion secondary to segmental defects in the mandibular bodies as a result of nonhealing mandibular fractures. The problems of fibrous nonunions with large fracture gaps, the potential for infection, and the severe malocclusion were addressed in considering definitive surgical correction. The segmental defects in both dogs were spanned by use of autogenous cortical grafts (full-thickness rib segments or full cortical diaphyseal ulnar segments), supplemented with autogenous cancellous graft, and were stabilized with screw-and-plate fixation. Radiographic evaluation of bone healing and graft incorporation was difficult because of the implants, which obscured full observation of the bone graft sites. Successful graft revascularization, determined by 99mradiophosphate localization, was shown in both dogs; fairly uniform isotope uptake was observed throughout the graft sites and was continuous with the recipient bone. Mildly increased uptake was observed at 6 months and at 1 year after surgery and was considered consistent with remodeling associated with fracture healing. Observation of complete graft revascularization within 1 year provided ample evidence that the autografts were incorporated, with sufficient remodeling to characterize bone union.

Diagnostic pulmonary imaging.

This article examines four common but often confusing radiologic problems: the normal thoracic radiograph (performed when clinical suspicion of pulmonary disease is high), the solitary thoracic mass, loss of organ margination, and the mixed pulmonary pattern. Through the use of case examples, a systematic approach to each of the four problems is taken. Contrast and positional radiography, scintigraphy, ultrasonography, and computed tomography are discussed to demonstrate their applications in pulmonary imaging. A brief review of image formation and interpretation of alternate techniques will be provided. The discussion identifies some of the limitations of the radiographic examination, shows why they exist, and illustrates ways of overcoming them.