COMPUTED TOMOGRAPHIC CHARACTERISTICS OF INTRAPELVIC MASSES IN DOGS

In people, the computed tomography (CT) characteristics of intrapelvic masses can be used to distinguish a malignant from a benign mass. As prognosis varies greatly between malignant and benign intrapelvic masses, knowledge of their biological behavior can aid treatment planning before surgery. The purpose of this study was to determine if CT characteristics exist to help differentiate benign from malignant intrapelvic masses in dogs. The CT images of 14 dogs with a histopathologically confirmed intrapelvic mass were evaluated. Postcontrast internal heterogeneity of the mass was the only characteristic significantly associated with malignancy (P=0.005). Preoperative CT examination of intrapelvic masses in dogs can provide prognostic information before invasive surgical treatment.     

COMPUTED TOMOGRAPHIC APPEARANCE OF INFLAMMATORY POLYPS IN THREE CATS

This report describes the use of computed tomography (CT) to evaluate the inner ear, tympanic bullae, nasopharyngeal area, and external ear canals of three cats. All cats presented for evaluation of upper respiratory signs or chronic ear infection. Nasopharyngeal masses were present in two cats, and a mass in the external ear canal was present in the third cat. In all three cats, CT was able to define the extent of osseous bulla involvement, which was confirmed at surgery. Computed tomography also defined the extent of the polyp in the nasopharyngeal area in two cats, and in the external ear canal in one cat. Surgical removal of the polyps was accomplished with a combined oral approach and ventral bulla osteotomy in cats 1 and 2. The polyp was removed from cat 3 using a combination of ventral bulla osteotomy and excision of the mass through the external ear canal. Microscopic examination confirmed all masses as nasopharyngeal (inflammatory) polyps.     

COMPUTED TOMOGRAPHY OF NECROTIZING MENINGOENCEPHALITIS IN 3 YORKSHIRE TERRIERS

A necrotizing meningoencephalitis of Yorkshire terriers has recently been reported in 6 dogs in Switzerland, 1 dog in Japan and 1 dog in the United States. The purpose of this report is to describe the computed tomographic (CT) findings in 3 dogs with this disease, and to correlate the CT abnormalities with the clinical and pathologic findings in each case. Three Yorkshire Terriers between 2 and 10 years old were evaluated. Physical and neurologic examinations, complete blood count (CBC), serum biochemistry profile, cerebrospinal fluid analysis, and CT scan were performed on all 3 dogs. Brainstem auditory evoked responses (BAER) were evaluated for 2 dogs. Two dogs were euthanized at the owners' request and necropsies were performed. Neurologic examination findings were consistent with a multifocal/diffuse encephalitis involving the cerebrum and brainstem in all 3 dogs. Complete blood count and biochemistry profiles were normal. Elevated protein concentration and a mononuclear pleocytosis were demonstrated in 2 of 3 dogs on cerebrospinal fluid evaluation. Multifocal, extensive areas of decreased opacity throughout the cerebral hemispheres, asymmetric ventriculomegaly, and lack of contrast enhancement were appreciated on CT images of all three dogs. No mass effect was seen. These findings correlated well with pathologic findings at necropsy, which included multiple malacic cavitations within the brain, representing areas of locally extensive necrosis. CT abnormalities in combination with signalment, clinical findings and cerebrospinal fluid analysis should facilitate a presumptive diagnosis of Yorkshire Terrier necrotizing meningoencephalitis.     

COMPUTED TOMOGRAPHIC FEATURES OF BASIHYOID ECTOPIC THYROID CARCINOMA IN DOGS

Eight dogs with a firm, nonpainful swelling in the ventral laryngeal region and with a final diagnosis of ectopic thyroid carcinoma were investigated by Computed Tomography (CT) at six different institutions. Computed Tomography findings were reviewed, focusing on lesion volume, shape, margins, relationship with surrounding structures and adjacent vessels, attenuation characteristics, and presence of metastases. Ectopic thyroid carcinomas were seen as oval‐to‐bilobed masses centered on the basihyoid bone with associated bone lysis, highly vascularized capsules with central poorly contrast enhancing areas. In all cases there was laryngeal wall infiltration, in two dogs invasion of the laryngeal lumen and in one case invasion of the ventral muscular and subcutaneous plane. Metastases were found in retropharyngeal lymph nodes (three cases) and in the lung (two cases). Ectopic thyroid carcinoma should be considered in the differential diagnosis when a mass in the basihyoid region is present. Described CT features may be typical for ectopic thyroid neoplasia and could be used to help decide the therapeutic plan.     

COMPUTED TOMOGRAPHIC APPEARANCE OF PRIMARY LUNG TUMORS IN DOGS

Canine primary lung tumors typically appear radiographically as a well‐circumscribed solitary mass in the periphery of a caudal lung lobe. Consolidated and diffuse forms of primary lung tumors have also been described. Nineteen dogs with computed tomographic (CT) images of the thorax and a histological diagnosis of primary lung tumor (17 primary carcinomas and two primary sarcomas) were evaluated retrospectively to characterize the CT findings. All primary lung tumors were bronchocentric in origin with internal air bronchograms. The bronchi were typically narrowed, displaced, and often obstructed by the tumor. Eighteen of 19 (95%) of the tumors were solitary and there was one pneumonic/alveolar form. Most solitary tumors were well circumscribed (17/18), located in the central to periphery of the lung (14/18), and in a cranial or caudal lobe (16/19). Most primary lung tumors (11/17) had mild to moderate heterogeneous contrast enhancement. Five of 19 dogs (26%) had evidence of pulmonary metastasis. Internal mineralization (3/19) and tracheobronchial lymphadenopathy (4/19) were also identified. On CT examination, solitary, well circumscribed, bronchocentric masses with internal air bronchograms are consistent with a primary pulmonary tumor in dogs.     

COMPUTED TOMOGRAPHIC IMAGING OF INFILTRATIVE LIPOMA IN 22 DOGS

Twenty two dogs with an infiltrative lipoma had computed tomographic (CT) images acquired to evaluate the extent of local disease. Ten dogs had undergone at least one cytoreductive surgical procedure (range = 1-3; median = 2) prior to imaging. Twenty dogs had measurable disease on CT images; 2 dogs had diffuse disease at a previous surgical site that could not be measured. Tumor volume (n = 20) ranged from 20 to 5,632 cm3 (median = 345 cm3; mean = 996 cm3). None of the dogs had evidence of bone involvement on the CT images; 2 of the 22 dogs had tumors that did not come into direct contact with osseous structures. All dogs with measurable disease had evidence of a fat opacity mass with variable degrees of muscle infiltration. Eleven of 22 dogs were given intravenous contrast medium prior to image acquisition and there was not evidence of enhancement of the infiltrative lipoma in any dog. Based on CT images, tumors were classified as well-defined in 9 dogs, moderately well-defined in 4, not well-defined in 3 and a mix of well-defined and not well-defined in 6 dogs. Tumors tended to be less well-defined in regions where the infiltrative lipoma interdigitated with normal body fat. It appears CT imaging allows adequate discrimination of tumor with the caveat that differentiation of normal fat from infiltrative lipoma can be problematic.     

USE OF COMPUTED TOMOGRAPHY IN THE DIAGNOSIS OF A CEREBRAL ABSCESS IN A GOAT

A 7-month-old La Mancha doe was presented with a right head tilt and ventral strabismus while circling to the left. History and physical examination led to a tentative diagnosis of a cerebral abscess. Computed tomography revealed a large, complex mass with ring enhancement in the left cerebral hemisphere, supporting the diagnosis. Postmortem examination confirmed the cerebral abscess. Bacterial cultures yielded heavy growth of Actinomyces pyogenes.     

RETROSPECTIVE ASSESSMENT OF COMPUTED TOMOGRAPHIC IMAGING OF FELINE SINONASAL DISEASE IN 62 CATS

Sixty-two cats with sinonasal disease were evaluated with computed tomography. Findings that may lead to a computed tomographic diagnosis of nasal neoplasia versus rhinitis included osteolysis of the paranasal bones, moderate to severe turbinate destruction, lysis of the nasal septum, the presence of a homogenous space occupying mass, and extension of the disease process into the orbit or facial soft tissues. These findings were not pathognomonic for neoplasia and may be associated with severe rhinitis; therefore, nasal biopsy was recommended. When compared with parallel radiographic studies, computed tomography was not more sensitive than radiographs at detecting the presence of nasal cavity abnormalities in cats with referable clinical signs but was more sensitive at localizing these changes and determining the extent of disease.     

THE COMPUTED TOMOGRAPHIC APPEARANCE OF ACUTE THORACOLUMBAR INTERVERTEBRAL DISC HERNIATIONS IN DOGS

The appearance of herniated intervertebral disc material in the thoracolumbar vertebral canal was evaluated in 23 dogs using computed tomography (CT). The images were then compared with the myelographic and surgical findings. The normal spinal cord, outlined by epidural fat over intervertebral disc spaces, was of intermediate attenuation on transverse CT images. Herniated disc material was identified in all animals as a heterogeneous hyperattenuating extradural mass. The attenuation of the disc material increased with the degree of mineralization. In seven dogs, the herniated material was only slightly more attenuating than the spinal cord. In these dogs, small fragments of mineralized disc material and significant hemorrhage were found in the epidural space at surgery. In dogs with a long standing history of disc herniations, disc material identified in the vertebral canal had a more hyperattenuating and homogeneous appearance than recently herniated disc material. We conclude that mineralized, herniated disc material and hemorrhage can be identified quickly and safely in dogs using CT.     

COMPUTED TOMOGRAPHIC EVALUATION OF CANINE AND FELINE MEDIASTINAL MASSES IN 14 PATIENTS

A 15-year retrospective analysis of histologically proven canine and feline mediastinal malignancies at the University of Minnesota was conducted to identify patients imaged by computed tomography (CT). The goal of the study was to characterize the CT appearance, to determine if there were any tumor type-specific appearances, and to clarify the role of CT in patients with mediastinal masses. Fourteen patients meeting these criteria were available for evaluation. The masses were characterized based on the presence or absence of contrast enhancement, internal architecture, size, extent of local invasion, the presence of pleural fluid, and the presence of regional vascular invasion. Within the limits of this study and the histopathologic information available, there appeared to be no clinically exploitable relationship between the CT appearance and the histologic characterization of the mass. However, CT does provide reasonably accurate local staging information.     

COMPUTED TOMOGRAPHIC FINDINGS IN OVINE COENUROSIS

Computed tomographic imaging was conducted in twenty ewes with cerebral coenurosis. CT imaging allowed precise evaluation of the size and location of the cyst, which appeared as a hypoattenuating structure with a mass effect. No meaningful correlation between clinical signs and the location of parasitic cyst was detected.     

COMPUTED TOMOGRAPHIC APPEARANCE OF MELANOMAS IN THE EQUINE HEAD: 13 CASES

Melanomas are one of the most common neoplasms in the horse and are frequently found in the head region. There is a genetic predisposition in horses with a gray hair coat. Computed tomography (CT) is frequently used in referral practice to evaluate the equine head but there are few reports describing the CT appearance of melanomas in this location. The aim of this retrospective, case series study was to describe characteristics in a group of horses with confirmed disease. Case records from two referral hospitals were reviewed, and 13 horses were identified that had undergone CT of the head, with a diagnosis of melanoma based on cytology, histopathology, or visual assessment of black (melanotic) tissue. A median of 11 melanomas was identified per horse (range 3–60), with a total of 216 masses. Melanomas were found most frequently in the parotid salivary gland, guttural pouches, surrounding the larynx and pharynx and adjacent to the hyoid apparatus. In noncontrast CT images, all melanomas were hyperattenuating (median; 113.5 Hounsfield units (HU), IQR; 26 HU) compared to masseter musculature (median; 69 HU, IQR; 5.5 HU). Fifty‐six (25.9%) masses were partially mineralized and 41 (19.4%) included hypoattenuating areas. Histopathological assessment of these melanomas suggested that the hyperattenuation identified was most likely a result of abundant intracytoplasmic melanin pigment. Melanomas of the equine head appeared to have consistent CT features that aided detection of mass lesions and their distribution, although histopathological analysis or visual confirmation should still be obtained for definitive diagnosis .     

IMAGING DIAGNOSIS—COMPUTED TOMOGRAPHIC,SURGICAL, AND HISTOPATHOLOGIC CHARACTERISTICS OF AN INFILTRATIVE ANGIOLIPOMA IN A DOG

A 6‐year‐old female spayed Shetland Sheepdog presented for evaluation of a subcutaneous mass over the right prescapular region. The mass had been cytologically diagnosed as a lipoma by the referring veterinarian 20 months prior, but had grown significantly and was very firm. CT scan of the mass was suggestive of neoplasia; however, the tissue of origin could not be determined. Histopathologic evaluation diagnosed infiltrative angiolipoma, and marginal resection of the tumor was performed. Infiltrative angiolipomas are benign but locally aggressive neoplasms uncommonly reported in veterinary medicine. This report correlates the clinical, CT, and histopathologic characteristics of an infiltrative angiolipoma.     

A COMPUTED TOMOGRAPHIC STUDY OF VOLUME AND X-RAY ATTENUATION OF THE LUNGS OF BEAGLES IN VARIOUS BODY POSITIONS

The influence of body position on volume and x-ray attenuation of the lungs of three Beagles was investigated with computed tomography. In left and right lateral recumbency, the dependent lung had decreased volume and increased x-ray attenuation compared with ventral recumbency. Volume and x-ray attenuation of the nondependent lung, however, were unchanged. In dorsal recumbency, there was a vertical gradient of x-ray attenuation being increased dorsally and decreased ventrally compared with ventral recumbency where regional differences in x-ray attenuation were not found. Results indicate a risk of overlooking a mass in the dependent pulmonary parenchyma of dogs in lateral and dorsal recumbency. Regional differences in x-ray attenuation of the lungs of dogs can be avoided if the radiographs are obtained with the dog in ventral recumbency.     

COMPUTED TOMOGRAPHIC ANATOMY OF THE CANINE PANCREAS

Barium sulfate was administered into the coeliac artery of 5 canine cadavers to allow for contrast computed tomography of the pancreas. Contiguous, 2-mm-thick slices were acquired. Multiplanar and three-dimensional reformatting were performed to clarify the anatomic relationship. After imaging, the cadavers were frozen, cross sections obtained, and plastinated. These were compared to the computed tomography images. Five plain and contrast enhanced computed tomographic series of normal live controls were acquired and evaluated retrospectively. In the study of the canine cadavers the pancreas became opacified and appeared homogenous with irregular contour. In normal live controls, acquiring an image at the end of expiration allowed a detailed view of the pancreatic parenchyma in the non-alterated pancreas, but pancreatic and bile ducts could not be seen. Adjacent to the hepatic hilus the pancreatic body appeared as a dorsoventrally flattened structure bordering on the ventral surface of the portal vein, both in cadavers and normal live controls. The right lobe extended caudodorsally to the right abdominal wall and aligned with the cranial part of the duodenum. The left lobe was adjacent to the gastric body in all dogs although it was separated from the gastric fundus by the dorsal extremity of the spleen in normal live controls. Neither kidney was suitable as an anatomic marker for localization of the pancreas, unlike traditional references in textbooks. We recommended using the portal vein to localize the pancreatic body, the descending duodenum for the right lobe, and the dorsal extremity of the spleen as well as the gastric fundus for the left lobe.     

COMPUTED TOMOGRAPHIC ANATOMY OF THE EQUINE TARSUS

The purpose of this study was to provide a detailed computed tomographic (CT) anatomic reference for the equine tarsus. CT examinations of the tarsal regions from four clinically and radiographically normal adult horses, which were euthanized for reasons not related to musculoskeletal disease, were included in the study. Limbs were removed at the level of midtibia, and 3-mm contiguous transverse CT images were obtained, starting at a level proximal to the tuber calcanei and continuing distally into the proximal metatarsus. Soft tissue and bone windows were used to image different anatomic features, including bones, joints, and various soft tissue components of the tarsus. Each transverse slice was compared with bone models and dissected specimens to assist in the accurate identification of specific structures. The results of the study consist of nine CT images of the equine tarsus. Each image incorporates labeled soft tissue and bone-window images, a directional compass indicating cranial (Cr) or dorsal (D) and lateral (L), and a reconstructed scout image indicating the level through which the transverse slice was made.     

COMPUTED TOMOGRAPHIC DETERMINATION OF TIBIAL TORSION IN THE DOG

The goal of this study was to develop a method for computed tomographic (CT) measurement of tibial torsion, and to compare this technique with direct anatomic measurement of tibial torsion in cadaveric canine tibiae. Paired hind limbs of 10 cadaveric dogs were mounted on a custom-designed limb holding apparatus. One-millimeter thick, contiguous, transverse CT slices were obtained from the distal femur to the proximal tibia and 2 mm CT slices were obtained from the distal tibia to the proximal tarsus. The tibiae were freed of soft tissues and digital photographic images of the proximal and distal articular surfaces were obtained with the camera lens aligned perpendicular to the long axis of the tibia. Multiple proximal and distal tibial axes were identified on the images; two proximal and two distal axes were found to be repeatable in all specimens in both the direct and CT methods. The torsion angle was calculated by determining the difference between the axis angles for each pair of proximal and distal axes. There was no significant difference in torsion angle identified between the direct photographic and CT method for any pair of proximal and distal axes. CT determination of tibial torsion is a rapid and accurate method, and warrants investigation in clinical patients.     

DYNAMIC COMPUTED TOMOGRAPHY OF THE PANCREAS IN NORMAL DOGS AND IN A DOG WITH PANCREATIC INSULINOMA

To establish optimal imaging conditions for enhanced computed tomography (CT) for canine pancreatic tumors, 10 healthy beagles were subjected to dynamic CT. This technique was then applied to a dog with suspected insulinoma. The changes in mean peak enhancement and the delay time of the aorta and pancreas were determined. In normal beagles, maximal arterial and pancreatic CT enhancement was observed at 15 +/- 2 s (795 +/- 52 Housfield unit [HU]) and 28 +/- 9 s (118 +/- 16HU) after contrast medium injection, respectively. Multiphase enhanced CT was performed in a pug with suspected insulinoma using the CT protocol defined for the normal beagles with some parameters modified; the images were acquired at the arterial (14 s after contrast medium injection), pancreatic (after 28 s), and equilibrium (after 90 s) phases; scanning was followed by exploratory laparotomy. CT images were characterized by an enhanced mass in the left pancreatic lobe at the arterial phase, during which the difference between the CT values of the mass and normal pancreas was the highest. Histopathologic diagnosis of the pancreatic mass was insulinoma. Thus, it appears that enhanced CT imaging can be used to delineate the pancreas from a pancreatic mass, and it may be helpful in deciding the need for surgery.     

RADIOGRAPHIC AND COMPUTED TOMOGRAPHIC CHANGES AND CLINICAL PRESENTATION OF SPIROCERCOSIS IN THE DOG

A retrospective study of 39 dogs with spirocercosis is described, emphasizing radiographic and computed tomographic aspects and clinical presentation. Dogs were classified as complicated or uncomplicated, both clinically and radiographically. Besides the expected upper gastrointestinal signs, a high incidence of respiratory (77%) and locomotor (23%) complications were present. All dogs had thoracic radiographs. Esophageal masses were radiographically classified as typical or atypical according to their location. Twenty-seven dogs had a typical caudal esophageal mass. Six dogs had a mass atypically located in the hilar region. These masses were smaller and more difficult to visualize radiographically. The remaining 6 dogs did not have a radiographically detectable esophageal mass. Radiology as an initial diagnostic tool was effective in detecting and localizing the mass and to detect early respiratory abnormalities such as pleuritis, mediastinitis, pneumonia, and bronchial displacement. Endoscopy was the modality of choice to confirm antemortem esophageal masses. In dogs where the mass filled the whole esophageal lumen, endoscopy failed to give essential information necessary for surgical excision of neoplastic masses, such as the extent of esophageal wall attachment. Caudal esophageal sphincter involvement was difficult to determine endoscopically with large caudal esophageal masses. Computed tomography was performed on 3 dogs and did not address the latter problems completely, but was found to be a sensitive tool to detect focal aortic mineralization and early spondylitis, both typical for the disease, and essential in the diagnosis of non- or extramural esophageal abnormalities.