Evaluation of the normal gastrointestinal tract in cats using dual-phase computed tomography.

OBJECTIVES: In cats, although ultrasonography remains the preferred modality to evaluate the gastrointestinal tract, computed tomographic (CT) examination of the abdomen is commonly performed. However, a normal description of the gastrointestinal tract is lacking. This study describes the conspicuity and contrast enhancement pattern of the normal gastrointestinal tract in cats using dual-phase CT. MATERIALS AND METHODS: Pre- and dual-phase postcontrast (early scan at 30 seconds and late scan mean at 84 seconds) abdominal CT exams of 39 cats without history, clinical signs or diagnosis of gastrointestinal disease were reviewed. The gastrointestinal tract was examined for conspicuity and enhancement pattern using commercially available viewing software (Osirix, v.6.5.2), and diameters of 16 gastrointestinal segments were recorded and compared with published radiographic and ultrasonographic reference values. RESULTS: Of the 624 gastrointestinal segments, 530 (84.9%) were identified on precontrast studies and 545 (87.3%) segments on postcontrast studies. Of the gastrointestinal wall segments, 257 (41.2%) were identified on precontrast studies and 314 (50.3%) on postcontrast studies. Gastrointestinal segment diameters correlated well with published normal values, whereas wall thickness measurements usually were smaller compared with sonographic normal values. Early mucosal surface enhancement was frequently seen in the gastric cardia and fundus and ileocolic junction, and a mainly transmural wall enhancement in other gastrointestinal segments. CLINICAL SIGNIFICANCE: Dual-phase CT allows for the identification of gastrointestinal tract segments and walls in cats. Contrast enhancement improves conspicuity and demonstrates wall layering in the cardia, fundus and ileocolic junction.

Use of dual-phase contrast computed tomography for evaluation of the normal canine male genital tract.

OBJECTIVES: To evaluate the use of dual-phase contrast-enhanced computed tomography for the depiction of the features of the male genital tract, highlighting differences between entire and neutered dogs. METHODS: Computed tomography exams of 23 entire and 23 neutered male dogs with no history of urogenital disease were included in this retrospective study, with exams acquired pre-, 30 and 98·9 ±27·4 seconds after intravenous contrast administration. The genital structures were subjectively evaluated for visibility, contrast enhancement and enhancement pattern and differences between entire and neutered dogs were described. Objective measurements of attenuation and size of the prostatic tissue were acquired. RESULTS: The root, body and glans of the penis could be evaluated in all dogs and appeared larger in entire dogs, though objective measurements could not be reliably made because these structures are small and curved. There was contrast enhancement of the cavernous structures, most reliably in the bulb and corpus spongiosum and most frequently in entire dogs in the delayed post-contrast phase. In entire dogs, the small testicular vessels most commonly had a vermiform shape in the early post-contrast phase, and a homogeneous appearance in the delayed phase. Sternal recumbency with the coxofemoral joints extended improved visibility of the genital structures. CLINICAL SIGNIFICANCE: Dual-phase contrast-enhanced computed tomography is useful for depiction of the structures of the male genital tract, with the early phase especially highlighting the vascular and the delayed phase the cavernous structures.

Radiographic anatomy of juvenile bovine limbs.

Juvenile bovine patients who present with clinical signs of lameness are commonly evaluated using radiographic techniques both within a hospital setting and in a farm environment. The radiographic development of the juvenile bovine skeleton is currently poorly documented. In this study, the limbs of four heifer calves were sequentially radiographed to assess development of the juvenile bovine appendicular skeleton in the first 12 months of life. Images were acquired at three weeks, three months, six months, nine months and one year of age. The normal radiographic anatomy of the fore limbs and hindlimbs and the changes over the first 12 months are described. The majority of physes remain open throughout this period, with the exception of the proximal physes of the proximal and middle phalanges, the proximal radial physis, and the proximal humeral physis which close radiographically between 9 months and 12 months of age, and fusion of the fourth and central tarsal bones occurs between 9 months and 12 months of age. The results of this study may aid in differentiating normal and abnormal anatomy in the juvenile bovine limb.

Visceral smooth muscle α-actin deficiency associated with chronic intestinal pseudo-obstruction in a Bengal cat (Felis catus x Prionailurus bengalensis).

An adult Bengal cat (Felis catus × Prionailurus bengalensis) with a prolonged history of partial anorexia, regurgitation, and weight loss and a clinical, radiographic, and ultrasonographic diagnosis of persistent megaesophagus and gastrointestinal ileus was submitted for necropsy. The intestinal tract was diffusely distended by gas and fluid with appreciable loss of muscle tone and an absence of luminal obstruction, consistent with the clinical history of chronic intestinal pseudo-obstruction. Histologically, the autonomic nervous system was intact, but the smooth muscle within the gastrointestinal wall exhibited a marked basophilia that was most pronounced in the jejunum. Immunohistochemistry for neurofilament, synaptophysin, CD117, and desmin demonstrated that the number of myenteric ganglia, number of interstitial cells, and leiomyocyte desmin content were similar when compared with the unaffected age- and species-matched control. Immunohistochemistry for smooth muscle α-actin demonstrated a striking loss of immunoreactivity, predominantly in the circular layer of the jejunum, that corresponded with the tinctorial change in leiomyocytes. Transmission electron microscopy revealed loss of myofibrils, loss of organelle polarity, and significantly larger central mitochondria (megamitochondria) in affected leiomyocytes, as well as nonspecific degenerative changes. Although the presence of a primary leiomyopathy and a causal relationship could not be confirmed in this case, leiomyopathies are considered a cause of chronic intestinal pseudo-obstruction in human medicine, and loss of smooth muscle α-actin immunoreactivity is one recognized marker for intestinal dysmotility.

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.

Osteosarcoma of the maxilla with concurrent osteoma in a southern sea otter (Enhydra lutris nereis).

Southern sea otters (Enhydra lutris nereis) are threatened marine mammals that belong to the family Mustelidae and are native to the coast of Central California. Neoplasia is reported infrequently in sea otters. An adult female free-ranging southern sea otter was found alive at Pebble Beach, Monterey County, California, on January 1st, 1994 and died soon after capture. The carcass was submitted to the US Geological Survey - National Wildlife Health Center for necropsy examination. Grossly, a mass with rubbery texture was firmly attached to the left maxillary region of the skull and the nasopharynx was occluded by soft neoplastic tissue. Post-mortem skull radiographs showed an oval, smoothly marginated mineralized opaque mass centered on the left maxilla, extending from the canine tooth to caudal to the molar and replacing portions of the zygomatic arch and palatine and temporal bones. The majority of the mass protruded laterally from the maxilla and was characterized by central homogeneous mineral opacity. Microscopically, the mass was characterized by fully differentiated lamellar non-osteonal bone that expanded beyond the margins of the adjacent normal osteonal bone. Sections of the nasopharyngeal mass were comprised of moderately pleomorphic cells with bony stroma. Gross, microscopical and radiological findings were compatible with maxillary osteosarcoma with concurrent osteoma.

Comparison of computed tomography and magnetic resonance imaging for the evaluation of canine intranasal neoplasia.

OBJECTIVES: Canine intranasal neoplasia is commonly evaluated using computed tomography to indicate the diagnosis, to determine disease extent, to guide histological sampling location and to plan treatment. With the expanding use of magnetic resonance imaging in veterinary medicine, this modality has been recently applied for the same purpose. The aim of this study was to compare the features of canine intranasal neoplasia using computed tomography and magnetic resonance imaging. METHODS: Twenty-one dogs with confirmed intranasal neoplasia underwent both computed tomography and magnetic resonance imaging. The images were reviewed retrospectively for the bony and soft tissue features of intranasal neoplasia. RESULTS: Overall computed tomography and magnetic resonance imaging performed very similarly. However, lysis of bones bordering the nasal cavity and mucosal thickening was found on computed tomography images more often than on magnetic resonance images. Small amounts of fluid in the nasal cavity were more often seen on magnetic resonance images. However, fluid in the frontal sinuses was seen equally well with both modalities. CLINICAL SIGNIFICANCE: We conclude that computed tomography is satisfactory for evaluation of canine intranasal neoplasia, and no clinically relevant benefit is gained using magnetic resonance imaging for intranasal neoplasia without extent into the cranial cavity.

Peripheral washout phenomenon in an animal tumour model: comparison of dynamic magnetic resonance imaging using a small molecular contrast medium with histology.

The peripheral washout sign was first described in delayed dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a small molecular contrast medium in solid lesions of the human breast and liver. It was found to be 100% specific for malignant lesions and could therefore potentially be used as an additional noninvasive diagnostic tool differentiating malignant from benign lesions. The origin of this phenomenon has not yet been explained. The objective of this study was to translate the peripheral washout sign as seen in solid tumours in delayed DCE-MRI in human onto an animal model for further assessment of DCE-MRI characteristics and histological analysis. Small molecular contrast medium DCE-MRI was performed over 42 min in experimental colon carcinoma grown subcutaneously in rats. Qualitative and quantitative analyses for evaluation of presence and characteristics of the peripheral washout sign were accomplished, defining four centripetally distributed tumour zones (central, intermediate, peripheral and marginal). One hundred per cent of the carcinomas demonstrated a peripheral washout sign in DCE-MRI starting at 20 min after bolus injection. Histomorphological analysis was performed for tissue classification and evaluation of microvasculature. Quantitative analysis revealed different enhancement profiles of the four tumour zones. Histology indicated centripetally asymmetric vascularization and vascular endothelial growth factor VEGF/VEGF receptor 2 expression within the tumour tissue. Thus, peripheral washout sign can be translated to an animal model. However, comparison of small molecular contrast medium DCE-MRI with histology revealed that histology alone does not explain the occurrence of the peripheral washout.

Nonimaging light concentration using total internal reflection films.

We present a method of fabricating nonimaging light concentrators from total internal reflection film. A prototype has been made and tested and found to operate in agreement with predictions of ray-tracing codes. The performance of the prototype is comparable with that of concentrators made from specular reflecting materials.