Ultrasonographic, computed tomographic and magnetic resonance imaging anatomy of the normal canine stifle joint

Ultrasonographic (US), magnetic resonance (MR) and computed tomographic (CT) images of normal canine stifle joints were obtained and compared with plastinated cross-sectional slices of cadaver specimens from the same dogs. The bony and articular structures were identified and correlated with the three diagnostic imaging modalities. These results provide an atlas of normal cross-sectional US, MR and CT anatomy of the canine stifle, which can be used for the interpretation of stifle images from any of these imaging modalities.     

Computed tomographic and magnetic resonance imaging features of canine segmental caudal vena cava aplasia

O bjective : To describe the computed tomographic and magnetic resonance imaging features of segmental caudal vena cava aplasia and associated vascular anomalies in dogs.
M ethods : A retrospective study was performed reviewing computed tomographic and magnetic resonance imaging archives of eight institutions for dogs with segmental caudal vena cava aplasia. Inclusion criteria included a computed tomographic or magnetic resonance imaging study and supportive diagnostic and follow-up information. Abdominal vessels were reviewed for size, shape, location and course (including tributaries and branches) and classified as normal, abnormal or shunt vessels.
R esults : Ten dogs with segmental caudal vena cava aplasia were identified. In all dogs, postrenal caval blood was shunted to either a right or a left azygos vein, with seven different angiographic patterns. Affected dogs were predominantly female (70 per cent) and young (mean 2·6 years). Additional portocaval and porto-azygos shunt vessels were identified in two cases each. Computed tomographic angiography and magnetic resonance angiography depicted details of abdominal vessels including thrombus formation in one dog.
C linical S ignificance : Segmental caudal vena cava aplasia is a vascular congenital anomaly in the dog that can be associated with thrombosis and portosystemic shunts. Computed tomographic angiography and magnetic resonance angiography are excellent tools to demonstrate the complex vascular anatomy and to guide treatment planning for portosystemic shunts and thrombolytic therapy.     

Helical computed tomographic anatomy of the canine abdomen

The purpose of this study was to provide an atlas of the normal anatomy of the canine abdomen using helical computed tomographic (CT) images of the abdomen in four mature cross-breed dogs. The dogs were supported in sternal recumbency under general anaesthesia and scans were performed with 5 mm collimation and a pitch of 1. All sections were imaged with soft-tissue window settings and the cranial abdomen was also imaged with mediastinum-vascular window settings. CT scans were performed immediately after iodinated contrast medium was injected into the cephalic vein at 2 mL/kg. Iodinated contrast medium (10 mL/kg) was administered orally 2 h before the scan with a further 3 mL/kg administered immediately prior to scanning. A cross-sectional anatomy atlas was used to identify the structures of the abdominal cavity. Clinically relevant anatomical structures were identified and labelled in the CT images.     

Use of computed tomographic densitometry to quantify contrast enhancement of compressive soft tissues in the canine lumbosacral vertebral canal

OBJECTIVES: To evaluate computed tomography (CT) densitometry as a technique for quantifying contrast enhancement of compressive soft tissues in the canine lumbosacral vertebral canal and to determine whether the degree of contrast enhancement can be used to help predict tissue type or histopathologic characteristics. ANIMALS: 29 large breed dogs with lumbosacral stenosis. PROCEDURE: Contrast-enhanced CT of L5-S3 was performed by use of a previously described protocol. At each disk level, CT densities of a water-filled syringe, epaxial muscles, and 4 vertebral canal locations were measured. Mean tissue enhancement was calculated by vertebral canal location, using water-filled syringe enhancement as a correction factor. Corrected CT enhancement was compared with tissue type, degree of tissue inflammation, and degree of tissue activity. RESULTS: Intravenous contrast administration of contrast medium significantly increased CT densities of water-filled syringes and epaxial muscles. Corrected CT enhancement of vertebral canal soft tissues at stenotic sites was greater than at nonstenotic sites. There was no association between enhancement and tissue type for any vertebral canal location. There was no correlation between enhancement and degree of tissue inflammation. There was a correlation between enhancement and tissue activity in the dorsal vertebral canal only. CONCLUSIONS AND CLINICAL RELEVANCE: A water-filled syringe is a useful calibration tool for CT density measurements. The degree of tissue contrast enhancement, measured by CT densitometry, can be helpful for predicting the location of compressive soft tissues in dogs with lumbosacral stenosis. However, it is of limited value for predicting compressive soft-tissue types or histopathologic characteristics.     

Computed tomographic features of the normal canine thyroid gland.

The computed tomographic (CT) features of the normal thyroid gland were compiled from images acquired in 25 client-owned dogs without thyroid gland disease. The mean pre- and postcontrast attenuation values were 107.5 and 169.0 Hounsfield Units, respectively. After injection of intravenous contrast medium (600 mg iodine/kg), the apparent thyroid gland volume (both lobes combined) increased from a mean value of 1148.0 nm3 to a mean value of 1188.9 mm3. All thyroid lobes were homogeneous on pre- and postcontrast images. In a craniocaudal direction, the gland spanned a region from the 1st to the 8th tracheal ring and the right lobe was often more cranial than the left. On transverse images the lobe shape was ovoid in 72%, and its location was dorsolateral to the trachea in 90% of dogs. Parathyroid glands could not be identified and an isthmus connecting both thyroid lobes was only seen in one dog. Considering the excellent visibility of the normal canine thyroid gland, CT can be beneficial in the differentiation of thyroidal versus nonthyroidal neck masses. CT also yields potential in the staging of thyroid carcinomas.     

Computed tomographic features of incomplete ossification of the canine humeral condyle

Objectives— To describe computed tomographic (CT) features of canine elbows with incomplete ossification of the humeral condyle (IOHC) and investigate co-existing incongruence in the elbow joint.
Study Design— Case control study.
Animals— Dogs with IOHC (n=20; 38 elbows) and 25 normal elbows.
Methods— Elbows with IOHC and normal elbows were assessed by CT. Standardized dorsal and sagittal reconstructions were created at 3 levels using image analysis software to obtain single measurements of the humero-radial and humero-ulnar joint spaces. On dorsal plane reconstructions, joint space measurements were obtained at the center point of the humero-radial and humero-ulnar articulations. Joint incongruity was defined as the difference between the humero-radial and the humero-ulnar joint spaces.
Results— Nineteen dogs (95%), all Spaniel breeds, had either bilateral IOHC demonstrable as a saw-toothed intercondylar complete or incomplete hypoattenuating defect with hyperattenuating margins, or IOHC with contralateral humeral condylar fracture (HCF). Joint incongruity values for IOHC were compared with those of normal elbows. Significant differences were noted at the levels of the medial coronoid apex ( P <.0001) and base ( P <.004) indicative of humero-ulnar incongruence. Evidence of medial coronoid disease in 10 elbows (26%) and degenerative joint disease in 30 elbows (79%) was also found.
Conclusions— Presence of elbow incongruence may be an underlying factor in failure of ossification centers to fuse leading to IOHC.
Clinical Relevance— IOHC is clearly defined by CT, and it should be considered in larger Spaniel breeds, with a chronic forelimb lameness or HCF.     

Vertebral stabilization using positively threaded profile pins and polymethylmethacrylate, with or without laminectomy, for spinal canal stenosis and vertebral instability caused by congenital thoracic vertebral anomalies

Objective— To describe diagnostic findings, surgical technique, and outcome in dogs with thoracic spinal canal stenosis and vertebral instability secondary to congenital vertebral anomalies.
Study Design— Retrospective clinical study.
Animals— Dogs (n=9) with thoracic spinal canal stenosis.
Methods— Medical records (1995–1996; 2000–2006) of 9 dogs with a myelographic diagnosis of spinal canal stenosis and/or vertebral instability secondary to congenital vertebral anomaly that were surgically managed by vertebral stabilization with or without laminectomy were reviewed. Data on pre- and postoperative neurologic status, diagnostic findings, surgical techniques, and outcomes were retrieved. Follow-up evaluations were performed at 1, 2, and 6 months. Long-term outcome was assessed by means of clinical examination or owner telephone interviews.
Results— Spinal cord compression was confirmed by myelography, and in 2 dogs, dynamic compression by stress myelography. Eight dogs regained the ability to ambulate postoperatively. One dog with a partial recovery regained voluntary movement but did not become ambulatory.
Conclusions— Spinal cord injury secondary to congenital vertebral anomaly may have a good outcome when treated by vertebral stabilization with or without laminectomy. Adequate stabilization of the vertebrae and improved neurologic outcome were achieved in most dogs.
Clinical Relevance— Vertebral stabilization using positively threaded profile pins and polymethylmethacrylate with or without laminectomy is an effective treatment for spinal canal stenosis and vertebral instability secondary to congenital thoracic vertebral anomalies.     

Dynamic computed tomographic quantitation of hepatic perfusion in dogs with and without portal vascular anomalies

OBJECTIVE: To compare hepatic, pancreatic, and gastric perfusion on dynamic computed tomography (CT) scans of clinically normal dogs with those of dogs with portal vascular anomalies. SAMPLE POPULATION: Dynamic computed tomography (CT) scans of 10 clinically normal dogs and 21 dogs with portal vascular anomalies. PROCEDURES: Retrospective analysis of dynamic CT scans. Hepatic arterial perfusion, hepatic portal perfusion, total hepatic perfusion, hepatic perfusion index, gastric perfusion, and pancreatic perfusion were calculated from time attenuation curves. RESULTS: Mean +/- hepatic arterial perfusion was significantly higher in affected dogs (0.57 +/- 0.27 mL/min x mL(-1)) than in clinically normal dogs (0.23 +/- 0.11 mL/min x mL(-1)), and hepatic portal perfusion was significantly lower in affected dogs (0.52 +/- 0.47 mL/min x mL(-1)) than in clinically normal dogs (1.08 +/- 0.45 mL/min x mL(-1)). This was reflected in the hepatic perfusion index, which was significantly higher in affected dogs (0.59 +/- 0.34), compared with clinically normal dogs (0.19 +/- 0.07). Gastric perfusion was significantly higher in dogs with portal vascular anomalies (0.72 +/- 0.44 mL/min x mL(-1)) than in clinically normal dogs (0.41 +/- 0.21 mL/min x mL(-1)), but total hepatic perfusion and pancreatic perfusion were not significantly different. Among subgroups, dogs with congenital intrahepatic portosystemic shunts and dogs with arterioportal fistulae had higher hepatic arterial perfusion than did clinically normal dogs. Dogs with congenital intrahepatic portosystemic shunts also had an increase in gastric perfusion and hepatic perfusion index. CONCLUSIONS AND CLINICAL RELEVANCE: Hepatic perfusion variables measured on CT scans revealed differences in hemodynamics between clinically normal dogs and those with portal vascular anomalies.     

Magnetic resonance imaging of a canine eye with melanoma

An 8-year-old Beagle dog had exophthalmos of the left eye for the last two past months. On ophthalmoscopy, the intraocular lesion could not be evaluated due to the opacity of the cornea. Ultrasonography revealed that the eyeball was distorted in shape and shifted in position, however, the precise lesion could not be identified. On magnetic resonance (MR) imaging, the lesion was observed as hyperintense on T1-weighted and hypointense on T2-weighted images, similar to those reported in human melanoma. The lesion was histologically diagnosed to be malignant intraocular melanoma. Though this is only a case report, canine ocular melanoma may show the similar characteristic MR images as in human uveal malignant melanoma.     

Magnetic resonance imaging of the normal canine thyroid gland.

The magnetic resonance (MR) imaging features of the normal canine thyroid gland were retrospectively compiled from images acquired in 44 dogs presented for a variety of diseases unrelated to the thyroid gland. The appearance of the thyroid gland on different sequences, including pre- and postcontrast T1-weighted, T2-weighted, two-dimensional gradient echo, three-dimensional T2*-weighted gradient echo and proton density weighted images, were described in different image planes. The characteristic shape, location, and intensity of thyroid lobes compared with surrounding structures made them easily detectable in all dogs. The most common location of the thyroid lobes was dorsolateral to the trachea with the maximal cross-sectional area of the lobes located ventral to C2/3 or C3 in more than 85% of the dogs. The majority of the lobes were ovoid on transverse images. An isthmus was seen in one large dog and parathyroid glands could not be seen. The mean maximal thyroid lobe diameter on transverse images was 8.1 mm, being twice the mean diameter of the common carotid artery. Considering the excellent conspicuity and characteristic appearance of the canine thyroid gland, MR imaging can be beneficial in the diagnosis of diffuse thyroid diseases, in differentiating thyroid vs. nonthyroid neck masses and in staging and treatment planning of thyroid tumors in this species.     

Evaluation of the internal vertebral venous plexus, vertebral canal, dural sac, and vertebral body via nonselective computed tomographic venography in the cervical vertebral column in healthy dogs

OBJECTIVE: To evaluate nonselective computed tomographic (CT) venography for evaluating the cervical internal vertebral venous plexus (IVVP), define the diameter and area dimensions of the IVVP, and determine the relationship between dimensions of the cervical IVVP and other vertebral components in medium-sized dogs. Animals-6 healthy dogs that weighed 18 to 27 kg. Procedure-Helical CT scans were performed from C1 to C7 before and after IV injection of contrast medium (480 mg of iodine/kg) and a continuous infusion (240 mg of iodine/kg). Image data were transferred to a CT workstation, and measurements were performed on displayed transverse images. Diameter and area measurements of the vertebral canal, dural sac, IVVP, and vertebral body were obtained at C3 to C7. RESULTS: Opacification of vertebral venous structures was achieved in all dogs with no adverse reactions. Sagittal diameters of the IVVP for C3 to C7 ranged from 0.6 to 3.2 mm. Transverse diameters ranged from 2.32 to 5.74 mm. The IVVP area represented 12.4% of the mean vertebral canal transverse area and 30.61% of the mean vertebral epidural space area. Area measurements of the IVVP were significantly correlated with vertebral canal area and dural sac area. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that nonselective CT venography is a safe, sensitive method for performing morphometric assessments of the cervical IVVP in dogs. Findings support the theory that there may be a physiologic or developmental relationship between cervical vertebral canal components.     

In vitro prediction of canine urolith mineral composition using computed tomographic mean beam attenuation measurements

Determination of urolith mineral composition is critical for management of urolithiasis in dogs and cats. Using computed tomography, urolith physical density, and hence chemical composition, can be quantified using mean beam attenuation measurements (Hounsfield units; HU). This study was designed to establish in vitro reference ranges for three types of compositionally pure uroliths retrieved from dogs. Sixty-six canine uroliths (22 uric acid, 21 calcium oxalate, 14 struvite, nine mixed or compound) were placed in a phantom array. Uroliths were scanned at 120 kVp, 200 mA, and 80 kVp, 200 mA. The region of interest (ROI) for mean HU calculation was determined using two techniques, and reference ranges were calculated for each kVp using either ROI technique. HU for urolith types of pure composition were statistically different (Wilcoxon's two-sample test, P < 0.0083 [Bonferonni correction with six comparisons for total P < 0.05]) using both ROI techniques at either kVp. Struvite uroliths were not statistically different from mixed or compound uroliths. The accuracy for determination of composition of pure uroliths ranged from 86% to 93%; the prediction accuracy for each urolith mineral type and for all uroliths in general was highest when the ROI was hand-drawn just within the visible urolith border at 80 kVp. Technique of ROI determination and kVp that yielded the highest sensitivity, specificity, and positive and negative predictive values varied for each urolith type. Therefore, in this study, HU could be used to differentiate three types of uroliths of pure mineral composition in vitro. Further studies are needed to determine the predictive value of HU in vivo.     

Spectrum of computed tomographic findings in 58 canine elbows with fragmentation of the medial coronoid process

O bjective : To describe in detail the computed tomographic findings in elbows of dogs with fragmentation of the medial coronoid process of the ulna.
M ethods : Retrospective review of computed tomographic images of 58 elbows that had displaced medial coronoid process fragment(s), non-displaced medial coronoid process fragment or a stable fissure in the articular cartilage of the medial coronoid process at arthroscopy.
R esults : Bone fragments were observed in 85 per cent elbows with a displaced fragment at arthroscopy, in 18 per cent elbows with a non-displaced fragment and in 29 per cent elbows with a stable fissure. Fissures in the subchondral bone were observed in computed tomographic images of 43 per cent elbows that had a stable fissure at arthroscopy. Abnormal shape, sclerosis and lucency affecting the medial coronoid process, subchondral sclerosis of the ulna and humerus, irregular radial incisure of the ulna and periarticular osteophytes were observed in a similar proportion in dogs regardless of the arthroscopic findings. Kissing lesions affecting the medial aspect of the humeral condyle were mainly associated with displaced fragments. Signs of joint incongruity were observed in dorsal and sagittal reconstructed computed tomographic images in 24 per cent elbows.
C linical S ignificance : A wide range of abnormalities may be observed in computed tomographic images of dogs with fragmented medial coronoid process. Computed tomographic is moderately sensitive for detection of fragments.     

Magnetic resonance spectroscopy of the canine brain at 3.0 T and 7.0 T

The purpose of this study was to evaluate the feasibility of proton magnetic resonance spectroscopy (1H MRS) to study the concentration of metabolites in the brain of dogs at 3.0 and 7.0 T. Four healthy male beagles were scanned using 3.0 T and 7.0 T human magnetic resonance imaging (MRI) units. The results obtained showed that all dogs had excellent quality spectra for a small (1 cm3) and large (8 cm3) voxel at 3.0 T, whereas only 2 dogs had high quality spectra at 7.0 T due to insufficient water suppression. 1H MRS at 3.0 T appears to be a reliable method to study metabolite concentrations in the canine brain. The development of more advanced water suppression techniques is necessary to improve the results at 7.0 T.     

Magnetic resonance imaging in the diagnosis and treatment of a canine spinal cord injury

A nine-year-old female crossbred dog was presented with tetraplegia following a fall. No vertebral abnormalities were detectable on plain radiographs of the cervical spine. Magnetic resonance imaging scans revealed absence of extraparenchymal compression and an area of oedema within the cervical spinal cord, suggesting a favourable prognosis. Following nursing care and physiotherapy, the dog recovered the ability to walk, although mild neurological deficits persisted in the left limbs.     

Magnetic resonance imaging and pathological findings in a case of canine idiopathic eosinophilic meningoencephalitis

A case of idiopathic eosinophilic meningoencephalitis in a six-month-old male Maremma shepherd dog is reported. The dog was referred with a four month history of progressive weakness and depression with loss of trained habits. Tendency to recumbency, disorientation, visual impairment, bilaterally decreased menace response and hindlimb conscious proprioception deficits were detected. Magnetic resonance imaging showed a diffuse hypointense signal involving the cerebral grey matter with enlargement of the cerebral sulci on T1-weighted and fast fluid-attenuated inversion recovery (FLAIR) sequences consistent with a diffuse necrosis or atrophy of the cortical grey matter. Histological examination revealed severe inflammatory infiltration mainly composed of eosinophils and macrophages in the subarachnoid space and in the superficial layer of the cerebral cortex where parenchymal rarefaction and necrosis of neurones were also evident. No parasites, cysts or fungi were detected, and an immunologically mediated disorder was suspected. Magnetic resonance imaging may represent a useful diagnostic tool to differentiate idiopathic eosinophilic meningoencephalitis from other inflammatory brain diseases of young dogs.     

Occurrence, clinical features and outcome of canine pancreatitis (80 cases)

Medical records of 80 dogs diagnosed with acute pancreatitis during a 4-year period were evaluated regarding history, breed predilection, clinical signs and additional examination findings. Cases were selected if compatible clinical symptoms, increased serum activity of amylase or lipase and morphologic evidence of pancreatitis by ultrasonography, laparotomy or necropsy were all present. Like in other studies, neutered dogs had an increased risk of developing acute pancreatitis. Although breed predilection was consistent with earlier reports, some notable differences were also observed. Apart from Dachshunds, Poodles, Cocker Spaniels and Fox Terriers, the sled dogs (Laikas, Alaskan Malamutes) also demonstrated a higher risk for pancreatitis according to our results. Concurrent diseases occurred in 56 dogs (70%), diabetes mellitus (n = 29, 36%) being the most common. Clinical signs of acute pancreatitis were similar to those observed in other studies. The study group represented a dog population with severe acute pancreatitis, having a relatively high mortality rate (40%) compared to data of the literature. Breed, age, gender, neutering and body condition had no significant association with the outcome. Hypothermia (p = 0.0413) and metabolic acidosis (p = 0.0063) correlated significantly with poor prognosis and may serve as valuable markers for severity assessment in canine acute pancreatitis.