A 4-year-old intact female mixed-breed dog was admitted with a 2-month history of progressive thoracic and pelvic limb paresis. Neurological examination localized the lesion to the cervical spine. Magnetic resonance imaging (MRI) revealed a well-defined mass of the spinal cord extending from the third to fifth cervical vertebral level. The mass was T2-weighted hypointense, T1-weighted isointense, with homogeneous contrast enhancement. Based on the surgical, histopathological, and microbiologic findings, the lesion was diagnosed as an inflammatory pseudotumor. At 55 days postoperatively, the patient demonstrated marked gait improvement, and MRI confirmed successful mass removal with a small residual intramedullary lesion at the C5 level. Follow-up MRI at day 118 exhibited tumor recurrence, and hypofractionated radiotherapy was administered. One month after treatment, MRI demonstrated lesion size reduction.

Meningeal enhancement on magnetic resonance imaging (MRI) is commonly associated with pathological conditions, including inflammation, neoplasia, or ischemia. However, short and thin segments of contrast enhancement are considered normal in the brain meninges, but studies on spinal meningeal enhancement in dogs are limited. This prospective, exploratory study aimed to determine the presence and characteristics of cervical spinal meningeal enhancement in healthy dogs as well as the impact of acquisition time on enhancement. Cervical spinal MRI was performed from the dens of the axis to the C4-5 intervertebral disc (IVD) in 12 healthy beagles. T2-weighted, T1-weighted, contrast-enhanced T1-weighted (T1CE), immediate fat-saturated T1CE (T1CEFS), and 15-min delayed T1CEFS images were acquired. Enhancement patterns were categorized by their distribution, location (dorsal, lateral, or ventral aspect of the meninges), and shape (long segments, short segments, or spots). The enhancement percentage (E%) was calculated to quantitatively evaluate the enhancement. All dogs showed contrast enhancement at the IVD level, not the vertebral body. On immediate imaging, the enhanced regions predominantly appeared as short segments, most commonly at the C2-3, primarily in the dorsal aspect of the meninges. No significant differences were found between the two acquisitions except for the decrease in the E% in C3-4 after a 15-min delay. These results suggest that cervical spinal meningeal enhancement is a normal finding in healthy dogs, primarily appearing as short segments in the dorsal aspect of the meninges at the C2-3 level, with minimal changes between immediate and delayed imaging.

Magnetic resonance imaging has limitations in definitively diagnosing canine brain diseases due to overlapping lesion morphologies. Magnetic resonance spectroscopy (MRS) can complement conventional MR imaging by evaluating brain metabolites at a molecular level, though voxels under 1 cm3 have not been routinely evaluated in veterinary medicine. This study evaluated the usefulness of single-voxel spectroscopy (SVS) using small-sized voxels (0.125 cm3) by comparing it with multi-voxel spectroscopy (MVS). Both techniques were performed on the white matter and gray matter of the frontoparietal lobe, the caudate nucleus, and the thalamus in seven healthy beagle dogs using a 1.5T system. Brain metabolite concentrations and their ratios to creatine were compared. SVS had a significantly shorter mean acquisition time (4.79 ± 0.29 min) than MVS (11.64 ± 0.23 min). No significant differences were observed in metabolite concentrations or ratios between SVS and MVS following multiplicity correction, confirming no statistically significant discrepancies between the two protocols. No significant differences were found between the left and right hemispheres. While small-voxel SVS is technically feasible and reduces scan time, these findings represent protocol-specific descriptive data in a small sample of healthy dogs and do not establish clinical reference values or diagnostic accuracy.

Periportal halo (PPH) sign on contrast-enhanced computed tomography (CT) is considered a pathological finding; however, recent studies indicate that it may also appear in healthy individuals. We hypothesized that PPH can be observed in healthy dogs and can vary depending on the anesthetic agents. This study assessed the PPH sign in healthy dogs under different anesthetic agents and across different postcontrast phases. In this cross-over study, 10 healthy Beagle dogs underwent non-contrast and postcontrast CT examinations (arterial, venous, delayed, 5-min delayed, and 10-min delayed phases) under two anesthetic agents, medetomidine and alfaxalone, with a 1-week interval. The presence and severity of PPH were assessed on a scale of 0-3 and compared across different postcontrast phases. Significant differences in PPH were noted between the two anesthetic groups. In the medetomidine group, PPH was absent in the arterial phase, peaked at grade 3 in the delayed phase, and gradually decreased thereafter in the 5- and 10-min delayed phases. In contrast, PPH was minimal or absent in the alfaxalone group across all phases. In conclusion, PPH can be detected in healthy dogs depending on the sedative or anesthetic agent. It can particularly be detected with medetomidine in the delayed phase and should not be misinterpreted as a pathological change on postcontrast CT.

The application of deep learning-based reconstruction (DLR) to magnetic resonance imaging (MRI) has been recently introduced in human and veterinary medicine to improve image quality without prolonging acquisition time. We hypothesized that cranial abdominal MRI with DLR would have superior image quality than conventional MRI. This prospective comparative pilot study aimed to compare cranial abdominal MR image quality with versus without DLR application in dogs. Transverse T2-weighted and T1-weighted images with and without contrast enhancement of the cranial abdomen region were performed in 10 clinically healthy dogs. The original and DLR images were generated from a single set of raw data using the DLR network embedded reconstruction pathway. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for quantitative analysis. Qualitative analysis included evaluation of the edge sharpness of the liver and pancreas, the conspicuity of the adrenal glands, respiratory motion artifacts, coarseness, and overall image quality using a 4-point scale. Quantitative and qualitative values were compared between images with DLR and their counterparts. The mean SNR and CNR of all images with DLR were significantly higher than those of their counterparts (p < 0.05). Qualitative analysis parameters, except for respiratory motion artifacts, were significantly superior in images with DLR compared with counterparts for all sequences (p < 0.05). The present study demonstrated that cranial abdominal MRI with DLR is feasible to improve image quality without prolonging acquisition time.

This study aimed to investigate the computed tomography (CT) features of mast cell tumors (MCTs) and soft tissue sarcomas (STSs) in subcutaneous masses of dogs and to identify distinguishing characteristics between these two tumor types. This retrospective, multicenter study included 22 dogs with subcutaneous masses diagnosed as MCTs (n = 11) or STSs (n = 11) via fine needle aspiration or excisional biopsy. The CT features were evaluated based on four categories: location, morphological characteristics (including shape, margin, capsulation, size, and long axis to short axis (L/S) ratio of the lesion), internal parenchymal characteristics (including cavitation, vascularization, mineralization, homogeneity and Hounsfield Unit within the lesion), and tissue surrounding the lesion (including surrounding tissue involvement and fat stranding around the lesion). Capsulation (P = 0.024), L/S ratio (P = 0.019), cavitation (P = 0.004), and homogeneity in the post-contrast phase (P = 0.036) were significantly different between MCTs and STSs. STSs primarily showed capsulation and cavitation within the mass and were inhomogeneous to heterogeneous in the post-contrast phase, whereas MCTs rarely showed these features and had a higher L/S ratio. Other features did not show significant differences between the two types of tumors. This study reveals that CT analysis of capsulation, cavitation, and homogeneity in the post-contrast phase differentiates MCTs and STSs in subcutaneous masses in dogs.

An aorto-right ventricular fistula, a rare condition in humans, is characterized by communication between the ascending aorta and the right ventricle through a defect in the aortic wall. This report describes three cases of dogs with continuous murmurs: a 6-month-old Coton de Tulear, a 5-year-old Maltese, and a 6-month-old Jindo. Notably, all of the dogs presented with no severe clinical signs. Echocardiography revealed a turbulent jet through restrictive perimembranous ventricular septal defects (VSD) during systole and aorto-right ventricular fistulas secondary to ruptured sinuses of Valsalva aneurysm during diastole. In one case, a surgical closure of the VSD simultaneously resolved the aorto-right ventricular fistula. Follow-up echocardiography in the other two cases revealed mild left heart volume overload and a slight increase in the pulmonary-to-systemic blood flow ratio. However, the dogs remained asymptomatic. In conclusion, aorto-right ventricular fistulas with VSDs should be considered in the differential diagnosis of continuous murmurs in dogs.

A 6-year-old intact male Yorkshire Terrier, weighing 5.8 kg, presented with progressive ataxia of the thoracic and pelvic limbs with a four-month duration. A physical examination revealed proprioceptive ataxia and neck pain, with neurological signs indicating a C1–5 lesion. The radiographs revealed mild narrowing of the disc spaces at C2–3, C4–5, and C5–6, suggesting cervical intervertebral disc disease (IVDD). Magnetic resonance imaging (MRI) revealed bilateral symmetrical enlargement of the C2 nerve roots, causing spinal cord compression and distortion. The post-contrast T1-weighted images showed pronounced contrast enhancement, suggestive of hypertrophic ganglioneuritis. Mild disc protrusions at C4–5, C5–6, and C6–7 were also observed with minimal spinal compression, suggesting a lesser role in the clinical presentation. Considering the MRI findings, high-dose immunosuppressive prednisolone was administered under the tentative diagnosis of hypertrophic ganglioneuritis, leading to significant improvement in mobility and postural reactions. Follow-up MRI performed three months post-treatment revealed a significant decrease in the hypertrophy of the C2 nerve roots and alleviated spinal cord compression. This case underscores the essential role of MRI in differentiating hypertrophic ganglioneuritis from other spinal cord pathologies such as IVDD or spinal nerve tumors.

OBJECTIVE:To determine optimal portal position for thoracolumbar unilateral biportal endoscopy (UBE) spine surgery in dogs. STUDY DESIGN:Experimental ex vivo cadaveric and in vivo preclinical study. ANIMALS:Seven cadavers and three healthy purpose-bred Beagles. METHODS:In the ex vivo phase, thoracolumbar mini-hemilaminectomy was performed at T13-L1, L1-L2, and L2-L3 in seven cadavers using two UBE portal positions. The distance (X) from the spinous process to the mammillary process was measured fluoroscopically. Group A portals were placed from X to 2X; Group B portals from 2X to 3X. Visualization and instrument accessibility were compared. Based on cadaveric results, mini-hemilaminectomy was performed in three live dogs using the superior (Group B) portal position. Intraoperative epidural pressure was measured. Postoperative magnetic resonance image (MRI) on day 0, 14, and 28 evaluated muscle recovery, fluid extravasation, and spinal/dural compression. RESULTS:Mini-hemilaminectomy was successfully performed with both portal positions. Surgical time and number of fluoroscopic scans did not differ between groups. Scope insertion angles were steeper in Group B (p < .001), which also showed higher visualization and accessibility scores (p < .001). Group B portals were used in the in vivo study. Epidural pressure remained stable, and MRI revealed transient postoperative muscle edema that resolved by day 28. CONCLUSION:UBE was feasible in cadavers and safe in live dog models. Group B portal positioning provided better visualization and accessibility. CLINICAL SIGNIFICANCE:UBE presents a potential minimally invasive approach for thoracolumbar spinal surgery in dogs.

Subgaleal hematomas are accumulation of blood between periosteum and galea aponeurosis. A 2-year-old male Chihuahua was presented with a severe head swelling after trauma. Radiography and computed tomography (CT) showed a massive swelling encircling the entire calvarial vault, extending toward the cervical neck and crossing the suture line. It was heterogeneously, mild hyperdense fluid to soft tissue attenuating with contrast enhancement on CT images. On day 4, physical and imaging examination showed resolution of the calvarial swelling. Subgaleal hematoma should be considered as a differential diagnosis when there is a massive soft tissue swelling over the skull on physical and imaging examinations.

Intramuscular administration is a commonly used method for delivering sedatives and anesthetics in veterinary medicine. Previous studies have reported inflammation at the intramuscular injection site in laboratory animals and observed signal changes on MRI following intramuscular injections in humans. We hypothesized that following intramuscular injection, the site would exhibit T2 hyperintensity and contrast enhancement on MRI. To investigate this, this prospective study evaluated the pattern of signal changes and grade of T2 signal intensity and contrast enhancement over time after the intramuscular injection of medetomidine at a premedication dosage, comparing it to saline. MRI scans were performed immediately postinjection into the biceps femoris and quadriceps femoris muscles, as well as at 2, 8, 24, and 72 h, and 7 days postinjection. A semiquantitative scale was utilized to grade signal intensity and contrast enhancement. Both medetomidine and saline injections showed T2 hyperintensity immediately after injection and contrast enhancement from 2 h postinjection, manifesting as flame-shaped. These signal changes decreased up to 24 h postinjection (p < .05). The signal changes induced by medetomidine showed higher T2 hyperintense change and stronger contrast enhancement compared with saline at most time points, with the signal changes persisting for a longer duration (p < .05). These findings suggest that intramuscular administration of medetomidine induces a more severe tissue reaction compared with saline, and the results are expected to aid in the differentiation of various muscle diseases that present with similar MRI findings.

IMPORTANCE:The portal vein to aorta (PV/Ao) ratio is used to assess the clinical significance of extrahepatic portosystemic shunt (EHPSS). Previous studies using computed tomography (CT) were conducted in dogs but not in cats. OBJECTIVE:This study aimed to establish normal reference values for PV indices (PV/Ao ratio and PV diameter) in cats and determine the usefulness of these for predicting symptomatic EHPSS. METHODS:This study included 95 dogs and 114 cats that underwent abdominal CT. The canine normal (CN) group included dogs without EHPSS. The cats were classified into feline normal (FN, 88/114), feline asymptomatic (FA, 16/114), and feline symptomatic (FS, 10/114) groups. The PV and Ao diameters were measured in axial cross-sections. RESULTS:The group FN had a higher PV/Ao ratio than the group CN (p < 0.001). Within the feline groups, the PV indices were in the order FN > FA > FS (both p < 0.001). The mean PV diameter and PV/Ao ratio for group FN were 5.23 ± 0.77 mm and 1.46 ± 0.19, respectively. The cutoff values between groups FN and FS were 4.115 mm for PV diameter (sensitivity, 100%; specificity, 97.7%) and 1.170 for PV/Ao ratio (90%, 92.1%). The cutoff values between group FA and FS were 3.835 mm (90%, 93.8%) and 1.010 (70%, 100%), respectively. CONCLUSIONS AND RELEVANCE:The results demonstrated significant differences in PV indices between dogs and cats. In cats, the PV/Ao ratio demonstrated high diagnostic performance for symptomatic EHPSS. The PV diameter also performed well, in contrast to dogs.

IMPORTANCE:In human medicine, research using magnetic resonance imaging (MRI) has shown that an increase in the vertebral body fat signal fraction (FSF) is associated with the severity of intervertebral disc (IVD) degeneration. Nevertheless, veterinary medicine has limited information on the relationship between the vertebral body FSF and IVD degeneration. OBJECTIVE:This study evaluated the relationship between IVD degeneration and the vertebral body FSF in dogs and compared these factors between chondrodystrophic (CD) and non-chondrodystrophic (NCD) dogs. METHODS:IVD degeneration in dogs was classified morphologically using the Pfirrmann grade, and the vertebral body FSF was evaluated quantitatively. RESULTS:The vertebral body FSF showed a statistically significant difference among the age groups. The vertebral body FSF was significantly higher in Pfirrmann grades 3-5 than in grades 1 and 2. The mean Pfirrmann grade of CD dogs was higher than that of NCD dogs in the four-to-six-year-old group. The mean vertebral body FSF of CD dogs was higher than that of NCD dogs in the group of seven years and above. CONCLUSIONS AND RELEVANCE:In dogs, the vertebral body FSF increased significantly with age and Pfirrmann grade. The CD dogs showed a higher degree of IVD degeneration at a younger age than the NCD dogs. CD dogs appeared to experience more severe fat deposition of the vertebral body in old age than NCD dogs. MRI examinations are helpful for evaluating IVD degeneration and vertebral body fat deposition.

A two-year-old, intact female Golden Retriever had previously been diagnosed with a portosystemic shunt (PSS) during an ultrasonographic examination at a local animal hospital.The serum biochemistry revealed elevated liver enzymes and bile acid levels.The abdominal radiographic examination revealed mild serosal detail loss and microhepatica, while abdominal ultrasonography revealed mild ascites and high-velocity flow to the caudal vena cava (CVC) suspected as a PSS.The gallbladder was not observed within the hepatic parenchyma during ultrasonography.Computed tomography (CT) revealed an absent gallbladder and dilation of the common bile duct (CBD).Dilations of the gastroduodenal, splenic, colic and renal veins were also observed.A dilated left phrenico-abdominal vein that entered the CVC was previously misinterpreted as a PSS on the ultrasound examination.Based on the imaging examinations, the dog was diagnosed with congenital gallbladder agenesis associated CBD dilation.

Stertor, a clinical sign associated with obstructive airway syndrome, is often observed in non-brachycephalic dogs. This prospective, case-control study aimed to compare soft palate dimensions, nasopharyngeal cross-sectional area (CSA), and nasopharyngeal collapsibility at various locations in non-brachycephalic dogs with and without stertor. A total of 50 dogs were recruited and stratified into control (n = 34) and stertor (n = 13) groups. Static and dynamic computed tomography was conducted without tracheal intubation, and the following variables were calculated: normalized soft palate length and thickness, normalized maximum and minimum nasopharyngeal CSAs (rCSAmax and rCSAmin), and nasopharyngeal collapsibility at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The stertor group demonstrated significantly lower rCSAmax and rCSAmin, as well as higher nasopharyngeal collapsibility compared with the control group, while no significant differences were noted in the soft palate dimension. Evaluating nasopharyngeal collapse at the foramen lacerum level was recommended due to the clear presence of identifiable bony landmarks and lower overlap in the nasopharyngeal collapsibility between dogs with and without stertor. Physical dimensions of the soft palate may not be the primary contributing factor to nasopharyngeal collapse and clinical signs in non-brachycephalic dogs.