Radiation exposure during simulated equine head and limb fan beam standing computed tomography appears safe for personnel using lead shielding.

OBJECTIVE: To evaluate the radiation dose to personnel locations during simulated head and limb scans with a novel equine standing CT (sCT) system. METHODS: Measurements were made with the use of a helical fan beam sCT system (Equina; Asto CT Inc). Scatter radiation was measured in different positions in the sCT room to mimic the location of the control operator, horse handler, and lead rope handler during simulated equine head and limb imaging. Operator/handler dose was quantified at each location using entrance air kerma measured with a spherical ionization chamber and electrometer. RESULTS: Radiation dose to the control operator, horse handler, and lead rope handler locations wearing a lead apron during simulated head imaging was 13.3, 3.5, and 6.8 µGy, respectively. Radiation dose to the control operator location wearing a lead apron was 1.3 µGy, and dose to the lead rope handler location wearing a lead apron was 0.2 and 5.4 µGy during simulated pelvic limb and thoracic limb imaging, respectively. CONCLUSIONS: With the more widespread clinical use of equine sCT units in clinical practice, there is concern for increased risk of radiation exposure to personnel who stay in the sCT room during scanning. The control operator location had the highest dose during simulated head imaging, and the lead rope handler location in thoracic limb sCT had the highest dose during simulated limb imaging. Limiting the number of personnel in the sCT room, rotating personnel between handler positions, increasing operator distance from the scanner, and using lead shields and eyeglasses are recommended. CLINICAL RELEVANCE: Our findings suggest that scanning large numbers of horses per year with the Asto CT Equina would not lead to occupational radiation exposure above the recommended safe threshold for handlers using lead shields and eyeglasses.

Comparison of radiography and computed tomography for identification of third metacarpal structural change and associated assessment of condylar stress fracture risk in Thoroughbred racehorses.

BACKGROUND: Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses. OBJECTIVES: To determine sensitivity, specificity, and reliability for third metacarpal condylar stress fracture risk assessment from digital radiographs (DR) and standing computed tomography (sCT). STUDY DESIGN: Controlled ex vivo experiment. METHODS: A blinded set of metacarpophalangeal joint DR and sCT images were prepared from 31 Thoroughbreds. Four observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal bone for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging features. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG, and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment based on sCT and joint surface examination. Agreement between observers and the reference assessment and reliability between observers were determined. Intra-observer repeatability was also assessed. RESULTS: Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For agreement with the reference assessment of structural change, correlation coefficients were generally below 0.5 for DR and 0.49-0.82 for sCT. For horses categorised as normal risk on reference assessment, observer assessment often agreed with the reference. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a reference assessment of high risk of injury, observers generally underestimated risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses categorised as having elevated risk of injury from the reference assessment. Assessment repeatability and reliability was better with sCT than DR. MAIN LIMITATIONS: The ex vivo study design influenced DR image sets. CONCLUSIONS: Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection provides the critical guidance needed to improve racehorse screening programs. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo.

Lymphaticovenous anastomosis of the caudal thoracic duct to the azygous vein: A feline cadaver study.

OBJECTIVE: The aim of this study was to describe a technique for anastomosis of the thoracic duct (TD) to the azygos vein (AV) using a microvascular anastomotic coupler (MAC) device in feline cadavers. Our hypothesis was that a TD-AV lymphaticovenous anastomosis would be feasible in feline cadavers. STUDY DESIGN: Cadaveric study. ANIMALS: Eight domestic shorthair feline cadavers. METHODS: A left paracostal laparotomy and 9th or 10th intercostal thoracotomy was performed. Contrast media was injected into a mesenteric lymph node and lymphography was used to identify the TD and its branches. The TD and AV were isolated, ligated, and divided with the aid of a surgical microscope. The TD and AV were anastomosed end-to-end using a 1.5 or 2.0 mm MAC. Intraoperative patency was assessed by manipulation of chyle and venous blood across the anastomosis. Mesenteric lymphography was repeated to confirm postoperative anastomotic patency. RESULTS: The TD was identified via lymphography in seven of eight cats. The anastomosis was successful and patency was confirmed via intraoperative assessment and postoperative lymphography in all cats. The median (range) duration for the dissection and anastomosis portions of the procedure was 122 (80-150) min. CONCLUSION: End-to-end anastomosis of the TD to the AV using a MAC was feasible in the feline cadaver without major intraoperative technical challenges. CLINICAL SIGNIFICANCE: Anastomosis of the TD and AV may have application as an alternative treatment for idiopathic chylothorax in cats. By directly connecting the abdominal lymphatics to the central venous system, the stimulus for collateral vessel development around the site of TD ligation may be minimized, which may prevent leakage of chyle through the more cranial lymphatics.

Anastomosis of the caudal thoracic duct and intercostal vein using a microvascular anastomotic coupler device: Experimental study in six dogs.

OBJECTIVE: To describe the technique for anastomosis of the caudal thoracic duct (TD) to the 10th or 11th intercostal vein (ICV) using a microvascular anastomotic coupler (MAC) device in dogs and assess patency of the anastomosis on days 0 and 30. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Six adult Beagle dogs. METHODS: Under general anesthesia, fluoroscopic popliteal lymphangiography was performed and the TD identified. A right ninth or 10th intercostal thoracotomy was performed. Using an operating microscope, the TD and the 10th or 11th ICV were isolated, ligated, and anastomosed using a 1.5 or 2.0 mm MAC. Fluoroscopic popliteal lymphangiography was repeated immediately after surgery and on day 30. RESULTS: The anastomosis was successful and lymphangiography documented flow into the azygos vein in all six dogs immediately after surgery. At day 30, the anastomosis was patent in four of six dogs. In two dogs, flow through the anastomosis was obstructed due to kinking of the ICV just cranial to the MAC. CONCLUSION: Anastomosis of the TD and ICV using a MAC was feasible and was shown to maintain patency up to 30 days. When performing the anastomosis, care should be taken to ensure the ICV is not kinked by the MAC. CLINICAL SIGNIFICANCE: Direct anastomosis of the TD and ICV may have application for treatment of idiopathic chylothorax in dogs by maintaining flow from the abdominal lymphatics to the central venous circulation and thereby preventing the stimulus for collateral circulation and persistent chylous effusion. Further investigation is warranted to assess the efficacy of this technique in dogs affected with idiopathic chylothorax.

Computed tomographic laryngotracheal dimensions in adult domestic rabbits (Oryctolagus cuniculus) are positively associated with body weight and the laryngotracheal lumen is narrowest at the level of the thyroid cartilage.

OBJECTIVE: This retrospective study aimed to measure rabbit laryngotracheal dimensions at different locations on computed tomography (CT), assess the relationship of these measurements with rabbit body weight, determine the most common narrowest measurement and assess its relationship with endotracheal tube (ETT) size and body weight. ANIMALS: 66 adult domestic rabbits (Oryctolagus cuniculus) of different breeds and body weights. PROCEDURES: CT laryngotracheal luminal height, width, and cross-sectional area measurements were made at the rostral thyroid cartilage at the level of the arytenoids, caudal thyroid cartilage/rostral cricoid cartilage, caudal cricoid cartilage/cranial trachea, and trachea at the level of the fifth cervical vertebra. RESULTS: The data for every measurement of luminal airway dimensions revealed robust positive associations with body weight (P < .001). The narrowest laryngotracheal measurement was the width at the level of the caudal thyroid cartilage/rostral cricoid cartilage, and the smallest cross-sectional area was at the rostral thyroid cartilage at the level of the arytenoids. There was a strong association between body weight and the likelihood of appropriate ETT fit. To have at least an 80% chance of appropriate ETT fit with a 2.0, 2.5, and 3.0 mm ETT, the rabbits' weight predicted by the model (lower 95% confidence limit) were at least 2.99 (2.72) kg, 5.24 (4.65) kg, and 5.80 (5.21) kg, respectively. CLINICAL RELEVANCE: The laryngotracheal lumen was narrowest at the level of the caudal thyroid cartilage in rabbits, which indicates this location may be the limiting factor in determining ETT size in rabbits.

Computed tomography of testicular torsion in a juvenile dog with unilateral cryptorchidism.

A 14-week-old male unilaterally cryptorchid Clumber spaniel was presented for acute lethargy. Physical examination revealed abdominal pain, and a single testis was palpated in the scrotum. Abdominal ultrasound and computed tomography (CT) revealed a poorly vascularized, ovoid structure immediately caudal to the left kidney with scant regional peritoneal effusion. Left intra-abdominal testicular torsion was confirmed at surgery, and routine cryptorchidectomy was performed. The patient recovered uneventfully from anesthesia and surgery. Key clinical message: The most common CT characteristics of testicular torsion were present in this case and correlated well with sonographic findings to allow for rapid, accurate diagnosis and surgical planning of unilateral, non-neoplastic, intra-abdominal cryptorchid testicular torsion in a juvenile dog. Contrast enhanced CT facilitated accurate localization of the undescended testis and evaluation of testicular perfusion and may be a useful alternative to ultrasound for diagnosing testicular torsion, especially in indeterminate cases.

Tomodensitométrie d'une torsion testiculaire chez un chien juvénile atteint de cryptorchidie unilatérale. Un épagneul Clumber avec une cryptorchidie unilatérale âgé de 14 semaines a été présenté pour une léthargie aiguë. L'examen physique a révélé des douleurs abdominales et un seul testicule a été palpé dans le scrotum. L'échographie abdominale et la tomodensitométrie ont révélé une structure ovoïde mal vascularisée immédiatement caudale au rein gauche avec peu d'épanchement péritonéal régional. Une torsion testiculaire intra-abdominale gauche a été confirmée lors de la chirurgie et une cryptorchidectomie de routine a été réalisée. Le patient s'est remis sans incident de l'anesthésie et de la chirurgie.Message clinique clé:Les caractéristiques tomodensitométriques les plus courantes de la torsion testiculaire étaient présentes dans ce cas et bien corrélées avec les résultats échographiques pour permettre un diagnostic rapide et précis et une planification chirurgicale de la torsion testiculaire avec cryptorchidie unilatérale, non néoplasique et intra-abdominale chez un chien juvénile. La tomodensitométrie avec contraste a facilité la localisation précise du testicule non descendu et l'évaluation de la perfusion testiculaire et peut être une alternative utile à l'échographie pour diagnostiquer la torsion testiculaire, en particulier dans les cas indéterminés.(Traduit par Dr Serge Messier).

Ultrasonography and CT of the vas deferens in a neutered male dog with chronic exogenous estrogen exposure.

A 2-year-old male neutered Rat Terrier was presented for alopecia, recurrent urinary tract infections, and urinary incontinence. Abdominal ultrasound and CT identified a thin, tubular, paired structure arising from the craniodorsal aspect of an enlarged, cystic prostate. An atypical uterus masculinus was initially suspected, however it was then identified that the patient had chronic exogenous estrogen exposure, and surgical resection and histopathology was consistent with an enlarged and inflamed vas deferens. Vas deferens enlargement and vasitis secondary to chronic hyperestrogenism should be considered for a tubular, paired structure arising from the craniodorsal prostate in a male dog.

What Is Your Diagnosis?

In collaboration with the American College of Veterinary Radiology.

Lymphaticovenous anastomosis of the caudal thoracic duct to an intercostal vein: A canine cadaver study.

OBJECTIVE: To describe a technique for anastomosis of the thoracic duct (TD) to the 11th or 12th intercostal vein (ICV) using a microvascular anastomotic coupler (MAC) in the dog. STUDY DESIGN: Cadaveric study. ANIMALS: Eight beagles. METHODS: A right paracostal laparotomy and 10th intercostal thoracotomy were performed in each dog. Mesenteric contrast lymphography was used to identify the TD and its branches on fluoroscopy. The TD and adjacent 11th or 12th ICV were isolated, double ligated, and divided using a surgical microscope. The caudal TD and proximal ICV were anastomosed in an end-to-end fashion using a 1.5 mm or 2 mm MAC. Mesenteric lymphography was repeated to document patency of the anastomosis. RESULTS: The TD was identified via lymphography in all dogs; five dogs had a single duct, and three dogs had additional branches. The anastomosis was successful in all eight dogs, and flow into the azygos vein without leakage was confirmed via lymphography. CONCLUSION: End-to-end anastomosis of the TD to an ICV using a MAC was technically feasible in the canine cadaver. CLINICAL SIGNIFICANCE: Lymphaticovenous anastomosis combined with TD ligation may have application as a treatment for idiopathic chylothorax. By maintaining the flow of chyle from the abdominal lymphatics to the systemic circulation, this procedure may reduce the stimulus for collateral circulation and persistent flow to the cranial mediastinal lymphatics.