OBJECTIVE: To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with a range of clinical distal limb problems. ANIMALS: 167 horses. PROCEDURES: Medical records were reviewed of horses presented for CT of the distal limb at 2 university-based veterinary hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging. RESULTS: Most horses were Thoroughbreds and Quarter Horses. Procedure times ranged from 15 to 40 minutes, with scanning completed in 15 to 45 seconds for each region of interest. The foot or pastern region was commonly scanned (88/167 [53%] horses), with navicular bone disease diagnosed in 42 of 88 (48%) horses. The fetlock region was also commonly scanned (42/167 [40%] horses), with palmar or plantar osteochondral disease diagnosed in 17 of 42 (40%) horses. Horses were compliant during scanning, and no complications with sedation or damage to the scanner occurred. A specific imaging diagnosis for the lameness was achieved more frequently with CT imaging (166/167 [99%]) than with planar digital radiography (26/58 [45%]). CLINICAL RELEVANCE: The helical fan beam CT system could be used safely to scan sedated standing horses from the carpal or tarsal region distally. Subjectively, the machine was easy to operate, allowing CT to be incorporated into lameness investigations. CT imaging was very likely to result in a clinical diagnosis in horses with distal limb lameness.

Two horses were admitted for evaluation of mandibular swelling (horse 1) or maxillary distortion (horse 2). Both horses had radiographic evidence of tumors of dental origin that had the appearance of a compound odontoma. Extensive surgical resection was performed for treatment. Horse 1 was treated with 1-stage surgical resection, but an iatrogenic fracture occurred during surgery, which was managed successfully with a type I external fixator and extraoral alimentation. Horse 2 was treated in multiple stages to remove all portions of the tumor. To manage an extensive orosinal fistula, a custom-designed dental bridge was constructed to occlude the fistula. For both horses, the histopathologic diagnosis was compound odontoma. Compound odontomas are benign, locally expansive tumors of dental origin. Compound odontomas can be treated successfully; however, multiple surgeries may be necessary.

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.

OBJECTIVE: To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with clinical problems of the head and neck. ANIMALS: 120 horses. PROCEDURES: Medical records were reviewed of horses presented for CT of the head or neck at 2 university hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging. RESULTS: Quarter Horses and Warmbloods were the most common breeds, and the most common complaint was nasal discharge. The head (101/120 [84%] horses) was scanned most frequently, and the most common diagnoses were primary dental disease and a space-occupying lesion of the paranasal sinuses. Nuchal bursitis was the most common imaging diagnosis in the neck region. Procedure time ranged from 20 to 45 minutes with a scanning time of 30 to 40 seconds. No complications with horse sedation occurred, and horses tolerated scanning well. An imaging diagnosis was more frequently achieved with CT (109/120 [91%] horses) than with planar digital radiography (23/61 [38%] horses). CLINICAL RELEVANCE: The helical fan beam CT system had fast scanning times and could be used safely for routine imaging of the teeth and sinuses in horses. The caudal extent of scanning in the neck region was limited by the shape of the horse’s neck and thorax.

CASE DESCRIPTION: A 6-year-old castrated male Bactrian camel was evaluated because of a 14hour history of oliguria and stranguria that progressed to anuria. CLINICAL FINDINGS: Perineal urethral pulsations and intermittent tail flagging with no accompanying urination were observed. Ultrasonography of the urethra revealed multiple hyperechoic foci with shadowing artifact indicative of calculi present in the penile urethra distal to the sigmoid flexure. Rectal palpation revealed a pulsating hard urethra and intact distended urinary bladder. Further clinical examination was not possible because of challenges associated with handling the camel. TREATMENT AND OUTCOME: Urethral catheterization through a perineal urethral incision failed to achieve urinary bladder decompression. Tube cystostomy was performed to prevent bladder rupture. Urethrocystography performed 3 days after surgery revealed a urethral rupture at the level of the prepuce. Five weeks after surgery, the camel could urinate a steady stream via the urethrotomy site. Seven weeks after surgery, the cystostomy tube was removed, and the urethrotomy site was modified to provide a permanent urethral opening via perineal urethrostomy. During 6 years of subsequent periodic follow-up by telephone, the owner reported that the camel continued to do well and urinate through the revised opening. CLINICAL RELEVANCE: To the authors’ knowledge, this is the first detailed description of a tube cystostomy in an adult camel with obstructive urolithiasis that includes information on the patient's long-term outcome. This technique was a viable option in the surgical management of obstructive urolithiasis in this camel and may be useful for other large camelids as well.

Degenerative suspensory ligament desmitis is a progressive idiopathic condition that leads to scarring and rupture of suspensory ligament fibers in multiple limbs in horses. The prevalence of degenerative suspensory ligament desmitis is breed related. Risk is high in the Peruvian Horse, whereas pony and draft breeds have low breed risk. Degenerative suspensory ligament desmitis occurs in families of Peruvian Horses, but its genetic architecture has not been definitively determined. We investigated contrasts between breeds with differing risk of degenerative suspensory ligament desmitis and identified associated risk variants and candidate genes. We analyzed 670k single nucleotide polymorphisms from 10 breeds, each of which was assigned one of the four breed degenerative suspensory ligament desmitis risk categories: control (Belgian, Icelandic Horse, Shetland Pony, and Welsh Pony), low risk (Lusitano, Arabian), medium risk (Standardbred, Thoroughbred, Quarter Horse), and high risk (Peruvian Horse). Single nucleotide polymorphisms were used for genome-wide association and selection signature analysis using breed-assigned risk levels. We found that the Peruvian Horse is a population with low effective population size and our breed contrasts suggest that degenerative suspensory ligament desmitis is a polygenic disease. Variant frequency exhibited signatures of positive selection across degenerative suspensory ligament desmitis breed risk groups on chromosomes 7, 18, and 23. Our results suggest degenerative suspensory ligament desmitis breed risk is associated with disturbances to suspensory ligament homeostasis where matrix responses to mechanical loading are perturbed through disturbances to aging in tendon (PIN1), mechanotransduction (KANK1, KANK2, JUNB, SEMA7A), collagen synthesis (COL4A1, COL5A2, COL5A3, COL6A5), matrix responses to hypoxia (PRDX2), lipid metabolism (LDLR, VLDLR), and BMP signaling (GREM2). Our results do not suggest that suspensory ligament proteoglycan turnover is a primary factor in disease pathogenesis.