Disseminated hemangiosarcoma in a horse

A 6.5-year-old horse with a history of exercise-induced pulmonary hemorrhage was admitted because of acute onset of epistaxis, dyspnea, high respiratory rate, pale mucous membranes, and dark feces. There was no clinical or laboratory evidence of a bleeding disorder, and the horse's anemia was considered to be secondary to pulmonary hemorrhage. The cause of the hemorrhage was not found on thoracic sonograms or from cytologic examination of transtracheal aspirates. Despite supportive care, the horse's health deteriorated, and it was euthanatized. Necropsy revealed blood in the thoracic and peritoneal cavities and reddish black masses in many tissues. Histologic examination confirmed a diagnosis of hemangiosarcoma. Hemangiosarcoma is a rare tumor in horses; however, as this case demonstrates, it can cause pulmonary hemorrhage and respiratory distress and may be difficult to diagnose before death.     

T cell rich,B cell lymphoma in the small colon of a yearling horse

A one‐year‐old, Thoroughbred colt presented for evaluation due to a one month history of fever of unknown origin and progressive weight loss. On initial presentation, the horse was febrile and showed signs localised to the respiratory tract. These included bilaterally increased bronchovesicular sounds and a moderate, diffuse interstitial pattern on thoracic radiographs. A transtracheal wash yielded mucopurulent debris, culture of which grew small numbers of Staphylococcus epidermidis and Aspergillus spp. The horse was discharged with a diagnosis of bronchointerstitial pneumonia and placed on antibiotic therapy. Ten days after initial presentation, he developed abdominal pain that was unresponsive to on‐farm treatment. The horse was febrile, displayed increased respiratory rate and effort, and showed moderate signs of abdominal pain. On rectal examination, a firm, 8–10 cm mass was palpated on midline. The colt was admitted to the hospital and scheduled for exploratory laparotomy, but died a short time later before surgery could be performed. This report describes the clinical, diagnostic and histopathological findings of a case of alimentary lymphoma in a yearling colt.     

Safety and efficacy of a technique for thoracoscopically guided pulmonary wedge resection in horses

OBJECTIVE: To evaluate the safety and efficacy of thoracoscopically guided pulmonary wedge resection in horses. ANIMALS: 10 horses (5 control horses and 5 horses affected with recurrent airway obstruction [ie, heaves]). PROCEDURE: Each horse underwent a thoracoscopically guided pulmonary wedge resection. Before, during, and after surgery, heart rate, respiratory rate, arterial blood gases, and systemic and pulmonary arterial pressures were measured. Physical examination, CBC, and thoracic radiography and ultrasonography were performed 24 hours before and 2 and 48 hours after surgery. Pulmonary specimens were assessed by histologic examination. A second thoracoscopic procedure 14 days later was used to evaluate the resection site. RESULTS: The technique provided excellent specimens for histologic evaluation of the lung. Heart and respiratory rates decreased significantly after horses were administered sedatives. A significant transient decrease in Pao2 was detected immediately after pulmonary wedge resection, but we did not detect significant effects on arterial pH, Paco2, or mean arterial and pulmonary arterial pressures. All horses except 1 were clinically normal after thoracoscopic surgery; that horse developed hemothorax attributable to iatrogenic injury to the diaphragm. The second thoracoscopy revealed minimal inflammation, and there were no adhesions. CONCLUSIONS AND CLINICAL RELEVANCE: Thoracoscopically guided pulmonary wedge resection provides a minimally invasive method for use in obtaining specimens of lung tissues from healthy horses and those with lung disease. This technique may be useful for the diagnosis of diseases of the lungs and thoracic cavity.     

Disseminated lymphoma with large granular lymphocyte morphology diagnosed in a horse via abdominal fluid and transtracheal wash cytology

A 22‐year‐old Tennessee Walking Horse mare was presented to the Auburn University Large Animal Teaching Hospital with a 3‐day history of lethargy, anorexia, and mild signs of colic. The mare had a several‐month history of weight loss and refractory cough. Physical examination revealed an increased respiratory rate, and crackles and wheezes were heard on thoracic auscultation. Thoracic ultrasonographic examination showed disseminated, minor, bilateral comet tail‐like lesions on the parietal pleural surfaces. Abdominal ultrasonographic examination was unremarkable. Trans‐rectal palpation revealed a firm small colon impaction with concomitant diarrhea. Laboratory data were characterized by a very pronounced acute inflammatory leukogram with severe neutropenia and significant left shift, evidence of hepatocellular damage/necrosis, cholestasis, and possibly mixed metabolic alkalosis and acidosis. On cytologic evaluation of a peritoneal fluid sample, there were many large granular lymphocytes (LGL). Large numbers of LGL were also observed on cytologic examination of a subsequent transtracheal wash. The final cytologic interpretation was disseminated lymphoma with LGL morphology. Due to worsening of the clinical signs and poor prognosis, the mare was euthanized. On necropsy and in histopathologic examination, disseminated lymphoma with LGL morphology was noted in a mesenteric lymph node, lungs, liver, spleen, kidneys, and right dorsal colon. Lymphoma with LGL morphology is rarely diagnosed in the horse. This report provides unique cytologic findings of a case of disseminated lymphoma with LGL morphology in a horse, confirmed with histopathologic evaluation.     

Primary hyperparathyroidism in a 17‐year‐old Arab × Welsh Cob pony mare with a functional parathyroid adenoma

Primary hyperparathyroidism was identified in a 17‐year‐old Arab × Welsh Pony mare that experienced weight loss for 6 months and was presented with mild facial asymmetry, right forelimb lameness and weight shifting amongst all limbs. Osteodystrophia fibrosa was demonstrated on radiographic examination of the head and there was radiographic evidence of osteopenia of the appendicular skeleton. The horse had persistent hypercalcaemia (4.0 mmol/l), hypophosphataemia (0.59 mmol/l) and an increased concentration of circulating parathyroid hormone (1401 pg/ml). On scintigraphic examination, a subjective focal increase in uptake of ^99mtechnetium‐sestamibi was identified in the right thyroid gland and at the thoracic inlet in delayed images. Surgical exploration of the thyroid region was unrewarding, whereas surgery at the thoracic inlet was not undertaken. One year later, the horse developed a pathological fracture of the third metacarpal bone and was subjected to euthanasia. At post mortem examination, a parathyroid adenoma was found at the level of the thoracic inlet adjacent to the trachea. Gross and histological examination also confirmed severe osteodystrophia fibrosa and osteopenia.     

Bicavitary effusion in a horse with multicentric lymphoma

A 14-year-old Quarter Horse gelding presented for a 2-week history of increased respiratory rate, fever and weight loss. The referring veterinarian performed an ultrasonographic examination on the farm and considered a differential diagnosis of pleuritis and pleuropneumonia. On presentation, transtracheal wash showed suppurative septic inflammation with bacteria within macrophages. Thoracic ultrasonography showed increased hypoechoic fluid in the pleural and peritoneal cavities. Cytologic analysis of pleural and peritoneal fluids revealed lymphorrhagic effusion with atypical lymphocytes, suggestive of a lymphatic flow obstruction or lymphoma. Treatment consisted of drainage of the pleural fluid, anti-inflammatory agents, fluid therapy and antimicrobial therapy. Continued fluid accumulation in the thoracic cavity, tachypnoea, lack of response to pain medication and progressive lethargy resulted in the horse being subjected to euthanasia. At necropsy, bicavitary effusion was confirmed and histopathological diagnosis of multicentric lymphoma was made. Horses presenting with pleural effusion should also be evaluated for peritoneal effusion, as bicavitary effusion may indicate noninflammatory conditions such as neoplasia.     

Horner's Syndrome Associated with Disseminated Thoracic Melanoma in a Lipizzaner Horse

A 20-year-old gelding Lipizzaner horse was referred for onset of profuse sweating and increased heat on the right side of the head, neck, and thoracic limb. On physical examination, the horse presented tachycardia, muffled heart sounds with a pansystolic murmur, and signs of heart failure such as ventral edema, jugular distention, and pulsation. Ultrasonography examination revealed a bilateral pleural effusion and a large intrathoracic mass extending into the anterior mediastinum, which shifted the heart dorsocaudally. Thoracocentesis revealed serosanguineous fluid indicative of a melanocytic tumor. Thoracoscopy revealed a large dark mass extending into and filling the cranioventral mediastinum. The mass appearance was consistent with a melanoma, and because prognosis was poor, the owner elected euthanasia. A necropsy supported the presence of disseminated melanomas with a greater thoracic mass involving the right cervicothoracic ganglion, leading to clinical signs of sympathetic denervation.     

Unilateral degenerative joint disease of a cervical articular process joint between the fourth and fifth cervical vertebrae causing asymmetrical ataxia in a young horse

A 5-year-old horse was examined for investigation of asymmetrical, quadrilateral ataxia and paresis. Clinical examination was unremarkable, and a thorough neurological examination localised the lesion to the cervical spine. Following this, magnetic motor evoked potentials were acquired to allow for latency times to be determined. Abnormal conduction times were found to the right thoracic and right pelvic limbs, confirming that the horse had an asymmetrical cervical spinal myelopathy. Radiographs were acquired to ensure that the horse had no significant pathology which would contraindicate general anaesthesia. There were no abnormalities noted on these, so the horse underwent contrast-enhanced computed tomography of its cervical spine which revealed enlargement of the right articular process joint between C4 and C5 with dorsolateral impingement of the spinal canal and cord. Due to the poor prognosis for future performance, the horse was subsequently euthanised. A post-mortem examination confirmed the findings of degenerative joint disease, with some unexpected changes seen on histology of the spinal cord. The unilateral right-sided compression had caused degenerative changes to ascending and descending tract bilaterally indicating a dynamic component to this lesion, which would be more commonly understood to be static.     

Postanesthetic poliomyelomalacia in a horse

A clinically normal horse was anesthetized preparatory to surgery in dorsal recumbency for removal of a retained testicle. After recovery from the anesthetic, the horse was weak in the hind legs, subsequently deteriorated and became unable to rise and died on the eighth day after surgery. On microscopic examination, extensive poliomalacia of the thoracic and lumbar spinal cord was found. It is postulated that this lesion was a result of ischemic insult to the spinal cord during anesthesia and several possible pathogeneses are discussed.     

Small intestinal adenomatous polyps resulting in chronic obstruction in a 3-year-old Quarter Horse gelding

A 3-year-old, Quarter Horse gelding was admitted to Kansas State University Veterinary Health Center with a primary complaint of colic. The horse had a 3-month history of recurrent colic and progressive weight loss. On physical examination, the horse was quiet, alert and responsive. The horse's mucous membranes were pink and capillary refill time was 2 s. His rectal temperature was 37.6°C (99.6°F), heart rate was 56 beats/min and respiration rate was 16 breaths/min. Rectal palpation revealed an approximately 5 cm dilated, firm, tubular, mass traversing from left caudal abdomen to mid abdomen. Nasogastric intubation obtained 6 L net reflux. A 5 cm diameter small intestinal intraluminal mass was detected by abdominal ultrasound. Complete blood count, serum chemistry and peritoneal fluid analysis were performed and all results were unremarkable. The horse was humanely euthanised due to pain and financial constraints. Post-mortem examination and histopathology revealed a 15 × 5 × 5 cm polyp with multiple smaller satellite polyps that obstructed the distal duodenum. Colic was considered secondary to small intestinal obstruction and luminal distension caused by the adenomatous polyps. To the authors’ knowledge, this is the first report to include ultrasound images of a small intestine adenomatous polyp that caused small intestinal obstruction and colic in a 3-year-old horse.     

Treatment of tracheal collapse with an intraluminal stent in a miniature horse

A 7-month-old miniature horse was referred for respiratory distress. Tracheal collapse at the level of the thoracic inlet was diagnosed. An intraluminal nitinol stent was placed with endoscopic guidance. Respiratory function was restored immediately after stent placement. The main complication observed during a 14-month follow-up period was growth of granulation tissue through the stent, which was controlled satisfactorily by electrocautery performed during endoscopy with the horse standing. Treatment of tracheal collapse with an intraluminal stent is an effective, practical, and minimally invasive procedure in miniature and young equids and ponies.     

Dexamethasone for treatment of multisystemic eosinophilic epitheliotropic disease in a horse

A 4-year-old Paint mare was examined because of respiratory tract infection, dermatitis, and weight loss of 2 months' duration. Initial examination revealed generalized pruritic dermatitis, ocular and nasal discharges, and stranguria. Laboratory abnormalities included leukopenia and hypoalbuminemia. Further examination of the respiratory tract revealed grade III of IV pharyngitis and pyogranulomatous pneumonia. Endoscopic examination of the bladder revealed a prolific mass at the junction of the bladder and urethra. Hypoproteinemia was suspected to be caused by protein-losing enteropathy. On histologic examination, skin, rectal, pharyngeal, and urethral biopsy specimens were characterized by infiltration of eosinophils and lymphocytes, and a diagnosis of multisystemic eosinophilic epitheliotropic disease was made. The horse improved following treatment with dexamethasone, trimethoprim-sulfamethoxazole, and an antihistamine and was discharged after 19 days of hospitalization. Treatment with dexamethasone was continued for 4 weeks after hospitalization but was then discontinued. Eight months after discharge, the horse was performing as a pleasure horse and did not require any medical treatment. Multisystemic eosinophilic epitheliotropic disease is typically associated with a poor prognosis in horses. The dermatitis, protein-losing enteropathy, and lower respiratory tract disease in this horse were consistent with previous reports; however, pharyngitis and urethritis have not, to our knowledge, been previously reported in horses with this disease.     

Equine thoracoscopy: normal anatomy and surgical technique

Six normal, healthy horses age 3-10 years underwent left and right thoracoscopic examination using a rigid telescope. A minimum of 30 days was allowed between procedures. Horses were restrained in stocks and sedated with a continuous detomidine infusion. After surgical preparation of the hemithorax elected for surgery, and administration of local or regional anaesthesia of the surgery sites, thoracoscopy was completed during two 15 min pneumothorax periods. During the procedures, the thoracic structures were viewed using a 57 cm, 10 mm diameter, 30 degrees rigid telescope connected to a digital camcorder to allow computer capture of digital images. The telescope was inserted into the thoracic cavity via 3 different intercostal spaces. The 8th, 10th and 12th intercostal spaces were randomly selected and used among horses. The exploration of each hemithorax started from the dorsal-caudal quadrant continued toward the cranial thorax and was completed by observing the diaphragmatic and caudal pulmonary region. Collapsed lung, aorta, oesophagus and diaphragm were viewed readily in either hemithorax. On exploration of the right hemithorax, the azygos vein, thoracic duct and pulmonary veins were also identified. Horses tolerated thoracoscopy well. Signs of discomfort, such as increased respiratory rate, coughing and decreased level of sedation, were associated with lung collapse in one horse, with pneumothorax on 2 occasions, and when the thorax was approached through the 8th intercostal space. Surgery performed via the 8th intercostal space was hindered by the rigidity of the 8th and 9th ribs, and by the presence of a greater musculature, which did not allow easy cranial and caudal movements of the telescope.     

Poor performance due to epiglottic retroversion in a Standardbred trotter

A 3-year-old Standardbred trotting gelding presented to the Atlantic Veterinary College for diagnostic work-up of poor performance and abnormal respiratory noise during exercise. Physical examination was unremarkable, and no significant findings were identified on standing endoscopic examination of the upper respiratory tract. Treadmill endoscopy was utilised for dynamic evaluation of the upper respiratory tract; a diagnosis of epiglottic retroversion was confirmed. The owner requested euthanasia of the gelding, and a post-mortem evaluation was completed. Despite thorough gross and histological examination of the head and neck on post-mortem examination, no evidence was identified to support the postulated aetiologies for epiglottic retroversion currently found in the literature. This case represents the first reported findings from a post-mortem examination of a horse with epiglottic retroversion.     

Right Dorsal Colon Resection and Bypass for Treatment of Right Dorsal Colitis in a Horse

Objective: To describe a novel surgical technique for management of right dorsal colitis in the horse. Study Design: Clinical report. Animals: 14‐year‐old Warmblood gelding. Methods: The horse was referred for treatment of a stromal abscess and signs of right dorsal colitis. Plasma chemistry revealed marked hypoproteinemia. Abdominal ultrasonographic examination showed a thickened right dorsal colon (RDC). Medical treatment was unsuccessful. With the horse in left lateral recumbency under general anesthesia, an approach to the right side of the abdomen through a 16th rib resection was made. The thoracic cavity was entered during the approach. Surgical resection of the RDC and side‐to‐side anastomosis of the diaphragmatic flexure to the small colon (bypass) was performed. The thoracic cavity was closed by attaching the diaphragm to the body wall and air was removed at the completion of surgery. Results: Resection of the RDC and bypass of the resected area was successfully performed. The colic signs and hypoproteinemia resolved. Complications of surgery included a deep surgical site infection with development of a large intrathoracic abscess. The abscess was managed with drainage and long‐term antimicrobial treatment. Conclusion: Right dorsal colitis can be treated successfully with resection and bypass of the RDC. In cases where the thoracic cavity is penetrated during the abdominal approach, the diaphragm should be sutured to the body wall at the beginning of surgery to avoid development of an infection within the thoracic cavity. Clinical Relevance: RDC resection and bypass may be an alternative approach for management of horses with right dorsal colitis.     

Subcutaneous emphysema from an axillary wound that resulted in pneumomediastinum and bilateral pneumothorax in a horse.

A 5-year-old Thoroughbred gelding was examined because of a small axillary wound sustained 5 days earlier and had resulted in extensive subcutaneous emphysema. Three days after admission, the horse's respiratory rate had increased to 72 breaths/min, and the horse appeared anxious and distressed. Thoracic radiography revealed pneumomediastinum and severe bilateral pneumothorax. Tube thoracostomy was performed on both hemithoraxes. The drains were connected to one-way suction valves and suction devices to decompress the thorax. A nasopharyngeal catheter was inserted, and oxygen insufflation was started. Cross ties were placed on the horse to limit movement, and the wound was packed. The horse improved within 30 minutes after initiating treatment. The horse was released 15 days after the development of pneumothorax, at which time the pneumothorax had resolved, the wound was no longer open, and the subcutaneous emphysema had greatly decreased. Although subcutaneous emphysema is usually regarded as a temporary cosmetic disfigurement, it can lead to serious complications such as pneumothorax. This case demonstrates that subcutaneous emphysema can lead to a life-threatening pneumothorax if the pressure is great enough to migrate through the mediastinum and into the pleural cavity. Horses with subcutaneous emphysema should be kept in confinement and monitored for the development of pneumothorax.     

Esophageal phytobezoar in a horse

A 23-year-old Thoroughbred stallion was admitted to the hospital for treatment of acute esophageal obstruction. Clinical examination and contrast radiography confirmed the presence of an esophageal obstruction. The horse was euthanatized, and examination revealed a bolus of feed material occluding the esophageal lumen 6 cm caudal to the thoracic inlet, with underlying necrosis of the esophageal mucosa. A large pulsion diverticulum was identified in the caudocervical portion of the esophagus. Apparently, the phytobezoar was formed within the esophageal diverticulum and subsequently became dislodged, occluding the esophagus.     

Acute hindlimb paresis caused by extension of a peripheral nerve sheath tumour into the spinal canal of a horse

A 10-year-old Quarter Horse gelding presented for a large, slowly growing mass in the right thoracic region caudal to the withers (approximately at the level of thoracic vertebrae 10 to 16). The mass was surgically removed, the horse returned to normal riding activity, and no external regrowth was observed. Two years after surgery, the horse developed progressive signs of hindlimb weakness, ataxia and adopting a dog-sitting stance. Post-mortem examination confirmed spinal canal infiltration and spinal cord compression (at the level of the 12th thoracic vertebra) by a similar soft tissue sarcoma as diagnosed previously. Immunohistochemistry confirmed the tumour as a peripheral nerve sheath tumour (PNST) likely originating from the twelfth thoracic spinal nerve. This report demonstrates that with incomplete tumour resection, local recurrence and extension of a PNST into the central nervous system can occur even years after initial tumour removal. Immunohistochemistry to differentiate the type of soft tissue sarcoma in cases with close association to the nervous system may prove beneficial to anticipate this uncommon complication. Early surgical resection with adjunctive therapies should be considered in these cases.     

Clostridium perfringens type A myonecrosis in a horse in Korea

Acute hemorrhagic myonecrosis accompanied by severe inter- and intrafascicular edema and hemorrhage of the right gluteal area was diagnosed in a 13-year-old male thoroughbred horse. Once the muscular and fascicular changes were subsided, the horse then developed acute respiratory problem. Histologically, the lung had diffuse severe hemorrhage with mild neutrophilic infiltration. The cause of death was acute respiratory failure that is believed to occur secondary to toxaemic event. Alpha and beta2 toxin secreting Clostiridum perfringens type A was isolated from the muscle and lung. The diagnosis was based on the light microscopic examination, bacterial toxinotyping and toxin genotyping from the muscular and pulmonary lesion. Also, susceptibility of the isolates to antimicrobial agents was determined.