Multiple skeletal metastases from a penile squamous cell carcinoma in a horse

A 21‐year‐old gelding with ventral abdominal and preputial oedema was evaluated for right hindlimb lameness. Partial phallectomy had been performed 3 years prior for treatment of squamous cell carcinoma. Regional analgesia did not localise the source of lameness and nuclear scintigraphy was recommended. The results of the scan revealed severe increased radiopharmaceutical uptake in the proximal femur. Radiographic and ultrasound examinations were inconclusive. The horse was discharged with recommendations of stall confinement and a 2 week course of nonsteroidal anti‐inflammatory drugs. Four weeks later the horse presented for an inability to elevate his neck and persistent hindlimb lameness. The owner elected humane euthanasia. Post mortem examination revealed metastatic squamous cell carcinoma in the proximal femur and fifth cervical vertebrae consistent with metastasis from the penile squamous cell carcinoma. To the authors’ knowledge, multiple site bone metastasis of squamous cell carcinoma has not been reported previously in the horse.     

Osteosarcoma of the middle phalanx in a horse

An 11‐year‐old Thoroughbred gelding was presented for lameness investigation following acute onset hindlimb lameness, which developed during a period of paddock turnout. Clinical examination revealed a swelling over the dorsolateral aspect of the pastern that was painful on digital palpation. Radiography of this area was consistent with an aggressive bone lesion involving both joint surfaces of the middle phalanx with pathological fracture and distal collapse of this bone. On this basis, the horse was subjected to euthanasia. Post mortem histopathological examination revealed presence of an osteosarcoma without involvement of the articular cartilage. This bone tumour is extremely rare in horses and has not been reported in this anatomical location.     

Malignant melanoma of the third eyelid in a horse

An 8‐year‐old grey Quarter Horse gelding was referred for evaluation of a rapidly growing mass associated with the third eyelid of the left eye. A pigmented mass of approximately 2 cm in diameter was palpated and visualised associated with the conjunctival lining of the nictitans. It was not possible to palpate normal nictitans deep to the base of the mass. A full dermatological examination revealed no other melanomas in common sites. Based on the size and rapid growth of the mass, surgical excision and one application of local chemotherapy was performed under general anaesthesia. Histopathology confirmed the diagnosis of malignant melanoma and the presence of clean surgical margins. There was no recurrence at 5 weeks post surgery. To our knowledge, this is the first report of a primary malignant melanoma of the third eyelid in a horse.     

The use of CT and CT arthrography in diagnosing equine stifle injury in a Rheinlander gelding

A 5‐year‐old Rheinlander gelding was evaluated for left hindlimb stifle lameness. The lameness was localised to the stifle, but source of the lameness was not specifically diagnosed from the physical, radiographic and ultrasonographic examinations. Computed tomography (CT) and CT arthrography were therefore used for further investigation since these imaging techniques image bony structures, cartilage and soft tissues. This examination showed multiple lesions in the stifle: an osteochondrosis dissecans like lesion of the medial femoral condyle, bony fragments, cartilage trauma and caudal cruciate ligament injury. The prognosis for continuing use as a sports horse was regarded as unfavourable. Therefore, the horse was subjected to euthanasia. All CT findings were confirmed by gross pathology. The CT and CT arthrography examination in this case provided a diagnosis not achieved with other conventional imaging techniques.     

An unusual cyst‐like lesion in the metaphysis of the tibia in a horse

A 6‐year‐old Haflinger gelding was presented with a chronic right hindlimb lameness. Scintigraphy, radiography and computed tomography confirmed an active large cyst‐like lesion in the distal metaphysis of the right tibia. A transcortical surgical approach was used to curette the lesion and fill it with an autologous bone graft and a calcium phosphate bone substitute material. Histopathology revealed mild histiocytic inflammatory changes, mild fibrosis and bone necrosis. This case report describes an unusual cyst‐like lesion in the tibial metaphysis of a horse.     

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.     

Severe lameness caused by metastatic renal adenocarcinoma of the third phalanx in a Warmblood mare

Malignant osseous neoplasia has been extremely rarely reported in the horse and, therefore, it is not commonly considered as a differential diagnosis for acute lameness. In the present report, a 19‐year‐old Warmblood mare in poor body condition and with a history of chronic haematuria, presumably attributable to renal neoplasia, was referred with acute, progressive, unilateral right forelimb lameness with marked unilateral digital pulsation and metacarpal oedema. No hoof abscess was found. Radiographic examination revealed a well defined osteolytic area in the dorsomedial half of the third phalanx. Dermal laminae at the dorsomedial aspect of the hoof showed a dark red appearance with poor vascularisation. Thoracic radiographs revealed pulmonary nodules. As osseous metastasis of the third phalanx was suspected, the mare was subjected to euthanasia. Post mortem histopathological examination confirmed the diagnosis of primary renal adenocarcinoma with metastasis to the lungs, myocardium, along the perirenal lymphatic tract and to the third phalanx, with extensive osteolysis in the latter location. Post mortem computed tomography of the hoof provided excellent visualisation of the osseous metastasis. The rare possibility of osseous metastatic neoplasia should be included in the differential diagnosis of severe lameness, especially in aged horses with a history of chronic renal disease.     

Severe lameness associated with an impact fracture of the proximal phalanx in a filly

A 3‐year‐old filly was presented for severe lameness referable to the left front fetlock joint. Radiographs confirmed an osseous cyst‐like lesion and synovial fluid cytology ruled out sepsis. The filly responded poorly to medical management and was subsequently subjected to euthanasia. Post mortem examination confirmed an impact fracture of the proximal phalanx, previously undiagnosed in the horse.     

Osteosarcoma of the proximal radius in a donkey

A mature donkey was presented for evaluation of a forelimb lameness and presence of a large mass on the left forelimb distal to the elbow joint. Clinical examination, radiographs and cytological examination of ultrasound‐guided fine needle aspirates of the mass led to a presumptive diagnosis of osteosarcoma. The donkey was subsequently subjected to euthanasia. Post mortem examination confirmed the diagnosis of osteosarcoma in the proximal radius with expansion of the mass through the ulnar cortex and metastases to liver and regional lymph nodes, areas of metastasis previously unreported in the equine literature.     

Guttural pouch leiomyosarcoma causing nasopharyngeal compression in a pony

A 14‐year‐old Connemara cross gelding presented with abnormal respiratory noise and exercise intolerance. Upper airway endoscopy, ultrasonography, radiography and computed tomography revealed a large mass within the left guttural pouch causing marked left dorsal nasopharyngeal collapse and displacement and compression of the right guttural pouch. The horse was subjected to euthanasia and a post‐mortem examination confirmed the above findings. Histological and immunohistochemical examinations of the mass confirmed a diagnosis of guttural pouch leiomyosarcoma, a lesion previously unreported at this site.     

Primary haemangiosarcoma in the proximal humerus of a Clydesdale gelding

An 11‐year‐old Clydesdale gelding was presented for investigation of left forelimb lameness of 2 weeks' duration. The use of scintigraphic imaging helped to localise the source of lameness to the left proximal humerus. In this report, the clinical and diagnostic imaging features of a primary osseous haemangiosarcoma in a horse are described, along with the challenges of establishing a definitive diagnosis ante mortem. In addition, neoplasia of the appendicular skeleton should be considered a differential cause of lameness in the horse.     

Parotid salivary gland carcinoma in a geriatric horse

This case report describes a geriatric gelding with a 2 month history of fast‐growing masses within the parotid and submandibular regions. The horse was dyspnoeic on presentation and upper airway endoscopy revealed partial airway obstruction at the level of the pharynx, secondary to a space‐occupying mass. Cytological evaluation of multiple fine‐needle aspirates obtained from the masses were suggestive of salivary gland neoplasia, therefore the horse was subjected to humane euthanasia. A computed tomographical scan was obtained post mortem and revealed a large multi‐lobulated mass involving both guttural pouches, resulting in 80% occlusion of the naso‐ and oropharynx. Histopathology confirmed a parotid salivary gland carcinoma (papillary‐cystic type). Salivary gland tumours are extremely rare in horses, with only a few cases reported in the literature. Treatment of these malignancies proves to be challenging, requiring complete parotidectomy or surgical debulkment, in combination with adjunctive therapy.     

Fracture repair of the distal portion of the radius by use of a condylar screw implant in an adult horse.

An 8-year-old American Quarter Horse gelding was evaluated because of an open fracture involving the left radius. The horse had fallen during training and became immediately non-weight-bearing in the left forelimb. On initial evaluation, the horse was unable to bear weight on that limb; radiography revealed a long oblique fracture of the distal metaphysis of the radius with minimal displacement of the fracture fragments. Because of the configuration of the fracture, we recommended surgical intervention with internal fixation. A condylar screw implant and 4.5-mm broad dynamic compression plate were applied to the medial and dorsolateral aspects of the radius, respectively. The horse recovered in a sling and full-limb bandage. Six months after discharge, the horse was reevaluated because of a grade 4/5 lameness in the same limb. Palpation revealed signs of severe pain over the distomedial aspect of the radius. Radiography of the left radius revealed severe osteolysis beneath the distal aspect of the condylar screw implant. Surgical removal of the medial plate was performed. Sixteen months after the initial fracture repair, the horse had returned to light training without signs of lameness. Removal of the dorsal plate may be indicated if this horse is to return to aggressive training or becomes lame in the left forelimb.     

Two occurrences of presumptive venous air embolism in a gelding during cystoscopy and perineal urethrotomy

A 14‐year‐old Arabian gelding presented for evaluation of macroscopic haematuria. Routine cystoscopy was performed under standing sedation during which the horse collapsed with apparent seizure activity. General anaesthesia was induced and the horse recovered neurologically normal. Four days later, during a perineal urethrotomy procedure, the horse experienced a similar collapse with seizure‐like activity. General anaesthesia was again induced and cystoscopy performed through the urethrotomy incision. A ventral bladder mass was visualised and sampled. Cytology confirmed a neoplastic process and the horse was subjected to euthanasia. Histopathology confirmed transitional cell carcinoma. Air embolism was the suspected cause of loss of consciousness and seizure activity in both instances.     

Placement of bone screws in a standing horse for treatment of a fracture of the greater tubercle of the humerus

A mature Thoroughbred gelding that was used as a high level jumper presented for evaluation of a nonweightbearing forelimb lameness following a fall. Radiographs revealed a complete, noncomminuted, minimally displaced sagittal fracture of the greater tubercle. Supporting limb laminitis was a major concern in the short term based on the severe lameness at presentation. Open reduction with internal fixation was chosen over stall rest in an attempt to more rapidly return the weightbearing function to the limb. The procedure was performed standing and 3 bone screws were placed standing in an attempt to avoid implant or catastrophic bone failure that can accompany recovery from general anaesthesia. The day following surgery the lameness was significantly improved as the horse was able to bear some weight on the heel. The gelding was discharged 5 days following surgery and was fully weightbearing at the walk. Six months following surgery the horse was free of lameness and resumed training. This report describes our experience and rationale in placing bone screws in a standing horse for treatment of a greater tubercle fracture.     

Mastocytoma in the common carpal sheath of the digital flexor tendons of a horse

A 13-year-old Morgan gelding was examined for right forelimb lameness and tenosynovitis of the right common carpal sheath of the digital flexor tendons. The horse had moderate right forelimb lameness at the trot and marked effusion of the right common carpal sheath of the digital flexor tendons. Ultrasonographic examination revealed a soft tissue mass within the proximal pouch of the affected tendon sheath, located adjacent to the distal physis of the radius. Cytology and culture of the fluid revealed a sterile, eosinophilic tenosynovitis. Tenoscopic exploration confirmed the presence of a capsulated soft tissue mass. Thecotomy was required to fully debride the mass, which histology revealed to be a mast cell tumour. At 22 months postoperatively, the horse developed mild right forelimb lameness and eosinophilic tenosynovitis because of recurrence of the mastocytoma. Mastocytosis is a possible differential diagnosis in any horse exhibiting lameness associated with tenosynovitis. Surgical excision combined with rest and postoperative intrasynovial and systemic corticosteroids may be palliative.     

Ataxia and weakness as uncommon primary manifestations of hepatic encephalopathy in a 15‐year‐old trotter gelding

A 15‐year‐old trotter gelding was evaluated because of an acute onset of ataxia in all 4 limbs. There was no known history of trauma. The gelding showed grade 2/5 ataxia in all 4 limbs, which was localised after clinical neurological examination to the cervical vertebral spinal cord. Initial therapy consisted of oral anti‐inflammatory doses of prednisolone and antimicrobial treatment with potentiated sulphonamides. The ataxia progressed to grade 3/5 at Day 10 of hospitalisation. Additionally, the horse was slightly depressed and showed spontaneous yawning during examination. Facial sensation was blunted. Blood chemistry revealed a marked elevation of liver specific enzymes and blood ammonia levels. Transcutaneous abdominal ultrasonography revealed hepatomegaly. Due to a guarded prognosis, the horse was subjected to euthanasia. At necropsy the left lateral liver lobe was markedly enlarged and showed a firm texture, whereas the cranial part and the right and quadratic liver lobe displayed a severe and diffuse atrophy. Histopathologically, the left lateral liver lobe revealed a moderate to severe cirrhosis with a severe, diffuse hepatocellular iron‐accumulation. Increased numbers of Alzheimer type II astrocytes in the cerebral cortex and cerebral white matter vacuolisation were indicative for encephalopathy. These findings were interpreted as haemosiderosis and cirrhosis of the liver with consecutive hepatic encephalopathy. Aetiologically, haemosiderosis should be considered as a cause of liver cirrhosis with consecutive hepatic encephalopathy. Although hepatic encephalopathy in horses usually presents with predominating cerebral signs, it has to be taken into account as a differential diagnosis in cases of acute onset generalised ataxia.     

Clinical findings associated with chronic ischial fracture in a gelding

An 8-year-old show-jumper gelding was referred for examination as a result of a purchase dispute for reported back pain. Clinical examination identified back pain and atrophy of the left semimembranosus and semitendinosus muscles, but no lameness. Standing pelvic radiography demonstrated a chronic nonunion fracture of the left ischium, the clinical significance of which was uncertain. The apparent back pain was thought to be probably unrelated to the pelvic lesion. We conclude that chronic ischial fracture in the horse can lead to specific atrophy of the semimembranosus and semitendinosus muscles, which originate from this bone.     

Comminuted fracture of the accessory carpal bone removed via an arthroscopic-assisted arthrotomy

A 16-year-old American paint horse gelding was presented for evaluation of a left forelimb lameness grade III/V. Radiographs and computed tomography revealed a comminuted fracture of the accessory carpal bone involving the entire articulation with the distal radius and the proximal aspect of the articulation with the ulnar carpal bone. Multiple fragments were present in the palmar pouch of the antebrachiocarpal joint. An arthroscopic-assisted open approach was necessary to remove all fractured fragments. Subsequently the horse was re-admitted for lameness and was treated successfully with antibiotics and long-term supportive bandaging.     

Autologous Platelet Concentrates as a Treatment for Shoulder Injury in a Horse

Shoulder injury is an uncommon cause of lameness in horses. Trauma to the shoulder region may produce bone and soft-tissue damage. The present study describes the case of a severe left shoulder injury caused by blunt trauma in a 6-year-old gelding. Clinical and ultrasonographic examination revealed fracture of the supraglenoid tuberosity of the scapula and of the lesser tubercle of the humerus with fiber disruption and hematoma of the biceps brachii, bicipital bursitis, and suprascapular nerve damage. The gelding was successfully treated with three intralesional injections of autologous platelet concentrates administered at 2-week intervals. Although all these combined injuries took a minimum of 18 to 24 months for full recovery, the gelding reached full recuperation of the affected limb in 10 months. These results suggest that injections of autologous platelet concentrate could provide a therapeutic benefit in the treatment of shoulder bone fractures and soft-tissue injuries in horses.