Penile and preputial squamous cell carcinoma in the horse and proposal of a classification system

Squamous cell carcinoma (SCC) is the most common tumour of the penis and prepuce of the horse and is found mainly in older animals. Reports on breed predilection for penile tumour formation are equivocal but castration, coat colour, poor genital hygiene and various infectious agents have been suggested to predispose to the development of SCC. Careful assessment of the primary tumour is an important first step in the design of an optimal treatment protocol. Tumour size, invasiveness, differentiation grade and presence of metastases are relevant to the decision to pursue additional diagnostic procedures or specific treatment options. Complete elimination of the neoplasm and, therefore, risk of recurrence is highly dependent on the type of therapy chosen. However, the size and histopathological features of the primary tumour are also important factors with respect to prognosis. This review describes the clinical and pathological features of penile and preputial SCC in the horse and proposes a standard staging system.     

Retrobulbar dermoid cyst in a horse: a case report

A 4-year-old Andalusian horse was presented for examination following a 3-month history of exophthalmos of the right eye and a soft swelling of the right supraorbital fossa noted after blunt head trauma. Ultrasonographic examination of the swelling showed an anecogenic mass of 5 cm in diameter involving the retrobulbar space. Centesis of the mass through the supraorbital fossa was performed and yielded a serous fluid with 7.2 g/dL of total protein and density of 1040. No cells were seen in the sample. A tentative diagnosis of cyst was made. The cyst was surgically removed and the definitive histologic diagnosis was retrobulbar dermoid cyst. No recurrence has developed 18 months following the complete removal of the cyst capsule. To the authors' knowledge, there are no previous reports of retrobulbar dermoid cysts in horses. Localization, causes and success of surgical treatment of dermoid cysts are discussed.     

Episodic collapse in the horse

The term ‘collapse’ can be used to describe a variety of incidents in which a horse loses postural tone with or without progression to recumbency and with or without loss of consciousness. Depending on the aetiology of the condition the episode may be self‐limiting and may or may not recur. Alternatively the collapse may be secondary to serious injury or disease and require veterinary intervention. This article mainly discusses investigation of the former scenario of self‐limiting single or multiple episodes of collapse in apparently healthy horses. An overview of the various causes of collapse is followed by a suggested approach to the diagnosis of these challenging cases.     

Traumatic brain injury manifested as optic neuropathy in the horse: A commentary and clinical case

Blindness from head trauma is a serious debilitating disease in the horse. It appears that blunt trauma to the skull results in intracranial injury to the optic nerve at the optic chiasm from mechanical and vascular mechanisms. Systemically administered iron and calcium chelation therapy may enable some horses to recover vision.     

Pseudo‐polydactyly in a horse

A 14‐month‐old half‐breed horse showed a severe lameness due to a lesion of the right forefoot which appeared completely and asymmetrically cleaved, from the solar margin to the coronary band. The horse was presented to an abattoir for slaughter and both forelimbs were collected for diagnostic investigations. The hoof lesion described herein does not fulfil the diagnostic criteria of equine polydactyly since post mortem imaging and pathological investigations ruled out the presence of supernumerary digits. Based on the clinical signs, diagnostic imaging (computed tomography) and gross examination, a diagnosis of pseudo‐polydactyly was proposed. To the best of our knowledge, the features of the present case report are unique, thus widening the range of lesions observed at the level of the hoof, which is crucial for horse health and activity.     

Cutaneous blastomycosis in a horse

This report describes the case of a horse presented with cutaneous lesions caused by Blastomyces dermatitidis in the absence of signs of other organ involvement. Diagnosis was achieved through cytology, histopathology and culture. Surgical debulking associated with systemic therapy with oral fluconazole resulted in significant remission; however, recurrence occurred following presumed early cessation of treatment.     

Surgical treatment of colic in the miniature horse: a retrospective study of 57 cases (1993-2006)

REASONS FOR PERFORMING STUDY: It has been suggested that the rate of post operative abdominal adhesions in miniature horses is higher than that for other breeds. However, few reports exist in the veterinary literature describing complications and long-term survival following surgical treatment of colic in these horses. OBJECTIVES: To determine the prevalence of surgical lesions in miniature horses with acute abdominal disease in terms of clinical signs, surgical management, post operative treatment and complications, as well as short- and long-term survival. METHODS: Medical records of 57 American Miniature Horses undergoing surgical treatment for acute abdominal pain at the Michigan State University Large Animal Veterinary Teaching Hospital 1993-2006 were evaluated for clinical information. Owners and trainers were contacted to gain information regarding long-term survival. RESULTS: The most common surgical lesion was a faecalith (38/57 cases) located primarily within the descending colon and most frequently diagnosed in horses age <6 months (19/38 cases). Short-term survival to hospital discharge for horses recovered from anaesthesia was 98% (55/56) with the most common post operative complications being diarrhoea and inappetance. Intra-abdominal adhesions were identified in 2/8 horses requiring a second celiotomy. Long-term follow-up was available for 45 horses and 87% (39/45) were alive at least 12 months after surgery. CONCLUSIONS: As previously reported, faecalith obstruction is a frequent surgical lesion in the miniature horse and is most common in miniature horses age <6 months. The incidence of adhesion formation may be lower than previously reported.     

Paranasal sinus fibromatosis in a horse

A case of paranasal sinus fibromatosis in an 11‐year‐old Thoroughbred gelding is reported. At admission the gelding underwent a unilateral frontal sinusotomy and a paranasal sinus mass was extensively debulked. The mass was diagnosed via histopathology as a desmoid fibromatosis with bone invasion, reactive osteoclastic osteolysis and osteoproliferation. The gelding had radiographic evidence of slow recurrence of the mass 8 months post operatively. The histopathological appearance and short‐term outcome are presented for this previously undiagnosed condition of the horse. Recognition of paranasal fibromatosis and the resultant differentiation from other types of paranasal sinus neoplasia may allow for improved prognostication of equine sinus lesions.     

Severe polyuria and polydipsia as major clinical signs in a horse with unilateral renal adenocarcinoma

A 14‐year‐old Swiss Warmblood gelding was presented with chronic severe polyuria, polydipsia and weight loss. At the time of admission, water intake was 240 l/day. On rectal examination, a large mass was identified in the left dorsal abdominal quadrant, which was shown to originate from the left kidney by transabdominal ultrasonographic examination. Unilateral nephrectomy via flank incision was performed under general anaesthesia. Histopathological examination of the tumour revealed a papillary renal adenocarcinoma. Successful outcome and survival was documented 13 months after surgery. Severe polyuria and polydipsia should be considered as major clinical signs for renal carcinoma in horses, which can be successfully treated with unilateral nephrectomy if no signs of metastatic spread are evident.     

Haemangiosarcoma in the horse

Neoplasms arising from vascular endothelial cells include benign haemangioma and malignant haemangiosarcoma, both of which are rare in the horse. Haemangiosarcoma can arise as a solitary mass, typically involving the eye or skin, or as disseminated tumours throughout multiple organs. There is no sex, breed or age predilection but most cases are found in middle aged horses. Clinical presentations of haemangiosarcoma in the horse include the presence of a visible mass or reflect dysfunction of the organ involved, thus making it difficult to differentiate from other neoplasms. Ante mortem diagnosis through clinicopathological findings, cytological findings of body cavity effusions or fine needle aspirates are often unrewarding. Biopsy or mass submission for histopathological examination may aid in diagnosis of haemangiosarcoma. A majority of cases are diagnosed post mortem; however, if the mass is poorly differentiated additional diagnostics such as immunohistochemical staining may be needed. Unfortunately, treatment of haemangiosarcoma is often unrewarding and limited based on the location of the mass and the aggressive nature of this neoplasm.     

Uveitic glaucoma in the horse

Glaucoma is a serious complication of anterior uveitis that can result in significant ocular discomfort and loss of vision. As glaucoma is insidious and mostly asymptomatic until late in the course of disease, it is often undiagnosed. Equine recurrent uveitis is the most common underlying disorder: it is a disease of high prevalence, characterised by recurrent‐remitting episodes of ocular inflammation. Here, the inflammatory cells and mediators they release alter the normal anatomic structure of the anterior chamber and aqueous drainage pathways of the eye. These changes alter the homeostatic mechanisms of intraocular pressure control. Management of glaucoma secondary to uveitis can be challenging due to the difficulties of managing the underlying disorder and its effects on the eye. This article reviews the pathogenesis of uveitic glaucoma in the horse and medical and surgical management options.     

Caffeine clearance in the horse

The pharmacokinetic properties of intravenously administered caffeine were studied in 10 horses using a commercially available automated enzyme immunoassay. The harmonic mean for the distribution half-life was 5.2 min (range 1.4–18.7). The harmonic mean for the elimination half-life was 10.18 h (range 6.82–20.92). The harmonic mean of the volume of distribution was 0.32 L/kg (range 0.22–0.53). There was no correlation between the dose of caffeine/kg body weight and the elimination half-life (Spearman's coefficient of rank correlation =0.19).Abbreviations AUC area under the serum concentration-time curve - AUMC area under the moment curve - BSP sulphobromophthalein - ICG indocyanine green - SD standard deviation - t _1/2 elimination half-life - V _c apparent volume of the central compartment - V _d(ss) apparent volume of distribution at steady state     

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.     

Ophthalmic antimicrobial therapy in the horse

Effective antimicrobial therapy of infectious ocular disease in the horse may be difficult to achieve. This paper reviews the routes of delivery, the pharmacokinetics and the bioavailability of the various antimicrobial agents used in the treatment of ocular infection in the horse. The modes of action and the criteria for selection of the common antibacterial, antimycotic and antiviral drugs used are described.     

An undifferentiated sarcoma in the cervical region in a horse

An Italian Saddle Horse mare was admitted for a hard, nonpainful mass localised in the cervical region. Clinical and diagnostic investigations were performed, which were suggestive of a multilobulated ossifying mass of neoplastic origin. Due to poor prognosis the horse was subjected to euthanasia. Post mortem computed tomography, anatomopathological examination and immunohistochemistry were used to make a definitive diagnosis of undifferentiated sarcoma in the cervical region.     

Laryngeal neuroendocrine tumour in a horse

A 13‐year‐old Quarter Horse mare was presented to the Ontario Veterinary College Teaching Hospital with chronic progressive respiratory noise and exercise intolerance. Severe respiratory stridor associated with a laryngeal mass was seen on upper airway endoscopy. Ultrasonography revealed an intra‐cartilagenous mass and allowed for a guided biopsy. Histological analysis of the mass characterised a neuroendocrine tumour and the mare was subjected to euthanasia due to the poor prognosis. Ultrasound examination was paramount in making the diagnosis and facilitating the biopsy. To our knowledge, neuroendocrine tumours have not previously been reported in the equine larynx.     

Lead toxicosis in the horse: A review

Lead intoxication is rarely diagnosed in horses and can present a major challenge to the equine practitioner because of the variety of clinical signs. Horses with lead poisoning can develop gastrointestinal disturbances, neurological abnormalities, haematological changes, or nonspecific signs of weight loss, weakness and rough hair coat, which makes early diagnosis difficult. Fortunately, lead analysis of whole blood is routinely available and can confirm intoxication. Because of the well‐described lead‐induced peripheral neuropathies in horses, a thorough neurological examination is essential in the investigation of a suspect case. Once diagnosed, the source of lead has to be identified and further exposure prevented. Intoxication can be treated by administering chelating drugs and providing symptomatic and supportive care.