Fractures of the withers in horses

The objective was to determine the prognostic features and long‐term outcome of withers fractures in horses. Medical records and radiographs of 14 horses with withers fractures from 2 veterinary teaching hospitals were reviewed. Case details, presentation, clinical signs, radiographs, treatment and outcome were assessed. In all cases, withers fractures were found to occur following a fall on the back. Although horses were often presented with severe acute clinical signs, the long‐term prognosis was good, in the absence of neurological signs, and following extended conservative management (an approximate 6 month rest period).     

Mesothelioma in horses

Pleural mesothelioma and pericardial mesothelioma with spread to the pleural cavity were diagnosed in 2 horses. Clinical signs included respiratory distress, depression and pleural pain. The affected body cavities contained copious, serous effusions containing very large neoplastic mesothelial cells with densely-staining cytoplasm, hyperchromic nuclei and prominent, often multiple, nucleoli. Ultrastructurally, the neoplastic cells appeared as solid aggregates, with profuse microvillous borders and neolumen formation. Cytological examination, together with confirmative ancillary diagnostic tests, including electron microscopy and immunocytochemistry, may be used to obtain an ante-mortem diagnosis of mesothelioma.     

Intersexuality in horses

Intersexuality is a rare congenital anomaly of horses. Diagnosis of intersexuality is difficult because there are usually no specific changes in the reproductive tract visible. During a period of five years, ten patients with reduced fertility or suspected intersexuality respectively were investigated using cytogenetic, molecular genetic, histopathological and endocrinological methods. In one case a 64,XX/63,X0 mosaicism was found. In six cases male pseudohermaphroditism was verified. These patients showed a male karyotype, testes and rudimentary parts of a female reproductive tract were present. One horse was suspected to be a male pseudohermaphrodite but the gonads were not examined. One horse was suspected to be affected by an XX-sex several syndrome and in one case a SRY-negative XY-sex reversal syndrome was most likely. In the case of an XX-sex reversal syndrome, there is a female chromosomal constitution, an uterus and cranial parts of the vagina are present but also testes tissue and possibly an enlarged penis like clitoris. Here an XX-sex reversal syndrome was suspected but not confirmed as it was not possible to examine the gonads and verify tissue from testes. Therefore a pseudohermaphroditismus femininus could not be excluded. In cases of XY-sex reversal syndrome the patients show a male chromosomal constitution, parts of a female reproductive tract but no testes tissue is present. For the horse described here, a deletion of the SRY gene was the most likely cause for the XY-sex reversal syndrome.     

Microvascular circulation of the cecum in horses

The microvascular circulation of the cecum was studied in 15 adult horses, using microangiography and light microscopy combined with gross studies and scanning electron microscopy of vascular replicas. After heparinization, the horses were euthanatized and the cecum was transected at the cecocolic junction. Blood was flushed free of the circulation with isotonic NaCl and the cecal lumen was slightly distended. In 6 horses, the vascular system was injected with a modified radiopaque medium and evaluated radiographically. Sections evaluated radiographically were also prepared for histologic examination by standard methods. Eight horses were injected with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy. In 1 additional horse, the lateral and medial arteries were injected with different colored plastic for gross studies. The lateral and medial cecal arteries appear to supply the respective areas of the cecum with minimal mixing of the 2 circulations. The major vascular supply to the cecal apex appeared to be through the medial cecal artery. Both the lateral and medial cecal arteries gave rise to cecal retia, which formed a mesh-like network around the respective veins. Vessels from these retia supplied the cecal tissue and the cecal lymph nodes. The continuation of the retia was through long terminal arteries that coursed around the circumference in the submucosa, forming an extensive submucosal plexus. This plexus supplied both the mucosa, and the tunica muscularis and serosa. Vessels within the longitudinal and circular muscle layers of the muscularis externa ran parallel to the muscle fibers, and consequently, perpendicular to each other.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anesthesia of horses in the standing position

Painful interventions can be performed on horse in standing position by means of sedative analgesia, also called standing-position anaesthesia. Combinations of anaesthetics are quite often used, in that context, for the purpose of producing analgetic effects stronger and more reliable than those that would be obtainable from one anaesthetic alone. The following combinations were comparatively tested for their analgetic and sedative effects and their effects upon the organism: Chloralhydrate with Ursonarkon (oxazolidone), Chloralhydrate with Rompun (xylazine), Chloralhydrate with morphine hydrochloride, Chloralhydrate with morphine hydrochloride and Ursonarkon, local anaesthesia in conjunction with sedation by Ursonarkon. 50 experiments were conducted on an experimental group of 10 horses under standardised conditions together with complementary tests on 71 horses under field conditions. The experimental methodology used for assessment of analgetic effects was based on defined electrical and thermic stimuli to enable determination of reactive thresholds. An objective comparison was thus possible between the above variants. Local anaesthesia in combination with complementary sedation proved to meet all demands on standing-position anaesthesia, as it was found to eliminate pain and tactile reflexes. Defence movements have to be expected, whenever preparations are used that attack the central nervous system, since while sensations of pain are suppressed, tactile stimuli may be met with reflex responses via the spinal cord and its intrinsic function.     

Enteroliths in horses

Many cases of enteroliths were reported in the nineteenth century but the number greatly decreased in the early twentieth century. However, in recent years the number of cases in certain parts of the United States such as California has greatly increased. The reasons for the increase are obscure. The intake of nitrogen, magnesium and phosphorus (the primary components of enteroliths) from water and food is likely to be a factor. Arabians may be more likely to develop enteroliths than horses of other breeds. A nidus such as a small stone is needed because a nidus has been found in every enterolith that has been examined. Further studies in which the effect of mineral intake and form of the mineral on enterolith formation are needed. Studies of enterolith formation in the past have all been retrospective. Models for the development of enteroliths are needed.     

Subluxation of the carpus in thirteen horses

The records of 13 horses of various breeds with subluxation of the radiocarpal, intercarpal or carpometacarpal joint, or combinations of these were reviewed. Subluxation was most common at the carpometacarpal joint (n = 10) and concomitant fractures of individual carpal bones or metacarpus II and IV were seen (n = 12).

Treatment comprised of immobilization in a full leg plaster cast for from four to 18 weeks. Three animals were euthanized, two because of cast complications and one because of a request by the owner. The remaining ten were saved to function as breeding animals.

     

Fractures of the distal phalanx in horses

Summary. Nineteen cases of fracture of the distal phalanx in horses are reviewed. This represented 1.1% of the total number of horses seen at Murdoch University Veterinary Hospital (MUVH) over a 32-month period. All horses were managed conservatively. Eight horses made a complete recovery. Three are being trained again and are not lame. Four horses made a limited recovery. Two horses are still resting and one horse was killed humanely when it still showed lameness after 2 years. One horse was killed humanely after the fracture was first diagnosed.